U.S. patent application number 16/878505 was filed with the patent office on 2020-11-26 for low energy implantable devices and methods of use.
The applicant listed for this patent is Axonics Modulation Technologies, Inc.. Invention is credited to Rabih Nassif.
Application Number | 20200368534 16/878505 |
Document ID | / |
Family ID | 1000004868663 |
Filed Date | 2020-11-26 |
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United States Patent
Application |
20200368534 |
Kind Code |
A1 |
Nassif; Rabih |
November 26, 2020 |
LOW ENERGY IMPLANTABLE DEVICES AND METHODS OF USE
Abstract
Systems, devices, and methods for delivering one or more
electrical pulses to a target region within a patient's body are
disclosed herein. An implantable neurostimulator for delivering
such one or more electrical pulses can include a hermetic housing
made of a biocompatible material, an energy storage feature, and at
least one lead. The implantable neurostimulator can further include
stimulation circuitry that can include a first circuit and a second
circuit. The first circuit can include an adjustable resistance
element having a first terminal and a second terminal, a first
switch coupled to the first terminal of the adjustable resistance
element and selectively coupleable with a stimulation-voltage node
and a ground node, a second switch selectively coupling the a first
one of the plurality of electrodes to one of: the second terminal
of the adjustable resistance element; and the stimulation-voltage
node.
Inventors: |
Nassif; Rabih; (Santa Ana,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Axonics Modulation Technologies, Inc. |
Irvine |
CA |
US |
|
|
Family ID: |
1000004868663 |
Appl. No.: |
16/878505 |
Filed: |
May 19, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62852255 |
May 23, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/36007 20130101;
A61N 1/36125 20130101; A61N 1/36175 20130101; A61N 1/36192
20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. An implantable neurostimulator for delivering one or more
electrical pulses to a target region within a patient's body, the
implantable neurostimulator comprising: a hermetic housing
comprising a biocompatible material; an energy storage feature
configured to power the implantable neurostimulator; at least one
lead coupled to the hermetic housing and comprising a plurality of
electrodes located proximate to a distal end of the at least one
lead; and stimulation circuitry comprising: a first circuit
comprising: an adjustable resistance element having a first
resistance and comprising a first terminal and a second terminal; a
first switch coupled to the first terminal of the adjustable
resistance element, the first switch selectively coupleable with a
stimulation-voltage node and a ground node; a second switch
selectively coupling a first one of the plurality of electrodes to
one of: the second terminal of the adjustable resistance element;
and the stimulation-voltage node; and a second circuit selectively
coupleable to a second one of the plurality of electrodes.
2. The implantable neurostimulator of claim 1, wherein the
adjustable resistance element comprises a variable resistor
comprising at least one of: a potentiometer; or a rheostat.
3. The implantable neurostimulator of claim 1, wherein the
adjustable resistance element comprises at least one of: a digital
resistor; or a bank of resistors switchably connectable to generate
a desired combined resistance.
4. The implantable neurostimulator of claim 1, further comprising a
processor configured to control the first and second switches to
generate a stimulation pulse.
5. The implantable neurostimulator of claim 4, wherein the second
circuit comprises: a second adjustable resistance element having a
second resistance and comprising a first terminal and a second
terminal; a third switch coupled to the first terminal of the
second adjustable resistance element, the third switch selectively
coupleable with the stimulation-voltage node and the ground node;
and a fourth switch selectively coupling the second one of the
plurality of electrodes to one of: the second terminal of the
second adjustable resistance element; and the stimulation-voltage
node.
6. The implantable neurostimulator of claim 5, wherein the
processor is further configured to control the third and fourth
switches in connection with the control of the first and second
switches to generate the stimulation pulse.
7. The implantable neurostimulator of claim 6, further comprising a
first capacitor located between the second switch and the first one
of the plurality of electrodes and a second capacitor located
between the fourth switch and the second one of the plurality of
electrodes.
8. The implantable neurostimulator of claim 7, wherein the
processor is configured to control the first, second, third, and
fourth switches to selectively charge and discharge at least one of
the first and second capacitors.
9. The implantable neurostimulator of claim 8, wherein the
processor is configured to adjust the resistance of at least one of
the adjustable resistance element and the second adjustable
resistance element to control a rate of at least one of the
charging and the discharging of the at least one of the first and
second capacitors.
10. The implantable neurostimulator of claim 9, wherein the
processor is further configured to repeatedly determine an
impedance of tissue in the target region of the patient's body.
11. The implantable neurostimulator of claim 10, wherein the
processor is configured to repeatedly determine the impedance of
tissue in the target region of the patient's body based on a
current through the adjustable resistance element and a voltage of
the stimulation-voltage node.
12. The implantable neurostimulator of claim 10, wherein the
processor is further configured to control the stimulation
circuitry to deliver a stimulation pulse having a desired
amplitude.
13. The implantable neurostimulator of claim 12, wherein
controlling the stimulation circuitry to deliver a stimulation
pulse having a desired amplitude comprises controlling the
stimulation circuitry to deliver a plurality of stimulation pulses
with progressively increasing amplitudes until the stimulation
pulse having the desired amplitude is delivered.
14. A method of delivering stimulation to a target tissue of a
patient, the method comprising: coupling a first electrode of a
lead comprising a plurality of electrodes to a first circuit of a
stimulation circuitry an implantable pulse generator; coupling a
second electrode of the lead to a second circuit of the stimulation
circuitry of the implantable pulse generator; delivering a first
phase of a stimulation pulse via implementing of a first switch
configuration in the first circuit and in the second circuit of the
stimulation circuitry, wherein the first circuit comprises: an
adjustable resistance element comprising a first terminal and a
second terminal; a first switch coupled to the first terminal of
the adjustable resistance element, the first switch selectively
coupleable with a stimulation-voltage node and a ground node; a
second switch selectively coupling the a first one of the plurality
of electrodes to one of: the second terminal of the adjustable
resistance element; and the stimulation-voltage node; wherein the
first switch configuration couples the first switch of the first
circuit to a ground node and the second circuit to a stimulation
voltage node, implementing a second switch configuration
corresponding to an interphase delay in the first circuit and in
the second circuit; delivering a second phase of the stimulation
pulse via implementing of a third switch configuration, wherein the
third switch configuration couples both the first circuit and the
second circuit to a node; and adjusting a resistance of the
adjustable resistance element in the first circuit to control a
current of the second phase of the stimulation pulse.
15. The method of claim 14, further comprising measuring an
impedance of the target tissue prior to delivering the second phase
of the stimulation pulse.
16. The method of claim 15, wherein the adjustable resistance
element is adjusted according to the measured impedance of the
target tissue.
17. The method of claim 16, further comprising controlling a
current of the first phase of the stimulation pulse via at least
one of: controlling a voltage of the stimulation voltage node; or
adjusting the resistance of the adjustable resistance element.
18. The method of claim 17, wherein a second direction of the
current of the stimulation pulse in the second phase is in a
direction opposite to a first direction of the current of the
stimulation pulse in the first phase.
19. The method of claim 17, wherein the adjustable resistance
element comprises a plurality of resistors switchably connectable
to generate a desired combined resistance, and wherein adjusting
the resistance of the adjustable resistance element comprises
changing a switch configuration of at least one of the plurality of
resistors.
20. The method of claim 19, wherein the node comprises a common
voltage node.
21. The method of claim 19, wherein the node comprises the
stimulation voltage node.
22. The method of claim 21, wherein the voltage of the stimulation
voltage node is set to a first voltage during the first phase and
to a second voltage during the second phase.
23. The method of claim 14, wherein the second switch configuration
comprises opening of at least one switch of the stimulation
circuitry.
24. The method of claim 14, wherein a charge of the first phase of
the stimulation pulse is equal to a charge of the second phase of
the stimulation pulse.
25. A method of delivering stimulation to a target tissue of a
patient with an implantable pulse generator, the method comprising:
determining a desired value of a current of desired stimulation
pulse; delivering a first stimulation pulse having a first current,
wherein the first current of the first stimulation pulse has a
value less than the desired value of the current of the desired
stimulation pulse; measuring a first impedance of the target tissue
of the patient at the first current of the first stimulation pulse;
and delivering a second stimulation pulse having a second current
set based on the first impedance.
26. The method of claim 25, wherein the second current is equal to
the desired value of the current of the desired stimulation
pulse.
27. The method of claim 25, wherein the second current is less than
the desired value of the current of the desired stimulation
pulse.
28. The method of claim 27, further comprising: measuring a second
impedance of the target tissue of the patient at the second
current; and delivering a third stimulation pulse having a third
current set based on the second impedance.
29. The method of claim 28, wherein the third current is greater
than the second current, and wherein the second current is greater
than the first current.
30. The method of claim 28, wherein each of the first stimulation
pulse, the second stimulation pulse, and the third stimulation
pulse comprise a first pulse delivery phase having a first phase
current and a second pulse delivery phase having a second phase
current.
31. The method of claim 30, wherein the first phase current is
controlled via at least one of: control of a voltage of a node
selectably coupleable to the target tissue of the patient via
stimulation circuitry of the implantable pulse generator; or
control of a resistance of an adjustable resistance element of the
stimulation circuitry.
32. The method of claim 31, wherein the second phase current is
controlled via control of the resistance of the adjustable
resistance element of the stimulation circuitry.
33. The method of claim 29, wherein the third current is equal to
the desired value of the current of the desired stimulation
pulse.
34. A method of delivering stimulation to a target tissue of a
patient with an implantable pulse generator, the method comprising:
determining a desired value of a current of a desired stimulation
pulse; iteratively: delivering a test stimulation pulse with
stimulation circuitry having a setting to deliver a current less
than the desired value of the current of the desired stimulation
pulse; measuring an impedance of the target tissue of the patient
during delivery of the test stimulation pulse; and until the
current of the test stimulation pulse approximately matches the
desired value of the current of the desired stimulation pulse,
updating the setting of the stimulation circuitry to deliver an
increased stimulation current.
35. The method of claim 34, wherein each of the stimulation pulses
comprises a first pulse delivery phase having a first phase current
and a second pulse delivery phase having a second phase
current.
36. The method of claim 35, wherein a second direction of the
current of the stimulation pulse in the second phase is in a
direction opposite to a first direction of the current of the
stimulation pulse in the first phase.
37. The method of claim 35, wherein the current of the test
stimulation pulse approximately matches the desired value of the
current of the desired stimulation pulse when at least one of: the
first phase current; or the second phase current approximately
matches the desired value of the current of the desired stimulation
pulse.
38. The method of claim 35, wherein the at least one of: the first
phase current; or the second phase current approximately matches
the desired value of the current of the desired stimulation pulse
when the current of the at least one of: the first phase current;
or the second phase current is within predetermined range about the
desired value of the current of the desired stimulation pulse.
39. The method of claim 34, further comprising: repeatedly
delivering stimulation pulses with stimulation circuitry having the
setting to match the setting of the test stimulation pulse
approximately matching the desired value of the current of the
desired stimulation pulse; determining a change in the impedance of
the target tissue; and adjusting the setting of the stimulation
circuitry based on the changed impedance of the target tissue.
40. The method of claim 39, wherein updating the setting of the
stimulation circuitry comprises updating a resistance of an
adjustable resistance element.
41. The method of claim 39, wherein updating the setting of the
stimulation circuitry comprises updating the voltage of a voltage
node selectively coupled to the stimulation circuitry.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/852,255, filed on May 23, 2019, and entitled
"Low Energy Implantable Devices And Methods Of Use," the entirety
of which is hereby incorporated by reference herein.
FIELD
[0002] The present invention relates to neurostimulation treatment
systems and associated devices, as well as methods of treatment,
implantation and configuration of such treatment systems.
BACKGROUND
[0003] Treatments with implantable neurostimulation systems have
become increasingly common in recent years. While such systems have
shown promise in treating a number of conditions, effectiveness of
treatment may vary considerably between patients. A number of
factors may lead to the very different outcomes that patients
experience, and viability of treatment can be difficult to
determine before implantation. For example, stimulation systems
often make use of an array of electrodes to treat one or more
target nerve structures. The electrodes are often mounted together
on a multi-electrode lead, and the lead implanted in tissue of the
patient at a position that is intended to result in electrical
coupling of the electrode to the target nerve structure, typically
with at least a portion of the coupling being provided via
intermediate tissues. Other approaches may also be employed, for
example, with one or more electrodes attached to the skin overlying
the target nerve structures, implanted in cuffs around a target
nerve, or the like. Regardless, the physician will typically seek
to establish an appropriate treatment protocol by varying the
electrical stimulation that is applied to the electrodes.
[0004] Current stimulation electrode placement/implantation
techniques and known treatment setting techniques suffer from
significant disadvantages. The nerve tissue structures of different
patients can be quite different, with the locations and branching
of nerves that perform specific functions and/or enervate specific
organs being challenging to accurately predict or identify. The
electrical properties of the tissue structures surrounding a target
nerve structure may also be quite different among different
patients, and the neural response to stimulation may be markedly
dissimilar, with an electrical stimulation pulse pattern,
frequency, and/or voltage that is effective to affect a body
function for one patent may impose significant pain on, or have
limited effect for, another patient. Even in patients where
implantation of a neurostimulation system provides effective
treatment, frequent adjustments and changes to the stimulation
protocol are often required before a suitable treatment program can
be determined, often involving repeated office visits and
significant discomfort for the patient before efficacy is achieved.
While a number of complex and sophisticated lead structures and
stimulation setting protocols have been implemented to seek to
overcome these challenges, the variability in lead placement
results, the clinician time to establish suitable stimulation
signals, and the discomfort (and in cases the significant pain)
that is imposed on the patient remain less than ideal. In addition,
the lifetime and battery life of such devices is relatively short,
such that implanted systems are routinely replaced every few years,
which requires additional surgeries, patient discomfort, and
significant costs to healthcare systems.
[0005] Furthermore, current stimulation systems rely on recharging
of energy storage features such as batteries that are used in
generating stimulation of the patient's tissue. Many of the
recharging systems utilize wireless power transfer techniques to
transcutaneously provide power for recharging the energy storage
features. Such wireless power transfer techniques frequently
utilize coupling between a charging device external to the patient
and a stimulator implanted within the patient. The effectiveness of
this coupling can vary based on: the relative position of the
charging device with respect to the stimulator; the orientation of
the charging device with respect to the stimulator; and/or the
distance separating the charging device and the stimulator.
[0006] The tremendous benefits of these neural stimulation
therapies have not yet been fully realized. Therefore, it is
desirable to provide improved neurostimulation methods, systems and
devices, as well as methods for implanting and configuring such
neurostimulation systems for a particular patient or condition
being treated. It would be particularly helpful to provide such
systems and methods so as to improve ease of coupling between the
charging device and the implanted stimulator.
BRIEF SUMMARY
[0007] Some aspects of the present disclosure relate to low-power
consumption implantable pulse generators. Implantable pulse
generators can deliver energy to a patient in the form of one or
several stimulation pulses. This energy can be stored in an energy
storage feature such as one or several batteries and/or capacitors.
Some such implantable devices can be rechargeable to allow the
recharging of these energy storage features, whereas some
implantable devices are non-rechargeable. In rechargeable devices,
depletion of the energy in the energy storage features can
necessitate recharging of the energy storage features before
further treatment can be delivered, and in non-rechargeable
devices, depletion of the energy in the energy storage features can
necessitate a surgical intervention, such as, for example
replacement of the implantable device or replacement of the energy
storage features of the implantable device, before further
treatments can be delivered.
[0008] While the inconvenience caused by the depletion of the
energy storage features can, in some instances, be mitigated by
increasing the size or number of the energy storage features, such
increasing of the size or number of the energy storage features can
be detrimental. In some aspects of the present disclosure, the
implantable device includes stimulation circuitry that decreases
power consumption. This decrease in power consumption can be
accomplished via stimulation circuity that control the sourcing
and/or sinking of current via modulation of the voltage of a power
source and/or modification of a resistance of one or several
resistors. In some embodiments, these one or several resistors can
be one or several adjustable resistance elements. Through this
diminished power consumption of the implantable device, therapy can
be provided with less frequently depletion of the energy storage
features of the implantable device.
[0009] One aspect of the present disclosure relates to an
implantable neurostimulator for delivering one or more electrical
pulses to a target region within a patient's body. The implantable
neurostimulator can include a hermetic housing made of a
biocompatible material, an energy storage feature that can power
the implantable neurostimulator, and at least one lead coupled to
the hermetic housing. The lead can include a plurality of
electrodes located proximate to a distal end of the at least one
lead. The implantable neurostimulator can include stimulation
circuitry including a first circuit selectively coupleable to a
first one of the plurality of electrodes and a second circuit
selectively coupleable to a second one of the plurality of
electrodes. The first circuit can include an adjustable resistance
element having a first terminal and a second terminal. A first
switch can be coupled to the first terminal of the adjustable
resistance element, and the first switch can be selectively
coupleable with a stimulation-voltage node and with a ground node.
The first circuit can include a second switch selectively coupling
the first one of the plurality of electrodes to one of: the second
terminal of the adjustable resistance element; and the
stimulation-voltage node.
[0010] In some embodiments, the adjustable resistance element can
be a variable resistor that can be at least one of: a
potentiometer; or a rheostat. In some embodiments, wherein the
adjustable resistance element can be at least one of: a digital
resistor, or a bank of resistors switchably connectable to generate
a desired combined resistance. In some embodiments, the implantable
neurostimulator can further include a processor that can operate
according to stored instructions to control the first and second
switches to generate a stimulation pulse.
[0011] In some embodiments, the second circuit can include: a
second adjustable resistance element having a first terminal and a
second terminal, a third switch coupled to the first terminal of
the second adjustable resistance element, and a fourth switch
selectively coupling the second one of the plurality of electrodes
to one of: the second terminal of the second adjustable resistance
element; and the stimulation-voltage node. In some embodiments, the
third switch can be selectively coupleable with the
stimulation-voltage node and the ground node. In some embodiments,
the processor can further operate according to stored instructions
to control the third and fourth switches in connection with the
control of the first and second switches to generate the
stimulation pulse.
[0012] In some embodiments, the neurostimulator can further include
a first capacitor located between the second switch and the first
one of the plurality of electrodes, and a second capacitor located
between the fourth switch and the second one of the plurality of
electrodes. In some embodiments, the processor can operate
according to stored instructions to control the first, second,
third, and fourth switches to selectively charge and discharge at
least one of the first and second capacitors.
[0013] In some embodiments, the processor can operate according to
stored instructions to adjust the resistance of at least one of the
adjustable resistance element and the second adjustable resistance
element to control a rate of at least one of the charging and the
discharging of the at least one of the first and second capacitors.
In some embodiments, the processor can operate according to stored
instructions to repeatedly determine an impedance of tissue in the
target region of the patient's body. In some embodiments, the
processor can operate according to stored instructions to
repeatedly determine the impedance of tissue in the target region
of the patient's body based on a current through the adjustable
resistance element and a voltage of the stimulation voltage
node.
[0014] In some embodiments, the processor can operate according to
stored instructions to control the stimulation circuitry to deliver
a stimulation pulse having a desired amplitude. In some
embodiments, controlling the stimulation circuitry to deliver a
stimulation pulse having a desired amplitude includes controlling
the stimulation circuitry to deliver a plurality of stimulation
pulses with progressively increasing amplitudes until the
stimulation pulse having the desired amplitude is delivered.
[0015] One aspect of the present disclosure relates to a method of
delivering stimulation to a target tissue of a patient. The method
includes coupling a first electrode of a lead having a plurality of
electrodes to a first circuit of a stimulation circuitry an
implantable pulse generator, coupling a second electrode of the
lead to a second circuit of the stimulation circuitry of the
implantable pulse generator, delivering a first phase of a
stimulation pulse via implementing of a first switch configuration
in the first circuit and in the second circuit of the stimulation
circuitry, implementing a second switch configuration corresponding
to an interphase delay in the first circuit and in the second
circuit, delivering a second phase of the stimulation pulse via
implementing of a third switch configuration, and adjusting a
resistance of the adjustable resistance element in the first
circuit to control a current of the second phase of the stimulation
pulse.
[0016] In some embodiments, the third switch configuration couples
both the first circuit and the second circuit to a node. In some
embodiments, the first circuit includes: an adjustable resistance
element having a first terminal and a second terminal; a first
switch coupled to the first terminal of the adjustable resistance
element, the first switch selectively coupleable with a
stimulation-voltage node and a ground node, and a second switch
selectively coupling the a first one of the plurality of electrodes
to one of: the second terminal of the adjustable resistance
element; and the stimulation-voltage node. In some embodiments, the
first switch configuration couples the first switch of the first
circuit to a ground node and the second circuit to a stimulation
voltage node.
[0017] In some embodiments, the method includes measuring an
impedance of the target tissue prior to delivering the second phase
of the stimulation pulse. In some embodiments, the adjustable
resistance element is adjusted according to the measured impedance
of the target tissue. In some embodiments, the method includes
controlling a current of the first phase of the stimulation pulse
via at least one of: controlling a voltage of the stimulation
voltage node; or adjusting the resistance of the adjustable
resistance element. In some embodiments, a second direction of the
current of the stimulation pulse in the second phase is in a
direction opposite to a first direction of the current of the
stimulation pulse in the first phase.
[0018] In some embodiments, the adjustable resistance element can
be made from a plurality of resistors switchably connectable to
generate a desired combined resistance. In some embodiments,
adjusting the resistance of the adjustable resistance element can
include changing a switch configuration of at least one of the
plurality of resistors. In some embodiments, the node can be a
common voltage node. In some embodiments, the node can be the
stimulation voltage node.
[0019] In some embodiments, the voltage of the stimulation voltage
node is set to a first voltage during the first phase and to a
second voltage during the second phase. In some embodiments, the
second switch configuration includes opening of at least one switch
of the stimulation circuitry. In some embodiments, a charge of the
first phase of the stimulation pulse is equal to a charge of the
second phase of the stimulation pulse.
[0020] One aspect of the present disclosure relates to a method of
delivering stimulation to a target tissue of a patient with an
implantable pulse generator. The method includes determining a
desired value of a current of desired stimulation pulse, delivering
a first stimulation pulse having a first current, which current of
the first stimulation pulse has a value less than the desired value
of the current of the desired stimulation pulse, measuring a first
impedance of the target tissue of the patient at the first current
of the first stimulation pulse; and delivering a second stimulation
pulse having a second current set based on the first impedance.
[0021] In some embodiments, the second current is equal to the
desired value of the current of the desired stimulation pulse. In
some embodiments, the second current is less than the desired value
of the current of the desired stimulation pulse. In some
embodiments, the method includes measuring a second impedance of
the target tissue of the patient at the second current, and
delivering a third stimulation pulse having a third current set
based on the second impedance. In some embodiments, the third
current is greater than the second current, and the second current
is greater than the first current.
[0022] In some embodiments, each of the first stimulation pulse,
the second stimulation pulse, and the third stimulation pulse
include a first pulse delivery phase having a first phase current
and a second pulse delivery phase having a second phase current. In
some embodiments, the first phase current is controlled via at
least one of: control of a voltage of a node selectably coupleable
to the target tissue of the patient via stimulation circuitry of
the implantable pulse generator, or control of a resistance of an
adjustable resistance element of the stimulation circuitry. In some
embodiments, the second phase current is controlled via control of
the resistance of the adjustable resistance element of the
stimulation circuitry. In some embodiments, the third current is
equal to the desired value of the current of the desired
stimulation pulse.
[0023] One aspect of the present disclosure relates to a method of
delivering stimulation to a target tissue of a patient with an
implantable pulse generator. The method includes determining a
desired value of a current of a desired stimulation pulse,
iteratively: delivering a test stimulation pulse with stimulation
circuitry having a setting to deliver a current less than the
desired value of the current of the desired stimulation pulse,
measuring an impedance of the target tissue of the patient during
delivery of the test stimulation pulse, and until the current of
the test stimulation pulse approximately matches the desired value
of the current of the desired stimulation pulse, updating the
setting of the stimulation circuitry to deliver an increased
stimulation current.
[0024] In some embodiments, each of the stimulation pulses includes
a first pulse delivery phase having a first phase current and a
second pulse delivery phase having a second phase current. In some
embodiments, a second direction of the current of the stimulation
pulse in the second phase is in a direction opposite to a first
direction of the current of the stimulation pulse in the first
phase. In some embodiments, the current of the test stimulation
pulse approximately matches the desired value of the current of the
desired stimulation pulse when at least one of: the first phase
current; or the second phase current approximately matches the
desired value of the current of the desired stimulation pulse.
[0025] In some embodiments, the at least one of: the first phase
current; or the second phase current approximately matches the
desired value of the current of the desired stimulation pulse when
the current of the at least one of: the first phase current; or the
second phase current is within predetermined range about the
desired value of the current of the desired stimulation pulse. In
some embodiments, the method includes repeatedly delivering
stimulation pulses with stimulation circuitry having the setting to
match the setting of the test stimulation pulse approximately
matching the desired value of the current of the desired
stimulation pulse, determining a change in the impedance of the
target tissue, and adjusting the setting of the stimulation
circuitry based on the changed impedance of the target tissue. In
some embodiments, updating the setting of the stimulation circuitry
includes updating a resistance of an adjustable resistance element.
In some embodiments, updating the setting of the stimulation
circuitry includes updating the voltage of a voltage node
selectively coupled to the stimulation circuitry.
[0026] Further areas of applicability of the present disclosure
will become apparent from the detailed description provided
hereinafter. It should be understood that the detailed description
and specific examples, while indicating various embodiments, are
intended for purposes of illustration only and are not intended to
necessarily limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 schematically illustrates a nerve stimulation system,
which includes a clinician programmer and a patient remote used in
positioning and/or programming of both a trial neurostimulation
system and a permanently implanted neurostimulation system, in
accordance with aspects of the invention.
[0028] FIGS. 2A-2C show diagrams of the nerve structures along the
spine, the lower back and sacrum region, which may be stimulated in
accordance with aspects of the invention.
[0029] FIG. 3A shows an example of a fully implanted
neurostimulation system in accordance with aspects of the
invention.
[0030] FIG. 3B shows an example of a neurostimulation system having
a partly implanted stimulation lead and an external pulse generator
adhered to the skin of the patient for use in a trial stimulation,
in accordance with aspects of the invention.
[0031] FIG. 4 shows an example of a neurostimulation system having
an implantable stimulation lead, an implantable pulse generator,
and an external charging device, in accordance with aspects of the
invention.
[0032] FIGS. 5A-5C show detail views of an implantable pulse
generator and associated components for use in a neurostimulation
system, in accordance with aspects of the invention.
[0033] FIG. 6 shows a schematic illustration of one embodiment of
the architecture of the IPG.
[0034] FIG. 7 shows a schematic illustration of one embodiment of
the pulse control module.
[0035] FIG. 8 is a schematic depiction of one embodiment of
stimulation circuitry of an implantable pulse generator.
[0036] FIG. 9 is a schematic depiction of one embodiment of a bank
of switchably connectable resistors.
[0037] FIG. 10 is a schematic depiction of one embodiment of
stimulation circuitry of an implantable pulse generator in a first
configuration.
[0038] FIG. 11 is a schematic depiction of one embodiment of
stimulation circuitry of an implantable pulse generator in a second
configuration.
[0039] FIG. 12 is a graphical depiction of one embodiment of a
stimulation pulse.
[0040] FIG. 13 is a flowchart depicting one embodiment of a first
portion of a process for delivering stimulation and/or a
stimulation pulse to target tissue of a patient.
[0041] FIG. 14 is a flowchart depicting one embodiment of a second
portion of the process for delivering stimulation and/or a
stimulation pulse to target tissue of a patient.
[0042] FIG. 15 is a flowchart depicting one embodiment of a process
for delivering stimulation to a target tissue of a patient with an
implantable pulse generator.
DETAILED DESCRIPTION
[0043] The present invention relates to neurostimulation treatment
systems and associated devices, as well as methods of treatment,
implantation/placement and configuration of such treatment systems.
In one particular embodiment, the invention relates to sacral nerve
stimulation treatment systems configured to treat overactive
bladder ("OAB") and relieve symptoms of bladder related
dysfunction. It will be appreciated, however, that the present
invention may also be utilized for any variety of neuromodulation
uses, such as fecal dysfunction, the treatment of pain or other
indications, such as movement or affective disorders, as will be
appreciated by one of skill in the art.
I. Neurostimulation Indications
[0044] Neurostimulation (or neuromodulation as may be used
interchangeably hereunder) treatment systems, such as any of those
described herein, can be used to treat a variety of ailments and
associated symptoms, such as acute pain disorders, movement
disorders, affective disorders, as well as bladder related
dysfunction. Examples of pain disorders that may be treated by
neurostimulation include failed back surgery syndrome, reflex
sympathetic dystrophy or complex regional pain syndrome, causalgia,
arachnoiditis, and peripheral neuropathy. Movement orders include
muscle paralysis, tremor, dystonia and Parkinson's disease.
Affective disorders include depressions, obsessive-compulsive
disorder, cluster headache, Tourette syndrome and certain types of
chronic pain. Bladder related dysfunctions include but are not
limited to OAB, urge incontinence, urgency-frequency, and urinary
retention. OAB can include urge incontinence and urgency-frequency
alone or in combination. Urge incontinence is the involuntary loss
or urine associated with a sudden, strong desire to void (urgency).
Urgency-frequency is the frequent, often uncontrollable urges to
urinate (urgency) that often result in voiding in very small
amounts (frequency). Urinary retention is the inability to empty
the bladder. Neurostimulation treatments can be configured to
address a particular condition by effecting neurostimulation of
targeted nerve tissues relating to the sensory and/or motor control
associated with that condition or associated symptom.
[0045] In one aspect, the methods and systems described herein are
particularly suited for treatment of urinary and fecal
dysfunctions. These conditions have been historically
under-recognized and significantly underserved by the medical
community. OAB is one of the most common urinary dysfunctions. It
is a complex condition characterized by the presence of bothersome
urinary symptoms, including urgency, frequency, nocturia and urge
incontinence. It is estimated that about 33 million Americans
suffer from OAB. Of the adult population, about 30% of all men and
40% of all women live with OAB symptoms.
[0046] OAB symptoms can have a significant negative impact on the
psychosocial functioning and the quality of life of patients.
People with OAB often restrict activities and/or develop coping
strategies. Furthermore, OAB imposes a significant financial burden
on individuals, their families, and healthcare organizations. The
prevalence of co-morbid conditions is also significantly higher for
patients with OAB than in the general population. Co-morbidities
may include falls and fractures, urinary tract infections, skin
infections, vulvovaginitis, cardiovascular, and central nervous
system pathologies. Chronic constipation, fecal incontinence, and
overlapping chronic constipation occur more frequently in patients
with OAB.
[0047] Conventional treatments of OAB generally include lifestyle
modifications as a first course of action. Lifestyle modifications
include eliminating bladder irritants (such as caffeine) from the
diet, managing fluid intake, reducing weight, stopping smoking, and
managing bowel regularity. Behavioral modifications include
changing voiding habits (such as bladder training and delayed
voiding), training pelvic floor muscles to improve strength and
control of urethral sphincter, biofeedback and techniques for urge
suppression. Medications are considered a second-line treatment for
OAB. These include anti-cholinergic medications (oral, transdermal
patch, and gel) and oral beta-3 adrenergic agonists. However,
anti-cholinergics are frequently associated with bothersome,
systemic side effects including dry mouth, constipation, urinary
retention, blurred vision, somnolence, and confusion. Studies have
found that more than 50% of patients stop using anti-cholinergic
medications within 90 days due to a lack of benefit, adverse
events, or cost.
[0048] When these approaches are unsuccessful, third-line treatment
options suggested by the American Urological Association include
intradetrusor (bladder smooth muscle) injections of Botulinum Toxin
(BoNT-A), Percutaneous Tibial Nerve Stimulation (PTNS) and Sacral
Nerve Stimulation (SNM). BoNT-A (Botox.RTM.) is administered via a
series of intradetrusor injections under cystoscopic guidance, but
repeat injections of Botox are generally required every 4 to 12
months to maintain effect and Botox may undesirably result in
urinary retention. A number of randomized controlled studies have
shown some efficacy of BoNT-A in OAB patients, but long-term safety
and effectiveness of BoNT-A for OAB is largely unknown.
[0049] Alternative treatment methods, typically considered when the
above approaches prove ineffective, is neurostimulation of nerves
relating to the urinary system. Such neurostimulation methods
include PTNS and SNM. PTNS therapy consists of weekly, 30-minute
sessions over a period of 12 weeks, each session using electrical
stimulation that is delivered from a hand-held stimulator to the
sacral plexus via the tibial nerve. For patients who respond well
and continue treatment, ongoing sessions, typically every 3-4
weeks, are needed to maintain symptom reduction. There is potential
for declining efficacy if patients fail to adhere to the treatment
schedule. Efficacy of PTNS has been demonstrated in a few
randomized-controlled studies; however, long-term safety and
effectiveness of PTNS are relatively unknown at this time.
II. Sacral Neuromodulation
[0050] SNM is an established therapy that provides a safe,
effective, reversible, and long-lasting treatment option for the
management of urge incontinence, urgency-frequency, and
non-obstructive urinary retention. SNM therapy involves the use of
mild electrical pulses to stimulate the sacral nerves located in
the lower back. Electrodes are placed next to a sacral nerve,
usually at the S3 level, by inserting the electrode leads into the
corresponding foramen of the sacrum. The electrodes are inserted
subcutaneously and are subsequently attached to an implantable
pulse generator (IPG), also referred to herein as an "implantable
neurostimulator" or a "neurostimulator." The safety and
effectiveness of SNM for the treatment of OAB, including durability
at five years for both urge incontinence and urgency-frequency
patients, are supported by multiple studies and are
well-documented. SNM has also been approved to treat chronic fecal
incontinence in patients who have failed or are not candidates for
more conservative treatments.
A. Implantation of Sacral Neuromodulation System
[0051] Currently, SNM qualification has a trial phase, and is
followed if successful by a permanent implant. The trial phase is a
test stimulation period where the patient is allowed to evaluate
whether the therapy is effective. Typically, there are two
techniques that are utilized to perform the test stimulation. The
first is an office-based procedure termed the Percutaneous Nerve
Evaluation (PNE) and the other is a staged trial.
[0052] In the PNE, a foramen needle is typically used first to
identify the optimal stimulation location, usually at the S3 level,
and to evaluate the integrity of the sacral nerves. Motor and
sensory responses are used to verify correct needle placement, as
described in Table 1 below. A temporary stimulation lead (a
unipolar electrode) is then placed near the sacral nerve under
local anesthesia. This procedure can be performed in an office
setting without fluoroscopy. The temporary lead is then connected
to an external pulse generator (EPG) taped onto the skin of the
patient during the trial phase. The stimulation level can be
adjusted to provide an optimal comfort level for the particular
patient. The patient will monitor his or her voiding for 3 to 7
days to see if there is any symptom improvement. The advantage of
the PNE is that it is an incision free procedure that can be
performed in the physician's office using local anesthesia. The
disadvantage is that the temporary lead is not securely anchored in
place and has the propensity to migrate away from the nerve with
physical activity and thereby cause failure of the therapy. If a
patient fails this trial test, the physician may still recommend
the staged trial as described below. If the PNE trial is positive,
the temporary trial lead is removed and a permanent quadri-polar
tined lead is implanted along with an IPG under general
anesthesia.
[0053] A staged trial involves the implantation of the permanent
quadri-polar tined stimulation lead into the patient from the
start. It also requires the use of a foramen needle to identify the
nerve and optimal stimulation location. The lead is implanted near
the S3 sacral nerve and is connected to an EPG via a lead
extension. This procedure is performed under fluoroscopic guidance
in an operating room and under local or general anesthesia. The EPG
is adjusted to provide an optimal comfort level for the patient and
the patient monitors his or her voiding for up to two weeks. If the
patient obtains meaningful symptom improvement, he or she is
considered a suitable candidate for permanent implantation of the
IPG under general anesthesia, typically in the upper buttock area,
as shown in FIGS. 1 and 3A.
TABLE-US-00001 TABLE 1 Motor and Sensory Responses of SNM at
Different Sacral Nerve Roots Response Nerve Innervation Pelvic
Floor Foot/calf/leg Sensation S2 Primary somatic "clamp"* Leg/hip
rotation, Contraction contributor of of anal plantar flexion of
base pudendal nerve sphincter" of entire foot, of penis, for
external contraction vagina sphincter, leg, of calf foot S3
Virtually all "bellows"** Plantar flexion Pulling in pelvic
autonomic of of great toe, rectum, functions and perineum
occasionally extending striated muscle other toes forward to
(levator ani) scrotum or labia S4 Pelvic autonomic "bellows"** No
lower Pulling in and somatic extremity motor rectum only No leg or
foot stimulation *Clamp contraction of anal sphincter and, in
males, retraction of base of penis. Move buttocks aside and look
for anterior/posterior shortening of the perineal structures.
**Bellows: sitting and dropping of pelvic floor. Look for deepening
and flattening of buttock grove.
[0054] In regard to measuring outcomes for SNM treatment of voiding
dysfunction, the voiding dysfunction indications (e.g., urge
incontinence, urgency-frequency, and non-obstructive urinary
retention) are evaluated by unique primary voiding diary variables.
The therapy outcomes are measured using these same variables. SNM
therapy is considered successful if a minimum of 50% improvement
occurs in any of primary voiding diary variables compared with the
baseline. For urge incontinence patients, these voiding diary
variables may include: number of leaking episodes per day, number
of heavy leaking episodes per day, and number of pads used per day.
For patients with urgency-frequency, primary voiding diary
variables may include: number of voids per day, volume voided per
void and degree of urgency experienced before each void. For
patients with retention, primary voiding diary variables may
include: catheterized volume per catheterization and number of
catheterizations per day.
[0055] The mechanism of action of SNM is multifactorial and impacts
the neuro-axis at several different levels. In patients with OAB,
it is believed that pudendal afferents can activate the inhibitory
reflexes that promote bladder storage by inhibiting the afferent
limb of an abnormal voiding reflex. This blocks input to the
pontine micturition center, thereby restricting involuntary
detrusor contractions without interfering with normal voiding
patterns. For patients with urinary retention, SNM is believed to
activate the pudendal nerve afferents originating from the pelvic
organs into the spinal cord. At the level of the spinal cord,
pudendal afferents may turn on voiding reflexes by suppressing
exaggerated guarding reflexes, thus relieving symptoms of patients
with urinary retention so normal voiding can be facilitated. In
patients with fecal incontinence, it is hypothesized that SNM
stimulates pudendal afferent somatic fibers that inhibit colonic
propulsive activity and activates the internal anal sphincter,
which in turn improves the symptoms of fecal incontinence patients.
The present invention relates to a system adapted to deliver
neurostimulation to targeted nerve tissues in a manner that
disrupts, inhibits, or prevents neural activity in the targeted
nerve tissues so as to provide therapeutic effect in treatment of
OAB or bladder related dysfunction. In one aspect, the system is
adapted to provide therapeutic effect by neurostimulation without
inducing motor control of the muscles associated with OAB or
bladder related dysfunction by the delivered neurostimulation. In
another aspect, the system is adapted to provide such therapeutic
effect by delivery of sub-threshold neurostimulation below a
threshold that induces paresthesia and/or neuromuscular response or
to allow adjustment of neurostimulation to delivery therapy at
sub-threshold levels.
B. Positioning Neurostimulation Leads with EMG
[0056] While conventional approaches have shown efficacy in
treatment of bladder related dysfunction, there exists a need to
improve positioning of the neurostimulation leads and consistency
between the trial and permanent implantation positions of the lead.
Neurostimulation relies on consistently delivering therapeutic
stimulation from a pulse generator, via one or more
neurostimulation electrodes, to particular nerves or targeted
regions. The neurostimulation electrodes are provided on a distal
end of an implantable lead that can be advanced through a tunnel
formed in patient tissue. Implantable neurostimulation systems
provide patients with great freedom and mobility, but it may be
easier to adjust the neurostimulation electrodes of such systems
before they are surgically implanted. It is desirable for the
physician to confirm that the patient has desired motor and/or
sensory responses before implanting an IPG. For at least some
treatments (including treatments of at least some forms of urinary
and/or fecal dysfunction), demonstrating appropriate motor
responses may be highly beneficial for accurate and objective lead
placement while the sensory response may not be required or not
available (e.g., patient is under general anesthesia).
[0057] Placement and calibration of the neurostimulation electrodes
and implantable leads sufficiently close to specific nerves can be
beneficial for the efficacy of treatment. Accordingly, aspects and
embodiments of the present disclosure are directed to aiding and
refining the accuracy and precision of neurostimulation electrode
placement. Further, aspects and embodiments of the present
disclosure are directed to aiding and refining protocols for
setting therapeutic treatment signal parameters for a stimulation
program implemented through implanted neurostimulation
electrodes.
[0058] Prior to implantation of the permanent device, patients may
undergo an initial testing phase to estimate potential response to
treatment. As discussed above, PNE may be done under local
anesthesia, using a test needle to identify the appropriate sacral
nerve(s) according to a subjective sensory response by the patient.
Other testing procedures can involve a two-stage surgical
procedure, where a quadri-polar tined lead is implanted for a
testing phase to determine if patients show a sufficient reduction
in symptom frequency, and if appropriate, proceeding to the
permanent surgical implantation of a neuromodulation device. For
testing phases and permanent implantation, determining the location
of lead placement can be dependent on subjective qualitative
analysis by either or both of a patient or a physician.
[0059] In exemplary embodiments, determination of whether or not an
implantable lead and neurostimulation electrode is located in a
desired or correct location can be accomplished through use of
electromyography ("EMG"), also known as surface electromyography.
EMG is a technique that uses an EMG system or module to evaluate
and record electrical activity produced by muscles, producing a
record called an electromyogram. EMG detects the electrical
potential generated by muscle cells when those cells are
electrically or neurologically activated. The signals can be
analyzed to detect activation level or recruitment order. EMG can
be performed through the skin surface of a patient, intramuscularly
or through electrodes disposed within a patient near target
muscles, or using a combination of external and internal
structures. When a muscle or nerve is stimulated by an electrode,
EMG can be used to determine if the related muscle is activated,
(i.e. whether the muscle fully contracts, partially contracts, or
does not contract), in response to the stimulus. Accordingly, the
degree of activation of a muscle can indicate whether an
implantable lead or neurostimulation electrode is located in the
desired or correct location on a patient. Further, the degree of
activation of a muscle can indicate whether a neurostimulation
electrode is providing a stimulus of sufficient strength,
amplitude, frequency, or duration to affect a treatment regimen on
a patient. Thus, use of EMG provides an objective and quantitative
means by which to standardize placement of implantable leads and
neurostimulation electrodes, reducing the subjective assessment of
patient sensory responses.
[0060] In some approaches, positional titration procedures may
optionally be based in part on a paresthesia or pain-based
subjective response from a patient. In contrast, EMG triggers a
measureable and discrete muscular reaction. As the efficacy of
treatment often relies on precise placement of the neurostimulation
electrodes at target tissue locations and the consistent,
repeatable delivery of neurostimulation therapy, using an objective
EMG measurement can substantially improve the utility and success
of SNM treatment. The measureable muscular reaction can be a
partial or a complete muscular contraction, including a response
below the triggering of an observable motor response, such as those
shown in Table 1, depending on the stimulation of the target
muscle. In addition, by utilizing a trial system that allows the
neurostimulation lead to remain implanted for use in the
permanently implanted system, the efficacy and outcome of the
permanently implanted system is more consistent with the results of
the trial period, which moreover leads to improved patient
outcomes.
C. Example Embodiments
[0061] FIG. 1 schematically illustrates an exemplary nerve
stimulation system, which includes both a trial neurostimulation
system 200 and a permanently implanted neurostimulation system 100,
in accordance with aspects of the invention. The EPG 80 and IPG 10
are each compatible with and wirelessly communicate with a
clinician programmer 60 and a patient remote 70, which are used in
positioning and/or programming the trial neurostimulation system
200 and/or permanently implanted system 100 after a successful
trial. As discussed above, the clinician programmer can include
specialized software, specialized hardware, and/or both, to aid in
lead placement, programming, re-programming, stimulation control,
and/or parameter setting. In addition, each of the IPG and the EPG
allows the patient at least some control over stimulation (e.g.,
initiating a pre-set program, increasing or decreasing
stimulation), and/or to monitor battery status with the patient
remote. This approach also allows for an almost seamless transition
between the trial system and the permanent system.
[0062] In one aspect, the clinician programmer 60 is used by a
physician to adjust the settings of the EPG and/or IPG while the
lead is implanted within the patient. The clinician programmer can
be a tablet computer used by the clinician to program the IPG, or
to control the EPG during the trial period. The clinician
programmer can also include capability to record
stimulation-induced electromyograms to facilitate lead placement
and programming. The patient remote 70 can allow the patient to
turn the stimulation on or off, or to vary stimulation from the IPG
while implanted, or from the EPG during the trial phase.
[0063] In another aspect, the clinician programmer 60 has a control
unit which can include a microprocessor and specialized
computer-code instructions for implementing methods and systems for
use by a physician in deploying the treatment system and setting up
treatment parameters. The clinician programmer generally includes a
user interface which can be a graphical user interface, an EMG
module, electrical contacts such as an EMG input that can couple to
an EMG output stimulation cable, an EMG stimulation signal
generator, and a stimulation power source. The stimulation cable
can further be configured to couple to any or all of an access
device (e.g., a foramen needle), a treatment lead of the system, or
the like. The EMG input may be configured to be coupled with one or
more sensory patch electrode(s) for attachment to the skin of the
patient adjacent a muscle (e.g., a muscle enervated by a target
nerve). Other connectors of the clinician programmer may be
configured for coupling with an electrical ground or ground patch,
an electrical pulse generator (e.g., an EPG or an IPG), or the
like. As noted above, the clinician programmer can include a module
with hardware and computer-code to execute EMG analysis, where the
module can be a component of the control unit microprocessor, a
pre-processing unit coupled to or in-line with the stimulation
and/or sensory cables, or the like.
[0064] In some aspects, the clinician programmer is configured to
operate in combination with an EPG when placing leads in a patient
body. The clinician programmer can be electronically coupled to the
EPG during test simulation through a specialized cable set. The
test simulation cable set can connect the clinician programmer
device to the EPG and allow the clinician programmer to configure,
modify, or otherwise program the electrodes on the leads connected
to the EPG.
[0065] The electrical pulses generated by the EPG and IPG are
delivered to one or more targeted nerves via one or more
neurostimulation electrodes at or near a distal end of each of one
or more leads. The leads can have a variety of shapes, can be a
variety of sizes, and can be made from a variety of materials,
which size, shape, and materials can be tailored to the specific
treatment application. While in this embodiment, the lead is of a
suitable size and length to extend from the IPG and through one of
the foramen of the sacrum to a targeted sacral nerve, in various
other applications, the leads may be, for example, implanted in a
peripheral portion of the patient's body, such as in the arms or
legs, and can be configured to deliver electrical pulses to the
peripheral nerve such as may be used to relieve chronic pain. It is
appreciated that the leads and/or the stimulation programs may vary
according to the nerves being targeted.
[0066] FIGS. 2A-2C show diagrams of various nerve structures of a
patient, which may be used in neurostimulation treatments, in
accordance with aspects of the invention. FIG. 2A shows the
different sections of the spinal cord and the corresponding nerves
within each section. The spinal cord is a long, thin bundle of
nerves and support cells that extend from the brainstem along the
cervical cord, through the thoracic cord and to the space between
the first and second lumbar vertebra in the lumbar cord. Upon
exiting the spinal cord, the nerve fibers split into multiple
branches that innervate various muscles and organs transmitting
impulses of sensation and control between the brain and the organs
and muscles. Since certain nerves may include branches that
innervate certain organs, such as the bladder, and branches that
innervate certain muscles of the leg and foot, stimulation of the
nerve at or near the nerve root near the spinal cord can stimulate
the nerve branch that innervate the targeted organ, which may also
result in muscle responses associated with the stimulation of the
other nerve branch. Thus, by monitoring for certain muscle
responses, such as those in Table 1, either visually, through the
use of EMG as described herein or both, the physician can determine
whether the targeted nerve is being stimulated. While stimulation
at a certain threshold may trigger the noted muscle responses,
stimulation at a sub-threshold level may still provide stimulation
to the nerve associated with the targeted organ without causing the
corresponding muscle response, and in some embodiments, without
causing any paresthesia. This is advantageous as it allows for
treatment of the condition by neurostimulation without otherwise
causing patient discomfort, pain or undesired muscle responses.
[0067] FIG. 2B shows the nerves associated with the lower back
section, in the lower lumbar cord region where the nerve bundles
exit the spinal cord and travel through the sacral foramens of the
sacrum. In some embodiments, the neurostimulation lead is advanced
through the foramen until the neurostimulation electrodes are
positioned at the anterior sacral nerve root, while the anchoring
portion of the lead proximal of the stimulation electrodes are
generally disposed dorsal of the sacral foramen through which the
lead passes, so as to anchor the lead in position. FIG. 2C shows
detail views of the nerves of the lumbosacral trunk and the sacral
plexus, in particular, the S1-S5 nerves of the lower sacrum. The S3
sacral nerve is of particular interest for treatment of
bladder-related dysfunction, and in particular OAB.
[0068] FIG. 3A schematically illustrates an example of a fully
implanted neurostimulation system 100 adapted for sacral nerve
stimulation. Neurostimulation system 100 includes an IPG implanted
in a lower back region and connected to a neurostimulation lead
extending through the S3 foramen for stimulation of the S3 sacral
nerve. The lead is anchored by a tined anchor portion 30 that
maintains a position of a set of neurostimulation electrodes 40
along the targeted nerve, which in this example, is the anterior
sacral nerve root S3 which enervates the bladder so as to provide
therapy for various bladder related dysfunctions. While this
embodiment is adapted for sacral nerve stimulation, it is
appreciated that similar systems can be used in treating patients
with, for example, chronic, severe, refractory neuropathic pain
originating from peripheral nerves or various urinary dysfunctions
or still further other indications. Implantable neurostimulation
systems can be used to either stimulate a target peripheral nerve
or the posterior epidural space of the spine.
[0069] Properties of the electrical pulses can be controlled via a
controller of the implanted pulse generator. In some embodiments,
these properties can include, for example, the frequency, strength,
pattern, duration, or other aspects of the electrical pulses. These
properties can include, for example, a voltage, a current, or the
like. This control of the electrical pulses can include the
creation of one or more electrical pulse programs, plans, or
patterns, and in some embodiments, this can include the selection
of one or more pre-existing electrical pulse programs, plans, or
patterns. In the embodiment depicted in FIG. 3A, the implantable
neurostimulation system 100 includes a controller in the IPG having
one or more pulse programs, plans, or patterns that may be
pre-programmed or created as discussed above. In some embodiments,
these same properties associated with the IPG may be used in an EPG
of a partly implanted trial system used before implantation of the
permanent neurostimulation system 100.
[0070] FIG. 3B shows a schematic illustration of a trial
neurostimulation system 200 utilizing an EPG patch 81 adhered to
the skin of a patient, particularly to the abdomen of a patient,
the EPG 80 being encased within the patch. In one aspect, the lead
is hardwired to the EPG, while in another the lead is removably
coupled to the EPG through a port or aperture in the top surface of
the flexible patch 81. Excess lead can be secured by an additional
adherent patch. In one aspect, the EPG patch is disposable such
that the lead can be disconnected and used in a permanently
implanted system without removing the distal end of the lead from
the target location. Alternatively, the entire system can be
disposable and replaced with a permanent lead and IPG. When the
lead of the trial system is implanted, an EMG obtained via the
clinician programmer using one or more sensor patches can be used
to ensure that the leads are placed at a location proximate to the
target nerve or muscle, as discussed previously.
[0071] In some embodiments, the trial neurostimulation system
utilizes an EPG 80 within an EPG patch 81 that is adhered to the
skin of a patient and is coupled to the implanted neurostimulation
lead 20 through a lead extension 22, which is coupled with the lead
20 through a connector 21. This extension and connector structure
allows the lead to be extended so that the EPG patch can be placed
on the abdomen and allows use of a lead having a length suitable
for permanent implantation should the trial prove successful. This
approach may utilize two percutaneous incisions, the connector
provided in the first incision and the lead extensions extending
through the second percutaneous incision, there being a short
tunneling distance (e.g., about 10 cm) therebetween. This technique
may also minimize movement of an implanted lead during conversion
of the trial system to a permanently implanted system.
[0072] In one aspect, the EPG unit is wirelessly controlled by a
patient remote and/or the clinician programmer in a similar or
identical manner as the IPG of a permanently implanted system. The
physician or patient may alter treatment provided by the EPG
through use of such portable remotes or programmers and the
treatments delivered are recorded on a memory of the programmer for
use in determining a treatment suitable for use in a permanently
implanted system. The clinician programmer can be used in lead
placement, programming and/or stimulation control in each of the
trial and permanent nerve stimulation systems. In addition, each
nerve stimulation system allows the patient to control stimulation
or monitor battery status with the patient remote. This
configuration is advantageous as it allows for an almost seamless
transition between the trial system and the permanent system. From
the patient's viewpoint, the systems will operate in the same
manner and be controlled in the same manner, such that the
patient's subjective experience in using the trial system more
closely matches what would be experienced in using the permanently
implanted system. Thus, this configuration reduces any
uncertainties the patient may have as to how the system will
operate and be controlled such that the patient will be more likely
to convert a trial system to a permanent system.
[0073] As shown in the detailed view of FIG. 3B, the EPG 80 is
encased within a flexible laminated patch 81, which includes an
aperture or port through which the EPG 80 is connected to the lead
extension 22. The patch may further include an "on/off" button 83
with a molded tactile detail to allow the patient to turn the EPG
on and/or off through the outside surface of the adherent patch 81.
The underside of the patch 81 is covered with a skin-compatible
adhesive 82 for continuous adhesion to a patient for the duration
of the trial period. For example, a breathable strip having
skin-compatible adhesive 82 would allow the EPG 80 to remain
attached to the patient continuously during the trial, which may
last over a week, typically two weeks to four weeks, or even
longer.
[0074] FIG. 4 illustrates an example neurostimulation system 100
that is fully implantable and adapted for sacral nerve stimulation
treatment. The implantable system 100 includes an IPG 10 that is
coupled to a neurostimulation lead 20 that includes a group of
neurostimulation electrodes 40 at a distal end of the lead. As seen
in FIG. 4, the lead is coupled to the header portion 11, the
titanium case portion 17, and/or the ceramic case portion 14 of the
housing of the IPG 10 via the connector stack and/or the strain
relief. The lead includes a lead anchor portion 30 with a series of
tines extending radially outward so as to anchor the lead and
maintain a position of the neurostimulation lead 20 after
implantation. The lead 20 may further include one or more
radiopaque markers 25 to assist in locating and positioning the
lead using visualization techniques such as fluoroscopy. In some
embodiments, the IPG provides monopolar or bipolar electrical
pulses that are delivered to the targeted nerves through one or
more neurostimulation electrodes, typically four electrodes. In
sacral nerve stimulation, the lead is typically implanted through
the S3 foramen as described herein.
[0075] The IPG can be rechargeable or non-rechargeable. In one
aspect, the IPG is rechargeable wirelessly through conductive
coupling by use of a charging device 50 (CD), which is a portable
device powered by a rechargeable battery to allow patient mobility
while charging. The CD 50 is used for transcutaneous charging of
the IPG through RF induction. The CD 50 can either be either
patched to the patient's skin using an adhesive or can be held in
place using a belt 53 or by an adhesive patch 52. The CD 50 may be
charged by plugging the CD directly into an outlet or by placing
the CD in a charging dock or station 51 that connects to an AC wall
outlet or other power source.
[0076] The CD 50 can include a housing 51. The housing 51 can
comprise a variety of shapes and sizes. In some embodiments, the
housing 51 can be cylindrically shaped as shown in FIG. 4, and
specifically, can comprise a plurality of connected cylindrical
portions, wherein the connected cylindrical portions have different
diameters and/or lengths. In some embodiments, the housing 51 can
be a metal or polymer such as a plastic or the like.
[0077] The CD 50 can include a processor and/or memory adapted to
provide instructions to and receive information from the other
components of the implantable neurostimulation system. The
processor can include a microprocessor, such as a commercially
available microprocessor from Intel.RTM. or Advanced Micro Devices,
Inc..RTM., or the like. The CD 50 may include an energy storage
feature, such as one or more capacitors, and typically includes a
wireless charging unit. Some details of CD 50 will be discussed at
greater lengths below with respect to FIG. 7.
[0078] The system may further include a patient remote 70 and
clinician programmer 60, each configured to wirelessly communicate
with the implanted IPG, or with the EPG during a trial. The
clinician programmer 60 may be a tablet computer used by the
clinician to program the IPG and the EPG. The device also has the
capability to record stimulation-induced electromyograms (EMGs) to
facilitate lead placement, programming, and/or re-programming. The
patient remote may be a battery-operated, portable device that
utilizes radio-frequency (RF) signals to communicate with the EPG
and IPG and allows the patient to adjust the stimulation levels,
check the status of the IPG battery level, and/or to turn the
stimulation on or off.
[0079] FIG. 5A-5C show detail views of the IPG and its internal
components. In some embodiments, the pulse generator can generate
one or more non-ablative electrical pulses that are delivered to a
nerve to control pain or cause some other desired effect, for
example to inhibit, prevent, or disrupt neural activity for the
treatment of OAB or bladder related dysfunction. In some
applications, the pulses having a pulse amplitude in a range
between 0 mA to 1,000 mA, 0 mA to 100 mA, 0 mA to 50 mA, 0 mA to 25
mA, and/or any other or intermediate range of amplitudes may be
used. One or more of the pulse generators can include a processor
and/or memory adapted to provide instructions to and receive
information from the other components of the implantable
neurostimulation system. The processor can include a
microprocessor, such as a commercially available microprocessor
from Intel.RTM. or Advanced Micro Devices, Inc..RTM., or the like.
An IPG may include an energy storage feature, such as one or more
capacitors, and typically includes a wireless charging unit.
[0080] One or more properties of the electrical pulses can be
controlled via a controller of the IPG or EPG. In some embodiments,
these properties can include, for example, the frequency, strength,
pattern, duration, or other aspects of the timing and magnitude of
the electrical pulses. These properties can further include, for
example, a voltage, a current, or the like. This control of the
electrical pulses can include the creation of one or more
electrical pulse programs, plans, or patterns, and in some
embodiments, this can include the selection of one or more
pre-existing electrical pulse programs, plans, or patterns. In one
aspect, the IPG 100 includes a controller having one or more pulse
programs, plans, or patterns that may be created and/or
pre-programmed. In some embodiments, the IPG can be programmed to
vary stimulation parameters including pulse amplitude in a range
from 0 mA to 10 mA, pulse width in a range from 50 .mu.s to 500
.mu.s, pulse frequency in a range from 5 Hz to 250 Hz, stimulation
modes (e.g., continuous or cycling), and electrode configuration
(e.g., anode, cathode, or off), to achieve the optimal therapeutic
outcome specific to the patient. In particular, this allows for an
optimal setting to be determined for each patient even though each
parameter may vary from person to person.
[0081] As shown in FIGS. 5A-5B, the IPG may include a header
portion 11 at one end and a ceramic portion 14 at the opposite end.
The header portion 11 houses a feed-through assembly 12 and
connector stack 13, while the ceramic case portion 14 houses an
antennae assembly 16 to facilitate wireless communication with the
clinician program, and/or the patient remote. The ceramic case
portion 14 can, in embodiments in which the IPG is rechargeable,
house a charging coil to facilitate wireless charging with the CD.
The remainder of the IPG is covered with a titanium case portion
17, which encases the printed circuit board, memory and controller
components that facilitate the electrical pulse programs described
above. The ceramic portion 14 includes an end 23, sides 24, and a
connection portion 26 that connects the ceramic portion 14 to the
case portion 17. In the example shown in FIG. 5B, the antennae
assembly 16 is positioned such that a plane 28, in which loops of a
radiating element lay, is perpendicular to and extends through the
sides 24 of the ceramic portion 14.
[0082] In the example shown in FIG. 5C, the header portion of the
IPG includes a four-pin feed-through assembly 12 that couples with
the connector stack 13 in which the proximal end of the lead is
coupled. The four pins correspond to the four electrodes of the
neurostimulation lead. In some embodiments, a Balseal.RTM.
connector block is electrically connected to four platinum/iridium
alloy feed-through pins which are brazed to an alumina ceramic
insulator plate along with a titanium alloy flange. This
feed-through assembly is laser seam welded to a titanium-ceramic
brazed case to form a complete hermetic housing for the
electronics. In some embodiments, some or all of the pieces of the
IPG 10 forming the hermetic housing can be biocompatible, and
specifically, can have external surfaces made of biocompatible
materials.
[0083] In some embodiments, such as that shown in FIG. 5A, the
ceramic and titanium brazed case is utilized on one end of the IPG
where the ferrite coil and PCB antenna assemblies are positioned. A
reliable hermetic seal is provided via a ceramic-to-metal brazing
technique. The zirconia ceramic may comprise a 3Y-TZP (3 mol
percent Yttria-stabilized tetragonal Zirconia Polycrystals)
ceramic, which has a high flexural strength and impact resistance
and has been commercially utilized in a number of implantable
medical technologies. It will be appreciated, however, that other
ceramics or other suitable materials may be used for construction
of the IPG, and that ceramic may be used to form additional
portions of the case.
[0084] In one aspect, utilization of ceramic material provides an
efficient, radio-frequency-transparent window for wireless
communication with the external patient remote and clinician's
programmer as the communication antenna is housed inside the
hermetic ceramic case. This ceramic window has further facilitated
miniaturization of the implant while maintaining an efficient,
radio-frequency-transparent window for long term and reliable
wireless communication between the IPG and external controllers,
such as the patient remote and clinician programmer. The IPG's
wireless communication is generally stable over the lifetime of the
device, unlike prior art products where the communication antenna
is placed in the header outside the hermetic case. The
communication reliability of such prior art devices tends to
degrade due to the change in dielectric constant of the header
material in the human body over time.
[0085] In some embodiments, the ferrite core is part of the
charging coil assembly 15, shown in FIG. 5B, which can be
positioned inside the ceramic case 14. The ferrite core
concentrates the magnetic field flux through the ceramic case as
opposed to the metallic case portion 17. This configuration
maximizes coupling efficiency, which reduces the required magnetic
field and in turn reduces device heating during charging. In
particular, because the magnetic field flux is oriented in a
direction perpendicular to the smallest metallic cross section
area, heating during charging is minimized. This configuration also
allows the IPG to be effectively charged at a depth of 3 cm with
the CD, when positioned on a skin surface of the patient near the
IPG, and reduces re-charging time.
[0086] FIG. 6 shows a schematic illustration of one embodiment of
the architecture of the IPG 10. In some embodiments, each of the
components of the architecture of the IPG 10 can be implemented
using the processor, memory, and/or other hardware component of the
IPG 10. In some embodiments, the components of the architecture of
the IPG 10 can include software that interacts with the hardware of
the IPG 10 to achieve a desired outcome, and the components of the
architecture of the IPG 10 can be located within the housing.
[0087] In some embodiments, the IPG 10 can include, for example, a
communication module 600. The communication module 600 can be
configured to send data to and receive data from other components
and/or devices of the exemplary nerve stimulation system including,
for example, the clinician programmer 60, the charging device 50,
and/or the patient remote 70. In some embodiments, the
communication module 600 can include one or several antennas and
software configured to control the one or several antennas to send
information to and receive information from one or several of the
other components of the IPG 10. In some embodiments, for example,
when connecting with the charging device 50, the communications
module 600 can be configured to send data identifying the IPG 10
and/or characterizing one or several attributes of the IPG 10. In
some embodiments, this information can be, for example, a number
uniquely identifying the IPG 10 such as, for example, a serial
number, or the like. In some embodiments, this data can
characterize one or several attributes of the IPG 10 such as, for
example, the natural frequency of a charging module 606 of the IPG
10 and/or of one or several components of the charging module 606
of the IPG.
[0088] The IPG 10 can further include a data module 602. The data
module 602 can be configured to manage data relating to the
identity and properties of the IPG 10. In some embodiments, the
data module can include one or several databases that can, for
example, include information relating to the IPG 10 such as, for
example, the identification of the IPG 10, one or several
properties of the IPG 10, or the like. In one embodiment, the data
identifying the IPG 10 can include, for example, a serial number of
the IPG 10 and/or other identifier of the IPG 10 including, for
example, a unique identifier of the IPG 10. In some embodiments,
the information associated with the property of the IPG 10 can
include, for example, data identifying the function of the IPG 10,
data identifying the power consumption of the IPG 10, data
identifying the charge capacity of the IPG 10 and/or power storage
capacity of the IPG 10, data identifying potential and/or maximum
rates of charging of the IPG 10, and/or the like. In some
embodiments, the information associated with the property of the
IPG 10 can include, for example, data identifying the natural
frequency of the IPG 10 and/or components thereof. In some
embodiments, this information identifying the natural frequency can
be generated at the time of the manufacture of the IPG 10.
[0089] The IPG 10 can include a pulse control 604. In some
embodiments, the pulse control 604 can be configured to control the
generation of one or several pulses by the IPG 10. In some
embodiments, for example, this can be performed based on
information that identifies one or several pulse patterns,
programs, or the like. This information can further specify, for
example, the frequency of pulses generated by the IPG 10, the
duration of pulses generated by the IPG 10, the strength and/or
magnitude of pulses generated by the IPG 10, or any other details
relating to the creation of one or several pulses by the IPG 10. In
some embodiments, this information can specify aspects of a pulse
pattern and/or pulse program, such as, for example, the duration of
the pulse pattern and/or pulse program, and/or the like. In some
embodiments, the pulse control 604 can be configured to determine
an impedance of the tissue of the patient, and specifically of the
target tissue of the patient. In some embodiments, this
determination of impedance can be periodically and/or repeatedly
performed. In some embodiments, the impedance of the tissue can be
measured after a predetermined number of stimulation pulses have
been delivered, and in some embodiments, the impedance of the
tissue can be determined with the delivery of each stimulation
pulse. In some embodiments, the impedance of the tissue can be
determined at the beginning of the delivery of a stimulation pulse.
In some embodiments, information relating to and/or for controlling
the pulse generation of the IPG 10 can be stored within the memory
of the IPG 10.
[0090] In some embodiments in which the IPG 10 is rechargeable, the
IPG 10 can include a charging module 606. In some embodiments, the
charging module 606 can be configured to control and/or monitor the
charging/recharging of the IPG 10. In some embodiments, for
example, the charging module 606 can include one or several
features configured to receive energy for recharging the IPG 10
such as, for example, one or several inductive coils/features that
can interact with one or several inductive coils/features of the
charging device 50 to create an inductive coupling to thereby
recharge the IPG 10. In some embodiments, the charging module 606
can include hardware and/or software configured to monitor the
charging of the IPG 10 including, for example, the charging coil
assembly 15, also referred to herein as the receiving coil assembly
15 or the elongate receiving coil assembly 15.
[0091] The charging module 606 of the IPG 10 can include a charging
circuit 607, also referred to herein as the resonant circuit 607,
the secondary charging circuit 607, the secondary resonant circuit
607, the receiving charging circuit 607, or the receiving resonant
circuit 607. In some embodiments, the charging circuit 607 can
comprise, for example, at least one of: an inductor; a capacitor;
or a resistor. The charging circuit 607 can be characterized by a
natural frequency, which natural frequency can be determined at,
for example, the time of assembly of the charging circuit 607 or
after the implantation of the IPG 10 in the body. In some
embodiments, because of the relatively constant temperature and
environment in the body, the natural frequency of the charging
circuit 607 can remain constant after the implantation of the IPG
10 into the body.
[0092] The IPG 10 can include an energy storage device 608. The
energy storage device 608, which can include the energy storage
features, can be any device configured to store energy and can
include, for example, one or several batteries, capacitors, fuel
cells, or the like. In some embodiments, the energy storage device
608 can be configured to receive charging energy from the charging
module 606.
[0093] FIG. 7 shows a schematic illustration of one embodiment of
components of the pulse control module 604. The pulse control
module 604 includes a stimulation controller 702, a digital to
analog converter DAC 706, stimulation circuitry 708, an anodic
switch array 710, a cathodic switch array 712, and switch controls
714. Although a single box depicting the stimulation circuitry 708
is shown, the stimulation circuitry 708 can comprises multiple
circuits and/or components configured to selectively connect the
stimulation circuitry 708 to at least one of the leads to thereby
allow the sourcing/sinking of current to or from the at least one
of the leads. In some embodiments, the stimulation circuitry 708
can comprise a plurality of circuits including, for example, a
first circuit and a second circuit, and in some embodiments, each
of the anodic switch array 710 and the cathodic switch array 712
can comprise a plurality of switches.
[0094] The pulse control module 604 provides for the sourcing and
sinking of current to one or several leads, and/or one or several
electrodes on the leads. In some embodiments, this can include
sourcing current to at least one lead and/or at least one electrode
on at least one lead, and completing a circuit through the target
tissue by sinking current from at least one lead and/or at least
one electrode on at least one lead. In some embodiments, multiple
currents can be sourced to one or several leads and/or electrodes,
and similarly, in some embodiments, multiple currents can be sinked
from one or several leads and/or electrodes. In some embodiments,
the amount of sinked current can match the amount of sourced
current.
[0095] The pulse control module 604 can, in some embodiments,
include both an anodic switch array 710 and a cathodic switch array
712. The pulse control module 604 provides for selecting one or
several electrodes for stimulation based upon tissue stimulation
requirements determined by a clinician. This selection is made by a
combination of the switch arrays 710, 712 and the switch controls
714. The outputs of the switch arrays 710, 712 are selected by
setting the corresponding "bits" in switch controls 714. Switch
controls 714 generate digital control signals DCS, which control
the switching of switch arrays 710, 712 to select one or several
electrodes for delivery of stimulation.
[0096] In some embodiments, the switch controls 714 can store
information regarding stimulation pulse duration, amplitude and
profile as well as other operational parameters. Based upon
information stored in switch controls 714 and the CLOCK signal 704,
stimulation controller 702 generates the desired stimulation pulse
amplitude and triggers digital to analog converter DAC 706 to
generate an output. Based upon the DAC 706 output, the stimulation
circuitry 708 provides a sink for I.sub.sink current and provides a
source current I.sub.source.
[0097] FIG. 8 depicts a schematic illustration of one embodiment of
the stimulation circuitry 708 creating a circuit target tissue of a
patient, the tissue represented by resistor 800. The stimulation
circuitry 708 includes circuits, and specifically includes a first
circuit 802 and a second circuit 804. As shown in FIG. 8, all or
portions of one or more of the circuits of the stimulation
circuitry 708 are connected to the tissue 800 via electrodes 40
that are part of lead 20. In some embodiments, one or more of the
electrodes 40 can be coupled, and more specifically can be
selectively and/or switchably coupled, to one or more of the
circuits 802, 802 via the switch array 710, 712.
[0098] The first circuit 802 can include an adjustable resistance
element 806 having a first terminal 808 and a second terminal 810.
The adjustable resistance element 806 can be controlled to have a
desired resistance, and can be, in some embodiments, a variable
resistor that can be a potentiometer, and/or a rheostat. In some
embodiments, the adjustable resistance element 806 can be a digital
resistor, and/or a bank of switchably connectable resistors. In
some embodiments, the digital resistor and/or the bank of
switchably connectable resistors can create a digital first circuit
802 in that resistance of the adjustable resistance element can set
at one or several discrete resistance levels. One embodiment of a
bank of switchably connectable resistors 900 is shown in FIG. 9.
The bank of resistors 900 can further comprise a first path 904 and
a second path 906 that is parallel to the first path 904. The first
path 904 of the bank of resistors 900 can include a plurality of
resistors 902-A, 902-B, 902-C, 902-D. In some embodiments, each of
resistors 902 can have the same resistance, and in some
embodiments, some or all of resistors 902 can have different
resistance. The second path 906 of the bank of resistors 900 can
include a plurality of switches 908 that can each be move to an
open position or to a closed position. The first and second paths
904, 906 can be coupled via a plurality of links 910. Via the
selective opening and/or closing of one or several of the switches
908 a current path can be created that can include all or portions
of one or both of the first path 904 and the second path 906. In
some embodiments, for example, the opening of a switch 908 can
cause current to flow through a resistor 902 associated with that
switch 908. Thus, in some embodiments, opening switch 908-A can
create a current path through resistor 908-A, and closing of switch
908-B can create a current path around resistor 908-B, although
some amount of current may still flow through resistor 908-B. Thus,
the opening and closing of switches 908 can control the resistance
of the adjustable resistance element 900. In some embodiments, the
adjustable resistance element 806, and specifically, the opening
and/or close of one or several of the switches 908 can be
controlled by a processor of the IPG 10 such as, for example, the
stimulation controller 702 of the pulse control 604.
[0099] The first circuit 802 can further comprise a first switch
812 and a second switch 814. The first switch 812 can be coupled to
the first terminal 808 of the adjustable resistance element 806,
and the first switch 812 can selectively couple the first terminal
808 of the adjustable resistance element 806 to one of a voltage
node 816 and a ground node 818. In the embodiment shown in FIG. 8,
the first switch 812 is in an open position. In some embodiments,
the voltage node 816, also referred to herein as a
stimulation-voltage node 816 can have a voltage controlled by, for
example, the stimulation controller 702 of the pulse control
604.
[0100] The first circuit 802 further includes the second switch
814, which can selectively couple at least one of the electrodes
40, either directly, or indirectly such as via one of the switch
arrays 710, 712, to the first circuit 802, and specifically to one:
of the second terminal 810 of the adjustable resistance element
806; or a voltage node 816, which can, in some embodiments, be the
same voltage node 816 to which the first switch 812 can couple. In
some embodiments, the voltage node 816 to which the first switch
812 and the second switch 814 couple can be the same in that the
voltage of both locations of coupling are the same and/or are
controlled by a single voltage source and/or current source, thus,
these nodes can have a common voltage. In the embodiment depicted
in FIG. 8, the second switch 814 is shown in an open position. In
some embodiments, the position of one or both of the first switch
812 and the second switch 814 can be controlled by a processor of
the IPG 10 such as, for example, the stimulation controller 702 of
the pulse control 604. In some embodiments, the first switch 812
and/or the second switch 814 can be controlled to generate all or
portions of a stimulation pulse, which can be delivered to the
tissue of the patient, which tissue can be tissue targeted for
stimulation.
[0101] The first circuit 802 can further include a first capacitor
828 that can be located between the second switch 814 and the
electrode 40. In some embodiments, and as depicted in FIG. 8, the
first capacitor 828 can be part of the first circuit 802, and in
some embodiments, the first capacitor 828 can be a part of the lead
20 and/or electrically coupled to the electrode 40.
[0102] The second circuit 804 can include an adjustable resistance
element 818 having a first terminal 820 and a second terminal 822.
The adjustable resistance element 818, also referred to herein as a
second adjustable resistance element 818 can be controlled to have
a desired resistance, and can be, in some embodiments, a variable
resistor such as a potentiometer and/or a rheostat, or can be a
digital resistor, and/or a bank of switchably connectable
resistors. One embodiment of such a bank of switchably connectable
resistors 900 is shown in FIG. 9 and is discussed above. In some
embodiments, the adjustable resistance element 818, and
specifically, the opening and/or close of one or several of the
switches 908 can be controlled by a processor of the IPG 10 such
as, for example, the stimulation controller 702 of the pulse
control 604.
[0103] The second circuit 804 can further comprise a third switch
824 and a fourth switch 826. The third switch 824 can be coupled to
the first terminal 820 of the adjustable resistance element 818,
and the third switch 820 can selectively couple the first terminal
820 of the adjustable resistance element 818 to one of a voltage
node 816 and a ground node 818. In the embodiment shown in FIG. 8,
the third switch 824 is in an open position. In some embodiments,
the voltage node 816 can have a voltage controlled by, for example,
the stimulation controller 702 of the pulse control 604.
[0104] The second circuit 804 further includes the fourth switch
826, which can selectively couple at least one of the electrodes
40, either directly, or indirectly such as via one of the switch
arrays 710, 712, to the second circuit 804, and specifically to
one: of the second terminal 822 of the adjustable resistance
element 818; or the voltage node 816. The voltage nodes 816 to
which the switches 812, 814, 824, 826 can connect can have a common
voltage, and thus can be common voltage nodes. In the embodiment
depicted in FIG. 8, the fourth switch 826 is shown in an open
position. In some embodiments, the position of one or both of the
third switch 824 and the fourth switch 826 can be controlled by a
processor of the IPG 10 such as, for example, the stimulation
controller 702 of the pulse control 604. In some embodiments, the
third switch 824 and/or the fourth switch 826 can be controlled to
generate all or portions of a stimulation pulse, which can be
delivered to the tissue of the patient, which tissue can be tissue
targeted for stimulation.
[0105] The second circuit 804 can further include a second
capacitor 830 that can be located between the fourth switch 826 and
the electrode 40 coupled to the fourth switch 826. In some
embodiments, and as depicted in FIG. 8, the second capacitor 830
can be part of the first circuit 802, and in some embodiments, the
first capacitor 802 can be a part of the lead 20 and/or
electrically coupled to the electrode 40.
[0106] In some embodiments, the position of one, some, or all of
the switches 812, 814, 824, 826 can be controlled to selectively
charge and/or discharge one or both of the capacitors 828, 830.
Similarly, in some embodiments, the processor can adjust the
resistance of one or both of the adjustable resistance elements
806, 818 to control a rate of at least one of the charging and the
discharging of the at least one of the first and second capacitors
828, 830.
[0107] In some embodiments, the processor such as the stimulation
controller 702 can control the switches, the voltage of the voltage
node 816 and/or the resistance of one or both of the adjustable
resistance elements 816, 818 to control a duration of the
stimulation pulse, and/or an amplitude of the stimulation pulse.
Thus, in some embodiments, the processor such as the stimulation
controller 702 can control the stimulation circuitry 708 to deliver
a stimulation pulse having a desired amplitude and/or duration.
[0108] In some embodiments, and as will be discussed in greater
detail below, controlling the stimulation circuitry 708 to deliver
a stimulation pulse having a desired amplitude and/or duration can
include controlling the stimulation circuitry 708 to deliver a
plurality of stimulation pulses with progressively increasing
amplitudes until the stimulation pulse having the desired amplitude
is delivered. Thus, in some embodiments, when a desired amplitude
of a stimulation pulse is determined, the stimulation circuitry 708
can be iteratively controlled to increase amplitude of stimulation
pulses until the desired stimulation pulse is achieved. In some
embodiments, this iterative control can prevent the delivery of a
stimulation pulse having a larger than desired current. In some
embodiments, for example, impedance of target tissue can change as
the stimulation current increases, and thus a step-wise method of
increasing stimulation current, measuring impedance at the
increased stimulation current, and delivering a new, increased
stimulation current based on the measured impedance can prevent
delivery of a larger than desired stimulation current.
[0109] The switches 812, 814, 824, 826 of the stimulation circuitry
708 can be controlled by a processor, and specifically by, in some
embodiments, the stimulation controller 702 of the pulse control
604 to generate and/or deliver one or several stimulation pulses to
the tissue of the patient. In some embodiments, this control of the
switches 812, 814, 824, 826 can be phase-wise controlled such that
some or all of the switches 812, 814, 824, 826 are arranged: in a
first configuration for a first phase of delivery of a stimulation
pulse; in an interphase configuration, also referred to as a second
configuration or second switch configuration; in a third
configuration for a second phase of delivery of the stimulation
pulse; and in a neutral configuration upon completion of delivery
of the stimulation pulse. In some embodiments, the interphase
configuration can be the same as the neutral configuration.
[0110] The processor, such as the stimulation controller 702 can
control the switches 812, 814, 824, 826 to create one or several
switch configuration to thereby control and deliver a stimulation
pulse. In some embodiments, for example, the switches can be in a
neutral configuration, also referred to as an open configuration as
shown in FIG. 8. In this configuration, no current is delivered to
the target tissue and all of the switches 812, 814, 824, 826 are
open. The switches 812, 814, 824, 826 can be in a first
configuration for delivering of a first phase of a stimulation
pulse.
[0111] One embodiment of this first configuration is shown in FIG.
10. As seen in FIG. 10, the first switch 812 couples the first
terminal 808 of the first adjustable resistance element 806 to the
ground 818, the second switch 814 couples to the second terminal
810 of the adjustable resistance element 806, and the fourth switch
826 couples to the voltage node 816. In this configuration, current
as represented by arrow 850 flows between the ground 818 and the
voltage node 816 through the target tissue. In some embodiments,
this current flow in the first phase can charge the capacitors 828,
830. The current flowing through the target tissue can be
controlled by control of the voltage of the voltage node 816 and/or
control of the resistance of the adjustable resistance element
806.
[0112] One embodiment of the second configuration is shown in FIG.
11. As seen in FIG. 11, the first switch 812 couples the first
terminal 808 of the first adjustable resistance element 806 to the
voltage node 816, the second switch 814 couples to the second
terminal 810 of the adjustable resistance element, and the fourth
switch 826 couples to the voltage node 816. The coupling of both
the first circuit 802 and portions of the second circuit 804 to the
voltage node 816 eliminates any voltage differential as the voltage
node 816 to which the first circuit 802 and portions of the second
circuit 804 is coupled is controlled to a single voltage. This
elimination of any voltage differential allows the discharge of the
capacitors 828, 830 creating a current, represented by arrow 852,
flowing through the target tissue of the patient. This current
flowing through the target tissue can be controlled by control of
the resistance of the adjustable resistance element 806. In some
embodiments, the charge of the capacitors can be known from
information collected during the first phase, and, based on this
charge information and the impedance of the target tissue, the
resistance of the adjustable resistance element 806 can be set to
achieve a desired current through the target tissue and/or to
maintain a current below a desired level.
[0113] In some embodiments, the voltage of the voltage node 816 can
be variable. In some embodiments, for example, the voltage of the
voltage node 816 can be set to a first level during the first phase
of the stimulation, and the voltage of the voltage node 816 can be
set to a second level during the second phase of the stimulation.
In some embodiments, the second level can be less than the first
level.
[0114] As seen in FIGS. 10 and 11, in some embodiments, only
portions of the second circuit 804 are used to create the
stimulation pulse. In such embodiments, the remaining portions of
the second circuit 804, and specifically, the adjustable resistance
element 818 of the second circuit 804 can be coupled to an
additional electrode 40 and can be used to deliver a stimulation
pulse to other targeted tissue.
[0115] FIG. 12 shows a graphical depiction of a stimulation pulse
860. As depicted, the stimulation pulse starts at time "a" and
extends through time "d." Prior to time "a", when the switches 812,
814, 824, 826 are in the neutral configuration, no current is
flowing through the target tissue. At time "a", the first phase 862
starts via controlling some or all of switches 812, 814, 824, 826
to the first configuration, and terminates at time "b" via
controlling some or all of switches 812, 814, 824, 826 to the
interphase configuration, which in some embodiments is the neutral
configuration. In some embodiments, impedance of the tissue of the
patient can be measured shortly after the starting of the first
phase 862. In such an embodiments, the voltage of the voltage node
816 can be combined with the current through the adjustable
resistance element 806, which can be determined based on the
resistance of the adjustable resistance element 806 and the voltage
drop across the adjustable resistance element 806, to determine the
impedance of the tissue of the patient. In some embodiments, this
determination of the impedance of the patient's tissue can be made
by the pulse control 604 and/or the stimulation controller 702.
[0116] In some embodiments, the transition to the neutral
configuration can comprises the opening of at least one switch 812,
814, 824, 826. The interphase configuration creates the interphase
delay 864 during which delay, in some embodiments, no current flows
through the target tissue. The interphase delay 864 lasts until
time "c", at which time the second phase 866 starts via controlling
some or all of switches 812, 814, 824, 826 to the second
configuration. In some embodiments, the transition The second phase
866 lasts until some or all of switches 812, 814, 824, 826 are
controlled to transition to the third configuration, in which
configuration current no longer flows through the target tissue. As
seen in FIG. 12, the direction of current through the target tissue
in the second phase 866 may be in the opposite direction of the
current through the target tissue in the first phase 862. In some
embodiments, the charge delivered during the second phase 866 is
equal to the charge delivered during the first phase 862.
[0117] FIG. 13 is a flowchart depicting one embodiment of a process
1300 for delivering stimulation and/or a stimulation pulse to
target tissue of a patient. The process 1300 can be performed by
the IPG 10 or by components or modules of the IPG 10 such as, for
example, the pulse control 604. The process 1300 begins at block
1302, wherein a stimulation configuration is determined. In some
embodiments, the determining of the stimulation configuration can
include determining a desired coupling of one or several electrodes
40 of the lead 20 to the stimulation circuitry 708. This
determining of the stimulation configuration can be performed by
the pulse control 604. In some embodiments, this determining of the
stimulation configuration can include the retrieving of information
specifying the stimulation configuration from the memory of the IPG
10, which memory can be includes in the pulse control 604 and/or
can be accessible by the pulse control 604.
[0118] After the stimulation configuration has been determined, the
stimulation configuration can be implemented, as indicated in block
1304, by coupling stimulation circuitry to the electrodes 40. In
some embodiments, this can be performed by the generation of one or
several control signals by the stimulation controller 702, which
control signals can control one or several switches of one or both
of the switch arrays 710, 712. In some embodiments, this can
include the coupling of all or portions of the first circuit 802 to
a first electrode and coupling all or portions of the second
circuit 804 to a second electrode.
[0119] At block 1306, a desired stimulation current is determined.
In some embodiments, the determining of the desired stimulation
current can be performed by the pulse control 604 and/or by the
stimulation controller 702. In some embodiments, the determination
of the desired stimulation current can include retrieving
information specifying the desired stimulation current from the
memory of the IPG 10. In some embodiments, the desired stimulation
current can be determined based, at least in part, on one or
several signals received from the patient remote.
[0120] At block 1308, impedance data for the target tissue to which
the stimulation is to be delivered is acquired and/or determined.
In some embodiments, the impedance of the target tissue can be
measured and the acquiring of the impedance data can comprise the
receipt of measurement data. In some embodiments, for example, the
memory can contain previously measured impedance data for the
target tissue and/or can include information specifying an
impedance for use if the impedance of the target tissue has not
been measured. In some embodiments, the impedance data may be
associated with metadata identifying one or several attributes of
the impedance data. This metadata can identify, for example, the
age of the impedance data, the time/date of measuring of the
impedance data, conditions under which the impedance data was
gathered, or the like. In some embodiments, for example, the
impedance of the target tissue may vary over time and/or may vary
based on the current passed through the target tissue. In some
embodiments, metadata associated with the impedance data can allow
selection of impedance data most relevant to the desired current
for a stimulation pulse. In some embodiments, for example, based on
the desired current of the stimulation pulse, impedance data
relevant to that desired current and/or most relevant to that
desired current can be selected. In some embodiments, impedance
data can be further selected based on the age of impedance data,
specifically, the selection of impedance data can be according to
function that diminishes the relevance of impedance data as the age
of the impedance data increases.
[0121] At decision step 1310, it is determined if the impedance
data from 1308 is reliable and/or sufficiently reliable for use. In
some embodiments, for example, because of the age of the impedance
data and/or because of the difference between the conditions under
which the impedance data was gathered and current conditions, the
impedance data may be identified as insufficiently reliable. In
some embodiments, metadata associated with the impedance data may
be compared to one or more thresholds delineating between reliable
and unreliable data. If it is determined that the impedance data is
unreliable, then the process 1300 proceeds to block 1312, wherein
an impedance measuring process in entered and/or initiated.
[0122] If it is determined that the impedance data is reliable
and/or is sufficiently reliable, then the process 1300 proceeds to
block 1314 wherein a current source match is determined. In some
embodiments, this can include determining one or several settings
for use in controlling the current of the stimulation pulse and/or
of one or more phases of the stimulation pulse. In some
embodiments, this can include, for example, controlling the voltage
of the voltage node 816 and/or the resistance of the adjustable
resistance element 806 during the first phase of delivery of the
stimulation pulse and controlling of the resistance of the
adjustable resistance element 806 during the second phase of
delivery of the stimulation pulse.
[0123] At block 1316, pulse characteristics of the stimulation
pulse are determined. In some embodiments, this can include
determining the duration of the stimulation pulse, determining the
duration of one or several phases of the stimulation pulse, or the
like. In some embodiments, the pulse characteristics of the
stimulation pulse can be determined based on information retrieved
from the memory of the IPG 10, the retrieved information specifying
the characteristics of the stimulation pulse.
[0124] At block 1320 shown in FIG. 14, one or several pulse switch
configurations are determined. In some embodiments, this can
include determining the phases for delivery of the stimulation
pulse, and/or the duration of the phases for delivery of the
stimulation pulse. In some embodiments, this determining of the
switch configurations can be performed by the pulse control 604,
and specifically by the stimulation controller 702. In some
embodiments, determining of the one or several pulse phase
configurations can include retrieving information specifying the
one or several pulse phase configurations from the memory.
[0125] At block 1322, the first phase current source match is set.
In some embodiments, this can include setting the voltage of the
voltage node 816 and/or setting and/or adjusting the resistance of
the adjustable resistance element 806. In some embodiments, the
adjustable resistance element 806 can comprise a bank of switchably
connected resistors, and adjusting the resistance of the adjustable
resistance element can include changing a switch configuration of
at least one of the plurality of resistors. The setting of the
first phase current source match can be performed by the
stimulation controller 702.
[0126] At block 1324, the first phase switch configuration is
implemented and the first phase of the stimulation pulse is
delivered via the implementing of the first switch configuration in
the first circuit 802 and in the second circuit 804 of the
stimulation circuitry 708. In some embodiments, this can include
transitioning one or several of the switches 812, 814, 824, 826 of
the first circuit 802 and/or the second circuit 804 from the
neutral switch configuration to the first switch configuration. In
some embodiments, the transitioning of the one or several switches
812, 814, 824, 826 can be simultaneously performed and/or the
control signals for the transitioning of the switches 812, 814,
824, 826 can be simultaneously sent.
[0127] At block 1326, the duration of the first phase is monitored.
In some embodiments, this can include triggering a timer tracking
the duration of the first phase, triggering a count-down timer that
expires at the time of desired termination of the first phase, or
the like. In some embodiments, the pulse control 604 can include a
timer and/or a count-down timer that can be used in determining the
duration of the first phase.
[0128] At the termination of the first phase, in some embodiments,
the interphase switch configuration can be implemented, via, for
example, the generation and delivery of control signals directing
the transitioning of the switches 812, 814, 824, 826 from the first
configuration to the interphase switch configuration, the
interphase switch configuration causing an interphase delay between
the delivery of the first phase of the stimulation pulse and the
second phase of the stimulation pulse. In some embodiments, this
interphase switch configuration is the second switch configuration
in the process 1300. In some embodiments, the transitioning of the
one or several switches 812, 814, 824, 826 can be simultaneously
performed and/or the control signals for the transitioning of the
switches 812, 814, 824, 826 can be simultaneously sent.
[0129] At block 1328, the duration of the second phase is
monitored. In some embodiments, this can include triggering a timer
tracking the duration of the interphase, triggering a count-down
timer that expires at the time of desired termination of the
interphase, or the like. In some embodiments, the pulse control 604
can include a timer and/or a count-down timer that can be used in
determining the duration of the second phase.
[0130] At block 1332, the second phase current source match is set.
In some embodiments, this can include setting and/or adjusting the
resistance of the adjustable resistance element 806. In some
embodiments, this resistance can be set and/or adjusted based on
the measured and/or expected impedance of the target tissue, and
the charge of the capacitors 828, 830. The setting of the first
phase current source match can be performed by the stimulation
controller 702.
[0131] At block 1334, the second phase switch configuration, which
is the third switch configuration of process 1300, is implemented
and the second phase of the stimulation pulse is delivered via the
implementing of the third switch configuration in the first circuit
802 and/or in the second circuit 804 of the stimulation circuitry
708. In some embodiments, this can include transitioning one or
several of the switches 812, 814, 824, 826 of the first circuit 802
and/or the second circuit 804 from the interphase switch
configuration, which can be the neutral switch configuration to the
third switch configuration. In some embodiments, the transitioning
of the one or several switches 812, 814, 824, 826 can be
simultaneously performed and/or the control signals for the
transitioning of the switches 812, 814, 824, 826 can be
simultaneously sent.
[0132] At block 1336, the duration of the second stimulation phase
is monitored. In some embodiments, this can include triggering a
timer tracking the duration of the second phase, triggering a
count-down timer that expires at the time of desired termination of
the second phase, or the like. In some embodiments, the pulse
control 604 can include a timer and/or a count-down timer that can
be used in determining the duration of the second phase. At block
1338, the second phase is terminated. In some embodiments, the
second stimulation phase can last until a termination threshold is
met. The termination threshold can be a duration of time, a current
level, or the like. In some embodiments, for example, the second
phase terminates when current through the target tissue drops below
a predetermined value. The pulse control 604, and specifically the
stimulation controller 702 can terminate the second phase via the
reconfiguration of the switches 812, 814, 824, 826 to, for example,
the neutral configuration.
[0133] At decision step 1340, it is determined if additional
stimulation pulses are desired. In some embodiments, for example,
stimulation delivery can include the delivery of a plurality of
stimulation pulses. In some embodiments, the delivery of
stimulation can be limited by a predetermined number of pulses, a
predetermined amount of time, or the like. In some embodiments, the
pulse control 604, and specifically the stimulation controller 702
can track the number of pulses delivered and/or the duration of
time that stimulation has been provided and can determine if
delivery of stimulation is terminated.
[0134] If it is determined that no additional pulses are to be
delivered, the process 1300 proceeds to block 1342 and waits for
receipt of the next pulse command. In some embodiments, receipt of
a pulse command can result in the generation and/or delivery of a
stimulation pulse. After a pulse command is received, or
alternatively, returning to decision step 1340, if it is determined
that additional pulses are to be provided, the process 1300
proceeds to block 1344 and returns to block 1302.
[0135] FIG. 15 depicts one embodiment of a process 1500 for
delivering stimulation to a target tissue of a patient with an IPG
10. The process 1500 can be performed by the IPG 10 or by
components or modules of the IPG 10 such as, for example, the pulse
control 604. The process 1500 can be performed when impedance data
is not sufficiently reliable. In some embodiments, the process 1500
can be performed when impedance data acquired in block 1308 of
process 1300 is too old to be reliable, and/or is not applicable to
one or several attributes of a desired stimulation, such as was
measured at a different current than the desired stimulation. In
some embodiments, the performing of process 1500 iteratively:
increases a current of a delivered stimulation pulse and measures
the impedance of the target tissue during the delivery of the
stimulation pulse or determines the impedance of the target tissue
based on data gathered during delivery of the stimulation pulse.
This iterative approach allows the quick determination of tissue
impedance at, or approximately at the desired current, and allows
the IPG 10 to quickly deliver the desired stimulation current
without exceeding, or significantly exceeding the desired current.
In some embodiments, a desired current of a stimulation pulse is
significantly exceeded when a patient experiences an adverse effect
of the stimulation pulse.
[0136] The process begins at block 1502, wherein a desired current
is determined. In some embodiments, the determining of the desired
stimulation current can be performed by the pulse control 604
and/or by the stimulation controller 702. In some embodiments, the
determination of the desired stimulation current can include
retrieving information specifying the desired stimulation current
from the memory of the IPG 10. In some embodiments, the desired
stimulation current can be determined based, at least in part, on
one or several signals received from the patient remote.
[0137] At block 1504, the impedance data for the targeted tissue is
retrieved and/or acquired. In some embodiments, the impedance data
for the target tissue to which the stimulation is to be delivered
is retrieved and/or acquired from the memory of the IPG 10. At
block 1506 the current source match is determined, or in other
words, the settings of the stimulation circuitry are determined. In
some embodiments, this can include determining a voltage of the
voltage node 816 and/or a resistance of the adjustable resistance
element 806. In some embodiments, the current source match is
determined based on a combination of the desired current and the
retrieved impedance data. In some embodiments, and to prevent the
delivery of too much current to the target tissue, the current
source match can be determined to deliver a current lower than the
desired current. In some embodiments, the delivered current can be
significantly lower than the desired current. In some embodiments,
the delivered current can be less than 10% of the desired current,
less than 25% of the desired current, less than 50% of the desired
current, less than 75% of the desired current, and/or less than 80%
of the desired current. In such embodiments, the current source
match is determined based on the retrieved impedance data and a
target value for the delivered current.
[0138] At block 1508 a stimulation pulse is delivered. In some
embodiments, this stimulation pulse, which can be a test
stimulation pulse, can be delivered according to steps 1320 through
1338 of process 1300. A test stimulation pulse can be a stimulation
pulse delivered with circuit settings intended to create a current
through the target tissue less than the desired current. In some
embodiments, for example, the IPG 10 may immediately transition to
a pulse with a desired current, and in some embodiments, the IPG 10
may transition to a pulse with a desired current via one or several
test stimulation pulses, which can have a current less than the
desired current. In some embodiments, and as tissue impedance may
change with current, one or several test stimulation pulses can be
delivered to measure tissue impedance and to facilitate the
delivery of a stimulation pulse having, and in some embodiments,
not exceeding, the desired current.
[0139] At block 1510 impedance in the target tissue is measured
and/or determined. In some embodiments, the impedance in the target
tissue can be measured during all or portions of the delivery of
the stimulation pulse and/or can be determined based on data
gathered during all or portions of the delivery of the stimulation
pulse. In some embodiments, for example, current through the
adjustable resistance element 806 can be measured during delivery
of the all or portions of the stimulation pulse and/or the charger
and/or change in charge in one or both of the capacitors 828, 830
can be measured during delivery of all or portions of the
stimulation pulse. This gathered data can then be used to determine
the impedance of the target tissue of the patient.
[0140] At block 1512, a next current value is determined. In some
embodiments, this can include determining a target value for
current of a next delivered stimulation pulse. This next current
and/or the target value for current of the next delivered
stimulation pulse can be greater than the previously delivered
current and/or than the previous target value for current. In some
embodiments, this next current, though larger than the previously
delivered stimulation current, can still be less than the desired
current, and in some embodiments, this next current can be equal to
the desired current.
[0141] At block 1514, the current source match for the next
stimulation pulse is determined, or in other words, the settings of
the stimulation circuitry are determined. In some embodiments, this
can include determining a voltage of the voltage node 816 and/or a
resistance of the adjustable resistance element 806. In some
embodiments, determination of the current source match for the next
stimulation pulse can include, for example, controlling the voltage
of the voltage node 816 and/or the resistance of the adjustable
resistance element 806 during the first phase of delivery of the
stimulation pulse and controlling of the resistance of the
adjustable resistance element 806 during the second phase of
delivery of the stimulation pulse. In some embodiments, the current
source match can determined based on a combination of the desired
current and the retrieved impedance data.
[0142] At block 1516, a stimulation pulse is delivered, which
stimulation pulse can be a test stimulation pulse. In some
embodiments, this stimulation pulse can be delivered according to
steps 1320 through 1338 of process 1300. This stimulation pulse can
have current that is greater than the current of the stimulation
pulse delivered in block 1508 and/or that is less than the desired
current determined in block 1502. At block 1518 impedance in the
target tissue is measured and/or determined. In some embodiments,
the impedance in the target tissue can be measured during all or
portions of the delivery of the stimulation pulse and/or can be
determined based on data gathered during all or portions of the
delivery of the stimulation pulse. In some embodiments, for
example, current through the adjustable resistance element 806 can
be measured during delivery of the all or portions of the
stimulation pulse and/or the charger and/or change in charge in one
or both of the capacitors 828, 830 can be measured during delivery
of all or portions of the stimulation pulse. This gathered data can
then be used to determine the impedance of the target tissue of the
patient.
[0143] At block 1520, the current of the stimulation pulse
delivered in block 1516 is compared to the desired current of the
stimulation pulse. In some embodiments, this comparison can include
the comparing of the desired current to the current of one or both
of: the first phase of the stimulation pulse; and the second phase
of the stimulation pulse. At decision step 1522, it is determined
if the current of the stimulation pulse delivered in block 1516
matches and/or approximately matches the desired current. In some
embodiments, this can include determining whether one or several
termination criteria for iteratively delivering a stimulation pulse
and measuring impedance of the target tissue have been met. In some
embodiments, the current of the test stimulation pulse
approximately matches the desired value of the current of the
desired stimulation pulse when at least one of: the first phase
current; or the second phase current approximately matches the
desired value of the current of the desired stimulation pulse. In
some embodiments, at least one of: the first phase current; or the
second phase current approximately matches the desired value of the
current of the desired stimulation pulse when the current of the at
least one of: the first phase current; or the second phase current
is within predetermined range about the desired value of the
current of the desired stimulation pulse. In some embodiments, for
example, the delivered current approximately matches the desired
current when the delivered current has a value between 80% and 120%
of the desired current, between 90% and 110% of the desired
current, between 95% and 105% of the desired current, between 98%
and 102% of the desired current, is at least 80% of the desired
current, is at least 90% of the desired current, is at least 95% of
the desired current, is at least 98% of the desired current, or is
any other or intermediate percent of the desired current or within
any other or intermediate range about the desired current.
[0144] If it is determined that the delivered current does not
match the desired current, then the process 1500 returns to block
1512 and proceeds as outlined above. In some embodiments, this can
include delivering a third stimulation pulse having a third
current, a fourth stimulation pulse having a fourth current, a
fifth stimulation pulse having a fifth current, and/or any other
number of stimulation pulses until one or several termination
criteria are met and/or until a delivered current matches the
desired current. In some embodiments, each subsequently delivered
stimulation pulse can have a current greater than previously
delivered stimulation pulses. Thus, in some embodiments, the third
stimulation pulse can have a third current that is greater than the
second current.
[0145] If it is determined that the delivered current matches the
desired current, then the process 1500 proceeds to block 1524,
wherein the measured impedance value is stored. In some
embodiments, this impedance value can be stored in the memory of
the IPG 10, and metadata associated with the impedance value can
likewise be stored in the memory of the IPG 10.
[0146] At block 1526, stimulation is delivered according to the
stored impedance value. In some embodiments, the delivery of
stimulation can be according to the process 1300 of FIGS. 13 and
14. In some embodiments, the delivery of stimulation can comprise
the delivery of a plurality of stimulation pulses. At block 1528,
impedance of the target tissue is periodically re-measured. In some
embodiments, this impedance of the target tissue can be re-measured
at a predetermine time interval and/or after a predetermined number
of delivered stimulation pulses. After the re-measuring of the
impedance of the target tissue, the process 1500 can proceed to
decision step 1530, wherein it is determined if there is a change
in impedance of the target tissue. If it is determined that there
is a change in the impedance of the target tissue, then the process
1500 proceeds to block 1524, and proceeds as outlined above.
Alternatively, if it is determined that there is not a change in
the impedance of the target tissue, then the process 1500 proceeds
to block 1526 and proceeds as outlined above.
[0147] In the foregoing specification, the invention is described
with reference to specific embodiments thereof, but those skilled
in the art will recognize that the invention is not limited
thereto. Various features and aspects of the above-described
invention can be used individually or jointly. Further, the
invention can be utilized in any number of environments and
applications beyond those described herein without departing from
the broader spirit and scope of the specification. The
specification and drawings are, accordingly, to be regarded as
illustrative rather than restrictive. It will be recognized that
the terms "comprising," "including," and "having," as used herein,
are specifically intended to be read as open-ended terms of
art.
* * * * *