U.S. patent application number 14/214752 was filed with the patent office on 2014-09-18 for neuromodulation system and method for transitioning between programming modes.
The applicant listed for this patent is BOSTON SCIENTIFIC NEUROMODULATION CORPORATION. Invention is credited to Rafael Carbunaru, Que T. Doan, Christopher E. Gillespie, Bradley L. Hershey, Justin Holley, Sridhar Kothandaraman, Dongchul Lee, Jordi Parramon, Dennis Allen Vansickle, Nazim Wahab, Changfang Zhu.
Application Number | 20140277267 14/214752 |
Document ID | / |
Family ID | 50440891 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140277267 |
Kind Code |
A1 |
Vansickle; Dennis Allen ; et
al. |
September 18, 2014 |
NEUROMODULATION SYSTEM AND METHOD FOR TRANSITIONING BETWEEN
PROGRAMMING MODES
Abstract
An external control device and method for programming an
implantable neuromodulator coupled to an electrode array implanted
adjacent tissue of a patient having a medical condition. Electrical
modulation energy is conveyed to tissue of the patient in
accordance with a series of modulation parameter sets. The patient
perceives paresthesia in response to the conveyance of the
electrical modulation energy to the tissue in accordance with at
least one of the modulation parameter sets. One of the modulation
parameter set(s) is identified based on the perceived paresthesia.
Another modulation parameter set is derived from the identified
modulation parameter set. Electrical modulation energy is conveyed
to the tissue of the patient in accordance with the other
modulation parameter set without causing the patient to perceive
paresthesia.
Inventors: |
Vansickle; Dennis Allen;
(Lancaster, CA) ; Lee; Dongchul; (Agua Dulce,
CA) ; Kothandaraman; Sridhar; (Valencia, CA) ;
Doan; Que T.; (Valencia, CA) ; Zhu; Changfang;
(Valencia, CA) ; Parramon; Jordi; (Valencia,
CA) ; Holley; Justin; (Santa Monica, CA) ;
Hershey; Bradley L.; (Valencia, CA) ; Gillespie;
Christopher E.; (Stevenson Ranch, CA) ; Carbunaru;
Rafael; (Valley Village, CA) ; Wahab; Nazim;
(Valencia, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOSTON SCIENTIFIC NEUROMODULATION CORPORATION |
Valencia |
CA |
US |
|
|
Family ID: |
50440891 |
Appl. No.: |
14/214752 |
Filed: |
March 15, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61801917 |
Mar 15, 2013 |
|
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|
Current U.S.
Class: |
607/46 ;
607/59 |
Current CPC
Class: |
A61N 1/36185 20130101;
A61N 1/37247 20130101; A61N 1/36071 20130101; A61N 1/36164
20130101 |
Class at
Publication: |
607/46 ;
607/59 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. An external control device for programming an implantable
neuromodulator coupled to an electrode array, comprising: a user
interface including a programming selection control element
configured for allowing a user to select one of a first programming
mode having a first limit on a modulation parameter and a second
programming mode having a second limit on the modulation parameter
different from the first limit; and controller/processor circuitry
configured for allowing a user to program the neuromodulator in the
first programming mode, and allowing the user to program the
neuromodulator in the second programming mode in response to
actuation of the programming selection control element.
2. The external control device of claim 1, wherein
controller/processor circuitry is configured for defining a series
of modulation parameter sets during the programming of the
neuromodulator in the first programming mode, and instructing the
neuromodulator to convey electrical energy to the electrode array
in accordance with the series of modulation parameter sets in a
manner that displaces a locus of a resulting electrical field
relative to the electrode array.
3. The external control device of claim 2, wherein the
controller/processor circuitry, in response to the actuation of the
programming selection control element, is configured for deriving
another modulation parameter set from the last modulation parameter
set of the series of modulation parameter sets, and instructing the
neuromodulator to convey electrical energy to the electrode array
in accordance with the other modulation parameter set during the
programming of the neuromodulation to device in the second
programming mode.
4. The external control device of claim 3, wherein the
controller/processor circuitry is configured for deriving the other
modulation parameter set in a manner that causes an electrical
field resulting from the conveyance of the electrical energy to the
electrode array in accordance with the other modulation parameter
set to have a locus that is the same as the locus of the electrical
field resulting from the conveyance of the electrical energy to the
electrode array in accordance with the last modulation parameter
set.
5. The external control device of claim 1, wherein the modulation
parameter is a pulse rate.
6. The external control device of claim 5, wherein the first limit
is an upper limit value less than 1500 Hz, and the second limit is
a lower limit value greater than 1500 Hz.
7. The external control device of claim 1, wherein the modulation
parameter is a pulse width.
8. The external control device of claim 7, wherein the first limit
is a lower limit value greater than 100 .mu.s, and the second limit
is an upper limit value less than 100 .mu.s.
9. The external control device of claim 1, wherein the modulation
parameter is an electrode combination.
10. The external control device of claim 9, wherein the first limit
is a range of electrode combinations having only anodic electrodes
as primary modulating electrodes, and the second limit is a range
of electrode combinations having only cathodic electrodes as
primary modulating electrodes.
11. The external control device of claim 9, wherein the first limit
is a range of monopolar electrode combinations, and the second
limit is a range of multipolar electrode combinations.
12. The external control device of claim 9, wherein the modulation
parameter is a fractionalized electrode combination.
13. The external control device of claim 1, wherein each of the
first and second programming modes is a semi-automated programming
mode.
14. The external control device of claim 1, wherein the
controller/processor circuitry is configured for defining a virtual
multipole relative to the electrode array when programming the
neuromodulator in the first programming mode, and computing
amplitude values for the electrode array that emulate the virtual
multipole, wherein the first modulation parameter set includes the
computed amplitude values.
15. The external control device of claim 14, wherein each of the
first and second programming modes is a semi-automated programming
mode configured for panning the virtual multipole across the
electrode array.
16. The external control device of claim 1, further comprising
telemetry circuitry, wherein the controller/processor circuitry is
configured for programming the neuromodulator via the telemetry
circuitry.
17. The external control device of claim 1, further comprising a
housing containing the user interface and the controller/processor
circuitry.
18. A method of operating an implantable neuromodulator coupled to
an electrode array implanted adjacent tissue of a patient having a
medical condition, comprising: conveying electrical modulation
energy to tissue of the patient in accordance with a series of
modulation parameter sets, thereby gradually displacing the locus
of the resulting electrical field relative to the tissue, such that
a plurality of different loci of the resulting electrical field can
be respectively associated with the series of modulation parameter
sets; causing the patient to perceive paresthesia in response to
the conveyance of the electrical modulation energy to the tissue in
accordance with at least one of the modulation parameter sets;
identifying one of the at least one modulation parameter sets based
on the perceived paresthesia; deriving another modulation parameter
set from the identified modulation parameter set; and conveying
electrical modulation energy to the tissue of the patient in
accordance with the other modulation parameter set, thereby
creating an electrical field having a locus relative to the tissue
that is the same as the locus of the electrical field associated
with the identified modulation parameter set, and without causing
the patient to perceive paresthesia.
19. The method of claim 18, wherein the medical condition affects a
body region of the patient, the electrical modulation energy
conveyed to the tissue in accordance with the identified modulation
parameter set causes the patient to perceive the paresthesia in the
body region.
20. The method of claim 18, wherein the medical condition is
chronic pain.
21. The method of claim 18, wherein the identified modulation
parameter set and the other modulation parameter set define
different pulse rates.
22. The method of claim 21, wherein the identified modulation
parameter set defines a pulse rate less than 1500 Hz, and the other
modulation parameter set defines a pulse rate greater than 1500
Hz.
23. The method of claim 18, wherein the identified modulation
parameter set and the other modulation parameter set define
different pulse widths.
24. The method of claim 23, wherein the identified modulation
parameter set defines a pulse width greater than 100 .mu.s, and the
other modulation parameter set defines a pulse width less than 100
.mu.s.
25. The method of claim 18, wherein the identified modulation
parameter set and the other modulation parameter set define
different electrode combinations.
26. The method of claim 25, wherein the identified modulation
parameter set is a monopolar electrode combination, and the other
modulation parameter set is a multipolar electrode combination.
27. The method of claim 25, wherein the different electrode
combinations are different fractionalized electrode
combinations.
28. The method of claim 18, further comprising: defining a series
of virtual poles relative to the electrode array; computing
amplitude values for electrode combinations that respectively
emulate the series of virtual poles, wherein the series of
modulation parameter sets respectively define the electrode
combinations; defining another virtual pole relative to the
electrode array; and computing amplitude values for another
electrode combination that emulates the other virtual pole, wherein
the other modulation parameter set defines the other electrode
combination.
29. The method of claim 28, wherein the series of virtual poles is
defined by panning a virtual pole across the electrode array.
30. The method of claim 18, further comprising programming the
neuromodulator with the other modulation parameter set.
31. The method of claim 18, wherein the neuromodulator is implanted
within the patient.
32. The method of claim 18, wherein the tissue is spinal cord
tissue.
33.-250. (canceled)
Description
RELATED APPLICATION DATA
[0001] The present application claims the benefit under 35 U.S.C.
.sctn.119 to U.S. provisional patent application Ser. No.
61/801,917, filed Mar. 15, 2013. The foregoing application is
hereby incorporated by reference into the present application in
its entirety.
FIELD OF THE INVENTION
[0002] The present inventions relate to tissue modulation systems,
and more particularly, to programmable neuromodulation systems.
BACKGROUND OF THE INVENTION
[0003] Implantable neuromodulation systems have proven therapeutic
in a wide variety of diseases and disorders. Pacemakers and
Implantable Cardiac Defibrillators (ICDs) have proven highly
effective in the treatment of a number of cardiac conditions (e.g.,
arrhythmias). Spinal Cord Stimulation (SCS) systems have long been
accepted as a therapeutic modality for the treatment of chronic
pain syndromes, and the application of tissue stimulation has begun
to expand to additional applications such as angina pectoralis and
incontinence. Deep Brain Stimulation (DBS) has also been applied
therapeutically for well over a decade for the treatment of
refractory chronic pain syndromes, and DBS has also recently been
applied in additional areas such as movement disorders and
epilepsy. Further, in recent investigations, Peripheral Nerve
Stimulation (PNS) systems have demonstrated efficacy in the
treatment of chronic pain syndromes and incontinence, and a number
of additional applications are currently under investigation.
Furthermore, Functional Electrical Stimulation (FES) systems, such
as the Freehand system by NeuroControl (Cleveland, Ohio), have been
applied to restore some functionality to paralyzed extremities in
spinal cord injury patients.
[0004] These implantable neuromodulation systems typically include
one or more electrode carrying neuromodulation leads, which are
implanted at the desired modulation site, and an implantable
neuromodulation device (e.g., an implantable pulse generator (IPG))
implanted remotely from the modulation site, but coupled either
directly to the neuromodulation lead(s) or indirectly to the
neuromodulation lead(s) via a lead extension. The neuromodulation
system may further comprise a handheld external control device
(e.g., a remote control (RC)) to remotely instruct the
neuromodulator to generate electrical pulses in accordance with
selected modulation parameters.
[0005] Implantable neuromodulation devices are active devices
requiring energy for operation, and thus, the neuromodulation
system oftentimes include an external charger to recharge a
neuromodulation device, so that a surgical procedure to replace a
power depleted neuromodulation device can be avoided. To wirelessly
convey energy between the external charger and the implanted
neuromodulation device, the charger typically includes an
alternating current (AC) charging coil that supplies energy to a
similar charging coil located in or on the neuromodulation device.
The energy received by the charging coil located on the
neuromodulation device can then be stored in a rechargeable battery
within the neuromodulation device, which can then be used to power
the electronic componentry on-demand. Depending on the settings,
the neuromodulation device may need to be recharged every 1-30
days.
[0006] Electrical modulation energy may be delivered from the
neuromodulation device to the electrodes in the form of an
electrical pulsed waveform. Thus, electrical modulation energy may
be controllably delivered to the electrodes to modulate neural
tissue. The configuration of electrodes used to deliver electrical
pulses to the targeted tissue constitutes an electrode
configuration, with the electrodes capable of being selectively
programmed to act as anodes (positive), cathodes (negative), or
left off (zero). In other words, an electrode configuration
represents the polarity being positive, negative, or zero. Other
parameters that may be controlled or varied include the amplitude,
width, and rate of the electrical pulses provided through the
electrode array. Each electrode configuration, along with the
electrical pulse parameters, can be referred to as a "modulation
parameter set."
[0007] With some neuromodulation systems, and in particular, those
with independently controlled current or voltage sources, the
distribution of the current to the electrodes (including the case
of the neuromodulation device, which may act as an electrode) may
be varied such that the current is supplied via numerous different
electrode configurations. In different configurations, the
electrodes may provide current or voltage in different relative
percentages of positive and negative current or voltage to create
different electrical current distributions (i.e., fractionalized
electrode configurations).
[0008] As briefly discussed above, an external control device can
be used to instruct the neuromodulation device to generate
electrical pulses in accordance with the selected modulation
parameters. Typically, the modulation parameters programmed into
the neuromodulation device can be adjusted by manipulating controls
on the external control device to modify the electrical modulation
energy delivered by the neuromodulation device system to the
patient. Thus, in accordance with the modulation parameters
programmed by the external control device, electrical pulses can be
delivered from the neuromodulation device to the electrode(s) to
modulate a volume of tissue in accordance with a set of modulation
parameters and provide the desired efficacious therapy to the
patient. The best modulation parameter set will typically be one
that delivers electrical energy to the volume of tissue that must
be modulate in order to provide the therapeutic benefit (e.g.,
treatment of pain), while minimizing the volume of non-target
tissue that is modulated.
[0009] However, the number of electrodes available, combined with
the ability to generate a variety of complex electrical pulses,
presents a huge selection of modulation parameter sets to the
clinician or patient. For example, if the neuromodulation system to
be programmed has an array of sixteen electrodes, millions of
modulation parameter sets may be available for programming into the
neuromodulation system. Today, neuromodulation system may have up
to thirty-two electrodes, thereby exponentially increasing the
number of modulation parameters sets available for programming.
[0010] To facilitate such selection, the clinician generally
programs the neuromodulation device through a computerized
programming system. This programming system can be a self-contained
hardware/software system, or can be defined predominantly by
software running on a standard personal computer (PC). The PC or
custom hardware may actively control the characteristics of the
electrical pulses generated by the neuromodulation device to allow
the optimum modulation parameters to be determined based on patient
feedback or other means and to subsequently program the
neuromodulation device with the optimum modulation parameter set or
sets. The computerized programming system may be operated by a
clinician attending the patient in several scenarios.
[0011] For example, in order to achieve an effective result from
conventional SCS, the lead or leads must be placed in a location,
such that the electrical modulation (and in this case, electrical
stimulation) will cause paresthesia. The paresthesia induced by the
stimulation and perceived by the patient should be located in
approximately the same place in the patient's body as the pain that
is the target of treatment. If a lead is not correctly positioned,
it is possible that the patient will receive little or no benefit
from an implanted SCS system. Thus, correct lead placement can mean
the difference between effective and ineffective pain therapy. When
leads are implanted within the patient, the computerized
programming system, in the context of an operating room (OR)
mapping procedure, may be used to instruct the neuromodulation
device to apply electrical stimulation to test placement of the
leads and/or electrodes, thereby assuring that the leads and/or
electrodes are implanted in effective locations within the
patient.
[0012] Once the leads are correctly positioned, a fitting
procedure, which may be referred to as a navigation session, may be
performed using the computerized programming system to program the
external control device, and if applicable the neuromodulation
device, with a set of modulation parameters that best addresses the
painful site. Thus, the navigation session may be used to pinpoint
the volume of activation (VOA) or areas correlating to the pain.
Such programming ability is particularly advantageous for targeting
the tissue during implantation, or after implantation should the
leads gradually or unexpectedly move that would otherwise relocate
the stimulation energy away from the target site. By reprogramming
the neuromodulation device (typically by independently varying the
stimulation energy on the electrodes), the volume of activation
(VOA) can often be moved back to the effective pain site without
having to re-operate on the patient in order to reposition the lead
and its electrode array. When adjusting the volume of activation
(VOA) relative to the tissue, it is desirable to make small changes
in the proportions of current, so that changes in the spatial
recruitment of nerve fibers will be perceived by the patient as
being smooth and continuous and to have incremental targeting
capability.
[0013] One known computerized programming system for SCS is called
the Bionic Navigator.RTM., available from Boston Scientific
Neuromodulation Corporation. The Bionic Navigator.RTM. is a
software package that operates on a suitable PC and allows
clinicians to program modulation parameters into an external
handheld programmer (referred to as a remote control). Each set of
modulation parameters, including fractionalized current
distribution to the electrodes (as percentage cathodic current,
percentage anodic current, or off), may be stored in both the
Bionic Navigator.RTM. and the remote control and combined into a
stimulation program that can then be used to stimulate multiple
regions within the patient.
[0014] To determine the modulation parameters to be programmed, the
Bionic Navigator.RTM. may be operated by a clinician in one of
three modes: (a) a manual programming mode to manually select the
cathodic current and anodic current flowing through the electrodes;
(b) an electronic trolling ("e-troll") mode to quickly sweep the
electrode array using a limited number of electrode configurations
to gradually move a cathode in bipolar stimulation; and (c) a
Navigation programming mode to fine tune and optimize stimulation
coverage for patient comfort using a wide number of electrode
configurations. These three modes allow the clinician to determine
the most efficient modulation parameter sets for a given
patient.
[0015] In the manual programming mode, the clinician directly
selects individual electrodes and the current magnitude and
polarity to be applied to each selected electrode. In the e-troll
and navigation programming modes, the Bionic Navigator.RTM.
semi-automatically transitions between different electrode
configurations to electrically "steer" the current along the
implanted leads in real-time (e.g., using a joystick or
joystick-like controls) in a systematic manner, thereby allowing
the clinician to determine the most efficacious modulation
parameter sets that can then be stored and eventually combined into
stimulation programs. In the context of SCS, current steering is
typically either performed in a rostro-caudal direction (i.e.,
along the axis of the spinal cord) or a medial-lateral direction
(i.e., perpendicular to the axis of the spinal cord).
[0016] The e-troll and navigation programming modes differ in part
in the way in which the clinician changes electrode configurations
from one configuration to another. The e-troll programming mode
utilizes a technique known as "panning", which shifts a pre-defined
electrode configuration down the sequence of electrodes without
changing the basic form of the electrode configuration. The
navigation programming mode utilizes a technique known as
"weaving," which moves the anode or anodes around the cathode,
while slowly progressing the cathode down the sequence of
electrodes. The e-troll and navigation programming modes may have
different clinical uses (e.g., finding the "sweet spot" in the case
of panning, or shaping the electrical field around the cathode in
the case of weaving).
[0017] In one novel current steering method, described in U.S.
patent application Ser. No. 12/938,282, entitled "System and Method
for Mapping Arbitrary Electric Fields to Pre-existing Lead
Electrodes," which is expressly incorporated herein by reference, a
stimulation target in the form of a virtual pole (e.g., a virtual
bipole or tripole) is defined and the modulation parameters,
including the fractionalized current values on each of the
electrodes, are computationally determined in a manner that
emulates these virtual poles. It can be appreciated that current
steering can be implemented by moving the virtual poles about the
leads, such that the appropriate fractionalized current values for
the electrodes are computed for each of the various positions of
the virtual pole. As a result, the current steering can be
implemented using an arbitrary number and arrangement of
electrodes, thereby solving the afore-described problems.
[0018] The virtual bipole or tripole can be determined using a
simplified virtual tripole consisting of a cathode, and an upper
(or rostral) anode and lower (or caudal) electrode located on a
longitudinal axis from the cathode. The virtual tripole may be
defined using three values consisting of (1) location of the
cathode relative to the electrodes; (2) a focus, which is the
distance between the cathode and the anode(s); and (3) a percentage
of current on the upper cathode. This technique is described in
U.S. Provisional Patent Application Ser. No. 61/452,965, entitled
"Neurostimulation System for Defining a Generalized Virtual
Multipole," which is expressly incorporated herein by
reference.
[0019] Although alternative or artifactual sensations are usually
tolerated relative to the sensation of pain, patients sometimes
report these sensations to be uncomfortable, and therefore, they
can be considered an adverse side-effect to neuromodulation therapy
in some cases. Because the perception of paresthesia has been used
as an indicator that the applied electrical energy is, in fact,
alleviating the pain experienced by the patient, the amplitude of
the applied electrical energy is generally adjusted to a level that
causes the perception of paresthesia. It has been shown that the
delivery of sub-threshold electrical energy (e.g., high-rate pulsed
electrical energy and/or low pulse width electrical energy) can be
effective in providing neuromodulation therapy for chronic pain
without causing paresthesia.
[0020] However, because there is a lack of paresthesia that may
otherwise indicate that the activated electrodes are properly
located relative to the targeted tissue site, it is difficult to
immediately determine if the delivered sub-threshold
neuromodulation therapy is optimized in terms of both providing
efficacious therapy and minimizing energy consumption. Furthermore,
if the implanted neuromodulation lead(s) migrate relative to the
target tissue site to be modulated, it is possible that the
sub-threshold neuromodulation may fall outside of the effective
therapeutic range (either below the therapeutic range if the
coupling efficiency between the neuromodulation lead(s) and target
tissue site decreases, resulting in a lack of efficacious therapy,
or above the therapeutic range if the coupling efficiency between
the neuromodulation lead(s) and the target tissue site increases,
resulting in the perception of paresthesia or inefficient energy
consumption).
[0021] There, thus, remains a need to provide a neuromodulation
system that is capable of compensating for the migration of
neuromodulation lead(s) during sub-threshold neuromodulation
therapy.
[0022] Another issue is that a patient receiving sub-threshold
therapy may not notice when the battery of the implanted
neuromodulation device has depleted, and because the sub-threshold
therapy is not accompanied by paresthesia, the patient may not
immediately realize that he or she is no longer receiving therapy.
There, thus, remains a need to alert a patient when the battery of
an implanted neuromodulation is almost depleted.
[0023] Conventional computerized programming systems typically have
one or more programming modes intended to achieve a singular
therapeutic effect (e.g., either super-threshold neuromodulation
therapy (e.g., therapy accompanied by paresthesia) or sub-threshold
neuromodulation therapy (e.g., therapy not accompanied by
paresthesia). To this end, a particular computer programming system
will typically limit the modulation parameters with which a
neuromodulation device can be programmed. For example, a
computerized programming system designed for super-threshold
neuromodulation may limit the modulation parameters to those known
to result in super-threshold neuromodulation therapy, whereas a
computerized programming system designed for sub-threshold
neuromodulation may limit the modulation parameters to those known
to result in sub-threshold neuromodulation therapy. To the extent
that a particular computer programming system has one or more
programming modes that are capable of providing multiple
therapeutic effects (e.g., both super-threshold neuromodulation
therapy and sub-threshold neuromodulation therapy), there is no
known computer programming system that transitions between multiple
programming modes that have been optimized to respectively achieve
multiple therapeutic effects.
[0024] There, thus, remains a need to provide a computer
programming system capable of transitioning between multiple
programming modes designed to achieve different therapeutic
results, such as super-threshold therapy and sub-threshold
therapy.
[0025] Furthermore, while it is possible, using conventional
computerized programming systems, to program a neuromodulator and
the accompanying with both super-threshold modulation programs and
sub-threshold modulation programs, this requires an extensive
programming or reprogramming fitting session to determine the
optimum modulation programs, typically requiring the presence of a
clinician. Furthermore, assuming that the neuromodulator and the
accompanying handheld external control device have been programmed
to selectively deliver super-threshold neuromodulation therapy or
sub-threshold neuromodulation therapy, the user may still be
required to navigate through a series of steps (e.g., via menus) to
switch between the super-threshold and sub-threshold modulation
programs. There, thus remains a need to provide the user with a
more efficient means for switching between super-threshold
modulation therapy and sub-threshold modulation therapy.
[0026] Furthermore, while super-threshold neuromodulation and
sub-threshold neuromodulation may provide different mechanisms for
providing therapy to a patient, under the assumption that a patient
needs only one or the other of these therapies, neuromodulation
systems have typically been programmed to take advantage of only
one of these therapies at any given time. There, thus, remains a
need deliver super-threshold modulation energy and sub-threshold
modulation therapy in a synergistic fashion.
SUMMARY OF THE INVENTION
[0027] In accordance with one aspect of the present inventions, an
external control device for programming an implantable
neuromodulator coupled to an electrode array is provided. The
external control device comprises a user interface including a
programming selection control element configured for allowing a
user to select one of a first programming mode (e.g., a
semi-automated programming mode) having a first limit on a
modulation parameter and a second programming mode (e.g., a
semi-automated programming mode) having a second limit on the
modulation parameter different from the first limit. In one
embodiment, the modulation parameter is a pulse rate, in which
case, the first limit may be, e.g., an upper limit value less than
1500 Hz, and the second limit may be, e.g., a lower limit value
greater than 1500 Hz. In another embodiment, the modulation
parameter is a pulse width, in which case, the first limit may be,
e.g., a lower limit value greater than 100 .mu.s, and the second
limit may be, e.g., an upper limit value less than 100 .mu.s. In
still another embodiment, the modulation parameter is an electrode
combination (e.g., a fractionalized electrode combination), in
which case, the first limit may be, e.g., a range of electrode
combinations having only anodic electrodes as primary modulating
electrodes, and the second limit may be, e.g., a range of electrode
combinations having only cathodic electrodes as primary modulating
electrodes, or the first limit may be, e.g., a range of monopolar
electrode combinations, and the second limit may be, e.g., a range
of multipolar electrode combinations.
[0028] The external control device further comprises
controller/processor circuitry configured for allowing a user to
program the neuromodulator in the first programming mode, and
allowing the user to program the neuromodulator in the second
programming mode in response to actuation of the programming
selection control element. The external control device may further
comprise telemetry circuitry, in which case, the
controller/processor circuitry may be configured for programming
the neuromodulator via the telemetry circuitry. The external
control device may further comprise a housing containing the user
interface and the controller/processor circuitry.
[0029] In one embodiment, the controller/processor circuitry may be
configured for defining a virtual multipole relative to the
electrode array when programming the neuromodulator in the first
programming mode, and computing amplitude values for the electrode
array that emulate the virtual multipole, wherein the first
modulation parameter set includes the computed amplitude values.
Each of the first and second programming modes may be a
semi-automated programming mode configured for panning the virtual
multipole across the electrode array.
[0030] In another embodiment, the controller/processor circuitry
may be configured for defining a series of modulation parameter
sets during the programming of the neuromodulator in the first
programming mode, and instructing the neuromodulator to convey
electrical energy to the electrode array in accordance with the
series of modulation parameter sets in a manner that displaces a
locus of a resulting electrical field relative to the electrode
array. In this case, the controller/processor circuitry, in
response to the actuation of the programming selection control
element, may be configured for deriving another modulation
parameter set from the last modulation parameter set of the series
of modulation parameter sets, and instructing the neuromodulator to
convey electrical energy to the electrode array in accordance with
the other modulation parameter set during the programming of the
neuromodulation to device in the second programming mode. The
controller/processor circuitry may further be configured for
deriving the other modulation parameter set in a manner that causes
an electrical field resulting from the conveyance of the electrical
energy to the electrode array in accordance with the other
modulation parameter set to have a locus that is the same as the
locus of the electrical field resulting from the conveyance of the
electrical energy to the electrode array in accordance with the
last modulation parameter set.
[0031] In accordance with a second aspect of the present
inventions, a method of operating an implantable neuromodulator
coupled to an electrode array implanted adjacent tissue (e.g.,
spinal cord tissue) of a patient having a medical condition (e.g.,
chronic pain) is provided. The neuromodulator may be implanted
within the patient. The method comprises conveying electrical
modulation energy to tissue of the patient in accordance with a
series of modulation parameter sets, thereby gradually displacing
the locus of the resulting electrical field relative to the tissue,
such that a plurality of different loci of the resulting electrical
field can be respectively associated with the series of modulation
parameter sets. The method further comprises causing the patient to
perceive paresthesia in response to the conveyance of the
electrical modulation energy to the tissue in accordance with at
least one of the modulation parameter sets, identifying one of the
at least one modulation parameter sets based on the perceived
paresthesia, and deriving another modulation parameter set from the
identified modulation parameter set.
[0032] In one method, the identified modulation parameter set and
the other modulation parameter set define different pulse rates, in
which case, the identified modulation parameter set may, e.g.,
define a pulse rate less than 1500 Hz, and the other modulation
parameter set may, e.g., define a pulse rate greater than 1500 Hz.
In another method, the identified modulation parameter set and the
other modulation parameter set define different pulse widths, in
which case, the identified modulation parameter set may, e.g.,
define a pulse width greater than 100 .mu.s, and the other
modulation parameter set may, e.g., define a pulse width less than
100 .mu.s. In still another method, the identified modulation
parameter set and the other modulation parameter set define
different electrode combinations (e.g., different fractionalized
electrode combinations), in which case, the identified modulation
parameter set may, e.g., be a monopolar electrode combination, and
the other modulation parameter set may, e.g., be a multipolar
electrode combination.
[0033] The method further comprises conveying electrical modulation
energy to the tissue of the patient in accordance with the other
modulation parameter set, thereby creating an electrical field
having a locus relative to the tissue that is the same as the locus
of the electrical field associated with the identified modulation
parameter set, and without causing the patient to perceive
paresthesia. The neuromodulator may be programmed with the other
modulation parameter set. In one method, the medical condition
affects a body region of the patient, in which case, the electrical
modulation energy conveyed to the tissue in accordance with the
identified modulation parameter set may cause the patient to
perceive the paresthesia in the body region.
[0034] The method may optionally comprise defining a series of
virtual poles relative to the electrode array (e.g., by panning a
virtual pole across the electrode array), computing amplitude
values for electrode combinations that respectively emulate the
series of virtual poles, such that the series of modulation
parameter sets respectively define the electrode combinations,
defining another virtual pole relative to the electrode array, and
computing amplitude values for another electrode combination that
emulates the other virtual pole, such that the other modulation
parameter set defines the other electrode combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The drawings illustrate the design and utility of preferred
embodiments of the present invention, in which similar elements are
referred to by common reference numerals. In order to better
appreciate how the above-recited and other advantages and objects
of the present inventions are obtained, a more particular
description of the present inventions briefly described above will
be rendered by reference to specific embodiments thereof, which are
illustrated in the accompanying drawings. Understanding that these
drawings depict only typical embodiments of the invention and are
not therefore to be considered limiting of its scope, the invention
will be described and explained with additional specificity and
detail through the use of the accompanying drawings in which:
[0036] FIG. 1 is a plan view of a Spinal Cord Modulation (SCM)
system constructed in accordance with one embodiment of the present
inventions;
[0037] FIG. 2 is a plan view of the SCM system of FIG. 1 in use
with a patient;
[0038] FIG. 3 is a profile view of an implantable pulse generator
(IPG) and percutaneous leads used in the SCM system of FIG. 1;
[0039] FIG. 4 is a plot of monophasic cathodic electrical
modulation energy;
[0040] FIG. 5a is a plot of biphasic electrical modulation energy
having a cathodic modulation pulse and an active charge recovery
pulse;
[0041] FIG. 5b is a plot of biphasic electrical modulation energy
having a cathodic modulation pulse and a passive charge recovery
pulse;
[0042] FIG. 6a is a timing diagram of a sub-threshold pulse train
delivered by the IPG of FIG. 3 to an electrode;
[0043] FIG. 6b is a timing diagram of a super-threshold pulse train
delivered by the IPG of FIG. 3 to an electrode;
[0044] FIG. 6c is a timing diagram of a sub-threshold pulse train
and a super-threshold pulse train delivered by the IPG of FIG. 3 to
different electrodes;
[0045] FIG. 6d is a timing diagram of a sub-threshold pulse train
and a super-threshold pulse train delivered by the IPG of FIG. 3
during two timing channels to two different electrodes;
[0046] FIG. 6e is a timing diagram of a pulse train with
alternating super-threshold and sub-threshold bursts delivered by
the IPG of FIG. 3;
[0047] FIG. 6f is a timing diagram of a bursted super-threshold
pulse train and a bursted sub-threshold pulse train delivered by
the IPG of FIG. 3 during two timing channels;
[0048] FIG. 7 is a flow diagram illustrating one method performed
by the IPG of FIG. 3 to remind a user to recharge the IPG;
[0049] FIG. 8 is front view of a remote control (RC) used in the
SCM system of FIG. 1;
[0050] FIG. 9 is a block diagram of the internal components of the
RC of FIG. 8;
[0051] FIG. 10 is a flow diagram illustrating one method performed
by the RC of FIG. 8 to calibrate the sub-threshold therapy provided
by the IPG of FIG. 3;
[0052] FIG. 11 is a block diagram of the internal components of a
clinician's programmer (CP) used in the SCM system of FIG. 1;
[0053] FIG. 12 is a plan view of a user interface of the CP of FIG.
11 for programming the IPG of FIG. 3 in a manual programming
mode;
[0054] FIG. 13 is a plan view of a user interface of the CP of FIG.
11 for programming the IPG of FIG. 3 in an electronic trolling
programming mode;
[0055] FIG. 14 is a plan view of a user interface of the CP of FIG.
11 for programming the IPG of FIG. 3 in a navigation programming
mode;
[0056] FIG. 15 is a plan view of a user interface of the CP of FIG.
11 for programming the IPG of FIG. 3 in an exploration programming
mode;
[0057] FIG. 16 is a plan view of a user interface of the CP of FIG.
11 for programming the IPG of FIG. 3 in a sub-threshold programming
mode;
[0058] FIG. 17 is a plan view of the user interface of FIG. 13,
particularly showing the expansion of the Advanced Tab into
resolution and focus controls; and
[0059] FIG. 18 is a flow diagram illustrating steps for using the
CP of FIG. 11 to program the IPG of FIG. 3 to provide sub-threshold
therapy to a patient to treat chronic pain.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0060] The description that follows relates to a spinal cord
modulation (SCM) system. However, it is to be understood that the
while the invention lends itself well to applications in SCM, the
invention, in its broadest aspects, may not be so limited. Rather,
the invention may be used with any type of implantable electrical
circuitry used to stimulate tissue. For example, the present
invention may be used as part of a pacemaker, a defibrillator, a
cochlear stimulator, a retinal stimulator, a stimulator configured
to produce coordinated limb movement, a cortical stimulator, a deep
brain stimulator, peripheral nerve stimulator, microstimulator, or
in any other neural stimulator configured to treat urinary
incontinence, sleep apnea, shoulder sublaxation, headache, etc.
[0061] Turning first to FIG. 1, an exemplary SCM system 10
generally includes a plurality (in this case, two) of implantable
neuromodulation leads 12, an implantable pulse generator (IPG) 14,
an external remote controller RC 16, a clinician's programmer (CP)
18, an external trial modulator (ETM) 20, and an external charger
22.
[0062] The IPG 14 is physically connected via one or more
percutaneous lead extensions 24 to the neuromodulation leads 12,
which carry a plurality of electrodes 26 arranged in an array. In
the illustrated embodiment, the neuromodulation leads 12 are
percutaneous leads, and to this end, the electrodes 26 are arranged
in-line along the neuromodulation leads 12. The number of
neuromodulation leads 12 illustrated is two, although any suitable
number of neuromodulation leads 12 can be provided, including only
one. Alternatively, a surgical paddle lead in can be used in place
of one or more of the percutaneous leads. As will be described in
further detail below, the IPG 14 includes pulse generation
circuitry that delivers electrical modulation energy in the form of
a pulsed electrical waveform (i.e., a temporal series of electrical
pulses) to the electrode array 26 in accordance with a set of
modulation parameters.
[0063] The ETM 20 may also be physically connected via the
percutaneous lead extensions 28 and external cable 30 to the
neuromodulation leads 12. The ETM 20, which has similar pulse
generation circuitry as the IPG 14, also delivers electrical
modulation energy in the form of a pulse electrical waveform to the
electrode array 26 accordance with a set of modulation parameters.
The major difference between the ETM 20 and the IPG 14 is that the
ETM 20 is a non-implantable device that is used on a trial basis
after the neuromodulation leads 12 have been implanted and prior to
implantation of the IPG 14, to test the responsiveness of the
modulation that is to be provided. Thus, any functions described
herein with respect to the IPG 14 can likewise be performed with
respect to the ETM 20. For purposes of brevity, the details of the
ETM 20 will not be described herein. Details of exemplary
embodiments of ETM are disclosed in U.S. Pat. No. 6,895,280, which
is expressly incorporated herein by reference.
[0064] The RC 16 may be used to telemetrically control the ETM 20
via a bi-directional RF communications link 32. Once the IPG 14 and
neuromodulation leads 12 are implanted, the RC 16 may be used to
telemetrically control the IPG 14 via a bi-directional RF
communications link 34. Such control allows the IPG 14 to be turned
on or off and to be programmed with different modulation parameter
sets. The IPG 14 may also be operated to modify the programmed
modulation parameters to actively control the characteristics of
the electrical modulation energy output by the IPG 14. As will be
described in further detail below, the CP 18 provides clinician
detailed modulation parameters for programming the IPG 14 and ETM
20 in the operating room and in follow-up sessions.
[0065] The CP 18 may perform this function by indirectly
communicating with the IPG 14 or ETM 20, through the RC 16, via an
IR communications link 36. Alternatively, the CP 18 may directly
communicate with the IPG 14 or ETM 20 via an RF communications link
(not shown). The clinician detailed modulation parameters provided
by the CP 18 are also used to program the RC 16, so that the
modulation parameters can be subsequently modified by operation of
the RC 16 in a stand-alone mode (i.e., without the assistance of
the CP 18).
[0066] The external charger 22 is a portable device used to
transcutaneously charge the IPG 14 via an inductive link 38. Once
the IPG 14 has been programmed, and its power source has been
charged by the external charger 22 or otherwise replenished, the
IPG 14 may function as programmed without the RC 16 or CP 18 being
present. For purposes of brevity, the details of the external
charger 22 will not be described herein. Details of exemplary
embodiments of the external charger are disclosed in U.S. Pat. No.
6,895,280, which is expressly incorporated herein by reference.
[0067] As shown in FIG. 2, the neuromodulation leads 12 are
implanted within the spinal column 42 of a patient 40. The
preferred placement of the neuromodulation leads 12 is adjacent,
i.e., resting upon, the spinal cord area to be modulated. Due to
the lack of space near the location where the neuromodulation leads
12 exit the spinal column 42, the IPG 14 is generally implanted in
a surgically-made pocket either in the abdomen or above the
buttocks. The IPG 14 may, of course, also be implanted in other
locations of the patient's body. The lead extension 24 facilitates
locating the IPG 14 away from the exit point of the neuromodulation
leads 12. As there shown, the CP 18 communicates with the IPG 14
via the RC 16.
[0068] Referring now to FIG. 3, the external features of the
neuromodulation leads 12 and the IPG 14 will be briefly described.
One of the neuromodulation leads 12a has eight electrodes 26
(labeled E1-E8), and the other neuromodulation lead 12b has eight
electrodes 26 (labeled E9-E16). The actual number and shape of
leads and electrodes will, of course, vary according to the
intended application. The IPG 14 comprises an outer case 44 for
housing the electronic and other components (described in further
detail below), and a connector 46 to which the proximal ends of the
neuromodulation leads 12 mates in a manner that electrically
couples the electrodes 26 to the electronics within the outer case
44. The outer case 44 is composed of an electrically conductive,
biocompatible material, such as titanium, and forms a hermetically
sealed compartment wherein the internal electronics are protected
from the body tissue and fluids. In some cases, the outer case 44
may serve as an electrode.
[0069] The IPG 14 comprises electronic components, such as a
controller/processor (e.g., a microcontroller) 39, memory 41, a
battery 43, telemetry circuitry 45, monitoring circuitry 47,
modulation output circuitry 49, and other suitable components known
to those skilled in the art. The microcontroller 39 executes a
suitable program stored in memory 41, for directing and controlling
the neuromodulation performed by IPG 14. Telemetry circuitry 45,
including an antenna (not shown), is configured for receiving
programming data (e.g., the operating program and/or modulation
parameters) from the RC 16 and/or CP 18 in an appropriate modulated
carrier signal, which the programming data is then stored in the
memory (not shown). The telemetry circuitry 45 is also configured
for transmitting status data to the RC 16 and/or CP 18 in an
appropriate modulated carrier signal. The battery 43, which may be
a rechargeable lithium-ion or lithium-ion polymer battery, provides
operating power to IPG 14. The monitoring circuitry 47 is
configured for monitoring the present capacity level of the battery
43.
[0070] The modulation output circuitry 49 provides electrical
modulation energy in the form of a pulsed electrical waveform via
electrical terminals (not shown) respectively to the electrodes 26
in accordance with a set of modulation parameters programmed into
the IPG 14. Such modulation parameters may comprise electrode
combinations, which define the electrodes that are activated as
anodes (positive), cathodes (negative), and turned off (zero),
percentage of modulation energy assigned to each electrode
(fractionalized electrode configurations), and electrical pulse
parameters, which define the pulse amplitude (measured in milliamps
or volts depending on whether the IPG 14 supplies constant current
or constant voltage to the electrode array 26), pulse width
(measured in microseconds), pulse rate (measured in pulses per
second), and burst rate (measured as the modulation on duration X
and modulation off duration Y).
[0071] Electrical modulation will occur between two (or more)
activated electrodes, one of which may be the IPG case 44.
Modulation energy may be transmitted to the tissue in a monopolar
or multipolar (e.g., bipolar, tripolar, etc.) fashion. Monopolar
modulation occurs when a selected one of the lead electrodes 26 is
activated along with the case of the IPG 14, so that modulation
energy is transmitted between the selected electrode 26 and case.
Bipolar modulation occurs when two of the lead electrodes 26 are
activated as anode and cathode, so that modulation energy is
transmitted between the selected electrodes 26. For example,
electrode E3 on the first lead 12a may be activated as an anode at
the same time that electrode E11 on the second lead 12b is
activated as a cathode. Tripolar modulation occurs when three of
the lead electrodes 26 are activated, two as anodes and the
remaining one as a cathode, or two as cathodes and the remaining
one as an anode. For example, electrodes E4 and E5 on the first
lead 12a may be activated as anodes at the same time that electrode
E12 on the second lead 12b is activated as a cathode.
[0072] Any of the electrodes E1-E16 and case electrode may be
assigned to up to k possible groups or timing "channels." In one
embodiment, k may equal four. The timing channel identifies which
electrodes are selected to synchronously source or sink current to
create an electric field in the tissue to be modulated. Amplitudes
and polarities of electrodes on a channel may vary. In particular,
the electrodes can be selected to be positive (sourcing current),
negative (sinking current), or off (no current) polarity in any of
the k timing channels.
[0073] The modulation energy may be delivered between a specified
group of electrodes as monophasic electrical energy or multiphasic
electrical energy. As illustrated in FIG. 4, monophasic electrical
energy takes the form of an electrical pulse train that includes
either all negative pulses (cathodic), or alternatively all
positive pulses (anodic).
[0074] Multiphasic electrical energy includes a series of pulses
that alternate between positive and negative. For example, as
illustrated in FIGS. 5a and 5b, multiphasic electrical energy may
include a series of biphasic pulses, with each biphasic pulse
including a cathodic (negative) modulation phase and an anodic
(positive) charge recovery pulse phase that is generated after the
modulation phase to prevent direct current charge transfer through
the tissue, thereby avoiding electrode degradation and cell trauma.
That is, charge is conveyed through the electrode-tissue interface
via current at an electrode during a modulation period (the length
of the modulation phase), and then pulled back off the
electrode-tissue interface via an oppositely polarized current at
the same electrode during a recharge period (the length of the
charge recovery phase).
[0075] The second phase may be an active charge recovery phase
(FIG. 5a), wherein electrical current is actively conveyed through
the electrode via current or voltage sources, or the second phase
may be a passive charge recovery phase (FIG. 5b), wherein
electrical current is passively conveyed through the electrode via
redistribution of the charge flowing from coupling capacitances
present in the circuit. Using active recharge, as opposed to
passive recharge, allows faster recharge, while avoiding the charge
imbalance that could otherwise occur. Another electrical pulse
parameter in the form of an interphase can define the time period
between the pulses of the biphasic pulse (measured in
microseconds). Although the modulation and charge recovery phases
of the biphasic pulses illustrated in FIGS. 5a and 5b are cathodic
and anodic, respectively, it should be appreciated that the
modulation and charge recovery pulses of biphasic pulses may be
anodic and cathodic, respectively, depending upon the desired
therapeutic result.
[0076] In the illustrated embodiment, IPG 14 can individually
control the magnitude of electrical current flowing through each of
the electrodes. In this case, it is preferred to have a current
generator, wherein individual current-regulated amplitudes from
independent current sources for each electrode may be selectively
generated. Although this system is optimal to take advantage of the
invention, other neuromodulators that may be used with the
invention include neuromodulators having voltage regulated outputs.
While individually programmable electrode amplitudes are optimal to
achieve fine control, a single output source switched across
electrodes may also be used, although with less fine control in
programming. Mixed current and voltage regulated devices may also
be used with the invention. Further details discussing the detailed
structure and function of IPGs are described more fully in U.S.
Pat. Nos. 6,516,227 and 6,993,384, which are expressly incorporated
herein by reference.
[0077] It should be noted that rather than an IPG, the SCM system
10 may alternatively utilize an implantable receiver-modulator (not
shown) connected to the neuromodulation leads 12. In this case, the
power source, e.g., a battery, for powering the implanted receiver,
as well as control circuitry to command the receiver-modulator,
will be contained in an external controller inductively coupled to
the receiver-modulator via an electromagnetic link. Data/power
signals are transcutaneously coupled from a cable-connected
transmission coil placed over the implanted receiver-modulator. The
implanted receiver-modulator receives the signal and generates the
modulation in accordance with the control signals.
[0078] More significant to some of the present inventions, the IPG
14 may be operated in either a super-threshold delivery mode, a
sub-threshold delivery mode, and a hybrid delivery mode.
[0079] While in the super-threshold delivery mode, the IPG 14 is
configured for delivering electrical modulation energy that
provides super-threshold therapy to the patient (in this case,
causes the patient to perceive paresthesia). For example, as shown
in FIG. 6a, an exemplary super-threshold pulse train may be
delivered at a relatively high pulse amplitude (e.g., 5 ma), a
relatively low pulse rate (e.g., less than 1500 Hz, preferably less
than 500 Hz), and a relatively high pulse width (e.g., greater than
100 .mu.s, preferably greater than 200 .mu.s). Although the
super-threshold pulse train is illustrated as a monophasic cathodic
pulse train, it should be appreciated that the super-threshold
pulse train is preferably biphasic.
[0080] While in the sub-threshold delivery mode, the IPG 14 is
configured for delivering electrical modulation energy that
provides sub-threshold therapy to the patient (in this case, does
not cause the patient to perceive paresthesia). For example, as
shown in FIG. 6b, an exemplary sub-threshold pulse train may be
delivered at a relatively low pulse amplitude (e.g., 2.5 ma), a
relatively high pulse rate (e.g., greater than 1500 Hz, preferably
greater than 2500 Hz), and a relatively low pulse width (e.g., less
than 100 .mu.s, preferably less than 50 .mu.s). Although the
sub-threshold pulse train is illustrated as a monophasic cathodic
pulse train, it should be appreciated that the sub-threshold pulse
train is preferably biphasic with an active charge recovery pulse,
as will be described in further detail below.
[0081] While in the hybrid delivery mode, the IPG 14 is configured
for delivered electrical modulation energy that both provides
super-threshold therapy and sub-threshold therapy to the patient.
In one embodiment, the super-threshold modulation energy and
sub-threshold energy is simultaneously delivered to different sets
of electrodes within a single timing channel. Preferably, the
different sets of electrodes have no common electrode, so that
there is no conflict between the different energies. For example,
as shown in FIG. 6c, an exemplary super-threshold pulse train may
be delivered to electrode E1, while an exemplary sub-threshold
pulse train may be delivered to electrode E2. Because the
super-threshold pulse train and the sub-threshold pulse train are
delivered to different electrodes, the pulses of the respective
pulse trains may overlap in time.
[0082] In another embodiment, the super-threshold modulation energy
and sub-threshold therapy is concurrently delivered to a common set
of electrodes within respective timing channels, which are combined
into a modulation program. For example, as shown in FIG. 6d, an
exemplary super-threshold pulse train may be delivered to electrode
E1 in timing channel A (coverage area A), and a sub-threshold pulse
train may be delivered to electrode E1 in timing channel B
(coverage area B), such that the pulses of the respective
super-threshold pulse train and sub-threshold pulse train are
interleaved with each other without temporal overlap.
[0083] In still another embodiment, the super-threshold modulation
energy and sub-threshold modulation energy can be respectively
bursted on and off within a single timing channel or multiple
timing channels. For example, as shown in FIG. 6e, an exemplary
super-threshold pulse train may be repeatedly bursted on and off,
with the exemplary sub-threshold pulse train being bursted on when
the super-threshold pulse train has been bursted off, and bursted
off when the super-threshold pulse train has been bursted on. Thus,
the super-threshold pulse train and sub-threshold pulse train will
be alternately bursted on and off (i.e., the super-threshold pulse
train will be bursted on and then off, the sub-threshold pulse
train will be bursted on and then off, the super-threshold pulse
train will then be bursted on and then off, the sub-threshold pulse
train will be bursted on and then off, and so on). Alternatively,
an exemplary super-threshold pulse train may be repeatedly bursted
on and off in a first timing channel A (coverage area A), and an
exemplary super-threshold pulse train may be repeatedly bursted on
and off in a second timing channel B (coverage area B), such that
an alternating super-threshold pulse train and sub-threshold pulse
train results, as illustrated in FIG. 6f. In either event, the
bursts of the super-threshold pulse train and the bursts of the
sub-threshold pulse train will be interleaved with each other.
[0084] In any event, the delivery of modulation energy during the
hybrid delivery mode exploits the advantages of both the
super-threshold therapy and the sub-threshold therapy. For example,
because they rely on different mechanisms for pain relief, the
delivery of both super-threshold modulation energy and
sub-threshold modulation energy to the same general region of the
patient may provide therapy that is more efficacious then either
can do alone.
[0085] Also significant to some of the present inventions, assuming
that the IPG 14 is currently operating in the sub-threshold
delivery mode, it alerts the patient when the battery capacity
level of the IPG 14 is about to be depleted. In particular, the
microcontroller 39 is configured for comparing the battery capacity
level obtained from the monitoring circuitry 47 to a threshold
previously stored within the memory 41, and switching the
modulation output circuitry 49 from the sub-threshold delivery mode
to the super-threshold (or alternatively, the hybrid) delivery mode
if the battery capacity level is less than the threshold, thereby
alerting the user to recharge the IPG 14.
[0086] As one example, the threshold may be 50% of the full
capacity of the battery 43. As another example, the threshold may
be 25% of the full capacity of the battery 43. Ultimately, the
value of the threshold will be selected to trade-off between
providing maximum use from the battery prior to recharge, and
allowing the user sufficient time to recharge the IPG 14 before the
battery is fully depleted. The microcontroller 39 is configured for
automatically switching the modulation output circuitry 49 from the
sub-threshold mode to the super-threshold delivery mode (or
alternatively the hybrid delivery mode) upon determination that the
battery capacity level falls below the threshold. In the case where
the battery capacity level does not fall below the threshold, the
microcontroller 39 is configured for maintaining the modulation
output circuitry 49 within the sub-threshold delivery mode.
[0087] It should be appreciated that although the IPG 14 is
described as being the device that performs the controlling and
processing functions for alerting the user that it needs to be
recharged, the controlling and processing functions can be
implemented in an external control device (e.g., the RC 16), which
can place the IPG 14 between the super-threshold delivery mode,
sub-threshold delivery mode, and hybrid delivery mode, as will be
described in further detail below.
[0088] Referring now to FIG. 7, one of method of alerting the user
to recharge the IPG 14 will be described. First, the IPG 14
delivers sub-threshold electrical modulation energy to the
electrode array 26 implanted within spinal cord tissue, thereby
providing sub-threshold therapy to the patient (step 200). In the
instant case, paresthesia will not perceived by the patient in the
body region corresponding to the pain in response to the delivery
of the sub-threshold modulation energy to the electrode array 26.
Next, the battery capacity level of the IPG 14 is measured (step
202), and compared to the predetermined threshold (204). If the
battery capacity level is not less than the threshold, the IPG 14
continues to deliver the sub-threshold electrical modulation energy
to the electrode 26, thereby maintaining sub-threshold therapy to
the patient (step 200). If the battery capacity level is less the
threshold, super-threshold electrical modulation energy is
delivered from the IPG 14 to the spinal cord tissue if the battery
capacity level is below the threshold, thereby providing
super-threshold therapy to the patient (step 206). In the instant
case, paresthesia will be perceived by the patient in the body
region corresponding to the pain in response to the delivery of the
sub-threshold modulation energy to the electrode array 26, thereby
alerting the patient that the IPG 14 needs to be recharged. The
external charger 22 is then used to conventionally recharge the IPG
14 (step 208).
[0089] Referring now to FIG. 8, one exemplary embodiment of an RC
16 will now be described. As previously discussed, the RC 16 is
capable of communicating with the IPG 14, CP 18, or ETS 20. The RC
16 comprises a casing 50, which houses internal componentry
(including a printed circuit board (PCB)), and a lighted display
screen 52 and button pad 54 carried by the exterior of the casing
50. In the illustrated embodiment, the display screen 52 is a
lighted flat panel display screen, and the button pad 54 comprises
a membrane switch with metal domes positioned over a flex circuit,
and a keypad connector connected directly to a PCB. In an optional
embodiment, the display screen 52 has touchscreen capabilities. The
button pad 54 includes a multitude of buttons 56, 58, 60, and 62,
which allow the IPG 14 to be turned ON and OFF, provide for the
adjustment or setting of modulation parameters within the IPG 14,
and provide for selection between screens.
[0090] In the illustrated embodiment, the button 56 serves as an
ON/OFF button that can be actuated to turn the IPG 14 ON and OFF.
The button 58 serves as a select button that can be actuated to
switch the RC 16 between screen displays and/or parameters. The
buttons 60 and 62 serve as up/down buttons that can be actuated to
increment or decrement any of modulation parameters of the pulsed
electrical train generated by the IPG 14, including pulse
amplitude, pulse width, and pulse rate. For example, the selection
button 58 can be actuated to place the RC 16 in a "Pulse Amplitude
Adjustment Mode," during which the pulse amplitude can be adjusted
via the up/down buttons 60, 62, a "Pulse width Adjustment Mode,"
during which the pulse width can be adjusted via the up/down
buttons 60, 62, and a "Pulse Rate Adjustment Mode," during which
the pulse rate can be adjusted via the up/down buttons 60, 62.
Alternatively, dedicated up/down buttons can be provided for each
modulation parameter. Rather than using up/down buttons, any other
type of actuator, such as a dial, slider bar, or keypad, can be
used to increment or decrement the modulation parameters.
[0091] Referring to FIG. 9, the internal components of an exemplary
RC 16 will now be described. The RC 16 generally includes a
controller/processor 64 (e.g., a microcontroller), memory 66 that
stores an operating program for execution by the
controller/processor 64, as well as modulation parameter sets;
input/output circuitry, and in particular, telemetry circuitry 68
for outputting modulation parameters to the IPG 14 or otherwise
directing the IPG 14 to deliver modulation energy in accordance
with the modulation parameters, and receiving status information
from the IPG 14; and input/output circuitry 70 for receiving
modulation control signals from the button pad 54 or other control
elements and transmitting status information to the display screen
52 (shown in FIG. 8). Further details of the functionality and
internal componentry of the RC 16 are disclosed in U.S. Pat. No.
6,895,280, which has previously been incorporated herein by
reference.
[0092] More significant to the present inventions, to allow the
user to easily and quickly select between the different modes, the
RC 16 comprises a modulation selection control element 65, which in
the illustrated embodiment, takes the form of a button. The
modulation selection control element 65 may be repeatedly actuated
to toggle the IPG 14 between the super-threshold, sub-threshold,
and hybrid delivery modes. For example, the modulation selection
control element 65 may be actuated once to switch the IPG 14 from
the super-threshold delivery mode to the sub-threshold delivery
mode, actuated once again to switch the IPG 14 from the
sub-threshold delivery mode to the hybrid delivery mode, actuated
once again to switch the IPG 14 from the hybrid delivery mode back
to the super-threshold delivery mode, and so forth. Of course, the
order of the mode selection can be changed. For example, the
modulation selection control element 65 may be actuated once to
switch the IPG 14 from the sub-threshold delivery mode to the
super-threshold delivery mode, actuated once again to switch the
IPG 14 from the super-threshold delivery mode to the hybrid
delivery mode, actuated once again to switch the IPG 14 from the
hybrid delivery mode back to the sub-threshold delivery mode, and
so forth. In any event, each of the modulation delivery modes can
be selected by toggling the modulation selection control element
65.
[0093] The different modulation programs that are utilized by the
IPG 14 when operating in the different delivery modes may be
generated in any one of a variety of manners. For example, if the
IPG 14 and/or RC 16 are pre-programmed via the CP 18 (described in
further detail below) with a pre-existing super-threshold
modulation program, a pre-existing sub-threshold modulation
program, and a pre-existing hybrid modulation program, the RC 16
simply selects one of these pre-existing modulation programs in
response to the actuation of the modulation selection control
element 65. In this case, the RC 16 may identify which of the
pre-existing modulation programs correspond to the respective
super-threshold, sub-threshold, and hybrid programs based on the
characteristics of the modulation parameter set or sets defined by
these programs, or the user may identify and label each
pre-existing modulation program as either a super-threshold,
sub-threshold, or hybrid modulation program when generating these
modulation programs with the CP 18.
[0094] In the case where a pre-existing modulation program does not
exist for one or more of the super-threshold, sub-threshold, and
hybrid delivery modes, the RC 16, in response to actuation of
either the modulation selection control element 65 or a different
control element, may generate a new modulation program from one or
more of the pre-existing modulation programs.
[0095] In the case where only a super-threshold modulation program
exists, the RC 16 may quickly derive a sub-threshold modulation
program from the pre-existing super-threshold modulation program.
In particular, the RC 16 may substitute one or more of the
electrical pulse parameter values (pulse amplitude, pulse rate,
pulse width) of the pre-existing super-threshold modulation program
with electrical pulse parameter values that are consistent with
sub-threshold therapy. For example, the RC 16 may compute a new
pulse amplitude value as function of the super-threshold pulse
amplitude value. The computed function may be, e.g., a percentage
(preferably in the range of 30%-70%, and more preferably in the
range of 40%-60%) of the super-threshold pulse amplitude value, or
a difference between the super-threshold pulse amplitude value and
a constant (e.g., 1 mA). The RC 16 may select a relatively high
pulse rate value (e.g., greater than 1500 Hz) as new pulse rate
value and/or a relatively low pulse width value (e.g., less than
100 .mu.s) for the new sub-threshold modulation program. The RC 16
may also compute a new fractionalized electrode combination from
the fractionalized electrode combination defined in the
pre-existing super-threshold modulation program (e.g., by
transforming from anodic to cathodic modulation, or vice versa, or
transforming from monopolar modulation to multipolar modulation, or
vice versa). However, the locus of the electrical field that would
result from delivering modulation energy in accordance with the
pre-existing super-threshold program should be maintained in the
new sub-threshold modulation program. As described in further
detail below with respect to the CP 18, this can be accomplished
with the use of virtual target poles.
[0096] In the case where only a sub-threshold modulation program
exists, the RC 16 may quickly derive a super-threshold modulation
program from the pre-existing sub-threshold modulation program. In
particular, the RC 16 may substitute one or more of the electrical
pulse parameters values (pulse amplitude, pulse rate, pulse width)
of the pre-existing sub-threshold modulation program with
electrical pulse parameter values that are consistent with
super-threshold therapy. For example, the RC 16 may compute a new
pulse amplitude value as function of the super-threshold pulse
amplitude value. The computed function may be, e.g., a percentage
(preferably in the range of 150% to 300%, and more preferably in
the range of 175%-250%) of the sub-threshold pulse amplitude value,
or a summation of the sub-threshold pulse amplitude value and a
constant (e.g., 1 mA). The RC 16 may select a relatively low pulse
rate value (e.g., less than 1500 Hz) as new pulse rate value and/or
a relatively high pulse width value (e.g., greater than 100 .mu.s)
for the new sub-threshold modulation program. The RC 16 may also
compute a new fractionalized electrode combination from the
fractionalized electrode combination defined in the pre-existing
sub-threshold modulation program (e.g., by transforming from anodic
to cathodic modulation, or vice versa, or transforming from
monopolar modulation to multipolar modulation, or vice versa).
However, the locus of the electrical field that would result from
delivering modulation energy in accordance with the pre-existing
sub-threshold program should be maintained in the new
super-threshold modulation program. As described in further detail
below with respect to the CP 18, this can be accomplished with the
use of virtual target poles.
[0097] In the case where only a hybrid modulation program exists,
the RC 16 can simply copy the modulation parameters of
super-threshold component of the hybrid modulation program to a new
super-threshold modulation program (to the extent that one is
needed), and/or copy the modulation parameters of the sub-threshold
component of the hybrid modulation program to a new sub-threshold
modulation program (to the extent that one is needed). In the case
where both the super-threshold program and the sub-threshold
program exist, the RC 16 can combine the modulation parameters of
these programs together to define a new hybrid modulation program
(to the extent that one is needed). Or, if only one of the
super-threshold modulation program and a sub-threshold modulation
program exists, it and a modulation program derived from the other
of the super-threshold modulation program and sub-threshold
modulation program, and combined into the new hybrid modulation
program.
[0098] Also significant to some of the present inventions, in
response to a particular event, the RC 16, assuming that the IPG 14
is currently programmed to deliver sub-threshold therapy to the
patient (e.g., a sub-threshold modulation program or a hybrid
modulation program), initiates calibration of the sub-threshold
therapy that may have fallen outside of the therapeutic range due
to the migration of the modulation lead(s) 12 relative to a target
tissue site in the patient. Migration of the modulation lead(s) 12
may alter the coupling efficiency between the modulation lead(s) 12
and the target tissue site. A decreased coupling efficiency may
cause the sub-threshold therapy to fall below the therapeutic range
and result in ineffective therapy, whereas an increased coupling
efficiency may cause the sub-threshold therapy to rise above the
therapeutic range and result in the perception of paresthesia or
otherwise inefficient energy consumption. The particular event that
triggers calibration of the sub-threshold therapy may be a user
actuation of a control element located on the RC 16 (e.g., one of
the buttons on the button pad 54 or a dedicated button), a sensor
signal indicating that one or more of the neuromodulation leads 12
has migrated relative to a target site in the patient, or a
temporal occurrence, such as an elapsed time from a previous
calibration procedure, a time of day, day of the week, etc.).
[0099] Once the sub-threshold calibration is initiated, the RC 16
is configured for directing the IPG 14 to deliver the modulation
energy to the electrodes 26 at incrementally increasing amplitude
values (e.g., at a 0.1 mA step size). The RC 16 may be configured
for automatically incrementally increasing the amplitude of the
electrical pulse train delivered by the IPG 14 without further user
intervention or may be configured for incrementally increasing the
amplitude of the electrical pulse train delivered by the IPG 14
each time the user actuates a control element, such as the up
button 60. Preferably, the other modulation parameters, such as the
electrode combination, pulse rate, and pulse width are not altered
during the incremental increase of the amplitude. Thus, the only
modulation parameter of the sub-threshold modulation program that
is altered is the pulse amplitude.
[0100] The RC 16 is configured for prompting the user via the
display 52 or speaker (not shown) to actuate a control element,
such as a specified button on the button pad 54 or another
dedicated button (not shown), once paresthesia is perceived by the
patient. In response to this user input, the RC 16 is configured
for automatically computing a decreased amplitude value as a
function of the last incrementally increased amplitude value that
caused the patient to perceive paresthesia, and modifying the
sub-threshold modulation program stored in the IPG 14, such that
the modulation energy is delivered to the electrodes 26 in
accordance with this modified modulation program at this computed
amplitude value. Alternatively, rather than relying on user input,
the RC 16 may be configured for automatically computing the
decreased amplitude value in response to a sensed physiological
parameter indicative of super-threshold stimulation of the neural
tissue (e.g., evoked compound action potentials (eCAPs) sensed by
the IPG 14 at one or more electrodes 26 as a result of the delivery
of the modulation energy). Further details on eCAPs are disclosed
in U.S. Provisional Patent Application Ser. No. 61/768,295,
entitled "Neurostimulation system and method for automatically
adjusting stimulation and reducing energy requirements using evoked
action potential," which is expressly incorporated herein by
reference.
[0101] In any event, the function of the last incrementally
increased amplitude value is designed to ensure that the modulation
energy subsequently delivered to the patient at the computed
amplitude value falls within the sub-threshold therapy range. For
example, the computed function may be a percentage (preferably in
the range of 30%-70%, and more preferably in the range of 40%-60%)
of the last incrementally increased amplitude value. As another
example, the computed function may a difference between the last
incrementally increased amplitude value and a constant (e.g., 1
mA).
[0102] It should be appreciated that if calibration is initiated
when the IPG 14 is being operated in the hybrid delivery mode such
that the delivered electrical modulation energy comprises both
super-threshold electrical pulse train(s) and sub-threshold
electrical pulse train(s), the super-threshold electrical pulse
train (or trains) is automatically suspended temporarily such that
calibration is conducted only based on the remaining sub-threshold
electrical pulse train. For example, referring back to the hybrid
delivery mode illustrated in FIG. 6c, when calibration is
initiated, delivery of the super-threshold pulse train to electrode
E1 is stopped, and the sub-threshold pulse train is delivered to
electrode E2 at incrementally increasing amplitude values until the
perception threshold is determined and a decreased amplitude is
computed based on the perception threshold as the sub-threshold
amplitude value, as described above.
[0103] In another example, referring back to FIG. 6d, when
calibration is initiated, delivery of the super-threshold pulse
train to electrode E1 is stopped, and the calibration process is
continued using the sub-threshold pulse train delivered to
electrode E1. Referring to FIG. 6e, when calibration is initiated,
the illustrated super-threshold bursts are stopped, such that the
calibration process is continued only based on the sub-threshold
bursts of the hybrid modulation program. Referring to FIG. 6f, when
calibration is initiated, the super-threshold pulse train of timing
channel A is stopped, such that the calibration process is
continued only based on the sub-threshold pulse train of timing
channel B.
[0104] Once the calibration process is completed and the
sub-threshold amplitude is computed, as discussed above, the hybrid
delivery mode is resumed such that electrical energy is delivered
in accordance to both the original super-threshold pulse train and
the sub-threshold pulse train having the calibrated sub-threshold
amplitude.
[0105] It should also be appreciated that, in a preferred
embodiment, the RC 16 may be configured for storing the computed
sub-threshold amplitude resulting from each calibration process.
This is significant because it provides the user important metrics
regarding the sub-threshold therapy that may allow the user to
modify modulation parameters of the sub-threshold pulse train more
intelligently at a later programming session.
[0106] Referring now to FIG. 10, one method of using the RC 16 to
calibrate the sub-threshold therapy will now be described. First,
the RC 16 is operated to direct the IPG 14 to deliver electrical
modulation energy to a target tissue site of the patient in
accordance with a sub-threshold modulation program stored within
the IPG 14, thereby providing therapy to the patient without the
perception of paresthesia (step 220). Next, a calibration
triggering event occurs (step 222). Such triggering input can be a
user input, a detected migration of one or more of the modulation
leads relative to the target tissue site, or a temporal occurrence.
Next, it is determined whether the patient perceives paresthesia in
the region of pain as a result of the delivery of the modulation
energy in accordance with the unmodified sub-threshold modulation
program (step 204).
[0107] If the patient does not currently perceive paresthesia in
the region of pain at step 204, the RC 16 increases the programmed
amplitude value by a step size, and directs the IPG 14 to deliver
electrical modulation energy to the patient at the increased
amplitude value (step 226). Next, it is determined whether the
patient perceives paresthesia in the region of pain as a result of
the delivery of the modulation energy at the increased amplitude
value (step 228). If the patient does not perceive paresthesia in
the region of pain at step 228, the RC 16 returns to step 226 to
again increase the programmed amplitude value by a step size, and
direct the IPG 14 to deliver electrical modulation energy to the
patient at the increased amplitude value.
[0108] If the patient perceived paresthesia in the region of pain
at step 224 or step 228, the RC 16 computes a decreased amplitude
value as a function of the last incrementally increased amplitude
value at which the delivered electrical modulation caused the
patient to perceive the paresthesia in the region of pain (step
230). Such computation can be performed in response to a user
input, or alternatively, sensing a physiological parameter
indicating that the patient is perceiving paresthesia. As described
above, such function can be, e.g., a percentage of the last
incrementally increased amplitude value or a difference between the
last incrementally increased amplitude value and a constant. The RC
16 then modifies the sub-threshold modulation program with the
computed amplitude value (step 232), and returns to step 220 to
direct the IPG 14 to deliver electrical modulation energy to a
target tissue site of the patient in accordance with a modified
sub-threshold modulation program, thereby providing therapy to the
patient without the perception of paresthesia.
[0109] Thus, it can be appreciated that the sub-threshold
calibration technique ensures that any intended sub-threshold
therapy remains within an efficacious and energy efficient
therapeutic window that may otherwise fall outside of this window
due to environmental changes, such as lead migration or even
posture changes or patient activity. Although the sub-threshold
calibration technique has been described with respect to
sub-threshold therapy designed to treat chronic pain, it should be
appreciated that this calibration technique can be utilized to
calibrate any sub-threshold therapy provided to treat a patient
with any disorder where the perception of paresthesia may be
indicative of efficacious treatment of the disorder. Furthermore,
although the sub-threshold calibration technique has been described
as being performed in the RC 16, or should be appreciated that this
technique could be performed in the CP 18, or even the IPG 14. If
performed by the IPG 14, any user input necessary to implement the
sub-threshold calibration technique can be communicated from the RC
16 to the IPG 14 via the telemetry circuitry 68. In the case, where
no user input is necessary, e.g., if super-threshold stimulation is
detected at one or more of the electrodes 26 in lieu of patient
feedback of paresthesia, the IPG 14 may implement the sub-threshold
calibration technique without any communication with the RC 16.
[0110] As briefly discussed above, the CP 18 greatly simplifies the
programming of multiple electrode configurations, allowing the user
(e.g., the physician or clinician) to readily determine the desired
modulation parameters to be programmed into the IPG 14, as well as
the RC 16. Thus, modification of the modulation parameters in the
programmable memory of the IPG 14 after implantation is performed
by a user using the CP 18, which can directly communicate with the
IPG 14 or indirectly communicate with the IPG 14 via the RC 16.
That is, the CP 18 can be used by the user to modify operating
parameters of the electrode array 26 near the spinal cord.
[0111] As shown in FIG. 2, the overall appearance of the CP 18 is
that of a laptop personal computer (PC), and in fact, may be
implemented using a PC that has been appropriately configured to
include a directional-programming device and programmed to perform
the functions described herein. Alternatively, the CP 18 may take
the form of a mini-computer, personal digital assistant (PDA),
etc., or even a remote control (RC) with expanded functionality.
Thus, the programming methodologies can be performed by executing
software instructions contained within the CP 18. Alternatively,
such programming methodologies can be performed using firmware or
hardware. In any event, the CP 18 may actively control the
characteristics of the electrical stimulation generated by the IPG
14 to allow the optimum modulation parameters to be determined
based on patient feedback and for subsequently programming the IPG
14 with the optimum modulation parameter.
[0112] To allow the user to perform these functions, the CP 18
includes a user input device (e.g., a mouse 72 and a keyboard 74),
and a programming display screen 76 housed in a case 78. It is to
be understood that in addition to, or in lieu of, the mouse 72,
other directional programming devices may be used, such as a
trackball, touchpad, joystick, or directional keys included as part
of the keys associated with the keyboard 74.
[0113] In the illustrated embodiment described below, the display
screen 76 takes the form of a conventional screen, in which case, a
virtual pointing device, such as a cursor controlled by a mouse,
joy stick, trackball, etc., can be used to manipulate graphical
objects on the display screen 76. In alternative embodiments, the
display screen 76 takes the form of a digitizer touch screen, which
may either passive or active. If passive, the display screen 76
includes detection circuitry (not shown) that recognizes pressure
or a change in an electrical current when a passive device, such as
a finger or non-electronic stylus, contacts the screen. If active,
the display screen 76 includes detection circuitry that recognizes
a signal transmitted by an electronic pen or stylus. In either
case, detection circuitry is capable of detecting when a physical
pointing device (e.g., a finger, a non-electronic stylus, or an
electronic stylus) is in close proximity to the screen, whether it
be making physical contact between the pointing device and the
screen or bringing the pointing device in proximity to the screen
within a predetermined distance, as well as detecting the location
of the screen in which the physical pointing device is in close
proximity. When the pointing device touches or otherwise is in
close proximity to the screen, the graphical object on the screen
adjacent to the touch point is "locked" for manipulation, and when
the pointing device is moved away from the screen the previously
locked object is unlocked. Further details discussing the use of a
digitizer screen for programming are set forth in U.S. Provisional
Patent Application Ser. No. 61/561,760, entitled "Technique for
Linking Electrodes Together during Programming of Neurostimulation
System," which is expressly incorporated herein by reference.
[0114] As shown in FIG. 11, the CP 18 includes a
controller/processor 80 (e.g., a central processor unit (CPU)) and
memory 82 that stores a modulation programming package 84, which
can be executed by the controller/processor 80 to allow the user to
program the IPG 14, and RC 16. The CP 18 further includes an output
circuitry 86 for downloading modulation parameters to the IPG 14
and RC 16 and for uploading modulation parameters already stored in
the memory 66 of the RC 16 or memory of the IPG 14. In addition,
the CP 18 further includes a user input device 88 (such as the
mouse 72 or keyboard 74) to provide user commands. Notably, while
the controller/processor 80 is shown in FIG. 11 as a single device,
the processing functions and controlling functions can be performed
by a separate controller and processor. Thus, it can be appreciated
that the controlling functions described below as being performed
by the CP 18 can be performed by a controller, and the processing
functions described below as being performed by the CP 18 can be
performed by the processor.
[0115] Execution of the programming package 84 by the
controller/processor 80 provides a multitude of display screens
(not shown) that can be navigated through via use of the mouse 72.
These display screens allow the clinician to, among other
functions, to select or enter patient profile information (e.g.,
name, birth date, patient identification, physician, diagnosis, and
address), enter procedure information (e.g., programming/follow-up,
implant trial system, implant IPG, implant IPG and lead(s), replace
IPG, replace IPG and leads, replace or revise leads, explant,
etc.), generate a pain map of the patient, define the configuration
and orientation of the leads, initiate and control the electrical
modulation energy output by the neuromodulation leads 12, and
select and program the IPG 14 with modulation parameters in both a
surgical setting and a clinical setting. Further details discussing
the above-described CP functions are disclosed in U.S. patent
application Ser. No. 12/501,282, entitled "System and Method for
Converting Tissue Stimulation Programs in a Format Usable by an
Electrical Current Steering Navigator," and U.S. patent application
Ser. No. 12/614,942, entitled "System and Method for Determining
Appropriate Steering Tables for Distributing Modulation energy
Among Multiple Neuromodulation Electrodes," which are expressly
incorporated herein by reference. Execution of the programming
package 84 provides a user interface that conveniently allows a
user to program the IPG 14.
[0116] Referring first to FIG. 12, a graphical user interface (GUI)
100 that can be generated by the CP 18 to allow a user to program
the IPG 14 will be described. In the illustrated embodiment, the
GUI 100 comprises three panels: a program selection panel 102, a
lead display panel 104, and a modulation parameter adjustment panel
106. Some embodiments of the GUI 100 may allow for closing and
expanding one or both of the lead display panel 102 and the
parameter adjustment panel 106 by clicking on the tab 108 (to show
or hide the parameter adjustment panel 106) or the tab 110 (to show
or hide the full view of both the lead selection panel 104 and the
parameter adjustment panel 106).
[0117] The program selection panel 102 provides information about
modulation programs and coverage areas that have been, or may be,
defined for the IPG 14. In particular, the program selection panel
102 includes a carousel 112 on which a plurality of modulation
programs 114 (in this case, up to sixteen) may be displayed and
selected. The program selection panel 102 further includes a
selected program status field 116 indicating the number of the
modulation program 114 that is currently selected (any number from
"1" to "16"). In the illustrated embodiment, program 1 is the only
one currently selected, as indicated by the number "1" in the field
116. The program selection panel 102 further comprises a name field
118 in which a user may associate a unique name to the currently
selected modulation program 114. In the illustrated embodiment,
currently selected program 1 has been called "lower back," thereby
identifying program 1 as being the modulation program 114 designed
to provide therapy for lower back pain.
[0118] The program selection panel 102 further comprises a
plurality of coverage areas 120 (in this case, up to four) with
which a plurality of modulation parameter sets can respectively be
associated to create the currently selected modulation program 114
(in this case, program 1). Each coverage area 120 that has been
defined includes a designation field 122 (one of letters "A"-"D"),
and an electrical pulse parameter field 124 displaying the
electrical pulse parameters, and specifically, the pulse amplitude,
pulse width, and pulse rate, of the modulation parameter set
associated with the that coverage area. In this example, only
coverage area A is defined for program 1, as indicated by the "A"
in the designation field 122. The electrical pulse parameter field
124 indicates that a pulse amplitude of 5 mA, a pulse width of 210
.mu.s, and a pulse rate of 40 Hz has been associated with coverage
area A.
[0119] Each of the defined coverage areas 120 also includes a
selection icon 126 that can be alternately actuated to activate or
deactivate the respective coverage area 120. When a coverage area
is activated, an electrical pulse train is delivered from the IPG
14 to the electrode array 26 in accordance with the modulation
parameter set associated with that coverage area. Notably, multiple
ones of the coverage areas 120 can be simultaneously activated by
actuating the selection icons 126 for the respective coverage
areas. In this case, multiple electrical pulse trains are
concurrently delivered from the IPG 14 to the electrode array 26
during timing channels in an interleaved fashion in accordance with
the respective modulation parameter sets associated with the
coverage areas 120. Thus, each coverage area 120 corresponds to a
timing channel.
[0120] To the extent that any of the coverage areas 120 have not
been defined (in this case, three have not been defined), they
include text "click to add another program area"), indicating that
any of these remaining coverage areas 120 can be selected for
association with a modulation parameter set. Once selected, the
coverage area 120 will be populated with the designation field 122,
electrical pulse parameter field 124, and selection icon 126.
[0121] The lead display panel 104 includes graphical leads 128,
which are illustrated with eight graphical electrodes 130 each
(labeled electrodes E1-E8 for the first lead 128 and electrodes
E9-E16 for second lead 128). The lead display panel 104 also
includes a graphical case 132 representing the case 44 of the IPG
14. The lead display panel 104 further includes lead group
selection tabs 134 (in this case, four), any of which can be
actuated to select one of four groups of graphical leads 128. In
this case, the first lead group selection tab 134 has been
actuated, thereby displaying the two graphical leads 128 in their
defined orientation. In the case where additional leads 12 are
implanted within the patient, they can be associated with
additional lead groups.
[0122] The parameters adjustment panel 106 also includes a pulse
amplitude adjustment control 136 (expressed in milliamperes (mA)),
a pulse width adjustment control 138 (expressed in microseconds
(.mu.s)), and a pulse rate adjustment control 140 (expressed in
Hertz (Hz)), which are displayed and actuatable in all the
programming modes. Each of the controls 136-140 includes a first
arrow that can be actuated to decrease the value of the respective
modulation parameter and a second arrow that can be actuated to
increase the value of the respective modulation parameter. Each of
the controls 136-140 also includes a display area for displaying
the currently selected parameter. In response to the adjustment of
any of electrical pulse parameters via manipulation of the
graphical controls in the parameter adjustment panel 106, the
controller/processor 80 generates a corresponding modulation
parameter set (with a new pulse amplitude, new pulse width, or new
pulse rate) and transmits it to the IPG 14 via the telemetry
circuitry 86 for use in delivering the modulation energy to the
electrodes 26.
[0123] The parameter adjustment panel 106 includes a pull-down
programming mode field 142 that allows the user to switch between a
manual programming mode, an electronic trolling programming mode, a
navigation programming mode, an exploration programming mode, and a
sub-threshold programming mode. Each of these programming modes
allows a user to define a modulation parameter set for the
currently selected coverage area 120 of the currently selected
program 114 via manipulation of graphical controls in the parameter
adjustment panel 106 described above, as well as the various
graphical controls described below. In the illustrated embodiment,
when switching between programming modes via actuation of the
programming mode field 142, the last electrode configuration with
which the IPG 14 was programmed in the previous programming mode is
converted into another electrode configuration, which is used as
the first electrode configuration with which the IPG 14 is
programmed in the subsequent programming mode.
[0124] The electronic trolling programming mode and navigation
programming mode are designed to allow a user to determine one or
more efficacious modulation parameter sets for providing
super-threshold therapy to the patient, whereas the exploration
programming mode and sub-threshold programming mode are designed to
allow the user to determine one or more efficacious modulation
parameter sets for providing sub-threshold therapy to the patient.
In particular, the electronic trolling programming mode is designed
to quickly sweep the electrode array using a limited number of
electrode configurations to gradually steer an electrical field
relative to the modulation leads until the targeted modulation site
is located. Using the electrode configuration determined during the
electronic trolling programming mode as a starting point, the
navigation programming mode is designed to use a wide number of
electrode configurations to shape the electrical field, thereby
fine tuning and optimization the modulation coverage for patient
comfort. Both the electronic trolling mode and navigation
programming mode rely on immediate feedback from the patient in
response to the sensation of paresthesia relative to the region of
the body in which the patient experiences pain. Like the electronic
trolling programming mode, the exploration programming mode is
designed to quickly sweep the electrode array using a limited
number of electrode configurations to gradually steer an electrical
field relative to the modulation leads until the targeted
modulation site is located. Like the electronic trolling mode, the
exploration programming mode relies on immediate feedback from the
patient in response to the sensation of paresthesia relative to the
region of the body in which the patient experiences pain. However,
unlike the electronic trolling programming mode, navigation
programming mode, and exploration programming mode, the
sub-threshold programming mode cannot rely on immediate feedback
from the patient due to the lack of paresthesia experience by the
patient during sub-threshold modulation. Instead, the sub-threshold
programming mode uses a transformation of the electrode
configuration determined during the exploration programming mode to
provide efficacious sub-threshold modulation to the determined
target site of the patient.
[0125] As shown in FIG. 12, the manual programming mode has been
selected. In the manual programming mode, each of the electrodes
130 of the graphical leads 128, as well as the graphical case 132,
may be individually selected, allowing the clinician to set the
polarity (cathode or anode) and the magnitude of the current
(percentage) allocated to that electrode 130, 132 using graphical
controls located in an amplitude/polarity area 144 of the parameter
adjustment panel 106.
[0126] In particular, a graphical polarity control 146 located in
the amplitude/polarity area 144 includes a "+" icon, a "-" icon,
and an "OFF" icon, which can be respectively actuated to toggle the
selected electrode 130, 132 between a positive polarization
(anode), a negative polarization (cathode), and an off-state. An
amplitude control 148 in the amplitude/polarity area 144 includes
an arrow that can be actuated to decrease the magnitude of the
fractional ized current of the selected electrode 130, 132, and an
arrow that can be actuated to increase the magnitude of the
fractionalized current of the selected electrode 130, 132. The
amplitude control 148 also includes a display area that indicates
the adjusted magnitude of the fractionalized current for the
selected electrode 134. The amplitude control 148 is preferably
disabled if no electrode is visible and selected in the lead
display panel 104. In response to the adjustment of fractionalized
electrode combination via manipulation of the graphical controls in
the amplitude/polarity area 144, the controller/processor 80
generates a corresponding modulation parameter set (with a new
fractionalized electrode combination) and transmits it to the IPG
14 via the telemetry circuitry 86 for use in delivering the
modulation energy to the electrodes 26.
[0127] In the illustrated embodiment, electrode E2 has been
selected as a cathode to which 100% of the cathodic current has
been allocated, and electrodes E1 and E3 have been respectively
selected as anodes to which 25% and 75% of the anodic current has
been respectively allocated. Electrode E15 is shown as being
selected to allow the user to subsequently allocate the polarity
and fractionalized electrical current to it via the graphical
controls located in the amplitude/polarity area 144. Although the
graphical controls located in the amplitude/polarity area 144 can
be manipulated for any of the electrodes, a dedicated graphical
control for selecting the polarity and fractionalized current value
can be associated with each of the electrodes, as described in U.S.
Patent Publication No. 2012/0290041, entitled "Neurostimulation
System with On-Effector Programmer Control," which is expressly
incorporated herein by reference.
[0128] The parameters adjustment panel 106, when the manual
programming mode is selected, also includes an equalization control
150 that can be actuated to automatically equalize current
allocation to all electrodes of a polarity selected by respective
"Anode +" and "Cathode -" icons. Unlike the other programming modes
described in further detail below, the ranges of pulse rates and
pulse widths of the modulation parameter sets defined during the
manual programming mode are not limited to those known to result in
only one of super-threshold therapy and sub-threshold therapy. For
example, the lower limit of the pulse amplitude may be as low as
0.1 mA, wherein as the upper limit of the pulse amplitude may be as
high as 20 mA. The lower limit of the pulse width may be as low as
2 .mu.s, whereas the upper limit of the pulse width may be as high
as 1000 .mu.s. For example, the lower limit of the pulse rate may
be as low as 1 Hz, whereas the upper limit of the pulse rate may be
as high as 50 KHz. In the illustrated embodiment, a pulse amplitude
of 5 mA, a pulse width of 210 .mu.s, and a pulse rate of 40 Hz have
been selected. Thus, during the manual programming mode, the
selected coverage area 120 of the selected program 114 can be
programmed with a modulation parameter set designed to either
deliver super-threshold therapy or sub-threshold therapy to the
patient.
[0129] As shown in FIG. 13, the electronic trolling programming
mode has been selected. In this mode, the electrodes 130
illustrated in the lead display panel 104 that were individually
selectable and configurable in manual programming mode are used for
display only and are not directly selectable or controllable.
Instead of an amplitude/polarity area 144, the parameter selection
panel 106 includes a steering array of arrows 152 that allows
steering the electrical field up, down, left, or right relative to
the electrodes 26. In the illustrated embodiment, the electrical
current is steered by panning a virtual multipole (i.e., the
virtual multipole is moved relative to the actual electrodes 26
without changing the basic configuration (focus (F) and upper anode
percentage (UAP)) of the virtual multipole), and computing the
electrical amplitude values needed for the actual electrodes 26 to
emulate the virtual multipole. In the illustrated embodiment,
fractionalized cathodic currents of 40% and 60% have been
respectively computed for electrodes E2 and E3, and fractionalized
anodic currents of 25% and 75% have been computed for electrodes E1
and E4. In response to the steering of the electrical current via
manipulation of the steering array of arrows 152, the
controller/processor 80 generates a series of modulation parameter
sets (with different fractionalized electrode combination) and
transmits them to the IPG 14 via the telemetry circuitry 86 for use
in delivering the modulation energy to the electrode array 26 in a
manner that steers the locus of the resulting electrical field
relative to the electrode array 26.
[0130] In the illustrated embodiment, the virtual multipole used in
the electronic trolling programming mode is a bipole or tripole
that includes a modulating cathode (i.e., cathodic modulation is
providing during the electronic trolling programming mode).
Furthermore, the ranges of pulse rates and pulse widths of the
modulation parameter sets defined during the electronic trolling
programming mode are limited to those known to result in
super-threshold therapy (e.g., causing paresthesia) assuming a
nominal pulse amplitude. For example, the lower limit value of the
pulse width may be 100 .mu.s, and the upper limit of the pulse rate
may be 1500 Hz. In the illustrated embodiment, a pulse amplitude of
5 mA, a pulse width of 210 .mu.s, and a pulse rate of 40 Hz have
been selected.
[0131] As shown in FIG. 14, the navigation programming mode has
been selected. As in the electronic trolling programming mode, the
electrodes illustrated in the lead display panel 104 that were
individually selectable and configurable in manual programming mode
are used for display only and are not directly selectable or
controllable in the navigation programming mode, and instead of an
amplitude/polarity area 144, the The parameter selection panel 106
includes a steering array of arrows 162 that allows steering the
electrical field up, down, left, or right relative to the
electrodes 26. In the illustrated embodiment, the electrical
current is steered by weaving one or more anodes around the cathode
of the virtual multipole as the cathode is displaced relative to
the electrode array 26, and computing the electrical amplitude
values needed for the electrodes 26 to emulate the virtual
multipole. In the illustrated embodiment, fractionalized cathodic
currents of 33%, 47%, and 20% have been respectively computed for
electrodes E2, E3, and E4, and fractionalized anodic currents of
54% and 46% have been respectively computed for electrodes E1 and
E5. In response to the steering of the electrical current via
manipulation of the steering array of arrows 162, the
controller/processor 80 generates a series of modulation parameter
sets (with different fractionalized electrode combination) and
transmits them to the IPG 14 via the telemetry circuitry 86 for use
in delivering the modulation energy to the electrode array 26 in a
manner that steers the locus of the resulting electrical field
relative to the electrode array 26.
[0132] As with the electronic trolling programming mode, the
virtual multipole used in the navigation programming mode is a
bipole or tripole that includes a modulating cathode (i.e.,
cathodic modulation is providing during the navigation programming
mode). Furthermore, the ranges of pulse rates and pulse widths of
the modulation parameter sets defined during the electronic
trolling programming mode are limited to those known to result in
super-threshold therapy (e.g., causing paresthesia) assuming a
nominal pulse amplitude. For example, the lower limit value of the
pulse width may be 100 .mu.s, and the upper limit of the pulse rate
may be 1500 Hz. In the illustrated embodiment, a pulse amplitude of
5 mA, a pulse width of 210 .mu.s, and a pulse rate of 40 Hz have
been selected.
[0133] Further details discussing the use of panning a virtual
multipole during the electronic trolling programming mode and
weaving a virtual multipole during the navigation programming mode,
as well as seamlessly switching between the manual programming
mode, electronic trolling programming mode, and navigation
programming mode, are described in U.S. patent application Ser. No.
13/715,751, entitled "Seamless Integration of Different Programming
Modes for a Neuromodulation device Programming System," which is
expressly incorporated herein by reference.
[0134] As shown in FIG. 15, the exploration programming mode has
been selected. As in the electronic trolling programming mode, the
electrodes illustrated in the lead display panel 104 that were
individually selectable and configurable in manual programming mode
are used for display only and are not directly selectable or
controllable in the navigation programming mode, and instead of an
amplitude/polarity area 144, the parameter selection panel 106
includes a steering array of arrows 172 that allows steering the
electrical field up, down, left, or right relative to the
electrodes 26. In the illustrated embodiment, the electrical
current is steered by panning a virtual monopole and computing the
electrical amplitude values needed for the actual electrodes 26 to
emulate the virtual multipole. In the illustrated embodiment, a
fractionalized cathodic current of 100% has been computed for the
case electrode, and fractionalized anodic currents of 36%, 20%, and
44% have been respectively computed for electrodes E4, E9, and E10.
In response to the steering of the electrical current via
manipulation of the steering array of arrows 172, the
controller/processor 80 generates a series of modulation parameter
sets (with different fractionalized electrode combinations) and
transmits them to the IPG 14 via the telemetry circuitry 86 for use
in delivering the modulation energy to the electrode array 26 in a
manner that steers the locus of the resulting electrical field
relative to the electrode array 26.
[0135] In the illustrated embodiment, the virtual monopole used in
the exploration programming mode includes a primary modulating
anode (i.e., anodic modulation is providing during the exploration
programming mode), because it is believed that the delivery of
anodic electrical current to the spinal cord tissue, and in
particular the neural network of the dorsal horn (as described in
U.S. patent application Ser. No. ______ (Attorney Docket No. BSC
12-0342-01), entitled "Method for Selectively Modulating Neural
Elements in the Dorsal Horn," which is expressly incorporated
herein by reference) provides sub-threshold pain relief to the
patient, although it is possible that the delivery of cathodic
electrical current to the spinal cord tissue may be therapeutic as
well.
[0136] It should also be noted that utilization of a virtual
monopole ensures that the neural tissue of interest is only
targeted by anodic electrical current. In contrast, if a virtual
bipole or tripole were to be utilized, one or more virtual cathodes
would necessarily be located adjacent the targeted neural tissue of
interest, which may confound the proper location of the virtual
anode by inadvertently contributing to the paresthesia experienced
by the patient. Furthermore, the electrical current delivered to
the patient during the exploration programming mode is biphasic
pulse waveform having a passive cathodic charge recovery phase,
thereby minimizing the possibility that the cathodic charge
recovery phase inadvertently contributes to the paresthesia
experienced by the patient. Furthermore, like in the electronic
trolling and navigation programming modes, the ranges of pulse
rates and pulse widths of the modulation parameter sets defined
during the exploration programming mode are limited to those known
to result in super-threshold therapy (e.g., causing paresthesia)
assuming a nominal pulse amplitude. For example, the lower limit
value of the pulse width may be 100 .mu.s, and the upper limit of
the pulse rate may be 1500 Hz. In the illustrated embodiment, a
pulse amplitude of 3.9 mA, a pulse width of 250 .mu.s, and a pulse
rate of 100 Hz have been selected.
[0137] As shown in FIG. 16, the sub-threshold programming mode has
been selected. As in the electronic trolling programming mode, the
electrodes illustrated in the lead display panel 104 that were
individually selectable and configurable in manual programming mode
are used for display only and are not directly selectable or
controllable in the navigation programming mode. The parameter
selection panel 106 has neither the amplitude/polarity area 144 nor
a steering array of arrows, since no paresthesia will presumably be
perceived by the patient. Alternatively, the parameter selection
panel 106 may have a steering array of arrows in order to adjust
the locus of modulation.
[0138] In any event, the controller/processor 80 transforms the
last virtual anodic monopole defined during the exploration
programming mode into a virtual cathodic multipole (i.e., a virtual
multiple having a primary modulating cathode). For example, the
cathode of the virtual cathodic multipole can be placed at the
location of the anode of the previously defined virtual anodic
multiple relative to the electrode array 26, and a (focus (F) and
upper anode percentage (UAP)) of the virtual cathodic multipole can
be assumed (e.g., a focus of two (i.e., double the electrode
spacing) and a UAP of zero (i.e., a virtual bipole)).
[0139] Although the exploration programming mode is specifically
designed to find the target site for sub-threshold modulation, in
an optional embodiment, the controller/processor 80 may transform
the last virtual cathodic multipole defined by either of the
electronic trolling programming mode or navigation programming mode
into the virtual cathodic multipole. In this case, the anode of the
virtual anodic multipole can be placed at the location of the
cathode of the virtual cathodic multipole, and the cathode(s) of
the virtual anodic multipole can be placed at the location(s) of
the anode(s) of the virtual cathodic multipole relative to the
electrode array 26. In another optional embodiment, the
controller/processor 80 may transform the last fractionalized
electrode combination defined by the manual programming mode into
the virtual cathodic multipole. In this case, the
controller/processor 80 may transform the manually generated
fractionalized electrode combination into a virtual cathodic
multipole in the manner described in U.S. patent application Ser.
No. 13/715,751, which has previously been expressly incorporated
herein by reference. Thus, it can be appreciated that the manual
programming mode, electronic trolling programming mode, navigation
programming mode, and exploration programming mode can be
seamlessly switched to the sub-threshold programming mode.
[0140] In any event, the controller/processor 80 then computes
amplitude values needed for the actual electrodes 26 to emulate the
virtual cathodic multipole. In the illustrated embodiment,
fractionalized cathodic currents of 44%, 9%, 34%, and 13% have been
respectively computed for electrodes E4, E5, E12, and E13, and
fractionalized anodic currents of 8%, 47%, 37%, and 8% have been
respectively computed for electrodes E3, E7, E15, and E16. In the
illustrated embodiment, the virtual multipole used in the
sub-threshold programming mode is a biphasic pulsed waveform having
an active cathodic charge recovery phase, although the biphasic
pulse waveform may alternative have an active anodic charge
recovery phase. In either case, the biphasic pulsed waveform will
have an anodic phase that will modulate the neural tissue.
[0141] The controller/processor 80 also automatically modifies the
electrical pulse parameters previously defined in the graphical
controls 136-140 of the parameter adjustment panel 106 during the
exploration programming mode (or alternatively, the manual
programming mode, electronic trolling programming mode, or
navigation programming mode) to predetermined values that ensure
sub-threshold modulation. For example, in the illustrated
embodiment, the pulse amplitude was reduced from 3.9 mA to 2.3 mA,
the pulse width was decreased from 210 .mu.s to 40 .mu.s, and the
pulse rate was increased from 100 Hz to 2 KHz. In general, it is
preferred that the super-threshold pulse amplitude used in the
exploration programming mode be reduced by 30%-70% to obtain the
sub-threshold pulse amplitude in order to ensure efficacious
sub-threshold therapy. Furthermore, although the sub-threshold
programming mode allows the user to modify the pulse amplitude,
pulse width, and pulse rate via manipulation of the graphical
controls 136-140 of the parameter adjustment panel 106, the ranges
of the pulse amplitudes, pulse rates, and pulse widths of the
modulation parameter sets defined during the exploration
programming mode are limited to those known to result in
sub-threshold therapy (e.g., not causing paresthesia). For example,
the upper limit value of the pulse amplitude may be 5 mA, the upper
limit value of the pulse width may be 100 .mu.s, and the lower
limit of the pulse rate may be 1500 Hz.
[0142] In any of the semi-automated modes (i.e., the electronic
trolling programming mode, navigation programming mode, or
exploration programming mode), the parameter adjustment panel 106
includes an advanced tab 154, as shown in FIGS. 13-16, which when
actuated, hides the lead display panel 104 and provides access to a
resolution control 156 and a focus control 158, as shown in FIG.
17. The resolution control 156 allows changing the modulation
adjustment resolution. In one embodiment, three possible settings
of Fine, Medium, and Coarse may be chosen. The resolution control
156 has a "+" icon and a "-" icon that can be used to adjust the
resolution. The resolution control 156 also includes a display
element that graphically displays the current resolution level.
When the resolution is set to Fine, each change caused by use of
the steering array makes less of a change to the electrode
configuration than when the resolution is set to Medium or Coarse.
The focus control 158 allows changing the modulation focus by
displacing the anode(s) and cathode of the virtual multipole toward
each other to increase the focus, or displacing the anode(s) and
cathode of the virtual multipole away from each other to decrease
the focus. The focus control 158 has a "+" icon and a "-" icon that
can be used to adjust the focus. The focus control 158 also
includes a display element that graphically displays the current
focus level. Notably, the focus control 158 is only available in
the electronic trolling programming mode and navigation programming
mode, since the exploration programming mode utilizes a virtual
monopole that assumes an infinite distance between the anode and
cathode of the virtual multipole.
[0143] Thus, it can be appreciated from the foregoing that the
controller/processor 80 is capable of deriving a modulation
parameter set (fractionalized electrode combination, pulse
amplitude, pulse width, and/or pulse rate) for the sub-threshold
programming mode from a modulation parameter set previously
determined during the exploration programming mode (or
alternatively, the manual programming mode, electronic programming
mode, and/or navigation programming mode). The electrical field
that results from the delivery of the electrical energy to the
electrode array 26 in accordance with the new modulation parameter
set defined for the sub-threshold programming mode will have a
locus that is the same as the locus of the electrical field
resulting from the conveyance of the electrical energy to the
plurality of electrodes in accordance with the last modulation
parameter set defined for the exploration programming mode (or
alternatively, the manual programming mode, electronic programming
mode, and/or navigation programming mode).
[0144] Having described the structure and function of the CP 18,
one method of using it to provide sub-threshold therapy to the
patient to treat chronic pain will now be described with reference
to FIG. 18. First, the SCM system 10 is placed in the exploration
programming mode (step 240). Then, the SCM system 10 is operated to
convey electrical modulation energy to the spinal cord tissue of
the patient in accordance with a series of modulation parameter
sets, such that the locus of the resulting electrical field is
gradually displaced relative to the tissue (e.g., by manipulating
the steering array 172 as discussed above) (step 242). Preferably,
each of the modulation parameter sets defines electrical pulse
parameters likely to cause the patient to perceive paresthesia. For
example, each of the modulation parameter sets can define a pulse
rate less than 1500 Hz and/or a pulse width greater than 100 .mu.s.
The conveyed electrical modulation energy may be monopolar in
nature, and may be monophasic or biphasic (with a passive charge
recovery phase), such that the polarity of the electrical energy
mostly likely to provide sub-threshold therapy can be isolated,
which in this case, is the anodic portion of the electrical energy.
The modulation parameter sets can be created using the
aforementioned virtual poles. In particular, a series of virtual
poles relative to the tissue may be defined by panning a virtual
pole across the electrodes, and amplitude values for electrode
combinations that respectively emulate the series of virtual poles
can then be computed.
[0145] The patient perceives paresthesia in response to the
conveyance of the electrical modulation energy to the tissue in
accordance with at least one of the modulation parameter sets (step
244). For example, if the patient experiences pain in a bodily
region, such as the lower back, the electrical modulation energy
conveyed in accordance with at least one of the modulation
parameter sets may cause the patient to perceive paresthesia in the
lower back. The modulation parameter set that results in the most
efficacious therapy based on feedback from the patient may then be
identified (step 246).
[0146] Next, the SCM system 10 is switched to the sub-threshold
programming mode (step 248). In response, a new modulation
parameter set is automatically derived from the previously
identified modulation parameter set (step 250). The new modulation
parameter set preferably defines electrical pulse parameters likely
to cause the patient to not perceive paresthesia. For example, each
of the modulation parameter sets can define a pulse rate greater
than 1500 Hz and/or a pulse width less than 100 .mu.s. The derived
modulation parameter set can be created using the aforementioned
virtual poles. In particular, a virtual pole relative to the tissue
may be defined, and amplitude values for the electrode combination
that respectively emulates the virtual poles can then be
computed.
[0147] The SCM system 10 is then operated to convey electrical
modulation energy to the spinal cord tissue of the patient in
accordance with new modulation parameter set, thereby creating an
electrical field having a locus relative to the spinal cord tissue
that is the same as the locus of the electrical field associated
with the identified modulation parameter set, and without causing
the patient to perceive paresthesia (step 252). The conveyed
electrical modulation energy preferably has an anodic component.
For example, the conveyed electrical modulation energy may be
bipolar in nature and be biphasic (with an active charge recovery
phase). Lastly, the SCM system 10 is programmed with the new
modulation parameter set (step 254).
[0148] Although particular embodiments of the present inventions
have been shown and described, it will be understood that it is not
intended to limit the present inventions to the preferred
embodiments, and it will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present inventions.
Thus, the present inventions are intended to cover alternatives,
modifications, and equivalents, which may be included within the
spirit and scope of the present inventions as defined by the
claims.
* * * * *