U.S. patent application number 15/962354 was filed with the patent office on 2018-08-23 for systems and methods for determining spinal cord stimulation parameters based on patient feedback.
The applicant listed for this patent is PACESETTER, INC.. Invention is credited to Gene A. Bornzin, Edward Karst, Alexander Kent.
Application Number | 20180236237 15/962354 |
Document ID | / |
Family ID | 58720407 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180236237 |
Kind Code |
A1 |
Kent; Alexander ; et
al. |
August 23, 2018 |
SYSTEMS AND METHODS FOR DETERMINING SPINAL CORD STIMULATION
PARAMETERS BASED ON PATIENT FEEDBACK
Abstract
The present disclosure provides a grip sensor for quantifying
pain experienced by a patient during spinal cord stimulation (SCS).
The grip sensor includes an electronics enclosure, an annular outer
shell substantially surrounding the electronics enclosure and sized
to be held by the patient, a pressure sensor embedded in the outer
shell and communicatively coupled to the electronics enclosure, the
pressure sensor configured to measure a grip strength of the
patient as SCS is applied to the patient, and a plurality of
galvanic skin response sensors communicatively coupled to the
electronics enclosure and configured to measure an electrical
impedance of the skin of the patient as SCS is applied to the
patient.
Inventors: |
Kent; Alexander; (Mountain
View, CA) ; Karst; Edward; (Los Angeles, CA) ;
Bornzin; Gene A.; (Simi Valley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PACESETTER, INC. |
Sunnyvale |
CA |
US |
|
|
Family ID: |
58720407 |
Appl. No.: |
15/962354 |
Filed: |
April 25, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14946538 |
Nov 19, 2015 |
9981131 |
|
|
15962354 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/4824 20130101;
A61B 5/0533 20130101; A61N 1/37247 20130101; A61B 5/225 20130101;
A61N 1/36021 20130101; A61N 1/3614 20170801; A61N 1/36062 20170801;
G06F 3/015 20130101; A61N 1/36071 20130101; A63B 21/4035 20151001;
A61B 5/4836 20130101; A61B 2562/046 20130101; A61N 1/36132
20130101; A61N 1/0551 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61B 5/22 20060101 A61B005/22; A61B 5/053 20060101
A61B005/053; A61B 5/00 20060101 A61B005/00 |
Claims
1. A system for quantifying pain experienced by a patient during
spinal cord stimulation (SCS). the system comprising: a grip sensor
sized to be gripped by the patient and comprising at least one
sensor configured to measure at least one value as different SCS
configurations are applied to the patient; a computing device
communicatively coupled to the grip sensor and configured to
calculate a pain level for each SCS configuration based on the at
least one value measured by the at least one sensor; and a display
device communicatively coupled to the grip sensor and configured to
display a plot including the calculated pain level for each SCS
configuration.
2. The system of claim 1, wherein the grip sensor comprises: an
electronics enclosure; an annular outer shell substantially
surrounding the electronics enclosure and sized to be held by the
patient; a pressure sensor embedded in the outer shell and
communicatively coupled to the electronics enclosure, the pressure
sensor configured to measure a grip strength of the patient; and a
plurality of galvanic skin response sensors communicatively coupled
to the electronics enclosure and configured to measure an
electrical impedance of the skin of the patient.
3. The system of claim 2, further comprising a thermometer
configured to measure a skin temperature of the patient.
4. The system of claim 2, wherein the electronics enclosure and the
outer shell form a substantially cylindrical housing.
5. The system of claim 4, further comprising; a first mechanical
support member extending from a first end of the housing; and a
second mechanical support member extending from a second end of the
housing.
6. The system of claim 2, wherein the electronics enclosure is
configured to: receive a first measurement from the pressure
sensor; receive a second measurement from the plurality of galvanic
skin response sensors; receive a third measurement from a
thermometer; and calculate the pain level based on the first,
second, and third measurements.
7. The system of claim 2, wherein the computing device is included
within the electronics enclosure.
8. The system of claim 1, wherein the display device is configured
to display a plot that includes an electrode configuration
display.
9. A method for determining SCS therapy parameters for a patient,
the method comprising: applying tonic stimulation at a fixed
frequency; varying at least one parameter of the applied tonic
stimulation until paresthesia coverage of a target area of the
patient is achieved; and further manipulating the applied tonic
stimulation to achieve one of burst stimulation and high-frequency
stimulation that provides pain relief with reduced paresthesia.
10. The method of claim 9, wherein further manipulating the applied
tonic stimulation comprises: dividing each pulse of the applied
tonic stimulation into a plurality of pulses to produce burst
stimulation; and adjusting an intra-burst frequency and an
inter-burst frequency of the burst stimulation until pain relief
with reduced paresthesia is achieved.
11. The method of claim 9, wherein further manipulating the applied
tonic stimulation comprises: adjusting the frequency of the tonic
stimulation to a lower threshold frequency to produce
high-frequency stimulation; and increasing the frequency from the
lower threshold frequency until pain relief with reduced
paresthesia is achieved. 12, The method of claim 9, wherein further
manipulating the applied tonic stimulation comprises: adjusting the
frequency of the tonic stimulation to an upper threshold frequency
to produce high-frequency stimulation; and decreasing the frequency
from the upper threshold frequency until a minimum frequency at
which pain relief with reduced paresthesia is generated is
reached.
13. The method of claim 9, wherein varying at least one parameter
comprises varying at least one of a contact configuration, an
amplitude, a pulse width, and a frequency of the applied tonic
stimulation.
14. The method of claim 9, wherein applying tonic stimulation
comprises applying tonic stimulation at approximately 50 Hz.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. patent application
Ser. No. 14/946,538, filed Nov. 19, 2015, entitled "Systems And
Methods For Determining Spinal Cord Stimulation Parameters Based On
Patient Feedback," and is incorporated herein by reference in its
entirety to provide continuity of disclosure.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to neurostimulation
systems, and more particularly to determining stimulation
parameters and quantifying patient pain for spinal cord
stimulation.
BACKGROUND ART
[0003] Neurostimulation is a treatment method utilized for managing
the disabilities associated with pain, movement disorders such as
Parkinson's Disease (PD), dystonia, and essential tremor, and also
a number of psychological disorders such as depression, mood,
anxiety, addiction, and obsessive compulsive disorders.
[0004] At least some known neurostimulation systems are closed-loop
spinal cord stimulation (SCS) systems based on neurological sensing
systems. In at least some known systems, selecting parameters for
SCS relies on a "guess-and-check" approach to find therapeutically
effective parameter sets for chronic pain. For example, for
traditional tonic (La, single pulse) stimulation waveforms, there
are several parameters that can be independently tuned, including
stimulation amplitude, pulse width, frequency, and contact
configuration (e.g., the location of cathodes and anodes).
Moreover, with the introduction of other stimulation waveforms,
such as burst stimulation, there are even more parameters to tune,
including inter-burst and intra-burst frequency. Finally, it is
also desirable to determine which stimulation waveform (tonic,
burst, etc.) generates the best response in each individual
patient. In at least some known systems, however, the process for
selecting stimulation parameters may not be well-defined for
efficiently and rationally identifying parameters that facilitate
generating optimal therapy.
[0005] In tonic SCS, stimulation parameters may be adjusted until
there is paresthesia coverage of painful regions of the patient's
body. The stimulation amplitude generally determines the extent of
neuronal activation. Accordingly, in at least some known systems,
amplitude is titrated between a perception threshold (i.e., a level
at which the patient senses paresthesia) and a discomfort threshold
(i.e., a level at which the patient experiences discomfort). The
discomfort threshold may be, for example, 1.4 to 1.7 times the
perception threshold. In addition, pulse width may be adjusted.
Increasing pulse width generally leads to smaller differences in
stimulation thresholds between large and small diameter fibers.
[0006] In high-frequency SCS, a tonic waveform may be applied at
frequencies in the 2 to 10 kilohertz (kHz) range to generate pain
relief with reduced paresthesia. For example, for 10 kHz
stimulation, amplitude may be 0.5 to 5 milliamps (mA) and pulse
width may be 30 microseconds (.mu.s). Paresthesia mapping is not
generally used for high-frequency SCS, and instead, a stimulation
site is more consistent, with stimulation typically applied at
C4-C5 for chronic pain of the upper limbs/hands, and at T8-T12 for
the back and lower limbs.
[0007] For burst SCS, a waveform including packets of
high-frequency pulses that are separated by a quiescent period is
used. Burst SCS often results in paresthesia-free stimulation.
Typical waveform parameters may be, for example, a 500-1000 hertz
(Hz) intra-burst frequency, a 40 Hz intra burst frequency, five
pulses per burst, and 0.5-1 millisecond (ms) pulse width. The
amplitude is typically subsensory (e.g., 90% of the paresthesia
threshold), and may average around 3.4 mA.
[0008] In addition to selecting parameters, another difficulty in
SCS programming arises when attempting to quantify patient pain.
For example, patients may be asked to quantify their pain on a
scale of 1 to 10, state their percentage pain relief compared to
baseline, and/or identify body locations where pain relief and
paresthesia are felt. The patient must continuously provide these
subjective measures with each parameter adjustment, which can be
time-consuming for both the patient and the programmer. Moreover,
the reliability of these subjective pain measures is
questionable.
[0009] Further, when delivering SCS stimulation, it may be
desirable to extend the battery life of one or more components of
an SCS system. As such, there is a need to identify SCS waveforms
that provide substantially paresthesia-free stimulation while
minimizing the amount of energy delivered.
BRIEF SUMMARY OF THE DISCLOSURE
[0010] In one embodiment, the present disclosure is directed to a
grip sensor for quantifying pain experienced by a patient during
spinal cord stimulation (SCS). The grip sensor includes an
electronics enclosure, an annular outer shell substantially
surrounding the electronics enclosure and sized to be held by the
patient, a pressure sensor embedded in the outer shell and
communicatively coupled to the electronics enclosure, the pressure
sensor configured to measure a grip strength of the patient as SCS
is applied to the patient, and a plurality of galvanic skin
response sensors communicatively coupled to the electronics
enclosure and configured to measure an electrical impedance of the
skin of the patient as SCS is applied to the patient.
[0011] In another embodiment, the present disclosure is directed to
a system for quantifying pain experienced by a patient during
spinal cord stimulation (SCS). The system includes a grip sensor
sized to be gripped by the patient and comprising at least one
sensor configured to measure at least one value as different SCS
configurations are applied to the patient, a computing device
communicatively coupled to the grip sensor and configured to
calculate a pain level for each SCS configuration based on the at
least one value measured by the at least one sensor, and a display
device communicatively coupled to the grip sensor and configured to
display a plot including the calculated pain level for each SCS
configuration.
[0012] In another embodiment, the present disclosure is directed to
a method for determining SCS therapy parameters for a patient. The
method includes applying tonic stimulation at a fixed frequency,
varying at least one parameter of the applied tonic stimulation
until paresthesia coverage of a target area of the patient is
achieved, and further manipulating the applied tonic stimulation to
achieve one of burst stimulation and high-frequency stimulation
that provides pain relief with reduced paresthesia.
[0013] The foregoing and other aspects, features, details,
utilities and advantages of the present disclosure will be apparent
from reading the following description and claims, and from
reviewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view of one embodiment of a
stimulation system.
[0015] FIGS. 2A-2C are schematic views of stimulation portions that
may be used with the stimulation system of FIG. 1.
[0016] FIG. 3 is a schematic diagram of one embodiment of a grip
sensor that may be used with the stimulation system of FIG. 1.
[0017] FIG. 4 is a block diagram of one embodiment of a computing
device that may be used with the grip sensor shown of FIG. 3.
[0018] FIG. 5 is one embodiment of a pain quantification plot that
may be produced using the grip sensor of FIG. 3.
[0019] FIGS. 6A-6C are diagrams illustrating operation of one
embodiment of a burst stimulation algorithm,
[0020] FIG. 7 is a flow chart of one embodiment of a burst
stimulation algorithm.
[0021] FIG. 8 is a flow chart of one embodiment of a high-frequency
stimulation algorithm.
[0022] FIG. 9 is a flow chart of another embodiment of a
high-frequency stimulation algorithm.
[0023] FIG. 10 is a flow chart of one embodiment of a method for
determining SCS therapy parameters for a patient.
[0024] Corresponding reference characters indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0025] The present disclosure provides programming algorithms for
semi-autonomous and rapid determination of therapeutically
effective stimulation parameters. These algorithms rely on signals
obtained from a hand-held grip sensor. This allows patients to
provide real-time, quantitative feedback on pain level as
parameters are adjusted, as described herein.
[0026] Neurostimulation systems are devices that generate
electrical pulses and deliver the pulses to nerve tissue of a
patient to treat a variety of disorders. Spinal cord stimulation
(SCS) is the most common type of neurostimulation within the
broader field of neuromodulation. In SCS, electrical pulses are
delivered to nerve tissue of the spinal cord for the purpose of
chronic pain control. While a precise understanding of the
interaction between the applied electrical energy and the nervous
tissue is not fully appreciated, it is known that application of an
electrical field to spinal nervous tissue can effectively inhibit
certain types of pain transmitted from regions of the body
associated with the stimulated nerve tissue to the brain.
Specifically, applying electrical energy to the spinal cord
associated with regions of the body afflicted with chronic pain can
induce "paresthesia" (a subjective sensation of numbness or
tingling) in the afflicted bodily regions.
[0027] SCS systems generally include a pulse generator and one or
more leads. A stimulation lead includes a lead body of insulative
material that encloses wire conductors. The distal end of the
stimulation lead includes multiple electrodes that are electrically
coupled to the wire conductors. The proximal end of the lead body
includes multiple terminals (also electrically coupled to the wire
conductors) that are adapted to receive electrical pulses. The
distal end of a respective stimulation lead is implanted within the
epidural space to deliver the electrical pulses to the appropriate
nerve tissue within the spinal cord that corresponds to the
dermatome(s) in which the patient experiences chronic pain. The
stimulation leads are then tunneled to another location within the
patient's body to be electrically connected with a pulse generator
or, alternatively, to an "extension."
[0028] The pulse generator is typically implanted within a
subcutaneous pocket created during the implantation procedure. In
SCS, the subcutaneous pocket is typically disposed in a lower back
region, although subclavicular implantations and lower abdominal
implantations are commonly employed for other types of
neuromodulation therapies.
[0029] Referring now to the drawings, and in particular to FIG. 1,
a stimulation system is indicated generally at 100. Stimulation
system 100 generates electrical pulses for application to tissue of
a patient, or subject, according to one embodiment. Stimulation
system 100 includes an implantable pulse generator (IPG) 150 that
is adapted to generate electrical pulses for application to tissue
of a patient. Implantable pulse generator 150 typically includes a
metallic housing that encloses a controller 151, pulse generating
circuity 152, a battery 153, far-field and/or near field
communication circuitry 154, and other appropriate circuitry and
components of the device. Controller 151 typically includes a
microcontroller or other suitable processor for controlling the
various other components of the device. Software code is typically
stored in memory of implantable pulse generator 150 for execution
by the microcontroller or processor to control the various
components of the device.
[0030] Implantable pulse generator 150 may comprise one or more
attached extension components 170 or be connected to one or more
separate extension components 170. Alternatively, one or more
stimulation leads 110 may be connected directly to implantable
pulse generator 150. Within implantable pulse generator 150,
electrical pulses are generated by pulse generating circuitry 152
and are provided to switching circuitry. The switching circuit
connects to output wires, traces, lines, or the like (not shown)
which are, in turn, electrically coupled to internal conductive
wires (not shown) of a lead body 172 of extension component 170.
The conductive wires, in turn, are electrically coupled to
electrical connectors (e.g., "Bal-Seal" connectors) within
connector portion 171 of extension component 170. The terminals of
one or more stimulation leads 110 are inserted within connector
portion 171 for electrical connection with respective connectors.
Thereby, the pulses originating from implantable pulse generator
150 and conducted through the conductors of lead body 172 are
provided to stimulation lead 110. The pulses are then conducted
through the conductors of stimulation lead 110 and applied to
tissue of a patient via electrodes 111. Any suitable known or later
developed design may be employed for connector portion 171.
[0031] For implementation of the components within implantable
pulse generator 150, a processor and associated charge control
circuitry for an implantable pulse generator is described in U.S.
Pat. No. 7,571,007, entitled "SYSTEMS AND METHODS FOR USE IN PULSE
GENERATION," which is incorporated herein by reference. Circuitry
for recharging a rechargeable battery of an implantable pulse
generator using inductive coupling and external charging circuits
are described in U.S. Pat. No. 7,212,110, entitled "IMPLANTABLE
DEVICE AND SYSTEM FOR WIRELESS COMMUNICATION" which is incorporated
herein by reference.
[0032] An example and discussion of "constant current" pulse
generating circuitry is provided in U.S. Patent Publication No.
2006/0170486 entitled "PULSE GENERATOR HAVING AN EFFICIENT
FRACTIONAL VOLTAGE CONVERTER AND METHOD OF USE," which is
incorporated herein by reference. One or multiple sets of such
circuity may be provided within implantable pulse generator 150.
Different pulses on different electrodes may be generated using a
single set of pulse generating circuitry using consecutively
generated pulses according to a "multi-stimset program" as is known
in the art. Alternatively, multiple sets of such circuitry may be
employed to provide pulse patterns that include simultaneously
generated and delivered stimulation pulses through various
electrodes of one or more stimulation leads as is also known in the
art. Various sets of parameters may define the pulse
characteristics and pulse timing for the pukes applied to various
electrodes as is known in the art. Although constant current puke
generating circuitry is contemplated for some embodiments, any
other suitable type of pulse generating circuitry may be employed
such as constant voltage pulse generating circuitry.
[0033] Stimulation lead(s) 110 may include a lead body of
insulative material about a plurality of conductors within the
material that extend from a proximal end of stimulation lead 110 to
its distal end. The conductors electrically couple a plurality of
electrodes 111 to a plurality of terminals (not shown) of
stimulation lead 110. The terminals are adapted to receive
electrical pulses and the electrodes 111 are adapted to apply
stimulation pulses to tissue of the patient. Also, sensing of
physiological signals may occur through electrodes 111, the
conductors, and the terminals. Additionally or alternatively,
various sensors (not shown) may be located near the distal end of
stimulation lead 110 and electrically coupled to terminals through
conductors within the lead body 172. Stimulation lead 110 may
include any suitable number of electrodes 111, terminals, and
internal conductors,
[0034] FIGS. 2A-2C respectively depict stimulation portions 200,
225, and 250 for inclusion at the distal end of stimulation lead
110. Stimulation portions 200, 225, and 250 each include one or
more electrodes 121. Stimulation portion 200 depicts a conventional
stimulation portion of a "percutaneous" lead with multiple ring
electrodes. Stimulation portion 225 depicts a stimulation portion
including several "segmented electrodes." The term "segmented
electrode" is distinguishable from the term "ring electrode." As
used herein, the term "segmented electrode" refers to an electrode
of a group of electrodes that are positioned at the same
longitudinal location along the longitudinal axis of a lead and
that are angularly positioned about the longitudinal axis so they
do not overlap and are electrically isolated from one another.
Example fabrication processes are disclosed in U.S. Patent
Publication No. 2011/0072657, entitled, "METHOD OF FABRICATING
STIMULATION LEAD FOR APPLYING ELECTRICAL STIMULATION TO TISSUE OF A
PATIENT," which is incorporated herein by reference. Stimulation
portion 250 includes multiple planar electrodes on a paddle
structure.
[0035] Controller device 160 (shown in FIG. 1) may be implemented
to recharge battery 153 of implantable pulse generator 150
(although a separate recharging device could alternatively be
employed), A "wand" 165 may be electrically connected to controller
device 160 through suitable electrical connectors (not shown). The
electrical connectors are electrically connected to a "primary"
coil 166 at the distal end of wand 165 through respective wires
(not shown). Typically, primary coil 166 is connected to the wires
through capacitors (not shown). Also, in some embodiments, wand 165
may comprise one or more temperature sensors for use during
charging operations.
[0036] The patient then places the primary coil 166 against the
patient's body immediately above the secondary coil (not shown),
i.e., the coil of the implantable medical device. Preferably, the
primary coil 166 and the secondary coil are aligned in a coaxial
manner by the patient for efficiency of the coupling between the
primary and secondary coils. Controller device 160 generates an AC
signal to drive current through primary coil 166 of wand 165.
Assuming that primary coil 166 and secondary coil are suitably
positioned relative to each other, the secondary coil is disposed
within the field generated by the current driven through primary
coil 166. Current is then induced in secondary coil. The current
induced in the coil of the implantable pulse generator is rectified
and regulated to recharge battery of implantable pulse generator
150. The charging circuitry may also communicate status messages to
controller device 160 during charging operations using
pulse-loading or any other suitable technique. For example,
controller device 160 may communicate the coupling status, charging
status, charge completion status, etc.
[0037] External controller device 160 is also a device that permits
the operations of implantable pulse generator 150 to be controlled
by user after implantable pulse generator 150 is implanted within a
patient, although in alternative embodiments separate devices are
employed for charging and programming. Also, multiple controller
devices may be provided for different types of users (e.g., the
patient or a clinician). Controller device 160 can be implemented
by utilizing a suitable handheld processor-based system that
possesses wireless communication capabilities. Software is
typically stored in memory of controller device 160 to control the
various operations of controller device 160. Also, the wireless
communication functionality of controller device 160 can be
integrated within the handheld device package or provided as a
separate attachable device. The interface functionality of
controller device 160 is implemented using suitable software code
for interacting with the user and using the wireless communication
capabilities to conduct communications with implantable pulse
generator 150.
[0038] Controller device 160 preferably provides one or more user
interfaces to allow the user to operate implantable pulse generator
150 according to one or more stimulation programs to treat the
patient's disorder(s). Each stimulation program may include one or
more sets of stimulation parameters including pulse amplitude,
pulse width, pulse frequency or inter-pulse period, pulse
repetition parameter (e.g., number of times for a given pulse to be
repeated for respective stimset during execution of program), etc.
Implantable pulse generator 150 modifies its internal parameters in
response to the control signals from controller device 160 to vary
the stimulation characteristics of stimulation pulses transmitted
through stimulation lead 110 to the tissue of the patient.
Neurostimulation systems, stimsets, and multi-stimset programs are
discussed in PCT Publication No. WO 2001/93953, entitled
"NEUROMODULATION THERAPY SYSTEM," and U.S. Pat. No. 7,228,179,
entitled "METHOD AND APPARATUS FOR PROVIDING COMPLEX TISSUE
STIMULATION PATTERNS," which are incorporated herein by
reference.
[0039] Example commercially available neurostimulation systems
include the EON MINI.TM. pulse generator and RAPID PROGRAMMER.TM.
device from St. Jude Medical, Inc. (Plano, Tex.). Example
commercially available stimulation leads include the QUATTRODE.TM.,
OCTRODE.TM., AXXESS.TM., LAMITRODE.TM., TRIPOLE.TM., EXCLAIM.TM.,
and PENTA.TM. stimulation leads from St. Jude Medical, Inc.
[0040] The systems and methods described herein facilitate
efficient and effective SCS parameter adjustment based on patient
feedback. A grip sensor allows patients to provide quantitative
feedback on their pain levels during parameter adjustment between
SCS configurations (e.g., varying, amplitude, pulse width,
electrode contact configuration, etc.). Further, programming
algorithms facilitate selecting parameters for non-tonic SCS,
including burst and high-frequency stimulation waveforms.
[0041] FIG. 3 is a schematic diagram of one embodiment of a grip
sensor 300 that may be used to facilitate efficient and effective
SCS parameter adjustment based on patient feedback. Grip sensor 300
is used during SCS programming to enable the patient to give
real-time, quantitative feedback on their pain level in an
office/clinical setting or remotely.
[0042] In this embodiment, grip sensor 300 includes a substantially
cylindrical housing 302 and mechanical support rods 304 that extend
from opposite ends of housing 302. Mechanical support rods 304
facilitate keeping grip sensor 300 elevated and in place. Housing
302 is formed by an electronics enclosure 306 and an annular outer
shell 308 that substantially surrounds electronics enclosure 306.
Outer shell 308, in this embodiment, is made of a deformable
material (e.g., rubber, soft plastic) that has elasticity when
squeezed. Grip sensor 300 is sized to be comfortably gripped by one
or two hands of the patient. Alternatively, grip sensor 300 may
have any suitable shape and/or configuration.
[0043] At least one pressure sensor 310 (e.g., a pressure
transducer) is embedded in outer shell 308 in this embodiment.
Pressure sensor 310 measures a patient's grip strength (which
generally increases with pain) on grip sensor 300. Pressure sensor
310 may include a strain gauge, a variable capacitor cooperating
with a diaphragm and a pressure cavity, and/or piezoelectric
materials. Pressure sensor 310 is placed within or underneath outer
shell 308 and extends substantially along the length of grip sensor
300 in this embodiment.
[0044] Grip sensor 300 also includes galvanic skin response (GSR)
sensors 312 in this embodiment. GSR sensors 312 measure changes in
an electrical impedance of the skin of the patient, which result
from physiochemical responses to emotional arousal (e.g., sweating)
that increase with sympathetic nervous system activity (e.g., the
so-called "fight-or-flight" response). Impedance measured by GSR
sensors 312 will also generally increase with a greater area of
contact between GSR sensors 312 and the patient's skin. The GSR
impedance will generally increase with pain. GSR sensors 312 are
embedded within outer shell 308, such that surfaces of GSR sensors
312 are exposed for contact with the patient's hands. In this
embodiment, a single GSR sensor or plurality of GSR sensors 312
span the length of grip sensor 300.
[0045] In some embodiments, grip sensor 300 includes other sensing
devices. For example, grip sensor 300 may include a thermometer
that measures a skin temperature of the patient and heat flux
(i.e., the rate of heat dissipation from the patient's body)
attributable to the patient. The thermometer may be a thermocouple
or thermistor. The skin temperature and/or heat flux, similar to
grip strength and electrical impedance, may correspond to a pain
level experienced by the patient. In another embodiment, grip
sensor 300 includes a heart rate sensor. The heart rate sensor may
be, for example, an optical transmitter/receiver that illuminates
capillaries on the hand and measures the frequency that blood pumps
past the sensor. Circuity (e.g., amplifiers, filters,
analog-to-digital converters) for processing signals from the
various sensors is contained within electronics enclosure 306. In
this embodiment, grip sensor 300 further includes a wired
connection 320 for communicatively coupling electronics enclosure
306 to a display (not shown in FIG. 3) for visualizations of
measurements acquired using grip sensor 300.
[0046] FIG. 4 is a block diagram of one embodiment of a computing
device 400 that may be used with grip sensor 300 to facilitate
processing measurements acquired using grip sensor 300. Computing
device 400 may be included within grip sensor 300 (e.g., as part of
electronics enclosure 306), or may be communicatively coupled
(e.g., wired or wirelessly connected) to grip sensor 300.
[0047] In this embodiment, computing device 400 includes at least
one memory device 410 and a processor 415 that is coupled to memory
device 410 for executing instructions. In some embodiments,
executable instructions are stored in memory device 410. In the
illustrated embodiment, computing device 400 performs one or more
operations described herein by programming processor 415. For
example, processor 415 may be programmed by encoding an operation
as one or more executable instructions and by providing the
executable instructions in memory device 410.
[0048] Processor 415 may include one or more processing units
(e.g., in a multi-core configuration). Further, processor 415 may
be implemented using one or more heterogeneous processor systems in
which a main processor is present with secondary processors on a
single chip. In another illustrative example, processor 415 may be
a symmetric multi-processor system containing multiple processors
of the same type. Further, processor 415 may be implemented using
any suitable programmable circuit including one or more systems and
microcontrollers, microprocessors, reduced instruction set circuits
(RISC), application specific integrated circuits (ASIC),
programmable logic circuits, field programmable gate arrays (FPGA),
and any other circuit capable of executing the functions described
herein.
[0049] In the illustrated embodiment, memory device 410 is one or
more devices that enable information such as executable
instructions and/or other data to be stored and retrieved. Memory
device 410 may include one or more computer readable media, such
as, without limitation, dynamic random access memory (DRAM),
read-only memory (ROM), electrically erasable programmable
read-only memory (EEPROM), static random access memory (SRAM), a
solid state disk, and/or a hard disk. Memory device 410 may be
configured to store, without limitation, application source code,
application object code, source code portions of interest, object
code portions of interest, configuration data, execution events
and/or any other type of data.
[0050] Computing device 400, in the illustrated embodiment,
includes a communication interface 440 coupled to processor 415.
Communication interface 440 communicates with one or more remote
devices, such as a clinician or patient programmer. To communicate
with remote devices, communication interface 440 may include, for
example, a wired network adapter, a wireless network adapter, a
radio-frequency (RF) adapter, and/or a mobile telecommunications
adapter.
[0051] Grip sensor 300 is used in conjunction with computing device
400 for semi-autonomous and rapid determination of therapeutically
effective stimulation parameters. In one example, an algorithm for
rational selection of burst stimulation parameters is utilized. The
burst stimulation algorithm initially identifies an optimal contact
configuration, amplitude, and pulse width using tonic stimulation,
and then switches each tonic pulse into multi-pulse bursts and
adjusts inter-burst and intra-burst frequencies for pain relief
with reduced paresthesia. In another example, an algorithm for
rational selection of high-frequency stimulation parameters is
utilized. The high-frequency algorithm first Identifies an optimal
contact configuration, amplitude, and pulse width using tonic
stimulation, and then adjusts the frequency to 1 kHz and increases
the frequency (or adjusts to 10 kHz and decreases the frequency) to
find the minimum frequency that generates pain relief with reduced
paresthesia.
[0052] During, SCS parameter adjustment, the patient is asked to
squeeze grip sensor 300 to provide a real-time indication of the
amount of pain he or she is experiencing. If the amount of pain
decreases, the patient loosens their grip, and releases grip sensor
300 completely if pain is absent. Conversely, if the pain
increases, the patient grips more tightly. If a parameter set is
applied that causes a spike in pain or generates a side effect
(e.g., muscle activation), the patient responds with a conscious or
reflexive squeezing of grip sensor 300 that will generate a rapid
rise in measured grip force (via pressure sensor 310) and measured
skin impedance (via GSR sensors 312). Additionally, changes in GSR
may indicate stress or pain levels outside of the patient's own
perception.
[0053] Parameter adjustment sessions may be conducted in an
office/clinical selling or remotely. For remote sessions, the
patient may be given grip sensor 300 for home use, and stimulation
parameters are adjusted remotely by clinicians, or by the patient
themselves.
[0054] FIG. 5 is one embodiment of a pain quantification plot 500
that may be displayed, for example, on a display device
communicatively coupled to grip sensor 300 and/or computing device
400. Plot 500 shows pain results 501 for different parameters (i.e.
amplitude and frequency) for tonic stimulation (the first and
second columns), high-frequency stimulation (the third and fourth
columns), and burst stimulation (the fifth column). In plot 500,
for each pain result 501, denser patterns indicate higher amounts
of pain, and less dense patterns indicate lower amounts of pain. In
this embodiment, computing device 400 determines a pain level for
each pain result 501 based on signals received from sensors (e.g.,
pressure sensors 310, GSR sensors 312) on grip sensor 300.
[0055] The pain level for each pain result 501 may be calculated
using any suitable method. In this embodiment, all sensors on grip
sensor 300 contribute to the calculation of the pain level.
[0056] For example, signals from pressure sensor 310 (shown in FIG.
3) may be analyzed within 1 second after a change hi stimulation
parameters, because there will likely be a sudden adjustment hi
grip strength of the patient in response to a change in pain
levels. Quantification of pressure sensor signals may be performed
in the time domain (e.g., calculating a pain level by rectifying
and integrating) or in the frequency domain (e.g., calculating a
pain level as a signal power of high-frequency components in the
signal). Pressure sensor signals will generally decrease with lower
pain levels, and increase with higher pain levels.
[0057] Signals from GSR sensors 312 may be analyzed, for example,
over the first ten seconds after a change in stimulation
parameters, because impedance will generally have a slow onset
change in response to a change in pain levels. The measured
impedance values will generally increase with lower pain levels
(due to decreasing sweat) and decrease with higher pain levels (due
to increasing sweat). Signals from other sensors, such as
temperature sensors and heart rate sensors, may be analyzed
similarly.
[0058] If pain levels change in response to a change in stimulation
parameters, one would expect a time-synchronized, consistent change
across all of the sensors. For example, if pain levels decrease for
a given parameter set, one would expect a sudden decrease in
pressure, and a gradual increase in measured impedance. The
absolute change in pain level may be calculated as a weighted
change in the pressure and GSR impedance signals. For example, each
signal may be weighted as 50% of the total calculated change in
pain level. Alternatively, any suitable weighting may be used. If
both the pressure and GSR impedance signals do not change, or the
signals change in an unexpected manner (e.g., pressure increase and
GSR impedance increase), this may indicate that another factor
caused the change in signals, and there is no quantifiable change
in pain level.
[0059] Plot 500 also includes an electrode configuration display
502 that indicates the configuration of each electrode in an
eight-electrode percutaneous SCS lead. In some embodiments,
electrode configuration display displays a paddle lead instead. In
this example, second and third electrodes are operating as
cathodes, a fourth electrode is operating as an anode, and all
other electrodes are inactive. As shown in plot 500, in this
example, tonic stimulation at 100 Hz is generally not as effective
as burst stimulation in decreasing pain. For a different set of
anodic and cathodic electrode settings, the pain quantification
plot may differ from that shown in plot 500.
[0060] For tonic stimulation, a range of parameters can be explored
(e.g., using plot 500), and the parameters that generate maximum
pain relief may be selected. Further, tonic stimulation parameters
may be modified randomly to facilitate ensuring that the patient is
unaware of the specific parameters used at any given time.
Moreover, settings may be tested more than once to ensure a
consistent response on pain levels is observed (e.g., switching
back and forth between parameter set A and parameter set B). For
burst stimulation and high-frequency stimulation, grip sensor 300
may be used in conjunction with the following algorithms.
[0061] FIGS. 6A-6C illustrate operation of one embodiment of a
burst stimulation algorithm. To facilitate rational selection of
burst stimulation waveform parameters, a burst stimulation
algorithm starts by providing tonic stimulation at a fixed
frequency (e.g., 50 Hz) (FIG. 6A). Parameters of the tonic
stimulation are varied to determine a contact configuration,
amplitude, and pulse width that generate paresthesia coverage of
the target area. This contact configuration, amplitude, and pulse
width are then kept constant for subsequent programming.
[0062] Next, as part of the burst stimulation algorithm, the
stimulation is switched from one pulse to two pulse bursts (FIG.
6B), and a range of inter-burst frequencies (e.g., 10-100 Hz) and
intra burst frequencies (e.g., 500-1000 Hz) are explored to
determine which inter-burst and intra-burst frequencies generate
pain relief with reduced paresthesia. If no such relief is
attainable, the stimulation is switched from two pulse bursts to
three pulse bursts (FIG. 6C) and the frequency ranges are again
explored for pain relief with reduced paresthesia. Switching to
higher numbers of pulses is continued (e.g., 4 pulses, 5 pulses,
etc.) until pain relief with reduced paresthesia is obtained.
[0063] For example, FIG. 7 is a flow chart of one embodiment of a
burst stimulation algorithm 700. Algorithm 700 may be implemented,
for example, using computing device 400 (shown in FIG. 4). At block
702, stimulation parameters for tonic SCS are determined that
generate paresthesia overage of the targeted body area. At block
704, each single tonic pulse is switched into two pulse bursts.
Subsequently, at block 706, a range of inter-burst frequencies
(e.g., 10-100 Hz) and intra burst frequencies (e.g., 500-1000 Hz)
are adjusted in an attempt to generate pain relief with reduced
paresthesia.
[0064] If pain relief with reduced paresthesia cannot be obtained
by adjusting inter- and intra-burst frequencies, flow proceeds to
block 708. At block 708, one more pulse is added to each pulse
burst (e.g., two pulses per burst becomes three pulses per burst),
and flow returns to block 706.
[0065] If pain relief with reduced paresthesia is obtained by
adjusting inter- and intra burst frequencies, flow proceeds to
block 710. At block 710, stimulation programming is ended, and the
optimal burst parameters identified with algorithm 700 are used for
stimulation.
[0066] Similar to the burst stimulation algorithm, to facilitate
rational selection of high-frequency stimulation waveform
parameters, a high-frequency stimulation algorithm starts by
providing tonic stimulation at a fixed frequency (e.g., 50 Hz).
Parameters of the tonic stimulation are varied to determine a
contact configuration, amplitude, and pulse width that generate
paresthesia coverage of the target area. This contact
configuration, amplitude, and pulse width are then kept constant
for subsequent programming.
[0067] Next, as part of the high-frequency stimulation algorithm,
the stimulation frequency is adjusted to lower threshold frequency
(e.g., approximately 1 kHz), and slowly increased until pain relief
with reduced paresthesia is obtained. Alternatively, the
stimulation frequency may be adjusted to an upper threshold
frequency (e.g., approximately 10 kHz), and slowly decreased until
a minimum frequency at which pain relief with reduced paresthesia
is still generated is reached.
[0068] For example, FIG. 8 is a flow chart of one embodiment of a
high-frequency stimulation algorithm 800. Algorithm 800 may be
implemented, for example, using computing device 400 (shown in FIG.
4). At block 802, stimulation parameters for tonic SCS are
determined that generate paresthesia overage of the targeted body
area. At block 804, the stimulation frequency is adjusted to a
lower threshold frequency (e.g., 1 kHz). Subsequently, at block
806, the frequency is increased relatively slowly (e.g., in
increments of 100 Hz) until pain relief with reduced paresthesia is
obtained.
[0069] For example, FIG. 9 is a flow chart of another embodiment of
a high-frequency stimulation algorithm 900. Algorithm 900 may be
implemented, for example, using computing device 400 (shown in FIG.
4). At block 902, stimulation parameters for tonic SCS are
determined that generate paresthesia overage of the targeted body
area. At block 904, the stimulation frequency is adjusted to an
upper threshold frequency (e.g., 10 kHz). Subsequently, at block
906, the frequency is decreased relatively slowly (e.g., in
increments of 100 Hz) until pain relief with reduced paresthesia is
obtained.
[0070] FIG. 10 is a flow chart of one embodiment of a method 1000
for determining SCS therapy parameters for a patient. Method 1000
may be implemented, for example, using computing device 400 (shown
in FIG. 4). Method includes 1000 applying tonic stimulation at a
fixed frequency al block 1002. At block 1004, at least one
parameter of the applied tonic stimulation is varied until
paresthesia coverage of a target area of the patient is achieved.
Subsequently, at block 1006, the applied tonic stimulation is
further manipulated to achieve one of burst stimulation and
high-frequency stimulation that provides pain relief with reduced
paresthesia. For example block 1006 may include one or more steps
of algorithm 700 (shown in FIG. 7), algorithm 800 (shown in FIG.
8), and algorithm 900 (shown in FIG. 9).
[0071] Although certain embodiments of this disclosure have been
described above with a certain degree of particularity, those
skilled in the art could make numerous alterations to the disclosed
embodiments without departing from the spirit or scope of this
disclosure. All directional references (e.g., upper, lower, upward,
downward, left, right, leftward, rightward, top, bottom. above,
below, vertical, horizontal, clockwise, and counterclockwise) are
only used for identification purposes to aid the reader's
understanding of the present disclosure, and do not create
limitations, particularly as to the position, orientation, or use
of the disclosure. Joinder references (e.g., attached, coupled,
connected, and the like) are to be construed broadly and may
include intermediate members between a connection of elements and
relative movement between elements. As such, joinder references do
not necessarily infer that two elements are directly connected and
in fixed relation to each other. It is intended that ail matter
contained in the above description or shown in the accompanying
drawings shall be interpreted as illustrative only and not
limiting. Changes in detail or structure may be made without
departing from the spirit of the disclosure as defined in the
appended claims.
[0072] When introducing elements of the present disclosure or the
preferred embodiment(s) thereof, the articles "a", "an", "the", and
"said" are intended to mean that there are one or more of the
elements. The terms "comprising", "including", and "having" are
intended to be inclusive and mean that there may be additional
elements other than the listed elements.
[0073] As various changes could be made in the above constructions
without departing from the scope of the disclosure, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *