U.S. patent application number 11/376258 was filed with the patent office on 2006-08-24 for apparatus and methods for applying neural stimulation to a patient.
This patent application is currently assigned to Northstar Neuroscience, Inc.. Invention is credited to Brad Fowler, Bradford Evan Gliner.
Application Number | 20060190056 11/376258 |
Document ID | / |
Family ID | 34115612 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060190056 |
Kind Code |
A1 |
Fowler; Brad ; et
al. |
August 24, 2006 |
Apparatus and methods for applying neural stimulation to a
patient
Abstract
Systems and methods for neural stimulation may include a
stimulus unit; a first electrode assembly having a first set of
contacts; and a second set of contacts. The stimulus unit can be an
implantable pulse generator including a first terminal that can be
biased at a first signal polarity and a second terminal that can be
biased at a second signal polarity. The first electrode assembly
includes a support member configured to be placed at the
stimulation site, the first set of contacts carried by the support
member, and a first lead configured to be attached to the first
terminal of the implantable pulse generator for biasing the surface
contacts at the first polarity. The second set of contacts is
detached from the surface electrode assembly. The second set of
contacts can be one or more conductive elements fixed to or forming
portions of the implantable pulse generator, or a separate
electrode array.
Inventors: |
Fowler; Brad; (Woodinville,
WA) ; Gliner; Bradford Evan; (Sammamish, WA) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Northstar Neuroscience,
Inc.
Seattle
WA
|
Family ID: |
34115612 |
Appl. No.: |
11/376258 |
Filed: |
March 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10910775 |
Aug 2, 2004 |
|
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11376258 |
Mar 15, 2006 |
|
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60492273 |
Aug 1, 2003 |
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Current U.S.
Class: |
607/45 |
Current CPC
Class: |
A61N 1/36082 20130101;
A61N 1/0531 20130101; A61N 1/0539 20130101 |
Class at
Publication: |
607/045 |
International
Class: |
A61N 1/18 20060101
A61N001/18 |
Claims
1-75. (canceled)
76. A system for applying electrical stimulation to a cortex of a
patient, comprising: an implantable housing having a first portion
and a second portion; a pulse generator carried by the implantable
housing; a plurality of first electrical contacts carried by the
first portion of the housing so as to be positioned at a cortical
stimulation site of the patient located at least approximately at
or below an inner surface of the patient's skull when the housing
is implanted, the first electrical contacts being generally fixed
laterally relative to the first portion of the housing, and
electrically biasable to different levels; and at least one second
electrical contact carried by the second portion of the housing so
as to be positioned at least approximately at or above an outer
surface of the patient's skull and beneath the patient's scalp when
the housing is implanted.
77. The system of claim 76 wherein the first and second portions of
the housing face in generally opposite directions.
78. The system of claim 76 wherein at least one of the first
electrical contacts is fixed in a direction generally normal to the
first portion of the housing.
79. The device of claim 76 wherein at least one of the first
electrical contacts is movable in a direction generally normal to
the housing to apply a force to adjacent tissue when the housing is
implanted.
80. The device of claim 76 wherein the housing includes a forcing
element to which at least one of the first electrical contacts is
coupled, the forcing element being positioned to apply a force to
the first electrical contact in a direction generally normal to the
housing.
81. The system of claim 76 wherein the at least one second
electrical contact includes multiple second electrical contacts
that have generally fixed lateral positions relative to the
housing.
82. The system of claim 76 wherein the first portion of the housing
includes a first surface and the second portion of the housing
includes a second, oppositely facing surface, and wherein the first
electrical contacts are accessible from the first surface and the
second electrical contacts are accessible from the second
surface.
83. The system of claim 76, further comprising an attachment
element carried by the housing and attachable to the skull.
84. The system of claim 76 wherein the pulse generator is
programmed to provide electrical signals at subthreshold
levels.
85. The system of claim 76 wherein the first electrical contacts
project from the housing in a direction generally normal to the
housing.
86. The system of claim 76, further comprising a switching circuit
having at least one switch coupled to the pulse generator and among
the first electrical contacts to apply electrical power to a subset
of one or more selected first electrical contacts.
87. The system of claim 76 wherein the switching circuit is coupled
to the second electrical contact and is changeable between a first
configuration in which a pair of the first electrical contacts
operate in a bipolar manner, and a second configuration in which
the second electrical contact and one of the first electrical
contacts operate in a unipolar manner.
88. The device of claim 76 wherein at least one of the first
electrical contacts has a generally blunt shape and is positioned
to bear against at least one of a dura mater and a pia mater of the
patient.
89. A system for applying electrical stimulation to a cortex of a
patient, comprising: an implantable housing having a first portion
and a second portion; a pulse generator carried by the implantable
housing; a first electrical contact carried by the first portion of
the housing so as to be positioned at a cortical stimulation site
of the patient located at least approximately at or below an inner
surface of the patient's skull when the housing is implanted, the
first electrical contact being generally fixed laterally relative
to the first portion of the housing; and a second electrical
contact carried by the second portion of the housing so as to be
positioned at least approximately at or above an outer surface of
the patient's skull and beneath the patient's scalp when the
housing is implanted.
90. The system of claim 89 wherein the first and second electrical
contacts are electrically biasable to different levels.
91. The system of claim 89 wherein the first electrical contact is
one of a plurality of first electrical contacts.
92. The system of claim 89 wherein the first and second portions of
the housing face in generally opposite directions.
93. The system of claim 89 wherein at least one of the first
electrical contacts is fixed in a direction generally normal to the
first portion of the housing.
94. The system of claim 89 wherein the second electrical contact is
one of multiple second electrical contacts that have generally
fixed lateral positions relative to the housing.
95. The device of claim 89 wherein the first electrical contact is
movable in a direction generally normal to the housing to apply a
force to adjacent tissue when the housing is implanted.
96. The device of claim 89 wherein the housing includes a forcing
element to which at least one of the first electrical contacts is
coupled, the forcing element being positioned to apply a force to
the first electrical contact in a direction generally normal to the
housing.
97. The system of claim 89 wherein the first portion of the housing
includes a first surface and the second portion of the housing
includes a second, oppositely facing surface, and wherein the first
electrical contacts are accessible from the first surface and the
second electrical contacts are accessible from the second
surface.
98. The system of claim 89, further comprising an attachment
element carried by the housing and attachable to the skull.
99. The system of claim 89 wherein the pulse generator is
programmed to provide electrical signals at subthreshold
levels.
100. The system of claim 89 wherein the first electrical contact
projects from the housing in a direction generally normal to the
housing.
101. The system of claim 89 wherein the first electrical contact is
one of a plurality of first electrical contacts, and wherein the
system further comprises a switching circuit having a at least one
switch coupled to the pulse generator and among the first
electrical contacts to apply electrical power to a subset of one or
more selected first electrical contacts.
102. The system of claim 89 wherein the switching circuit is
coupled to the second electrical contact and is changeable between
a first configuration in which a pair of the first electrical
contacts operate in a bipolar manner, and a second configuration in
which the second electrical contact and one of the first electrical
contacts operate in a unipolar manner.
103. The device of claim 89 wherein at least one of the first
electrical contacts has a generally blunt shape and is positioned
to bear against at least one of a dura mater and a pia mater of the
patient.
104. A system for applying electrical stimulation to a cortex of a
patient, comprising: an implantable housing; a pulse generator
carried by the implantable housing; a first electrical contact
electrically coupled to the pulse generator so as to be positioned
at a cortical stimulation site of the patient located at least
approximately at or below an inner surface of the patient's skull
when the housing is implanted; and a second electrical contact
carried by the housing and having a fixed position relative to the
housing so as to be positioned at least approximately at or above
an outer surface of the patient's skull and beneath the patient's
scalp when the housing is implanted.
105. The system of claim 104 wherein the first electrical contact
is coupled to a lead and is laterally movable relative to the
housing.
106. The system of claim 104 wherein the first electrical contact
includes a plurality of first electrical contacts that are
electrically biasable to different levels.
107. The system of claim 104 wherein the first electrical contact
is generally fixed laterally relative to the housing.
108. The system of claim 104 wherein the first and second
electrical contacts are electrically biasable to different
levels.
109. The device of claim 104 wherein the first electrical contact
is movable in a direction generally normal to the housing to apply
a force to adjacent tissue when the housing is implanted.
110. The device of claim 104 wherein the housing includes a forcing
element to which the first electrical contact is coupled, the
forcing element being positioned to apply a force to the first
electrical contact in a direction generally normal to the
housing.
111. The system of claim 104 wherein the at least one second
electrical contact includes multiple second electrical contacts
that have generally fixed lateral positions relative to the
housing.
112. The system of claim 104, further comprising an attachment
element carried by the housing and attachable to the skull.
113. The system of claim 104 wherein the pulse generator is
programmed to provide electrical signals at subthreshold
levels.
114. The device of claim 104 wherein the first electrical contact
has a generally blunt shape and is positioned to bear against at
least one of a dura mater and a pia mater of the patient.
115. A method for implanting a cortical stimulation device,
comprising: providing an implantable housing carrying a pulse
generator, the pulse generator being electrically coupled to a
first electrical contact, the housing carrying a second electrical
contact; forming a hole in a patient's skull; moving the first
electrical contact into the hole and positioning the first
electrical contact at a cortical stimulation site of the patient
located at least approximately at or below an inner surface of the
patient's skull; and placing the implantable housing in the hole so
as to position the second electrode at least approximately at or
above an outer surface of the patient's skull and beneath the
patient's scalp, with the second electrode having a fixed position
relative to the housing.
116. The method of claim 115 wherein forming a hole in the
patient's skull includes forming the hole to extend through the
patient's skull.
117. The method of claim 115 wherein placing the implantable
housing includes placing the implantable housing while the first
electrical contact has a laterally fixed position relative to the
housing, and wherein moving the first electrical contact into the
hole and placing the implantable housing in the hole are performed
simultaneously.
118. The method of claim 115 wherein moving the first electrical
contact includes moving the first electrical contact while the
first electrical contact is connected to the housing with a
flexible lead.
119. The method of claim 115, further comprising applying a
subthreshold stimulation signal to the patient via the first
electrical contact.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to pending U.S. Provisional
Application No. 60/492,273, filed on Aug. 1, 2003, and incorporated
herein in its entirety by reference.
INCORPORATION OF RELATED APPLICATIONS
[0002] This application is related to U.S. patent application Ser.
No. 09/802,808 entitled "Methods and Apparatus for Effectuating a
Lasting Change in a Neural-Function of a Patient," which claims the
benefit of U.S. Provisional Application 60/217,981, filed Jul. 31,
2000, both of which are herein incorporated by reference.
Additional applications are incorporated by reference in other
portions of this application.
TECHNICAL FIELD
[0003] The present disclosure is related to systems and methods for
applying stimulation to a target neural population within a
patient, for example, a surface site on the patient's cortex.
BACKGROUND
[0004] A wide variety of mental and physical processes are
controlled or influenced by neural activity in particular regions
of the brain. The neural-functions in some areas of the brain
(i.e., the sensory or motor cortices) are organized according to
physical or cognitive functions, and various areas of the brain
appear to have distinct functions in most individuals. In the
majority of people, for example, the occipital lobes relate to
vision, the left interior frontal lobes relate to language, and the
cerebral cortex appears to be involved with conscious awareness,
memory, and intellect.
[0005] Many problems or abnormalities can be caused by damage,
disease and/or disorders in the brain. Effectively treating such
abnormalities may be very difficult. For example, a stroke is a
common condition that damages the brain. Strokes are generally
caused by emboli (e.g., obstruction of a vessel), hemorrhages
(e.g., rupture of a vessel), or thrombi (e.g., clotting) in the
vascular system of a specific region of the brain. Such events
generally result in a loss or impairment of a neural function
(e.g., neural functions related to facial muscles, limbs, speech,
etc.). Stroke patients are typically treated using various forms of
physical therapy to rehabilitate the loss of function of a limb or
another affected body part. Stroke patients may also be treated
using physical therapy plus an adjunctive therapy such as
amphetamine treatment. For most patients, however, such treatments
are minimally effective and little can be done to improve the
function of an affected body part beyond the recovery that occurs
naturally without intervention.
[0006] Neurological problems or abnormalities are often related to
electrical and/or chemical activity in the brain. Neural activity
is governed by electrical impulses or "action potentials" generated
in neurons and propagated along synaptically connected neurons.
When a neuron is in a quiescent state, it is polarized negatively
and exhibits a resting membrane potential typically between -70 and
-60 mV. Through chemical connections known as synapses, any given
neuron receives excitatory and inhibitory input signals or stimuli
from other neurons. A neuron integrates the excitatory and
inhibitory input signals it receives, and generates or fires a
series of action potentials when the integration exceeds a
threshold potential. A neural firing threshold, for example, may be
approximately -55 mV.
[0007] It follows that neural activity in the brain can be
influenced by electrical energy supplied from an external source
such as a waveform generator. Various neural functions can be
promoted or disrupted by applying an electrical current to the
cortex or other region of the brain. As a result, researchers have
attempted to treat physical damage, disease and disorders in the
brain using electrical or magnetic stimulation signals to control
or affect brain functions.
[0008] Transcranial electrical stimulation is one such approach
that involves placing an electrode on the exterior of the scalp and
delivering an electrical current to the brain through the scalp and
skull. Another treatment approach, transcranial magnetic
stimulation, involves producing a high-powered magnetic field
adjacent to the exterior of the scalp over an area of the cortex.
Yet another treatment approach involves direct electrical
stimulation of neural tissue using implanted electrodes.
[0009] The neural stimulation signals used by these approaches may
comprise a series of electrical or magnetic pulses directed toward
affecting neurons within a target neural population. Stimulation
signals may be defined or described in accordance with stimulation
signal parameters including pulse amplitude, pulse frequency, duty
cycle, stimulation signal duration, and/or other parameters.
Electrical or magnetic stimulation signals applied to a population
of neurons can depolarize neurons within the population toward
their threshold potentials. Depending upon stimulation signal
parameters, this depolarization can cause neurons to generate or
fire action potentials. Neural stimulation that elicits or induces
action potentials in a functionally significant proportion of the
neural population to which the stimulation is applied is referred
to as supra-threshold stimulation; neural stimulation that fails to
elicit action potentials in a functionally significant proportion
of the neural population is defined as sub-threshold stimulation.
In general, supra-threshold stimulation of a neural population
triggers or activates one or more functions associated with the
neural population, but sub-threshold stimulation by itself does not
trigger or activate such functions. Supra-threshold neural
stimulation can induce various types of measurable or monitorable
responses in a patient. For example, supra-threshold stimulation
applied to a patient's motor cortex can induce muscle fiber
contractions in an associated part of the body.
[0010] Although electrical or magnetic stimulation of neural tissue
may be directed toward producing an intended type of therapeutic,
rehabilitative, or restorative neural activity, such stimulation
may result in collateral neural activity. In particular, neural
stimulation delivered beyond a certain intensity, period of time,
level, or amplitude can give rise to seizure activity and/or other
types of collateral activity. It will be appreciated that certain
types of collateral neural activity may be undesirable and/or
inconvenient in a neural stimulation situation.
[0011] Another concern that arises in association with stimulating
a surface site on a patient's cortex is conservation or
minimization of applied power while operating a stimulation device.
Various types of systems have an implanted pulse generator ("IPG")
and an electrode assembly. The electrode assembly generally has a
plurality of contacts that are carried by a common support member,
such that the contacts are positionally fixed in close or generally
close proximity relative to each other. In operation, the IPG
delivers an electrical waveform to the electrode assembly, such
that a first set of contacts provides a current delivery path and a
second set of contacts provides a current return path. Thus, at any
given time during waveform delivery, at least one contact has a
positive bias and at least one contact has a negative bias,
resulting in the generation of a bipolar field at the surface of
the cortex within the area of the stimulation site. The bipolar
field has a lower current density in the deeper layers of the
cortex compared to the current density at the surface layers, and
the bipolar field runs generally parallel to the cranium of the
patient in the deeper layers of the cortex. Systems that generate a
bipolar field at the stimulation site may require relatively high
current levels to achieve an intended or desired therapeutic
effect. This may result in increased power consumption, and
possibly increase the likelihood of inducing collateral neural
activity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a side view of a system for applying electrical
stimulation to a stimulation site on or proximate to the surface of
the cortex of a patient in accordance with an embodiment of the
invention.
[0013] FIG. 2 is a graph illustrating several parameters that may
describe, define, or characterize a stimulation signal.
[0014] FIG. 3A is a front view of a system for applying electrical
stimulation to a cortical stimulation site in accordance with FIG.
1A showing a different implementation of the system.
[0015] FIG. 3B is a cross-sectional view of a brain of a patient
illustrating the implementation of FIG. 3A in greater detail.
[0016] FIG. 3C is a schematic illustration of a combined electrode
assembly that may be used to apply or deliver unipolar stimulation
to a patient.
[0017] FIG. 4 is a schematic illustration showing an exemplary
electric field distribution generated by unipolar electrical
stimulation using a system for applying electrical stimulation to a
cortical stimulation site in accordance with an embodiment of the
invention.
[0018] FIG. 5 is a schematic illustration showing an exemplary
electrical field distribution generated by bipolar electrical
stimulation at a cortical stimulation site.
[0019] FIG. 6 is a side view of a system for applying electrical
stimulation to a cortical stimulation site in accordance with
another embodiment of the invention.
[0020] FIG. 7 is a side view of a system for applying electrical
stimulation to a cortical stimulation site in accordance with
another embodiment of the invention.
[0021] FIGS. 8A and 8B are an isometric view and a cross sectional
view, respectively, of a system for applying electrical stimulation
to a site on or proximate to the cortex in accordance with another
embodiment of the invention.
[0022] FIG. 8C is a cross sectional view of a system for applying
electrical stimulation to a site on or proximate to the cortex
according to another embodiment of the invention.
[0023] FIG. 9A is a schematic illustration of a system for applying
electrical stimulation to a site on or proximate to the cortex in
accordance with another embodiment of the invention.
[0024] FIG. 9B is a schematic illustration of a system for applying
electrical stimulation to a site on or proximate to the cortex in
accordance with another embodiment of the invention.
[0025] FIGS. 10-11 are flow charts illustrating methods for
applying electrical stimulation to a stimulation site in accordance
with embodiments of the invention.
DETAILED DESCRIPTION
[0026] The present disclosure describes systems and methods for
neural stimulation that may enhance the efficacy and/or increase
the efficiency of neural stimulation procedures. The neural
stimulation may comprise a set of stimulation signals applied or
delivered to or through target neural structures, target neural
projections, and/or one or more target neural populations
associated with controlling, influencing, or affecting one or more
neurological functions under consideration. The neural stimulation
may be directed toward facilitating and/or effectuating at least
some degree of symptomatic relief and/or restoration or development
of functional abilities in patients experiencing neurologic
dysfunction arising from neurological damage, neurologic disease,
neurodegenerative conditions, neuropsychiatric disorders, cognitive
or learning disorders, and/or other conditions. Such neurologic
dysfunction may correspond to Parkinson's Disease, essential
tremor, Huntington's disease, stroke, traumatic brain injury,
Cerebral Palsy, Multiple Sclerosis, a central pain syndrome, a
memory disorder, dementia, Alzheimer's disease, an affective
disorder, depression, bipolar disorder, anxiety,
obsessive/compulsive disorder, Post Traumatic Stress Disorder, an
eating disorder, schizophrenia, Tourette's Syndrome, Attention
Deficit Disorder, an addiction, autism, epilepsy, a sleep disorder,
a hearing disorder (e.g., tinnitis or auditory hallucinations), a
speech disorder (e.g., stuttering), and/or one or more other
disorders, states, or conditions.
[0027] For example, relative to controlling, influencing,
stabilizing, restoring, enhancing, or gaining a motor function, a
target neural population may comprise one or more portions of a
patient's motor cortex. A neural location at which or a neural
region in which stimulation signals are applied or delivered to or
through a target neural population may be defined as a stimulation
site. Thus, for a target neural population corresponding to the
motor cortex, an exemplary stimulation site may comprise a location
or region upon the patient's dura mater.
[0028] As another example, relative to controlling, influencing,
stabilizing, restoring, or enhancing an auditory function, a target
neural population may correspond to one or more portions of a
patient's auditory cortex. A stimulation site may comprise an
epidural or subdural cortical region that may facilitate the
application, delivery, and/or transfer of stimulation signals to
such a target neural population, for example, an epidural site
adjacent or proximate to the Sylvian fissure. The application of
unipolar stimulation signals to such a stimulation site in
accordance with particular embodiments of the invention may
increase a likelihood of affecting the target neural population in
an intended manner.
[0029] A stimulation site may be identified in accordance with a
variety of techniques, including (1) identification of one or more
anatomical landmarks; (2) preoperatively (e.g., using Transcranial
Magnetic Stimulation) and/or intraoperatively stimulating one or
more brain locations to identify or map particular neural regions
that induce or evoke a given type of patient response (for example,
a movement or a sensation); (3) estimating a location at which the
brain may recruit neurons to carry out a given type of neural
activity that was previously performed by a damaged portion of the
brain; (4) an electrophysiologic signal measurement and/or analysis
procedure (e.g., acquisition and/or analysis of EEG, EMG, MEG,
coherence, partial coherence, and/or other signals); and/or (5) a
neural imaging procedure. In general, the number and/or location of
stimulation sites under consideration may depend upon the nature,
number, and/or extent of a patient's neurological condition and/or
functional deficits.
[0030] Several embodiments of such systems and methods apply or
deliver a unipolar, monopolar, or isopolar stimulation signal that
may provide enhanced efficacy or efficiency stimulation using a low
current level that reduces power consumption and/or mitigates
collateral effects. Various embodiments of the present invention
may apply or deliver neural stimulation at a subthreshold level or
intensity, that is, at a level that raises or generally raises
membrane potentials associated with a target neural population
while avoiding the generation of a sufficient or statistically
significant number of action potentials capable of triggering a
neural function corresponding to the target neural population as a
result of neural stimulation alone.
[0031] Stimulation systems and methods in accordance with the
present invention may be used to treat various neurological
conditions and/or facilitate particular types of neurological or
functional patient outcomes. Depending upon the nature of a
particular condition, neural stimulation applied or delivered in
accordance with several embodiments of the invention may affect
neural firing likelihoods and/or influence, facilitate, and/or
effectuate reorganization of interconnections or synapses between
neurons to (a) provide at least some degree of functional recovery
and/or functional gain; and/or (b) develop one or more compensatory
mechanisms to at least partially overcome a functional deficit or
shortcoming. Such reorganization of neural interconnections may be
achieved, at least in part, by a change in the strength of synaptic
connections through a process that corresponds to a mechanism
commonly known as Long-Term Potentiation (LTP). Neural stimulation
applied or delivered in accordance with certain embodiments of the
invention may alternatively or additionally affect particular
neural populations through a process that corresponds to a
mechanism commonly known as Long-Term Depression (LTD). Neural
stimulation delivered or applied to one or more target neural
populations either alone or in conjunction or association with one
or more behavioral activities and/or other types of adjunctive or
synergistic therapies (e.g., a drug or chemical substance therapy,
a neurotrophic or growth factor therapy, and/or a cell implantation
therapy) may facilitate, effectuate, or enhance therapeutic
efficacy, for example, through neural plasticity and the
reorganization of synaptic interconnections between neurons.
[0032] A. Systems for Applying Electrical Stimulation
[0033] FIG. 1 is a side view of a system for applying electrical
stimulation to a neural stimulation site or region according to an
embodiment of the invention. In various embodiments, the
stimulation site may be upon, essentially upon, or proximate to the
surface of the cortex of a patient P. The stimulation system may
comprise a stimulus unit 120 and a patient interface that includes
a set of electrodes, electrode arrangements and/or electrode
assemblies 160 (hereinafter, "electrode assemblies"). In one
embodiment, the set of electrode assemblies 160 includes a first
electrode assembly 160a and a second electrode assembly 160b.
Various alternate embodiments may include additional electrode
assemblies, which may be positioned or implanted at or proximate to
a set of stimulation sites, or remote from one or more stimulation
sites. Electrode assemblies can stimulate different neural regions,
e.g., regions carrying out different neural functions and/or
regions carrying out neural functions at different locations of the
body, including different extremities of the body.
[0034] Depending upon embodiment details, the system may also
include a sensing unit 180 (shown schematically) configured to
monitor one or more types of patient responses, activities, and/or
behaviors. The sensing unit 180 may be further configured to
communicate with the stimulus unit 120. The sensing unit 180 may
include, for example, electrodes 182 and/or other devices (e.g., an
accelerometer or motion detector) configured to sense a patient's
neural activity (e.g., an EEG signal), neuromuscular activity
(e.g., an EMG signal), behavioral activity (e.g., patient motion),
and/or other types of patient activity.
[0035] The stimulus unit 120 generates and outputs stimulation
signals, and the set of electrode assemblies 160 facilitates
application or delivery of the stimulation signals to the patient
P. The stimulus unit 120 may perform, direct, and/or facilitate
neural stimulation procedures in a manner that enhances efficacy,
mitigates a likelihood of inducing collateral neural activity,
and/or conserves power, as described in detail below.
[0036] The stimulus unit 120 may comprise a pulse generator that is
implanted into the patient P. In the embodiment shown in FIG. 1,
the stimulus unit 120 is an IPG that is implanted in a thoracic,
subclavicular, or abdominal location. In other embodiments, the
stimulus unit 120 can be an IPG implanted in the patient's skull or
just under the patient's scalp. For example, the stimulus unit 120
can be implanted above the patient's neckline at a location in or
near the patient's cranium. Examples stimulus units 120 suitable
for implantation in a patient's cranium are set forth in U.S.
patent application Ser. No. 09/802,808 (previously incorporated by
reference), as well as herein with reference to FIGS. 8A through
9B.
[0037] The stimulus unit 120 may comprise a controller 130 and a
pulse system 140. The stimulus unit 120 may further comprise a
power source, a battery, an energy storage device, and/or power
conversion circuitry (not shown). The controller 130 may include a
processor, a memory, and a programmable computer medium. The
controller 130 may be implemented as a computer or a
microcontroller, and the programmable medium may comprise software,
instructions, and/or configuration information loaded into the
memory and/or hardware that performs, directs, and/or facilitates
neural stimulation procedures in accordance with one or more
methods of the present invention.
[0038] The pulse system 140 generates and outputs stimulation
signals. FIG. 2 is a graph illustrating several parameters that may
describe, define, or characterize a stimulation signal. A stimulus
start time t.sub.0 may define an initial point at which a
stimulation signal is applied to a target neural population. In one
embodiment, the stimulation signal may be a symmetric or asymmetric
biphasic waveform comprising a set or series of biphasic pulses,
and which may be defined, characterized, or described by parameters
including a pulse width t.sub.1 for a first pulse phase; a pulse
width t.sub.2 for a second pulse phase; and a pulse width t.sub.3
for a single biphasic pulse. The parameters can also include a
stimulus repetition rate 1/t.sub.4 corresponding to a pulse
repetition frequency; a stimulus pulse duty cycle equal to t.sub.3
divided by t.sub.4; a stimulus burst time t.sub.5 that defines a
number of pulses in a pulse train; and/or a pulse train repetition
rate 1/t.sub.6 that defines a stimulus burst frequency. Other
parameters include a peak current intensity I.sub.1 for the first
pulse phase and a peak current intensity I.sub.2 for the second
pulse phase. Those skilled in the art will understand that pulse
intensity or amplitude may decay during one or both pulse phases,
and a pulse may be a charge-balanced waveform. Those skilled in the
art will further understand that in an alternate embodiment, pulses
can be monophasic or polyphasic.
[0039] In certain embodiments, the pulse system 140 may generate
and/or output stimulation signals in accordance with a theta burst
pattern. In general, theta burst stimulation may comprise pulse
bursts and/or pulse packets separated by quiescent intervals, such
that the number of pulse packets per seconds corresponds or
approximately corresponds to theta wave frequencies exhibited by
the brain. In general, theta wave frequencies may range from
approximately 3 to 10 Hz, and more particularly in certain
embodiments, 4 to 8 Hz.
[0040] In particular embodiments, the pulse system 140 may vary
and/or modulate stimulation signals in one or more manners, for
example, in accordance with one or more mathematical operations
and/or functions upon or corresponding to particular stimulation
signal parameters. Exemplary manners of varying stimulation signals
are described in detail in U.S. Application No. 60/588,406, filed
on Jul. 15, 2004, entitled "System and Method for Enhancing or
Affecting Neural Stimulation Efficiency and/or Efficacy,"
incorporated herein by reference in its entirety.
[0041] The pulse system 140 may apply or output stimulation signals
to, across, or between a first terminal 142a and a second terminal
142b. Since a stimulation signal may comprise a time-varying
waveform, a relative polarity of the stimulation signal, and hence
that of the first and second terminals 142a-b, may change or vary
with time. With respect to outputting one or more stimulation
signals having phases that differ in polarity, an anode may be
defined as a terminal 142a-b to which a positive polarity phase
within an initial pulse is first applied. For example, for a
stimulation signal comprising a series of biphasic pulses where
each pulse includes a positive polarity phase followed by a
negative polarity phase, where positive and negative may
respectively be defined relative to a zero potential level or a
potential offset, an anode may be designated as the particular
terminal 142a-b that first receives a positive polarity phase
following the stimulus start time t.sub.0. A cathode may be defined
as a terminal 142a-b that provides electrical continuity for the
stimulation signal delivered through the anodal terminal 142a-b.
The polarity of the cathode may thus be opposite to that of the
anode, or neutral. Depending upon embodiment details, a cathode may
be defined as a terminal 142a-b to which a first negative polarity
or lower potential phase within an initial pulse is first applied.
Those skilled in the art will recognize that the terms anode and
cathode could be defined in an opposite or different manner than as
defined above, yet such opposite or different definitions would be
equivalent, essentially equivalent, or consistent from a
mathematical or circuit analysis perspective.
[0042] Depending upon embodiment details, (a) the first terminal
142a may be configured as an anode, while the second terminal 142b
may be configured as a cathode; (b) the first terminal 142a may be
configured as a cathode, while the second terminal 142b may be
configured as an anode; or (c) the first and second terminals
142a-b may be selectively or programmably configured as an anode
and a cathode, possibly in a predetermined, aperiodic, or
pseudo-random time dependent manner. Such anode/cathode selectivity
may occur on a subseconds-based, a seconds-based, an hours-based,
and/or another type of time domain, and/or may be facilitated by
signal selection circuitry (e.g., a multiplexor or a switch matrix)
and/or redundant output circuitry within the stimulus unit 120. In
particular embodiments, stimulus periods provided by the stimulus
unit 120 can have durations of 30 seconds or less, 10 seconds or
less, 2-5 seconds, about one second, and/or less than one second.
The stimulus periods can include but are not limited to alternating
cathodal and anodal periods, alternating unipolar periods,
alternating bipolar periods, and/or periods that alternate between
unipolar and bipolar. The electrical potential of the stimulation
signal can also alternate between subthreshold levels and
suprathreshold levels.
[0043] The first electrode assembly 160a may be positioned or
implanted at a stimulation site that is located upon, essentially
upon, or proximate to a target neural population upon, within, or
near the patient's cerebral cortex. The first electrode assembly
160a may comprise a support member 162a and one or more contacts
164a carried by the support member 162a. The support member 162a
may be configured for implantation at a stimulation site upon or at
least proximate to the surface of the patient's cortex. The support
member 162a, for example, can be a flexible or rigid substrate that
is implanted under the cranium S such that the contacts 164a are
positioned upon or adjacent to the dura mater at the stimulation
site. In other embodiments, the support member 162a can be a
portion of a cranial screw or a housing that is implanted through
the cranium S, in a manner identical or analogous to that described
in U.S. patent application Ser. No. 10/418,796, which is
incorporated herein by reference.
[0044] The first electrode assembly 160a can have one or more
contacts 164a arranged or positioned in a desired configuration.
For example, the first electrode assembly 160a may include a single
contact 164a, or a plurality of contacts 164a arranged as an array,
grid, or other pattern. In the embodiment shown in FIG. 1, the
first electrode assembly 160a also includes a first lead or link
170a that electrically couples some or all of the contacts 164a to
the pulse system's first terminal 142a. The first electrode
assembly 160a may therefore be configured as an anode or a cathode,
in accordance with the anodal or cathodal configuration of the
first terminal 142a of the pulse system 140. Contacts 164a that are
not coupled to the first terminal 142a at a particular time may
electrically float. The first link 170a may be a wired link or a
wireless link. The first electrode assembly 160a can comprise a
cortical neural-stimulation device, such as any of the devices
described in U.S. patent application Ser. No. 09/802,808
(previously incorporated herein by reference), and U.S. patent
application Ser. No. 10/418,976, which is also incorporated by
reference herein.
[0045] The second electrode assembly 160b can be similar to the
first electrode assembly 160a, or it can be a different type of
electrode assembly. The second electrode assembly 160b may be
positioned remotely from the first electrode assembly 160a. Since
the second electrode assembly 160b provides electrical continuity
with respect to the first electrode assembly 160a, the second
electrode assembly 160b may be defined to reside at a circuit
completion site. In the embodiment shown in FIG. 1, the second
electrode assembly 160b comprises a separate electrode array
including a support base 162b and one or more contacts 164b. In
accordance with particular embodiment details, the support base
162b can be configured for positioning at (a) a location or site
upon or proximate to the surface of the cortex spaced apart from
the stimulation site where the first electrode assembly 160a is
located; (b) a deep brain location; or (c) another area in the body
above or below the neck. The second electrode assembly 160b can
include a second link 170b that couples one or more contacts 164b
(i.e., each contact 164b that is not electrically floating) to the
second terminal 142b of the pulse system 140. Thus, the second
electrode assembly 160b may be configured as an anode or a cathode,
in accordance with the anodal or cathodal configuration of the
pulse system's second terminal 142b.
[0046] In the embodiment shown, the second electrode assembly 160b,
and more particularly the second electrode assembly's contacts
164b, are separate or otherwise detached from the first electrode
assembly 160a. Thus, the second electrode assembly's contacts 164b
are not attached to the first electrode assembly 160a, and the
second electrode assembly's contacts 164b may be movable with
respect to the contacts 164a of the first electrode assembly 164a
before being implanted in the patient. The second electrode
assembly 160b may accordingly be configured to be attached to or
implanted in the patient at a location spaced apart from a
stimulation site on or proximate to the cortex of the patient where
electrical stimulation is to be applied to facilitate and/or
effectuate a given neurological or neurofunctional outcome, such as
neural plasticity or another type of neural reorganization
corresponding to one or more neural populations.
[0047] In the embodiment shown in FIG. 1, each contact 164a of the
first electrode assembly 160a that is coupled to the pulse system's
first terminal 142a (i.e., each non-floating contact 164a) is
biased in accordance with a first signal polarity. Thus, the pulse
system 140 applies an identical polarity signal to each such
contact 164a at any given time. Correspondingly, each intentionally
biased or non-floating contact 164b of the second electrode
assembly 160b is biased in accordance with a second signal
polarity, where the second signal polarity is opposite or
complementary to the first signal polarity, or neutral, to
facilitate electrical current flow between the first and second
electrode assemblies 160a-b.
[0048] Neural stimulation in which both an anode and a cathode are
positioned, located, or situated within, essentially directly
across, or proximate to a stimulation site may be defined as
bipolar stimulation. In contrast, neural stimulation in which one
of an anode and a cathode is positioned, located, or situated
within or proximate to a stimulation site, while a respective
corresponding cathode or anode is positioned, located, or situated
remote from the stimulation site to provide electrical continuity
may be defined as unipolar, monopolar, or isopolar stimulation.
Thus, neural stimulation characterized by a biasing configuration
in which an anode and a cathode are positioned, located, or
situated in different neurofunctional areas or functionally
distinct anatomical regions may be defined as unipolar stimulation.
In a unipolar configuration, the pulse system 140 applies an
identical polarity signal to each non-floating contact 162a-b
positioned upon or proximate to a stimulation site. Unipolar
stimulation may be defined as anodal unipolar stimulation when an
anode is positioned upon or proximate to a stimulation site or a
target neural population; and as cathodal unipolar stimulation when
a cathode is positioned upon or proximate to a stimulation site or
a target neural population.
[0049] In several embodiments, the second electrode assembly 160b
is positioned apart or remote from the first electrode assembly
160a to establish an electric field that passes through deep layers
of the cortex and/or other neural regions in a direction that is
generally perpendicular or oblique with respect to (a) the first
electrode assembly's contacts 164a; (b) the surface of the cortex
under the first electrode assembly 160a; and/or (c) the cranium of
the patient at or proximate to the stimulation site. The electric
field, for example, is substantially normal to the first electrode
assembly 160a in the deep layers of the cortex and/or other neural
layers beneath the stimulation site.
[0050] FIGS. 3A and 3B illustrate a different implementation of a
system for applying electrical stimulation to a neural stimulation
site according to an embodiment of the invention. In this
embodiment, a first electrode assembly 160a may be implanted in the
patient at a stimulation site at least proximate to the surface of
the cortex C (FIG. 3B) over target neurons or a target neural
population N (FIG. 3B). A second electrode assembly 160b may be
positioned at a location in the patient that is spaced apart from
the stimulation site, for example, at a location that is above the
patient's neck, to establish an electric field orientation or
distribution that extends in a desired direction relative to the
target neurons N. The second electrode assembly 160b may
additionally or alternatively be positioned relative to other
neural structures to minimize or mitigate collateral neural
activity. The second electrode assembly 160b can be spaced apart
from the patient's brain as shown in FIG. 3A, or the second
electrode assembly 160b can be positioned at a different location
of the patient's brain as shown in FIG. 3B.
[0051] The stimulus unit 120 may provide an output at a first
polarity to the non-floating contacts 164a of the first electrode
assembly 160a, and provide an output at a second polarity to the
non-floating contacts 164b of the second electrode assembly 160b.
The first electrode assembly's contacts 164a accordingly provide a
unipolar, monopolar, or isopolar bias at the stimulation site upon
or proximate to the patient's cortex C. The first polarity may be
anodal or cathodal, and the second polarity may respectively be
cathodal or anodal (i.e., opposite to the first polarity or
neutral). A unipolar signal applied to the first electrode
assembly's contacts 164a may establish an electric field that
extends through deep layers of the cortex and/or other neural
regions along a vector V extending generally perpendicular to, or
at least oblique with respect to, the orientation of (a) the first
electrode assembly 160a; (b) the surface of the cortex C at or
proximate to the stimulation site; and/or (c) the cranium of the
patient adjacent to the stimulation site (FIG. 3A).
[0052] Certain systems and/or methods in accordance with the
present invention may utilize or rely upon a single electrode
assembly having a design that is suitable for providing unipolar
stimulation rather than relying upon separate electrode assemblies.
FIG. 3C is a schematic illustration of a combined electrode
assembly 260 capable of applying or delivering unipolar stimulation
to a patient. In one embodiment, the combined electrode assembly
260 includes a support member 262 having a local portion 263a, a
remote portion 263b, and a separation portion 263c. The local
portion 263a carries a first set of contacts 264a, and the remote
portion 263b carries a second set of contacts 264b. The support
member 262 may be formed from one or more flexible or generally
flexible biocompatible materials (e.g., plastic and/or silicone),
and the first and second sets of contacts 264a-b may be formed from
one or more biocompatible conductive materials (e.g., Titanium
and/or Platinum). Through appropriate couplings to a pulse system's
first and second terminals 142a-b (for example, via a first and a
second link 170a-b), the first set of contacts 264a may be
configured as an anode or a cathode, while the second set of
contacts 264b may respectively be configured as a cathode or an
anode to facilitate unipolar stimulation.
[0053] The combined electrode assembly 260 may be implanted into a
patient such that the local portion 263a resides at, upon, or
proximate to a stimulation site, while the remote portion 263b
resides at a circuit completion site that is distant or remote from
the stimulation site. The separation portion 263c may have a length
L that is sufficient to ensure that in a typical patient, an
electric field generated at or in the vicinity of the local portion
263a is substantially perpendicular to the patient's cranium,
cortical surface, and/or targeted neural tissues (which may include
deep cortical layers or regions, as discussed below) beneath the
stimulation site. In one embodiment, the value of L may be roughly
an order of magnitude greater than the distance between the
stimulation site and a target neural population or neural region
that is deepest or farthest from the stimulation site. For subdural
stimulation, an exemplary value of L may be roughly an order of
magnitude or more greater than approximately 2.5 to 3.0 mm; and for
epidural stimulation, an exemplary value of L may be roughly an
order of magnitude greater than approximately 4.0 to 6.0 mm.
[0054] The location, depth, and/or spatial boundaries of target
neural structures and/or a target neural population may depend upon
the nature of a neurological condition or disorder under
consideration. The extent to which an electric field reaches,
penetrates, and/or travels into or through target neural structures
and/or a target neural population may affect neural stimulation
efficiency and/or efficacy. An electric field generated by unipolar
stimulation may reach or penetrate deeper neural regions at a lower
current level than an electric field generated by bipolar
stimulation, as further described hereafter.
[0055] FIG. 4 is a schematic illustration showing an exemplary
electric field distribution generated by unipolar stimulation using
a system in accordance with an embodiment of the invention. In FIG.
4, a first contact 164a is positioned at a stimulation site
corresponding to a target neural population, while a second contact
(not shown) is positioned distant or remote from the first contact
164a at a different neurofunctional or anatomical region. The first
contact 164a may be biased as an anode, for example, and the second
contact may be biased as a cathode to establish an electrical
potential gradient or difference that facilitates the flow of
electrical current (i.e., a net movement of charged particles or
ions). A unipolar electric field distribution may be represented as
a plurality of field lines 300 that extend through, for example,
targeted deep layers of the cortex C and possibly other neural
regions in a direction that is at least substantially perpendicular
to (1) the surface of the cortex at or proximate to the stimulation
site; and/or (2) the first electrode assembly's contacts 164a.
[0056] FIG. 5 is a schematic illustration showing an exemplary
electric field distribution generated by bipolar stimulation, which
may be selectively produced in accordance with particular
embodiments of the invention as further described below. In FIG. 5,
a first contact 410a and a second contact 410b are configured to
deliver bipolar stimulation to one or more portions of a target
neural population. The first and second contacts 410a, 410b are
located proximate to each other, within or upon a stimulation site
that corresponds to the spatial extent of the target neural
population. In a bipolar configuration, contacts 410a-b positioned
at and/or near the stimulation site are biased at different
polarities. In FIG. 5, the first contact 410a is biased as an
anode, while a second contact 410b is biased as a cathode. A
bipolar electric field distribution may be represented as a
plurality of field lines 400 having field components that are
generally parallel to (1) the surface of the cortex at or proximate
to the stimulation site; and/or (2) a support member (not shown)
configured to carry the first and second contacts 410a-b.
[0057] In general, an electrical potential gradient or difference
between an anode and a cathode configured to provide unipolar
stimulation exists over a longer or greater distance than an
electrical potential gradient between an anode and a cathode
configured to provide bipolar stimulation. Thus, an anode to
cathode electrical current pathway associated with unipolar
stimulation will typically be longer than an electrical current
pathway associated with bipolar stimulation. Unipolar stimulation
may therefore provide a greater degree of therapeutic efficacy than
bipolar stimulation when stimulation of neural regions, structures,
and/or projections that are deeper or more distant than those just
beneath and/or in the near vicinity of the stimulation site may be
of importance. Moreover, unipolar stimulation may deliver more
current to such deeper or more distant neural regions at a lower
power level than bipolar stimulation, which may result in greater
stimulation efficiency and/or a reduced likelihood of inducing
collateral neural activity. Enhanced stimulation efficiency may be
important when treating chronic, near-chronic, and/or longer-term
conditions, for example, movement disorders or central pain
syndrome.
[0058] In addition to or association with the foregoing, an
electric field polarity, orientation and/or distribution relative
to particular types of neurons, neural projections, neural
structures, and/or neurofunctional regions may influence or affect
neural stimulation efficiency and/or efficacy. The cortex C may be
organized as a set of 6 layers, where layer 1 maintains a boundary
corresponding to the cortical surface. Successive cortical layers
exist or reside at increasing depths relative to the cortical
surface. Thus, layer 6 corresponds to a deepest cortical layer. The
thickness or extent of any given cortical layer, and the type,
number, and/or size of neurons, neural projections, and/or neural
structures therein depends upon the cortical neurofunctional region
under consideration.
[0059] Neurons convey input signals along their dendrites toward
their cell bodies. Neurons in the cortex C include pyramidal cells
302 and interneurons 304. In the motor cortex, the largest
pyramidal cells 320 have soma or cell bodies that reside in deep
cortical layer 5. Pyramidal cells 302 have dendrites that project
away from their cell bodies into overlying or superficial cortical
layers, toward the cortical surface in a manner that is
approximately perpendicular or normal to the layer structure of the
cortex C. Interneurons 304 have cell bodies that commonly reside in
cortical layers 2, 3, and 4, and include dendrites that tend to
project away from their cell bodies within the same layer or into
an adjacent layer in a manner that is generally lateral or parallel
with respect to the layer structure of the cortex C.
[0060] An optimal, near optimal, or desirable electric field
orientation for therapeutic neural stimulation may be based upon or
determined by the orientation of one or more types of neurons,
neural structures, and/or neural projections within or associated
with a target neural population N. For example, an electric field
that is oriented generally parallel to a main or overall direction
in which pyramidal cell dendrites project, that is, generally
perpendicular or normal to the cortical layer structure (or
equivalently, generally perpendicular or normal to the surface of
the cortex C or the cranium), may preferentially influence or exert
a more significant effect upon pyramidal cells 302 than
interneurons 304, which include dendrites that generally project
lateral to the cortical layer structure. In an analogous manner, an
electric field that is oriented generally parallel to a typical or
overall direction in which interneuron dendrites project, that is,
generally parallel or lateral to the cortical layer structure, may
preferentially influence or exert a more significant effect upon
interneurons 304 than pyramidal cells 302.
[0061] In view of the foregoing, systems and/or methods in
accordance with particular embodiments of the invention may apply
or deliver stimulation signals having one or more polarities that
may enhance a likelihood of facilitating or effectuating a desired
neurological and/or functional outcome based upon the types of
neurons, neural structures, and/or neural projections involved in
subserving such an outcome. For example, specific embodiments of
the invention may apply unipolar stimulation at one or more times
to patients experiencing certain types of central pain syndrome. As
another example, various embodiments of the invention may apply
unipolar stimulation, possibly in conjunction with a behavioral
therapy, to patients having functional deficits associated with
stroke, traumatic brain injury, cerebral palsy, and/or other
disorders (e.g., tinnitus). In certain situations, unipolar
stimulation may more effectively facilitate or effectuate neural
disinhibition and/or neuroplastic change associated with a target
neural population than bipolar stimulation, thereby enhancing the
extent to which such patients can recover lost functional abilities
and/or develop new abilities.
[0062] Unipolar stimulation may facilitate or effectuate enhanced
recovery or development of functional abilities in patients
experiencing particular types of neurologic dysfunction when
compared to bipolar stimulation. For example, cathodal unipolar
stimulation in conjunction or association with a behavioral therapy
such as an Activity of Daily Living (ADL) may facilitate or
effectuate a greater degree of functional development and/or
recovery in a patient experiencing functional deficits associated
with stroke, traumatic brain injury, and/or neurological damage
than bipolar stimulation either alone or in association or
conjunction with such a behavioral therapy. Moreover, such enhanced
recovery may occur using lower current or average power levels than
would be required for bipolar stimulation, thereby conserving power
and/or reducing a likelihood of inducing collateral neural
activity.
[0063] Certain systems and/or methods in accordance with the
invention may deliver unipolar stimulation during a unipolar
stimulation period and bipolar stimulation during a bipolar
stimulation period. For example, relative to facilitating or
effectuating neuroplasticity, both pyramidal cells 302 and
interneurons 304 may play a role in neural reorganization. Thus, a
system and/or method may deliver unipolar stimulation to more
selectively influence or affect pyramidal cells 302 during a
unipolar stimulation period, and deliver bipolar stimulation to
more selectively influence or affect interneurons 304 during a
bipolar stimulation period. One or more unipolar and/or bipolar
stimulation periods may be identical or different in duration, and
may occur in a successive or generally successive manner, with or
without one or more types of intervening delays, interruptions, or
cessations. Any given unipolar stimulation period, bipolar
stimulation period, and/or interruption period between unipolar
and/or bipolar stimulation periods may correspond to a
subseconds-based, a seconds-based, an hours-based, and/or another
type of time domain. Depending upon embodiment details, alternation
between unipolar and/or bipolar stimulation periods and/or
intervals between such periods may temporally occur in a
predetermined, aperiodic, or pseudo-random manner. Neural
stimulation may be delivered during one or more unipolar and/or
bipolar stimulation periods in conjunction or association with one
or more adjunctive or synergistic therapies, for example, a
behavioral therapy and/or a drug therapy. An adjunctive therapy
corresponding to a unipolar stimulation period may be identical to
or different from an adjunctive therapy corresponding to a bipolar
stimulation period.
[0064] In cortical regions associated with motor control, pyramidal
cell axons that project into the spinal cord, brain stem, basal
ganglia, and/or other areas may serve as cortical outputs involved
in facilitating or controlling movement. In view of manners in
which pyramidal cell dendrites and axons project as described
above, a given type of unipolar neural stimulation may elicit or
generate a patient response or movement at a different (e.g.,
lower) current level or intensity than bipolar stimulation. Thus,
unipolar stimulation may provide or induce an intended or desired
effect at a lower current level than bipolar stimulation, thereby
conserving power and/or reducing a likelihood of inducing
collateral activity. Similarly, unipolar stimulation may facilitate
determination of a therapeutic current level using lower amplitude
test stimulation signals than required by bipolar stimulation. In
some embodiments, a therapeutic current level corresponding to a
given type of unipolar stimulation may be mapped to a therapeutic
current level that corresponds to a different type of unipolar
stimulation and/or bipolar stimulation in accordance with a mapping
function and/or empirical data.
[0065] In addition to the foregoing, certain types of neural cells
may exhibit different types of signal conductance properties based
upon whether the motion of electrical charges or electrically
charged particles (i.e., ions) is toward or away from the axon
hillock, the initial axonal region proximate to the cell body
through which dendritic inputs are integrated. For instance, in
pyramidal cells 302, intracellular ions diffusing toward the axon
hillock experience a lower impedance than intracellular ions
diffusing toward the dendritic tree, thereby giving rise to an
intracellular differential impedance (Neurophysiological
Techniques: Applications to Neural Systems, Neuromethods 15, Eds.
A. A. Boulton, G. B. Baker, and C. H. Vanderwolf). As a result,
anodal unipolar stimulation may affect or influence a neural
population, neural structures, and/or neural projections
differently than cathodal unipolar stimulation.
[0066] Stimulation signal polarity characteristics may influence or
affect an extent to which and/or a manner in which particular
neural structures experience a potential difference and/or
depolarization or polarization relative to each other, which may
affect neural stimulation efficacy and/or efficiency. For example,
due to the existence of a potential gradient between a cathode and
an anode, a relative dendrite to axon hillock or axon
depolarization or hyperpolarization state may give rise to neural
stimulation efficacy differences between cathodal unipolar
stimulation and anodal unipolar stimulation.
[0067] During cathodal unipolar stimulation, a positive first pulse
phase applied at a stimulation site may give rise to an enhanced
extracellular concentration of negative ions in a localized region
at, just beneath, just around, and/or in the near vicinity of the
stimulation site. Such a localized region may correspond, for
example, to a small, relatively small, or generally small neural
tissue and/or neural structure volume within shallow or superficial
layers of the cortex. As a result of the enhanced extracellular
concentration of negative ions, dendrites within the localized
region may experience an enhanced intracellular concentration of
positive ions, thereby shifting the electrical state of such
dendrites toward a more depolarized state than, for example, axon
hillocks, corresponding to such dendrites.
[0068] In an analogous manner, during anodal unipolar stimulation,
a negative first pulse phase applied at a stimulation site may give
rise to an enhanced extracellular concentration of positive ions in
a localized region at, just beneath, just around, and/or in near
proximity to the stimulation site. As a result, dendrites within
the localized region may experience an enhanced intracellular
concentration of negative ions, thereby shifting the electrical
state of such dendrites toward a more hyperpolarized state than
axon hillocks corresponding to such dendrites.
[0069] A dendritic potential shift toward a more depolarized state
and/or a more hyperpolarized state may affect dendritic signal
processing and/or signal generation and/or signal transfer
mechanisms. Such a potential shift may affect neural stimulation
efficacy, for example, by influencing an extent to and/or manner in
which postsynaptic dendrites react or respond to and/or process
presynaptic input.
[0070] In certain neural stimulation situations directed toward
facilitating and/or effectuating neural plasticity, cathodal
unipolar stimulation may increase a likelihood that dendrites
within a target neural population respond to and/or process
neurofunctionally relevant synaptic input in a manner that enhances
a likelihood of generating action potentials that may subserve the
development and/or recovery of one or more functional abilities.
Neurofunctionally relevant synaptic input may arise from or
correspond to an adjunctive or synergistic therapy, for example, a
behavioral therapy. The aforementioned neural stimulation
situations may include, for example, neural stimulation directed
toward rehabilitation of patients experiencing symptoms associated
with neurological damage (e.g., arising from stroke or traumatic
brain injury), neurodegenerative disorders (e.g., Parkinson's
disease, Alzheimer's disease), neuropsychiatric disorders (e.g.,
depression, OCD), and/or other types of neurologic dysfunction.
[0071] In general, anodal or cathodal unipolar stimulation may be
more efficacious and/or efficient than cathodal or anodal unipolar
stimulation, respectively, or bipolar stimulation in the context of
particular neural stimulation situations, which may include, for
example, neural stimulation directed toward traumatic brain injury,
cerebral palsy, movement disorders, central pain syndrome,
tinnitus, neuropsychiatric disorders, auditory hallucinations,
and/or other conditions.
[0072] In particular neural stimulation situations, a likelihood of
realizing a given type of neurofunctional outcome may be enhanced
through multiple anodal unipolar, cathodal unipolar, and/or bipolar
stimulation procedures, which may be applied in a simultaneous,
alternating, and/or varying manner. Such stimulation procedures may
correspond to identical, generally identical, or different
stimulation sites and/or stimulation parameters (e.g., pulse
repetition frequency, first phase pulse width, a peak current
and/or voltage amplitude or magnitude, theta burst characteristics,
a waveform variation and/or modulation function, and/or other
parameters) depending upon the nature of a patient's neurologic
dysfunction, patient condition, and/or embodiment details.
Moreover, any given stimulation procedure and/or an interval
between stimulation procedures may correspond to a
subseconds-based, a seconds-based, an hours-based, and/or another
type of time period or domain. In one embodiment, before, during,
and/or after one or more portions of a cathodal stimulation
procedure directed toward a first target neural population, an
anodal unipolar stimulation procedure may be directed toward a
second target neural population. The first and second target neural
populations may reside in the same or different brain
hemispheres.
[0073] FIG. 6 is a side view of a system for applying electrical
stimulation to a surface site on the cortex in accordance with an
embodiment of the invention. In this embodiment, the system
includes a stimulus unit 520 and a patient interface including a
first electrode assembly 560a and a second electrode assembly 560b.
The stimulus unit 520 can include a controller 530 and a pulse
system 540 similar to the controller 130 and pulse system 140 of
the stimulation unit 120 described above with reference to FIG. 1.
The stimulus unit 520 can also include a housing 580 that is
configured to be implanted or otherwise attached to the
patient.
[0074] The first electrode assembly 560a can be similar to the
first electrode assembly 160a described above with reference to
FIG. 1. The first electrode assembly 560a can accordingly include a
support member 562a configured to be implanted proximate to the
cortex of the patient and at least one surface contact 564a. The
surface contacts 564a can be coupled to a first terminal 542a of
the stimulus unit 520 by a link 570.
[0075] The second electrode assembly 560b can be a separate item or
element attached to the stimulus unit 520, or the second electrode
assembly 560b can be an integral component of the stimulus unit
520. The second electrode assembly 560b, for example, can be a
conductive portion of the housing 580 of the stimulus unit 520. In
other embodiments, the entire housing 580 of the stimulus unit 520
can be a conductive material that defines the second electrode
assembly 560b, or a portion of the housing 580 can be covered with
an appropriate type of dielectric or insulating material or be
composed of such a material to limit the conductive surface area of
the second electrode assembly 560b to a desired shape or area. In
still other embodiments, the second electrode assembly 560b is a
separate set of contacts attached to the housing 580. The second
electrode assembly 560b is coupled to a second terminal 542b of the
pulse system 540.
[0076] The system shown in FIG. 6 operates by electrically biasing
the surface contacts 564a at an identical polarity, and biasing the
second electrode assembly 560b with an opposite or neutral
polarity. For example, the system may be configured to deliver
anodal unipolar stimulation to a stimulation site by biasing the
surface contacts 564a as an anode, and biasing the second electrode
assembly 560b as a cathode. It will be appreciated that the surface
contacts 564a could alternatively be biased as a cathode while the
second electrode assembly 560b is biased as an anode. The system
shown in FIG. 6 accordingly provides a unipolar signal at the
stimulation site on or proximate to the surface of the cortex of
the patient.
[0077] Another aspect of the invention may involve configuring a
neural stimulation system to induce a desired electrical field
and/or current density at or proximate to a stimulation site as
well as a remote circuit completion site. In one embodiment, the
aggregate surface area of conductive surfaces that provide circuit
completion or electrical continuity remote or generally remote from
the stimulation site (e.g., contacts 164b carried by a second
electrode assembly 160b or 560b, or an exposed conductive surface
of a housing 580) is approximately 200%-1500% of the aggregate
surface area of conductive surfaces that apply or deliver
stimulation signals to one or more stimulation sites (e.g.,
contacts 164a or 564a carried by a first electrode assembly 160a or
560a), and more specifically 250%-450%. The larger conductive
surface area corresponding to the circuit completion site reduces
the current density at the current completion site compared to the
stimulation site; this is expected to reduce collateral neural
activity, muscle activity, and/or patient sensation in the region
of the circuit completion site.
[0078] FIG. 7 is a side view illustrating a system for applying
electrical stimulation to a surface site on the cortex in
accordance with another embodiment of the invention. In this
embodiment, the system includes the stimulus unit 120, the second
electrode assembly 160b, and a surface electrode assembly 660. The
surface electrode assembly 660 can comprise an array including a
support member 662 configured to be implanted at the cortical
stimulation site, a plurality of first surface contacts 664 carried
by one portion of the support member 662, and a plurality of second
surface contacts 665 carried by another section of the support
member 662. The first surface contacts 664 are coupled to the first
link 170a to electrically couple the first surface contacts 664 to
the first terminal 142a of the stimulus unit 120. The second
surface contacts 665 can be coupled to the second link 170b to
electrically couple the second surface contacts 665 to the second
terminal 142b of the stimulus unit 120. The first surface contacts
664 can be biased as an anode, and the second surface contacts 665
can be biased as a cathode, or vice versa. In an alternate
embodiment, the second surface contacts 665 can be connected to a
separate link to be coupled to a third terminal of the stimulus
unit 120. The second surface contacts 665 can accordingly be biased
independently of either the first surface contacts 664 or the
second electrode assembly's contacts 164b.
[0079] The embodiment of the system illustrated in FIG. 7 can
provide a combination of unipolar and bipolar stimulation. For
example, the first surface contacts 664 can be biased at a first
polarity while the second surface contacts 665 or the return
contacts 164b are biased at a second polarity. In another
embodiment, the second surface contacts 665 are coupled to another
terminal on the stimulus unit 120 so that the second surface
contacts 665 can be biased separately from the return contacts
164b. This particular embodiment operates in a manner in which the
first surface contacts 664 and the second electrode assembly's
contacts 164b can be biased while not biasing the second surface
contacts 665 during a unipolar stimulation period, and then the
first surface contacts 664 can be biased at the first polarity
while the second surface contacts 665 are biased at the second
polarity during a bipolar stimulation period. The stimulus unit 120
can alternate unipolar stimulation and bipolar stimulation periods
according to a desired sequence to provide a combination of
unipolar and bipolar stimulation.
[0080] FIG. 8A is an isometric view and FIG. 8B is a cross
sectional view of a system for applying electrical stimulation to a
surface site on or proximate to the cortex in accordance with
another embodiment of the invention. In one embodiment, the system
comprises a support member 800 that may carry a control unit 830
and a pulse system 840, plus a first electrode assembly 860a and a
second electrode assembly 860b. The support member 800 may include
a housing 802 configured for implantation into the skull 890, and
an attachment element 804 configured for connection to the skull
890 by fasteners, an adhesive, and/or an anchor.
[0081] The first electrode assembly 860a may comprise a biasing
element 862 that carries a first set of electrical contacts 864a.
The biasing element 862 may be formed using a soft, conformable,
and/or compressible biocompatible material. In one embodiment, the
first electrode assembly 860a is coupled to a first terminal 842a
of the pulse system 840. The second electrode assembly 860b may
comprise one or more exposed conductive portions of the housing 802
and/or the attachment element 804, and/or a second set of
electrical contacts 864b that are carried by the housing 802 and/or
the attachment element 804. The second electrode assembly 860b may
be coupled to a second terminal 842b of the pulse system 840.
Depending upon embodiment details, the pulse system's first and
second terminals 842a-b may be configured as an anode and a
cathode, possibly in a selectable or programmable manner.
Additionally, configuration or establishment of an anodal and a
cathodal relationship between the pulse system's first and second
terminals 842a-b may occur in a predetermined, aperiodic, or
pseudo-random time-varying manner.
[0082] The support member 800 may be implanted into or through a
craniotomy that is above a stimulation site, such that one or more
portions of the biasing element 862 and/or the first set of
contacts 864a reside upon, essentially upon, or proximate to the
stimulation site. Following implantation, the attachment element
804 may be covered by the patient's scalp 892. The first electrode
assembly 860a may be biased in accordance with a first polarity to
apply or deliver unipolar stimulation to a target neural
population, neural projections, and/or neural structures associated
with the stimulation site. The second electrode assembly 860b may
be biased in accordance with a second polarity to provide
electrical continuity for stimulation signals delivered by the
first electrode assembly 860a. In such a configuration, an
electrical current pathway between the first and second electrode
assemblies 842a-b may include one or more portions of the patient's
cortex, one or more neural regions below the cortex, vasculature,
and/or portions of the patient's scalp. In order to eliminate,
essentially eliminate, or minimize electrical current flow from the
first electrode assembly 860a to the second electrode assembly 860b
along a current path that includes an interface between the skull
890 and the edge of the housing 802 and/or the attachment element
804, one or more portions of the housing 802 and/or the attachment
element 804 may comprise or include an insulating material that
forms a nonconductive seal or barrier between the skull 890 and the
housing 802 and/or the attachment element 804.
[0083] FIG. 8C is a cross sectional view of a system for applying
electrical stimulation to a surface site on or proximate to the
cortex according to another embodiment of the invention. Relative
to FIGS. 8A and 8B, like reference numbers indicate like elements.
In the embodiment shown in FIG. 8C, the first electrode assembly
860a includes a first subset of contacts 865 coupled to the pulse
system's first terminal 842a. Additionally, the pulse system 840
includes a signal selection module 880 capable of selectively
coupling (1) a second subset of contacts 866 to the first or second
terminal 842a-b of the pulse system 830; and/or (2) the second
electrode assembly 860b to the pulse system's second terminal 842b
(in a manner that avoids simultaneous coupling of the second subset
of contacts 866 to the first and second terminals 842a-b). The
embodiment shown in FIG. 8C may thus be configured to provide
unipolar stimulation by biasing the first subset of contacts 865
and possibly the second subset of contacts 866 at a first polarity,
and biasing the second electrode assembly 842b at a second
polarity; or bipolar stimulation by biasing the first subset of
contacts 865 at a first polarity and the second subset of contacts
866 at a second polarity.
[0084] FIG. 9A is a schematic illustration of a system for applying
electrical stimulation to a surface site on or proximate to the
cortex in accordance with another embodiment of the invention.
Relative to FIGS. 8A, 8B, and 8C, like reference numbers indicate
like elements. In one embodiment, the system comprises a support
member 800 that carries a controller 830, a pulse system 840, and a
local electrode assembly 860. The system may further include at
least one remote electrode assembly 960. The support member 800 may
include a housing 802 and an attachment element 804 as described
above.
[0085] The local electrode assembly 860 may comprise a biasing
element 862 that carries a first set of contacts 864. In one
embodiment, the local electrode assembly 860 is coupled to the
pulse system's first terminal 842a. The remote electrode assembly
960 may comprise a support member 962 that carries a second set of
contacts 964, and may have a structure analogous to one or more
types of electrodes described in U.S. patent application Ser. No.
10/877,830, which is incorporated herein by reference.
Alternatively, the remote electrode assembly 960 may comprise a
cranial screw or peg type electrode as described in U.S. patent
application Ser. No. 10/418,796 (previously incorporated herein by
reference); or a depth, deep brain, or other type of electrode. In
certain embodiments, the remote electrode assembly 960 may provide
an active or aggregate conductive surface area that is greater than
an active or aggregate conductive surface area associated with the
local electrode assembly 860 in a manner analogous to that
described above. The remote electrode assembly 960 may be coupled
to the pulse system's second terminal 842b by a link 970. Depending
upon embodiment details, the pulse system's first and second
terminals 842a-b may be configured as an anode and a cathode,
possibly in a selective, programmable, deterministic, and/or
pseudo-random manner.
[0086] The support member 800 may be implanted into or through a
craniotomy that is above a stimulation site in a manner analogous
to that described above. The remote electrode assembly 960 may be
implanted or positioned distant or remote from the support member
800. The remote electrode assembly 960, for example, may be
positioned upon or beneath the patient's skin at an anatomical
location that is above or below the patient's neck; or within the
patient's cranium at a cortical, subcortical, or deep brain
location that is distant, distinct, or remote from the local
electrode assembly 860. The local electrode assembly 860 may be
biased in accordance with a first signal polarity, and the remote
electrode assembly 960 may be biased in accordance with a second
signal polarity to provide unipolar stimulation.
[0087] FIG. 9B is a schematic illustration of a system for applying
electrical stimulation to a surface site on or proximate to the
cortex in accordance with another embodiment of the invention.
Relative to FIG. 9A, like reference numbers indicate like elements.
The embodiment shown in FIG. 9B includes a first and a second
remote electrode assembly 960a-b, which may be identical,
essentially identical, or different in structure. Any given remote
electrode assembly 960a-b may comprise an electrode of a type
indicated above. Depending upon embodiment details, the first
and/or the second remote electrode assembly 960a-b may provide an
active or aggregate conductive surface area that is greater than an
active or aggregate conductive surface area associated with the
local electrode assembly 860 in a manner analogous to that
described above. The first and second remote electrode assemblies
960a-b are respectively coupled to the pulse system's second
terminal 842b by a first and a second link 970a-b.
[0088] The embodiment shown in FIG. 9B may further include a signal
selection module 980 that facilitates selectable or programmable
coupling of the first and/or second remote electrode assembly
960a-b to the pulse system's second terminal 842b. Depending upon
embodiment details and/or the nature of the patient's neurological
condition, only one of the first and second remote electrode
assemblies 960a-b may be coupled to the pulse system's second
terminal 842b at any given time; or the first and second remote
electrode assemblies 960a-b may be coupled to the second terminal
842b simultaneously.
[0089] In various embodiments, the support member 800 may be
implanted at a stimulation site in a manner analogous to that
described above. The first and second remote electrode assemblies
960a-b may be respectively positioned or implanted at a first and a
second anatomical location that is distant, remote, or distinct
from the stimulation site. The local electrode assembly 860 may be
biased in accordance with a first signal polarity, while one or
both of the remote electrode assemblies 960a-b may be biased in
accordance with a second signal polarity at any given time to
provide unipolar stimulation.
[0090] The use of multiple remote electrode assemblies 960a-b
positioned at different anatomical locations may provide multiple
current pathways through which neural stimulation may affect or
influence particular target cortical and/or subcortical neural
populations, neural structures, and/or neural projections, possibly
in an alternating or time-dependent manner. For example, unipolar
stimulation delivered or applied along or with respect to a first
current pathway may be directed toward affecting neural activity in
a first hemisphere of the brain, while unipolar stimulation applied
with respect to a second current pathway may be directed toward
affecting neural activity in a second hemisphere of the brain.
Neural activity in each hemisphere may influence the development,
recovery, and/or retention of functional abilities, possibly
through neuroplastic mechanisms. In certain embodiments, one or
more stimulation parameters such as stimulation signal frequency,
amplitude, and/or polarity may differ or vary in accordance with a
current pathway that is active or under consideration at any given
time.
[0091] One or more embodiments described above may be modified to
include or exclude elements or features described in association
with other embodiments, for example a signal selection module 880,
980. Additionally or alternatively, particular embodiments may
include multiple local electrode assemblies positioned at multiple
stimulation sites, in conjunction with one or more remote electrode
assemblies positioned distant from such stimulation sites to
provide electrical continuity for unipolar stimulation.
[0092] B. Methods for Applying Electrical Stimulation
[0093] FIGS. 10-11 are flow charts illustrating various methods for
applying neural stimulation to a stimulation site in accordance
with the present invention. FIG. 10, more specifically, illustrates
a method 1000 including a start procedure 1002, at least one
unipolar stimulation procedure 1004, and a decision procedure 1008.
The unipolar stimulation procedure 1004 includes establishing an
electrical field by applying an electrical signal having an
identical first signal polarity to a first set of contacts located
at a stimulation site while applying a second signal polarity to a
second set of contacts that is spaced apart or remote from the
stimulation site. The unipolar stimulation procedure 1004 may
involve the application of anodal unipolar stimulation and/or
cathodal unipolar stimulation to the patient, possibly in a manner
that increases or enhances a likelihood or rate of patient
functional recovery and/or development. Moreover, the unipolar
stimulation procedure 1004 may involve the application or delivery
of stimulation signals at a subthreshold and/or a suprathreshold
level relative to the generation of a statistically and/or
functionally significant number of action potentials in one or more
target neural populations. The unipolar stimulation procedure 1004
may also involve the application or theta burst stimulation signals
during one or more time periods.
[0094] The unipolar stimulation procedure 1004 can be performed
using any of the systems set forth above with respect to FIGS.
1-9B. The second set of contacts can be located apart from the
stimulation site along a vector that passes through deep layers of
the cortex and/or other neural regions in a direction that is
oblique, and generally approximately normal, with respect to the
first set of contacts at the stimulation site. The unipolar
stimulation procedure 1004, for example, may involve applying a
cathodal and/or an anodal signal to a set of active surface
contacts 164a to restore or at least partially recover speech,
movement, and/or other functions that have been impaired by stroke
or other brain damage.
[0095] An optional or alternative embodiment of the method 1000 can
further include at least one bipolar stimulation procedure 1006 in
which a first set of contacts at a stimulation site are biased at a
first signal polarity, while a second set of contacts at a
stimulation site are biased at a second signal polarity. The
bipolar stimulation procedure 1006 may be performed in a manner
identical or analogous to that described above, and may involve the
delivery of stimulation signals at a subthreshold and/or a
suprathreshold level. The bipolar stimulation procedure 1006 may
also involve the application of theta burst stimulation signals
during one or more time periods.
[0096] The decision procedure 1008 may decide whether the
stimulation has been of sufficient or adequate duration and/or
effect. In particular embodiments, the decision procedure 1008 may
involve monitoring or measuring patient progress and/or functional
capabilities through one or more standardized measures, tests, or
tasks. Such standardized measures may include or be based upon, for
example, a FugI-Meyer Assessment of Sensorimotor Impairment; a
National Institute of Health (NIH) Stroke Scale; a Stroke Impact
Scale (SIS); an ADL scale; a Quality of Life (QoL) scale; physical
measures such as grip strength or finger tapping speed; a
neuropsychological testing battery; a walking, movement, and/or
dexterity test; a behavioral test; a language test; a comprehension
test; and/or other measures of patient functional ability. In
certain embodiments, the decision procedure 1008 may alternatively
or additionally involve an electrophysiological signal acquisition
and/or analysis procedure, and/or a neural imaging procedure (e.g.,
MRI, fMRI, or PET). The decision procedure 1008 may direct the
method 1000 to apply either a unipolar stimulation procedure 1004
and/or a bipolar stimulation procedure 1006 depending upon the
particular characteristics of the therapy and/or the nature or
extent of the patient's neurofunctional condition. One or more
stimulation sites and/or stimulation parameters (e.g., pulse
repetition frequency, first phase pulse width, peak current and/or
voltage amplitude, theta burst characteristics, a waveform
variation and/or modulation function, and/or other parameters)
corresponding to particular unipolar and/or bipolar stimulation
procedures 1004, 1006 may be identical, generally identical, or
different depending upon the nature of a patient's neurologic
dysfunction, patient condition, and/or embodiment details. The
method 1000 may further include a termination procedure 1010 that
is performed based upon the outcome of the decision procedure
1008.
[0097] FIG. 11 illustrates a method 1100 in accordance with another
embodiment of the invention. In one embodiment, the method 1100
includes a start procedure 1102, a unipolar stimulation procedure
1104, and possibly a first adjunctive or synergistic therapy
procedure 1106. The unipolar stimulation procedure 1104 may involve
the application or delivery of anodal and/or cathodal unipolar
stimulation signals to the patient, possibly in a manner that
increases or enhances a likelihood and/or rate of patient
functional recovery and/or development. Moreover, the unipolar
stimulation procedure 1104 may involve subthreshold and/or
suprathreshold stimulation, and/or theta burst stimulation during
one or more time periods.
[0098] The unipolar stimulation procedure 1104 and the first
adjunctive therapy procedure 1106 can be performed concurrently or
serially depending upon the nature and/or extent of a patient's
neurologic dysfunction, patient condition, and/or embodiment
details. The first adjunctive therapy procedure 1106 may comprise a
behavioral therapy procedure that can include a physical therapy,
an activity of daily living, an intentional use of an affected body
part, a speech therapy, a vision therapy, an auditory task or
therapy (e;g., an auditory discrimination task), a reading task, a
memory task, a visualization, imagination, or thought task, and/or
another type of task or therapy. A subthreshold unipolar
stimulation procedure 1104 may be performed concurrent with a first
behavioral therapy procedure 1106 to enhance or maximize a
likelihood generating action potentials that may subserve the
development and/or recovery of one or more functional
abilities.
[0099] The method 1100 may additionally include a first decision
procedure 1108 that may decide whether the unipolar stimulation
procedure 1104 and/or the first adjunctive therapy procedure 1106
have been of sufficient or adequate duration and/or effect. The
first decision procedure 1108 may involve measurement or assessment
of patient status, progress, and/or functional capabilities using
one or more standardized measures, tests, or tasks; an
electrophysiological signal acquisition and/or analysis procedure;
and/or a neural imaging procedure. If additional unipolar
stimulation and/or adjunctive therapy is warranted, the method 1100
may continue, resume, or restart a unipolar stimulation procedure
1104 and/or a first adjunctive therapy procedure 1106.
[0100] In certain embodiments, the method 1100 may further include
a bipolar stimulation procedure 1110, and/or a second adjunctive or
synergistic therapy procedure 1112. The bipolar stimulation
procedure 1110 may involve the application or delivery of
stimulation signals at a subthreshold and/or suprathreshold level,
and may possibly involve theta burst stimulation at one or more
times. The bipolar stimulation procedure 1110 may be directed
toward the same, essentially the same, or different target neural
structures, target neural projections, and/or target neural
populations than the unipolar stimulation procedure 1104. Thus, the
bipolar stimulation procedure 1110 may deliver or apply stimulation
signals to the same or a different stimulation site than the
unipolar stimulation procedure 1104, either in the same and/or a
different brain hemisphere. For example, both the unipolar and
bipolar stimulation procedures 1104, 1110 may deliver stimulation
signals to identical or essentially identical portions of a
patient's motor cortex; or the unipolar stimulation procedure 1104
may apply stimulation signals to portions of the patient's motor
cortex, while the bipolar stimulation procedure 1110 may apply
stimulation signals to portions of the patient's premotor cortex or
another region of the brain.
[0101] The second adjunctive therapy procedure 1112 may involve,
for example, a drug therapy and/or a behavioral therapy that is
identical or essentially identical to or different from a therapy
associated with the first adjunctive therapy procedure 1106. The
second adjunctive therapy procedure 1112 may involve, for example,
a visualization procedure such as thinking about performing one or
more types of motions and/or tasks, while the first adjunctive
therapy procedure 1106 may involve attempting to actually perform
such motions and/or tasks.
[0102] Depending upon the nature and/or extent of a patient's
neurologic dysfunction, patient condition, and/or embodiment
details, the bipolar stimulation procedure 1110 and the second
adjunctive therapy procedure 1112 may be performed concurrently or
serially, in a manner analogous to that described above for the
unipolar stimulation procedure 1104 and the first adjunctive
therapy procedure 1106. Moreover, the bipolar stimulation procedure
1110 and/or the second adjunctive therapy procedure 1112 may
precede or follow the unipolar stimulation procedure 1104 and/or
the first adjunctive therapy procedure 1106 in either a generally
continuous or an interrupted manner.
[0103] The method 1100 may further include a second decision
procedure 1114 that may decide whether the bipolar stimulation
procedure 1110 and/or the second adjunctive therapy procedure 1112
have been of sufficient or adequate duration and/or effect. The
second decision procedure 1114 may involve measurement or
assessment of patient status, progress, and/or functional
capabilities using one or more standardized measures, tests, or
tasks; an electrophysiological signal acquisition and/or analysis
procedure; and/or a neural imaging procedure. If additional bipolar
stimulation and/or adjunctive therapy is warranted, the method 1100
may continue, resume, or restart a bipolar stimulation procedure
1110 and/or a second adjunctive therapy procedure 1112. Finally,
the method 1100 may include a termination procedure 1116 that may
be performed based upon an outcome of the first and/or second
decision procedure 1108, 1116.
[0104] Depending upon embodiment details, a method 1100 may
comprise a number of anodal unipolar, cathodal unipolar, and/or
bipolar stimulation procedures 1104, 1110, where the number,
duration of, and/or time between such procedures and/or the
particular stimulation sites to which such procedures are directed
may be identical, essentially identical, or different. Moreover,
one or more stimulation signal parameters (e.g., pulse repetition
frequency, first phase pulse width, peak current and/or voltage
amplitude, theta burst characteristics, a waveform variation and/or
modulation function, and/or other parameters) corresponding to
particular unipolar and/or bipolar stimulation procedures 1104,
1110 may be identical, generally identical, or different depending
upon the nature of a patient's neurologic dysfunction, patient
condition, and/or embodiment details.
[0105] In certain embodiments, one or more procedures described
herein may form portions of a limited duration treatment program,
in a manner analogous to that described in U.S. application Ser.
No. 10/606,202, incorporated herein by reference. In accordance
with various embodiments of the present invention, a limited
duration treatment program may apply or deliver unipolar
stimulation, and possibly bipolar stimulation, to a patient for a
limited period of time to facilitate or effectuate complete,
essentially complete, significant, or partial rehabilitation,
restoration, or functional healing of or recovery from a
neurological condition such as a neurological malfunction and/or a
neurologically based deficit or disorder. Depending upon the extent
or nature of the patient's neurological condition and/or functional
deficits, a limited duration treatment program may last, for
example, a number of weeks, months, or possibly one or more
years.
[0106] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
For example, aspects of the invention described in the context of
particular embodiments can be combined or eliminated in other
embodiments. Accordingly, the invention is not limited except as by
the appended claims.
* * * * *