U.S. patent application number 13/414319 was filed with the patent office on 2012-06-28 for neural stimulation system and method responsive to collateral neural activity.
Invention is credited to Bradford Evan Gliner.
Application Number | 20120165899 13/414319 |
Document ID | / |
Family ID | 32106417 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120165899 |
Kind Code |
A1 |
Gliner; Bradford Evan |
June 28, 2012 |
NEURAL STIMULATION SYSTEM AND METHOD RESPONSIVE TO COLLATERAL
NEURAL ACTIVITY
Abstract
A neural stimulation system responsive to collateral neural
activity that may arise in association with a neural stimulation
procedure includes a stimulation interface configured to deliver
stimulation signals to a target neural population, a monitoring
interface positioned to receive signals corresponding to a neural
activity within the target neural population, a stimulus unit
coupled to deliver stimulation singals to the stimulation
interface, and a sensing unit coupled to the monitoring device and
the stimulus unit. The neural stimulation procedure may be directed
toward rehabilitating, restoring, and/or enhancing one or more
neural functions by facilitating and/or effectuating a neuroplastic
change or reorganization; and/or affecting a neurological condition
that exists on a continuous or essentially continuous basis absent
the stimulation procedure. The sensing unit determines whether
evidence of an collateral neural activity exists, whereupon the
stimulus unit attempts to abate the collateral neural activity.
Inventors: |
Gliner; Bradford Evan;
(Sammamish, WA) |
Family ID: |
32106417 |
Appl. No.: |
13/414319 |
Filed: |
March 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12941577 |
Nov 8, 2010 |
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13414319 |
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10271394 |
Oct 15, 2002 |
7831305 |
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12941577 |
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09978134 |
Oct 15, 2001 |
7305268 |
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10271394 |
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09802808 |
Mar 8, 2001 |
7010351 |
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09978134 |
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60217981 |
Jul 13, 2000 |
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Current U.S.
Class: |
607/45 ;
607/46 |
Current CPC
Class: |
A61N 1/0534 20130101;
A61B 5/1104 20130101; A61N 1/3756 20130101; A61N 1/0551 20130101;
A61N 1/36025 20130101; A61N 1/36017 20130101; A61N 1/36082
20130101; A61N 1/36185 20130101; A61N 1/0531 20130101; A61N 1/0553
20130101; A61B 5/4094 20130101; A61B 5/377 20210101; A61B 5/389
20210101; A61N 1/36071 20130101 |
Class at
Publication: |
607/45 ;
607/46 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. A neural stimulation system for neurostimulation of a patient,
comprising: a first set of electrodes configured to be positioned
upon a target neural population corresponding to a site at which
neuroplasticity is occurring, a site at which neuroplasticity is
expected to occur, and/or a site associated with neuropathic pain;
a monitoring device to receive signals corresponding to a neural
activity within a portion of the target neural population, wherein
the neural activity is related to an undesired collateral effect of
stimulation of the target neural population; a stimulus unit
coupled to deliver stimuli to the first set of electrodes, the
stimuli comprising a plurality of groups of pulses occurring
according to a burst frequency, wherein (i) multiple pulses are
generated within each respective group according to a pulse
repetition frequency, (ii) adjacent groups within the plurality of
groups are spaced apart from each other in time with a
substantially quiescent period; and a sensing unit coupled receive
signals from the monitoring device. wherein the sensing unit is
further coupled to the stimulus unit and the stimulus unit is
adapted to vary a burst characteristic of the stimuli in response
to feedback from the sensing unit.
2. The neural stimulation system of claim 1 wherein the stimulus
unit modifies a burst frequency of the stimuli in response to the
feedback from the sensing unit.
3. The neural stimulation system of claim 1 wherein the stimulus
unit modifies the pulse repetition frequency in response to the
feedback from the sensing unit.
4. The neural stimulation system wherein the stimulus unit and the
sensing unit are adapted for implantation within the patient.
5. The neural stimulation system of claim 1 wherein the monitoring
device comprises a second set of electrodes.
6. The neural stimulation system of claim 1, wherein the monitoring
device comprises a cerebral blood flow monitor.
7. A method of reducing seizure activity during neural stimulation
to treat a neural condition in a patient comprising: applying
electrical stimuli to a target neural population within the patient
by positioning at least a first set of electrodes in contact with
the patient's dura matter or pia matter, the electrical stimuli
directed to altering the neural condition other than a seizure, the
electrical stimuli comprising a plurality of groups of pulses
occurring according to a burst frequency, wherein (i) multiple
pulses are generated within each respective group according to a
pulse repetition frequency, (ii) adjacent groups within the
plurality of groups are spaced apart from each other in time with a
substantially quiescent period; monitoring a parameter associated
with seizure activity; determining if seizure activity is present;
reducing seizure activity, if present, by performing modifying at
least one burst characteristic of the electrical stimuli.
8. The method of claim 7 wherein the monitoring a parameter
associated with seizure activity comprises monitoring an
electrophysiological signal of the patient.
9. The method of claim 7 wherein the monitoring a parameter
comprises monitoring cerebral blood flow.
10. The method of claim 7 wherein the neural condition comprises
pain.
11. The method of claim 7 wherein the neural condition comprises a
functional deficit.
12. The method of claim 7 wherein the reducing modifies the burst
frequency of the stimuli in response to the feedback from the
sensing unit.
13. The method of claim 7 wherein the reducing modifies the pulse
repetition frequency in response to the feedback from the sensing
unit.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of Ser. No. 12/941,577,
filed Nov. 8, 2010, pending, which is a divisional of U.S.
application Ser. No. 10/271,394, filed Oct. 15, 2002, now U.S. Pat.
No. 7,831,305, which is a continuation-in-part of U.S. application
Ser. No. 09/978,134, filed Oct. 15, 2001, now U.S. Pat. No.
7,305,268, which is a continuation-in-part of U.S. application Ser.
No. 09/802,808, filed Mar. 8, 2001, which claims the benefit of
U.S. Provisional Application No. 60/217,981, filed Jul. 13, 2000,
the disclosures of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure is related to systems and methods for
detecting and responding to collateral neural activity that may
arise in association with or as a result of stimulation applied to
a region of the cortex or other area of the brain.
BACKGROUND
[0003] A wide variety of mental and physical processes are
controlled or influenced by neural activity in particular regions
of the brain. For example, the neural-functions in some areas of
the brain (i.e., the sensory or motor cortices) are organized
according to physical or cognitive functions. There are also
several other areas of the brain that appear to have distinct
functions in most individuals. In the majority of people, for
example, the areas of the occipital lobes relate to vision, the
regions of the left interior frontal lobes relate to language, and
the regions of the cerebral cortex appear to be consistently
involved with conscious awareness, memory, and intellect.
[0004] Many problems or abnormalities with body functions 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 very 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, which in turn generally cause 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 drug treatment. For
most patients, however, such treatments are not sufficient, and
little can be done to improve the function of an affected body part
beyond the limited recovery that generally occurs naturally without
intervention.
[0005] The neural activity in the brain can be influenced by
electrical energy that is supplied from a waveform generator or
other type of device. Various patient perceptions and/or neural
functions can thus 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 various neurological
conditions using electrical or magnetic stimulation signals to
control or affect brain functions.
[0006] Neural activity is governed by electrical impulses or
"action potentials" generated in and propagated by neurons. While
in a quiescent state, a neuron is negatively polarized, and
exhibits a resting membrane potential that is typically between -70
and -60 mV. Through electrical or chemical connections known as
synapses, any given neuron receives from other neurons excitatory
and inhibitory input signals or stimuli. A neuron integrates the
excitatory and inhibitory input signals it receives, and generates
or fires a series of action potentials in the event that the
integration exceeds a threshold potential. A neural firing
threshold may be, for example, approximately -55 mV. Action
potentials propagate to the neuron's synapses, where they are
conveyed to other neurons to which the neuron is synaptically
connected.
[0007] A neural stimulation signal may comprise a series or train
of electrical or magnetic pulses that deliver an energy dose to
neurons within a target neural population. The stimulation signal
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 fails to
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.
[0008] While electrical or magnetic stimulation of neural tissue
may be directed toward producing an intended type of neural
activity, such stimulation may result in unintended collateral
neural activity. In particular, neural stimulation for treating a
condition can induce seizure activity or other types of collateral
neural activity. It will be appreciated that such collateral neural
activity is undesirable and/or inconvenient in a neural stimulation
situation.
[0009] Seizure activity may originate at a seizure focus, which is
typically a collection of neurons (e.g., on the order of 1000
neurons) exhibiting a characteristic type of synchronous firing
activity. In particular, each neuron within a seizure focus
exhibits a firing response known as a paroxysmal depolarizing shift
(PDS). The PDS is a large magnitude, long duration depolarization
that triggers a neuron to fire a train or burst of action
potentials. Properly functioning feedback and/or feed-forward
inhibitory signaling mechanisms cause afterhyperpolarization
through which the neuron's membrane potential returns to a
hyperpolarized state below its firing threshold. Following
afterhyperpolarization, the neuron may undergo another PDS.
[0010] Afterhyperpolarization limits the duration of the PDS,
thereby helping to ensure that synchronous neural firing activity
remains localized to the seizure focus. Inhibitory feedback
signaling provided by neurons surrounding a seizure focus, commonly
referred to as "surround inhibition," is particularly important in
constraining seizure activity to the seizure focus. In the event
that inhibitory signaling mechanisms fail and/or are unable to
overcome or counter PDS activity, neurons within the seizure focus
recruit other neurons to which they are synaptically coupled into
their synchronous firing pattern. As a result, synchronous firing
activity spreads beyond the seizure focus to other areas of the
brain. This can lead to a cascade effect in which seizure activity
becomes increasingly widespread, and accompanying clinical
manifestations become increasingly significant.
[0011] In view of the foregoing, it may be important to detect
and/or respond to seizure activity. Various systems and/or devices
directed toward treating neurological conditions exist, including
those capable of detecting and responding to particular types of
neurological events. For example, some neural stimulators attempt
to treat involuntary motion disorders such as Parkinson's disease
by applying stimulation signals to the thalamus or other area of a
patient's brain. As another example, U.S. Pat. No. 6,134,474
describes an implantable device capable of detecting a neurological
event, such as seizure activity, and generating a responsive
electrical signal intended to terminate the detected event.
Additionally, European Patent Application Publication EP1145736
describes an implantable device capable of detecting electrical
activity in the brain; applying a nonresponsive signal to reduce
the likelihood of a seizure occurring; and applying a responsive
signal in the event that epileptiform activity is detected.
[0012] Unfortunately, present neural stimulation systems and
methods fail to automatically detect and/or respond to seizure
activity or other collateral neural activity induced in association
with and/or as a result of neural stimulation procedures directed
toward purposes other than epileptic seizure management. In
particular, conventional neural stimulation systems fail to
automatically detect seizure activity induced by neural stimulation
procedures directed toward patient neural function rehabilitation
and/or enhancement, or modulation of patient sensory
perceptions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic illustration of a neural stimulation
system responsive to specific neural activity according to an
embodiment of the invention.
[0014] FIG. 2 is a graph illustrating several parameters that may
describe or characterize a stimulation signal.
[0015] FIG. 3A is a plan view of a grid electrode configured as a
stimulation interface according to an embodiment of the
invention.
[0016] FIG. 3B is a plan view of an implantable stimulation and
monitoring interface configured for stimulating a target neural
population and detecting signals corresponding to specific neural
activity according to an embodiment of the invention.
[0017] FIG. 4 is a flowchart of a neural stimulation process
responsive to specific neural activity according to an embodiment
of the invention.
[0018] FIG. 5 is a flowchart of a neural stimulation process
responsive to specific neural activity according to another
embodiment of the invention.
[0019] FIG. 6 is a flowchart of a neural stimulation process
responsive to specific neural activity according to another
embodiment of the invention.
DETAILED DESCRIPTION
[0020] The following disclosure describes a system and method for
detecting and responding to collateral neural activity that may
arise in association with and/or as a result of a neural
stimulation procedure. In the context of the present invention, a
neural stimulation procedure may involve the application of stimuli
to one or more target neural populations within a patient, and may
be directed toward rehabilitating, restoring, and/or enhancing one
or more neural functions in the patient by facilitating and/or
effectuating a neuroplastic change or reorganization. A neural
stimulation procedure may alternatively or additionally be directed
toward modulating or ameliorating a patient sensory perception such
as pain, or affecting a neurological condition that is present on a
continuous or essentially continuous basis in the absence of the
applied stimuli. Collateral neural activity may comprise seizure
activity, migraine activity, and/or essentially any other type of
neural activity that may be undesirable, unwanted, unintended,
and/or counterproductive relative to an intended or desired neural
activity or outcome associated with the neural stimulation
procedure.
[0021] FIG. 1 is a schematic illustration of a neural stimulation
system 100 for detecting and responding to collateral neural
activity according to an embodiment of the invention. In one
embodiment, the system 100 comprises a stimulus unit 140 configured
to deliver stimulation signals to a patient 190 using a stimulation
interface 110. The system 100 may additionally comprise a sensing
unit 180 configured to identify or detect parameters associated
with collateral neural activity in the patient 190 using a
monitoring interface 112. The sensing unit 180 is configured to
communicate with the stimulus unit 140 upon detection of collateral
neural activity and/or periodically throughout a stimulation
procedure. The stimulus unit 140 may be coupled to the stimulation
interface 110 by a first link 114; the monitoring interface 112 may
be coupled to the sensing unit 180 by a second link 116; and the
sensing unit 180 may be coupled to the stimulus unit 140 by a third
link 118, where one or more of such links 114, 116, 118 may be
wire-based or wireless.
[0022] The stimulus unit 140 generates and outputs stimulation
signals. As considered herein, stimulation signals may include
treatment signals and/or response signals. Treatment signals may
comprise electrical and/or magnetic stimuli applied to one or more
target neural populations and directed toward treating and/or
rehabilitating one or more neurological conditions. The treatment
signals may also affect or influence particular types of
neurological activity. In general, treatment signals may be
directed toward affecting or altering one or more neurological
conditions that exist within the patient 190 on a continuous,
essentially continuous, or nearly continuous basis (i.e.,
non-intermittent or essentially non-intermittent through
potentially cyclical) in the absence of the treatment signal.
Treatment signals may be directed toward facilitating and/or
effectuating neuroplasticity in the patient 190, for example, in a
manner described in U.S. patent application Ser. No. 09/978,134,
which is incorporated herein by reference. Treatment signals may
alternatively or additionally be directed toward affecting or
modulating a patient sensation such as pain; or eliminating or
ameliorating the effects of neurodegenerative disorders, for
example, involuntary movements and/or other symptoms associated
with Parkinson's disease.
[0023] In general, response signals may comprise electrical,
magnetic, and/or other (e.g., sonic or vibratory) stimuli directed
toward disrupting, desynchronizing, abating, and/or eliminating
collateral neural activity arising in association with or as a
result of the application of treatment signals to the patient 190.
Depending upon their nature, response signals may be applied
proximate or directly to one or more target neural populations
and/or particular patient sensory systems or body locations. The
description that follows considers electromagnetic response
signals; however, the present invention may employ other or
additional types of response signals in a manner understood by
those skilled in the art.
[0024] FIG. 2 is a graph illustrating several parameters that may
define, describe, or characterize stimulation signals. A stimulus
start time t.sub.0 defines an initial point at which a stimulation
signal is applied to the stimulation interface 110. In one
embodiment, the stimulation signal may be a biphasic waveform
comprising a 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. Additional stimulation parameters may
include applying the stimulation to selected configurations of the
stimulation interface 110 for any given stimulation signal and/or
time.
[0025] In one embodiment, the stimulus unit 140 comprises a
controller 150, a pulse system 160, and a set of
controls/indicators 170. The controller 150 may include a
processor, a memory, and a programmable computer medium. The
controller 150 may be implemented as a computer or microcontroller,
and the programmable medium can be hardware and/or memory resident
software that performs, directs, and/or facilitates neural
stimulation procedures in accordance with the present invention.
The controls/indicators 170 can include a graphic user interface,
an input/output device, and/or other types of interface elements
for exchanging commands and/or output with the controller 150.
[0026] The pulse system 160 selectively generates stimulation
signals and sends, directs, or delivers such stimuli to the
stimulation interface 110. The pulse system 160 may be implanted
into the patient 190, in a manner described in U.S. application
Ser. No. 09/802,808 incorporated herein by reference.
Alternatively, the pulse system 160 may be an external unit capable
of delivering stimulation signals to the stimulation interface 110
using RF energy, electromagnetism, or wire terminals exposed on the
patient's scalp. The stimulation interface 110 may comprise one or
more stimulus delivery devices configured to apply treatment
signals and/or response signals to the patient 190. The stimulation
interface 110 may comprise a type of neural-stimulation device
described in U.S. application Ser. No. 09/802,808.
[0027] In one embodiment, the pulse system 160 is a component of a
Transcranial Magnetic Stimulation (TMS) device that delivers
magnetic stimulation signals to a patient 190. The stimulation
interface 110 in this embodiment may comprise an electromagnetic
coil arrangement in a manner understood by those skilled in the
art. In another embodiment, the pulse system 160 forms a portion of
an electrical stimulation device. The stimulation interface 110 of
this embodiment may comprise an electrode arrangement or
configuration capable of delivering electrical stimulation signals
to the patient 190. In such an embodiment, the stimulation
interface 110 may be implanted into the patient 190 to provide
cortical stimulation, deep brain stimulation, and/or other types of
neural stimulation.
[0028] Various portions or elements of the stimulation interface
110 may be configured to deliver treatment signals only, response
signals only, or either treatment or response signals. One or more
portions of the stimulation interface 110 may reside upon or
proximate to one or more target neural populations in and/or
through which a) neuroplasticity may be occurring and/or may be
expected to occur; and/or b) a patient sensation such as pain may
be modulated or influenced.
[0029] FIG. 3A is a plan view of an exemplary grid electrode 120
capable of implementing one or more portions of a stimulation
interface 110 according to an embodiment of the invention. The grid
electrode 120 comprises a support member or substrate 122 that
carries a plurality of electrical contacts 124. Those skilled in
the art will understand that the number of contacts 124 may vary in
accordance with embodiment details. The grid electrode 120 further
comprises a set of leads (not shown) that couple the contacts 124
to the pulse system 160 in a manner understood by those skilled in
the art. A grid electrode 120 of the type shown in FIG. 3A is
available from AdTech Medical Instrument Corporation of Racine,
Wis. (www.adtechmedical.com).
[0030] The contacts 124 can be divided so that one group of
contacts 124 delivers treatment signals while another group of
contacts 124 delivers response signals. For example, a central
contact group 126 may deliver treatment signals to a target neural
population while an outer contact group 128 may deliver response
signals in a manner that may enhance or promote surround
inhibition. In such an embodiment, response signals may be
delivered in a time-shared or a concurrent manner relative to
treatment signal delivery. Alternatively, the grid electrode 120
may be configured to deliver treatment signals or response signals
to all contacts 124 in a time-shared manner, or configured to
deliver treatment signals only or response signals only.
[0031] The sensing unit 180 comprises a system, device, or
apparatus configured to detect or identify collateral neural
activity or parameters of such activity that occur in association
with and/or as a result of a neural stimulation procedure. The
sensing unit 180 may include a processor, a memory, and a
programmable computer medium. The programmable medium of the
sensing unit 180 can comprise hardware and/or software capable of
analyzing signals corresponding to neural activity and determining
whether collateral neural activity or evidence of such activity
exists. The sensing unit 180 may communicate with the stimulus unit
140 upon detecting collateral neural activity so that the stimulus
unit 140 may respond to the sensing unit 180. The sensing unit 180
may monitor for collateral neural activity or evidence of such
activity on a periodic or continuous basis. The sensing unit 180,
for example, can operate under the direction of or in cooperation
with the controller 150. Communication between the stimulus unit
140 and the sensing unit 180 may occur through the third link 118.
Such communication may involve the exchange of operational
parameters, synchronization information, status information, and/or
information associated with the detection of collateral neural
activity.
[0032] The sensing unit 180 may receive from the monitoring
interface 112 one or more types of physiological signals and/or
physiological correlate signals useful for indicating the presence
of collateral neural activity. In general, a meaningful,
significant and/or sustained change in a physiological or
physiological correlate signal relative to the signal's normal or
background behavior can indicate the onset and/or occurrence of
collateral neural activity. The sensing unit 180 may comprise
hardware and/or software that performs signal filtering,
processing, and/or analysis operations. Depending upon the nature
of the physiological and/or physiological correlate signals under
consideration, the sensing unit 180 and/or the monitoring interface
112 may exhibit various embodiments.
[0033] The monitoring interface 112 can have several embodiments.
For example, one or more portions of the monitoring interface 112
may be oriented or positioned relative or proximate to a set of
target neural populations to which a neural stimulation procedure
is directed so that the monitoring interface 112 may detect or
receive signals corresponding or related to such neural
populations. Alternatively or additionally, one or more portions of
the monitoring interface 112 may be oriented or positioned within
or upon the patient's body to detect one or more types of patient
responses correlated to neural activity.
[0034] In one embodiment, the sensing unit 180 comprises an
electroencephalogram (EEG) monitoring and/or analysis device and
the monitoring interface 112 comprises one or more surface,
cortical, and/or subcortical electrodes, electrode arrays, and/or
electrical probes capable of receiving or detecting EEG signals.
The sensing unit 180 may analyze EEG signals received from the
monitoring interface 112 and determine whether collateral neural
activity or evidence of such activity exists. Those skilled in the
art will recognize that particular types of EEG activity, such as
interictal spikes and/or energy spectrum shifts, may be indicative
of seizure activity.
[0035] In addition to EEG signals, other types of physiological
signals and/or physiological correlate signals may be useful for
providing evidence of collateral neural activity. For example,
signals corresponding to cerebral blood flow (CBF) may be used to
indicate the onset or occurrence of seizure activity, as described
by M. E. Weinand et al. in an article entitled "Cerebral blood flow
and temporal lobe epileptogenicity" (J. Neurosurg. 1997 February;
86(2): 226-32). In one embodiment, the monitoring unit 112 may
comprise a CBF monitor, which may include a set of electrodes, a
thermistor, and/or a thermal diffusion probe; a set of near
infrared sources and sensors; a set of piezoelectric ultrasonic
emitters and sensors (to facilitate, for example, transit time
measurements); and/or one or more other types of CBF monitoring
devices. In such an embodiment, the sensing unit 180 may comprise a
CBF signal analysis system or device. In a related alternate
embodiment, the monitoring unit 112 may comprise a neural tissue
oxygenation monitor, and the sensing unit 180 may correspondingly
comprise a neural tissue oxygenation analysis system or device.
[0036] Particular types of muscle fiber activity may also be
indicative of collateral neural activity (e.g., extremely rapid
muscle fiber contractions, particularly when sustained). In one
embodiment, the sensing unit 180 comprises an electromyography
(EMG) device configured to detect, monitor, and/or analyze motor
evoked potentials (MEPs) associated with muscle fiber innervation,
in a manner understood by those skilled in the art. The monitoring
interface 112 correspondingly comprises a set of surface,
percutaneous, and/or implanted electrodes or probes that may be
positioned or configured to measure electrical activity associated
with the innervation of one or more muscles and/or muscle groups.
In another embodiment, the sensing unit 180 comprises a motion
analysis system and the monitoring interface 112 comprises a set of
motion detectors, strain gauges, and/or accelerometers configured
to detect or monitor one or more types of patient movements. The
sensing unit 180 may analyze motion signals received from the
monitoring interface 112 and determine whether patient motions
under consideration are indicative of seizure activity.
[0037] In other embodiments, the sensing unit 180 and monitoring
interface 112 may comprise one or more types of neural imaging
systems, such as a functional Magnetic Resonance Imaging (fMRI)
system, a Positron Emission Tomography (PET) system, and/or a
Magnetoencephalography (MEG) system. In general, the sensing unit
180 and/or the monitoring interface 112 may be configured to
receive, detect, monitor, measure, and/or analyze one or more types
of signals useful of indicating the presence of collateral neural
activity.
[0038] The stimulation interface 110 and the monitoring interface
112 may be implemented as devices and/or modules that reside upon
physically separate substrates or carriers positioned within and/or
upon the patient 190. Alternatively or additionally, one or more
portions of such interfaces 110, 112 may be implemented together
upon a single implantable carrier or substrate.
[0039] FIG. 3B is a plan view of an implantable stimulation and
monitoring interface 130 configured for stimulating a target neural
population and detecting signals corresponding to neural activity
according to an embodiment of the invention. In one embodiment, the
stimulation and monitoring interface 130 comprises a support member
132 carrying a stimulating element 134 and a monitoring element
136. The stimulating element 134 may comprise one or more
electrodes organized in accordance with a particular pattern, and
the monitoring element 126 may comprise a set of electrodes and/or
a CBF monitoring device positioned proximate or adjacent to the
stimulating element 134. A set of leads 138 may couple the
stimulating element 134 and the monitoring element 136 to the
stimulus unit 140 and the sensing unit 180, respectively. A
stimulation and monitoring interface 120 may be positioned or
oriented within a patient 190 such that a stimulating element 124
can deliver or apply stimulation signals to one or more particular
target neural populations, and the monitoring element 126 can
detect signals indicative of neural activity associated with the
targeted neural populations.
[0040] As previously indicated, one or more portions of the
monitoring interface 112 may comprise an electrode arrangement,
which may include a grid electrode 120 of the type shown in FIG.
3A, a deep brain electrode, and/or one or more other electrode
types. As a result, a stimulation and monitoring interface 130 may
comprise a grid electrode 120 of the type shown in FIG. 3A. In such
an embodiment, particular contacts 124 within the grid electrode
120 may be designated for neural activity monitoring and other
contacts 124 may be configured to deliver treatment and/or response
signals.
[0041] Depending upon the nature of the monitoring interface 112,
the delivery of stimulation signals to a target neural population
may interfere with the detection of signals corresponding to neural
activity. As a result, the controller 150 and/or the pulse system
160 may periodically interrupt a neural stimulation procedure, such
that during stimulation procedure interruptions, the sensing unit
180 may analyze signals received from the monitoring interface 112
relative to collateral neural activity. Outside of such
interruptions, the sensing unit 180 may be prevented from receiving
or processing signals received from the monitoring interface 112.
Alternatively, the sensing unit 180 may compensate for the presence
of stimulation signals, for example, through signal subtraction
and/or other compensation operations, to facilitate detection of
collateral neural activity or evidence of collateral neural
activity simultaneous with the delivery of stimulation signals to a
target neural population.
[0042] In embodiments in which a neural stimulation procedure is
periodically interrupted to facilitate detection of collateral
neural activity or evidence of such activity, the stimulation and
monitoring interface 120 may be implemented using a single
electrode arrangement or configuration in which any given electrode
element used to deliver stimulation signals during the neural
stimulation procedure may also be used to detect neural activity
during a neural stimulation procedure interruption. Thus, the
stimulation interface 110 and the monitoring interface 112 may
physically be one and the same.
[0043] One or more portions of the controller 150, the pulse system
160, the stimulation interface 110, monitoring interface 112,
and/or the sensing unit 180 can be integrated into a single
implantable stimulation delivery, monitoring, and/or management
apparatus in a manner identical analogous or similar to the devices
described in U.S. application Ser. No. 09/802,808. Such an
integrated apparatus may be configured for implantation into a
patient's skull so that the stimulation interface 110 and/or the
monitoring interface 112 can contact the patient's dura matter or
pia matter in one or more cortical regions. An integrated apparatus
of this type can have an internal power source that can be
implanted into the patient 190, and/or an external power source
coupled to the pulse system 160 via electromagnetic coupling or a
direct connection.
[0044] FIG. 4 is a flowchart of a neural stimulation process 400
responsive to collateral neural activity according to an embodiment
of the invention. In one embodiment, the process 400 begins with a
stimulation operation 402 by initiating or continuing a neural
stimulation procedure in which stimulation signals are delivered to
one or more target neural populations within a patient 190 in
accordance with a given set of stimulation signal parameters. After
initiating the stimulation operation 402, the process 400 also
includes a detection query 404 that determines whether collateral
neural activity or evidence of such activity exists. The detection
query 404 may be performed in a simultaneous or sequential manner
relative to the stimulation operation 402. If collateral neural
activity or evidence thereof does not exist, the process 400
continues with a termination query 406 that decides whether the
neural stimulation procedure is complete. If the process is not
complete, the process 400 returns to the stimulation operation 402;
otherwise, if the process 400 is complete, it is terminated. If the
detection query 404 the process 400 determines that collateral
neural activity exists, the process 400 halts the neural
stimulation procedure in a termination operation 410, and generates
and/or issues a notification signal indicative of such activity in
a notification procedure 412. Following the notification procedure
412, the process 400 ends.
[0045] FIG. 5 is a flowchart of a neural stimulation process 500
responsive to collateral neural activity according to another
embodiment of the invention. In one embodiment, the process 500
begins with a stimulation operation 502 by initiating or continuing
a neural stimulation procedure in which stimulation signals are
delivered to one or more target neural populations within a patient
190 in accordance with a first set of stimulation signal
parameters. Next, the process 500 includes a detection query 504
that determines whether collateral neural activity or evidence
thereof exists. If not, the process 500 proceeds to a termination
query 506 to determine whether the neural stimulation procedure is
complete. If the neural stimulation procedure is not complete, the
process 500 returns to the stimulation procedure 502; otherwise,
the stimulation process 500 is terminated.
[0046] If collateral neural activity or evidence of such activity
exists, the process 500 includes a termination operation 510 that
halts the neural stimulation procedure and a notification procedure
512 that generates and/or issues a notification signal indicative
of such activity. The stimulation process 500 proceeds to a
collateral activity query 520 that subsequently determines whether
the collateral neural activity has been abated or eliminated. If
so, the process 500 proceeds to a query 530 that determines whether
to resume the neural stimulation procedure. Such a determination
may be based upon, for example, an elapsed time between initiation
of a neural stimulation procedure and detection of collateral
neural activity; stored information characterizing and/or
specifying frequency and/or history information associated with
detection of collateral neural activity in the patient 190
undergoing the neural stimulation procedure; an authorization
signal received from a doctor or therapist through the
controls/indicators 170; and/or other information.
[0047] If resumption of the neural stimulation procedure is to
occur, the process 500 continues with a modification operation 532
in which one or more stimulation signal parameters may be modified.
Such a modification may involve changing (e.g., decreasing) a
stimulation current level or intensity; changing (e.g., increasing)
a stimulation signal pulse repetition frequency; and/or modifying
one or more other parameters shown in FIG. 2. Following the
modification operation 532, the process 500 includes time query 534
to determine whether a minimum time interval has elapsed. The time
query 534 may provide a quiescent period during which the patient's
neural activity becomes predominantly normal and/or representative
of an acceptable baseline condition. If a minimum time interval has
not elapsed, the process 500 remains at the time query 534;
otherwise, the process 500 returns to the stimulation operation
502.
[0048] If the collateral activity query 520 determines that
collateral neural activity has not been abated, the process 500
proceeds with a response query 540 that determines whether to apply
to the patient 190 one or more response signals directed toward
abating or terminating the collateral neural activity. If not, the
process 500 ends. Otherwise, the process 500 proceeds with a signal
selection procedure 542 that determines one or more appropriate
response signal types and corresponding signal parameters, and a
response procedure 544 that applies one or more response signals to
the patient 190. Response signals may include one or more neural
stimulation and/or other types of signals applied to the patient
190 through the stimulation interface 110. Following the response
procedure 544, the process 500 returns to the stimulation operation
520.
[0049] As previously indicated, a neural stimulation procedure in
accordance with the present invention may facilitate and/or
effectuate neuroplastic change or reorganization within a patient
190, which in turn may rehabilitate, restore, and/or enhance one or
more patient neural functions and/or behaviors. To facilitate
and/or effectuate neuroplasticity, a neural stimulation procedure
may be performed cooperatively with a behavioral therapy, such as
described in U.S. application Ser. No. 90/802,808. A behavioral
therapy may encompass, for example, physical therapy, cognitive
therapy, and/or a variety of behavioral tasks.
[0050] FIG. 6 is a flowchart of a neural stimulation process 600
responsive to collateral neural activity according to another
embodiment of the invention. Relative to FIG. 5, like reference
numbers indicate like steps. In one embodiment, the process 600
begins with a stimulation operation 602 by initiating or continuing
a neural stimulation procedure in conjunction or association with a
behavioral therapy. During the stimulation operation 602,
stimulation signals are delivered to one or more target neural
populations within a patient 190 in accordance with a first set of
stimulation signal parameters. Following the stimulation operation
602, other steps within the process 600 may proceed in manners
described above with reference to FIG. 5.
[0051] 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.
Accordingly, the invention is not limited except as by the appended
claims.
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