U.S. patent application number 15/144624 was filed with the patent office on 2016-08-25 for devices, systems and methods for the targeted treatment of movement disorders.
The applicant listed for this patent is St. Jude Medical Luxembourg Holdings SMI S.A.R.L. ("SJM LUX SMI"). Invention is credited to Jeffery M. Kramer, Robert M. Levy.
Application Number | 20160243365 15/144624 |
Document ID | / |
Family ID | 46603312 |
Filed Date | 2016-08-25 |
United States Patent
Application |
20160243365 |
Kind Code |
A1 |
Kramer; Jeffery M. ; et
al. |
August 25, 2016 |
DEVICES, SYSTEMS AND METHODS FOR THE TARGETED TREATMENT OF MOVEMENT
DISORDERS
Abstract
Devices, systems and methods are provided for the targeted
treatment of movement disorders. Typically, the systems and devices
are used to stimulate one or more dorsal root ganglia while
minimizing or excluding undesired stimulation of other tissues,
such as surrounding or nearby tissues, ventral root and portions of
the anatomy associated with body regions which are not targeted for
treatment. The dorsal root ganglia are utilized in particular due
to their specialized role in movement. It is in these areas that
sensory fibers are isolated from motor fibers. Sensory fibers are
involved in a variety of reflexes that are involved in movement
control, and these reflexes can be utilized in the treatment of
various movement disorders. Thus, by stimulating sensory fibers in
these areas, fundamental reflexes can be affected to lessen the
symptoms of movement disorders.
Inventors: |
Kramer; Jeffery M.; (San
Francisco, CA) ; Levy; Robert M.; (Jacksonville,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
St. Jude Medical Luxembourg Holdings SMI S.A.R.L. ("SJM LUX
SMI") |
Plano |
TX |
US |
|
|
Family ID: |
46603312 |
Appl. No.: |
15/144624 |
Filed: |
May 2, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13365163 |
Feb 2, 2012 |
9327110 |
|
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15144624 |
|
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|
|
12607009 |
Oct 27, 2009 |
9056197 |
|
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13365163 |
|
|
|
|
61438895 |
Feb 2, 2011 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/36017 20130101;
A61N 1/0551 20130101; A61N 1/36171 20130101; A61N 1/36139 20130101;
A61B 5/4082 20130101; A61N 1/36071 20130101; A61B 5/1123 20130101;
A61N 1/36067 20130101; A61B 5/0488 20130101; A61B 5/1116 20130101;
A61B 5/1118 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/05 20060101 A61N001/05 |
Claims
1. A method of treating a patient having a movement disorder
comprising: presenting the patient having the movement disorder;
positioning a lead having at least one electrode within the patient
so that the at least one electrode is disposed near a target dorsal
root ganglion associated with the movement disorder; and providing
stimulation energy to the at least one electrode so as to
selectively stimulate at least a portion of the target dorsal root
ganglion so as to reduce a symptom of the movement disorder while
providing no or imperceptible amounts of stimulation energy
directly to a ventral root.
2. A method as in claim 1, wherein the movement disorder includes
Parkinson's Disease, Multiple Sclerosis or a Demylenating Movement
Disorder.
3. A method as in claim 1, wherein the movement disorder includes
Cerebral Palsy, Chorea, Dystonia, Spasm, Tic disorder or
Tremor.
4. A method as in claim 1, wherein the target dorsal root ganglion
is associated with a reflex arc and wherein providing stimulation
energy comprises activating the reflex arc.
5. A method as in claim 4, wherein activating the reflex arc
comprises stimulating at least one sensory neuron so as to activate
at least one soma of an alpha motor neuron.
6. A method as in claim 5, wherein the at least one sensory neuron
comprises an Ia sensory fiber.
7. A method as in claim 5, wherein the at least one sensory neuron
comprises an Ib sensory fiber.
8. A method as in claim 1, wherein providing stimulation energy
comprises providing a stimulation signal having at least one
parameter selected to selectively stimulate the at least a portion
of the target dorsal root ganglion so as to reduce a symptom of the
movement disorder.
9. A method as in claim 8, wherein the at least one parameter
comprises frequency.
10. A method as in claim 9, wherein the at least one parameter
comprises frequency having a value of less than or equal to
approximately 100 Hz.
11. A method as in claim 1, wherein providing stimulation energy
comprises choosing size of the at least one electrode, shape of the
at least one electrode, and/or position of the at least one
electrode so as to selectively stimulate the at least a portion of
the target dorsal root ganglion so as to reduce the symptom of the
movement disorder.
12. A method as in claim 1, wherein providing stimulation energy
comprises providing stimulation energy in response to at least one
sensor configured to sense an indicator of the movement
disorder.
13. A method as in claim 12, wherein the indicator comprises an
onset of the symptom of the movement disorder, and wherein the
stimulation signal is provided to reduce or avoid the onset of the
symptom.
14. A method as in claim 12, wherein the indicator comprises a
status of the symptom of the movement disorder, and wherein the
stimulation signal is provided to treat the symptom in real
time.
15. A method as in claim 1, wherein providing stimulation energy
comprises providing stimulation energy in response to at least one
sensor configured to sense an activity or an activity level of the
patient.
16. A method as in claim 1, wherein providing stimulation energy
comprises providing stimulation energy in response to at least one
sensor configured to detect a position of at least a portion of a
body of the patient.
17. A method of treating a movement disorder of a patient
comprising: advancing a sheath having a curved distal end along an
epidural space of the patient; positioning the curved distal end so
as to direct a lead advanced therethrough toward a spinal nerve
associated with the disorder; advancing the lead having at least
one electrode through the sheath so that the at least one electrode
is disposed near the spinal nerve; and providing stimulation energy
to the at least one electrode so as to stimulate at least a portion
of the spinal nerve in a manner which reduces a symptom of the
movement disorder.
18. A method as in claim 16, wherein the movement disorder includes
Parkinson's Disease, Multiple Sclerosis or a Demylenating Movement
Disorder.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/365,163, filed Feb. 2, 2012, which is a
continuation-in-part of and claims priority to U.S. patent
application Ser. No. 12/607,009 filed on Oct. 27, 2009 (now U.S.
Pat. No. 9,056,197); and U.S. patent application Ser. No.
13/365,163, filed Feb. 2, 2012 claims priority under 35 U.S.C.
119(e) to U.S. Provisional Patent Application Ser. No. 61/438,895
filed on Feb. 2, 2011, all of which are incorporated herein by
reference in their entirety.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] NOT APPLICABLE
REFERENCE TO A "SEQUENCE LISTING," A TABLE, OR A COMPUTER PROGRAM
LISTING APPENDIX SUBMITTED ON A COMPACT DISK
[0003] NOT APPLICABLE
BACKGROUND
[0004] Movement disorders are neurological conditions that affect
the ability to produce and control body movement. In particular,
such disorders interfere with the speed, fluency, quality, and ease
of movement. And, in some cases, cognitive and autonomic functions
can be affected. Currently it is estimated that over 40 million
individuals suffer from some sort of movement disorders. They can
occur in all age groups from infancy to the elderly.
[0005] Treatment for movement disorders depends on the underlying
cause. In most cases, the goal of treatment is to relieve symptoms.
Treatment may include medication, botulinum toxin injection
therapy, and surgery. Medications that are typically used include
the following: antiepileptics, antiseizure medications,
beta-blockers, dopamine agonists, and tranquilizers. However, these
medications have a variety of side effects. Side effects of
antiepileptics include dizziness, drowsiness, nausea, and vomiting.
Antiseizure medications may cause a lack of coordination and
balance (ataxia), dizziness, nausea, and fatigue. Side effects
caused by beta-blockers include slowed heart rate (bradycardia),
depression, light-headedness, and nausea. Dopamine agonists may
cause nausea, headache, dizziness, and fatigue. Tranquilizers such
as benzodiazepines may cause blood clots (thrombosis), drowsiness,
and fatigue.
[0006] Botulinum toxin injection therapy is used to treat some
types of movement disorders (e.g., spasmodic torticollis,
blepharospasm, myoclonus, tremor). In this treatment, a potent
neurotoxin (produced by the bacterium Clostridium botulinum) is
injected into a muscle to inhibit the release of neurotransmitters
that cause muscle contraction. In some cases, treatment is repeated
every 3 to 4 months. However, patients may develop antibodies to
the toxin over time, causing treatment to become ineffective. Side
effects include temporary weakness in the group of muscles being
treated, unintentional paralysis of muscles other than those being
treated and rarely, flu-like symptoms.
[0007] When medication is ineffective, severe movement disorders
may require surgery. In such instances, deep brain stimulation may
be performed wherein a surgically implanted neurostimulator is used
to deliver electrical stimulation to areas of the brain that
control movement. The electrical charge blocks nerve signals that
trigger abnormal movement. In deep brain stimulation, a lead is
inserted through a small incision in the skull and is implanted in
the targeted area of the brain. An insulated wire is then passed
under the skin in the head, neck, and shoulder, connecting the lead
to the neurostimulator, which is surgically implanted in the chest
or upper abdomen. However, negative side effects of deep brain
stimulation can occur, including: bleeding at the implantation
site, depression, impaired muscle tone, infection, loss of balance,
slight paralysis (paresis), slurred speech (dysarthia), and
tingling (parethesia) in the head or the hands.
[0008] Another type of surgical treatment for motion disorders is
ablative surgery. Ablative surgery locates, targets, and then
destroys (ablates) a defined area of the brain that produces
chemical or electrical impulses that cause abnormal movements. In
this surgery, a heated probe or electrode is inserted into the
targeted area. The patient remains awake during the procedure to
determine if the problem has been eliminated. A local anesthetic is
used to dull the outer part of the brain and skull. The brain is
insensitive to pain, so the patient does not feel the actual
procedure. However, in some cases, it may be difficult to estimate
how much tissue to destroy and the amount of heat to use. This type
of surgery involves either ablation in the part of the brain called
the globus pallidus (called pallidotomy) or ablation of brain
tissue in the thalamus (called thalamotomy). Pallidotomy may be
used to eliminate uncontrolled dyskinesia (e.g., jerky, involuntary
movements) and thalamotomy may be performed to eliminate tremor. A
related procedure, cryothalamotomy, uses a supercooled probe that
is inserted into the thalamus to freeze and destroy areas that
produce tremors.
[0009] Aside from the risks and side effects associated with the
above described therapies, such treatments are not always effective
in treating the movement disorder. Therefore, improved therapies
with higher effectiveness and lower side effects are desired. At
least some of these objectives will be met by the following
invention.
SUMMARY OF THE DISCLOSURE
[0010] In a first aspect of the invention, a method is provided
treating a patient having a movement disorder. In some embodiments,
the method comprises presenting the patient having the movement
disorder, positioning a lead having at least one electrode within
the patient so that the at least one electrode is disposed near a
target dorsal root ganglion associated with the movement disorder,
and providing stimulation energy to the at least one electrode so
as to selectively stimulate at least a portion of the target dorsal
root ganglion so as to reduce a symptom of the movement disorder
while providing no or imperceptible amounts of stimulation energy
directly to a ventral root. In some embodiments, the movement
disorder includes Parkinson's Disease, Multiple Sclerosis or a
Demylenating Movement Disorder. In other embodiments, the movement
disorder includes Cerebral Palsy, Chorea, Dystonia, Spasm, Tic
disorder or Tremor. It may be appreciated that other movement
disorders may also be treated with the methods and devices of the
present invention.
[0011] In some embodiments, the target dorsal root ganglion is
associated with a reflex arc and providing stimulation energy
comprises activating the reflex arc. In some instances, activating
the reflex arc comprises stimulating at least one sensory neuron so
as to activate at least one soma of an alpha motor neuron. In some
embodiments, the at least one sensory neuron comprises an Ia
sensory fiber. In other embodiments, the at least one sensory
neuron comprises an Ib sensory fiber.
[0012] In some embodiments, providing stimulation energy comprises
providing a stimulation signal having at least one parameter
selected to selectively stimulate the at least a portion of the
target dorsal root ganglion so as to reduce a symptom of the
movement disorder. In some instances, the at least one parameter
comprises frequency. Optionally, the at least one parameter
comprises frequency having a value of less than or equal to
approximately 100 Hz.
[0013] In some embodiments, providing stimulation energy comprises
choosing size of the at least one electrode, shape of the at least
one electrode, and/or position of the at least one electrode so as
to selectively stimulate the at least a portion of the target
dorsal root ganglion so as to reduce the symptom of the movement
disorder.
[0014] In some embodiments, providing stimulation energy comprises
providing stimulation energy in response to at least one sensor
configured to sense an indicator of the movement disorder. In some
instances, the indicator comprises an onset of the symptom of the
movement disorder, and the stimulation signal is provided to reduce
or avoid the onset of the symptom. In some instances, the indicator
comprises a status of the symptom of the movement disorder, and the
stimulation signal is provided to treat the symptom in real
time.
[0015] In some embodiments, providing stimulation energy comprises
providing stimulation energy in response to at least one sensor
configured to sense an activity or an activity level of the
patient.
[0016] In some embodiments, providing stimulation energy comprises
providing stimulation energy in response to at least one sensor
configured to detect a position of at least a portion of a body of
the patient.
[0017] In second aspect of the invention, a method is provided of
treating a movement disorder of a patient comprising advancing a
sheath having a curved distal end along an epidural space of the
patient, positioning the curved distal end so as to direct a lead
advanced therethrough toward a spinal nerve associated with the
disorder, advancing the lead having at least one electrode through
the sheath so that the at least one electrode is disposed near the
spinal nerve, and providing stimulation energy to the at least one
electrode so as to stimulate at least a portion of the spinal nerve
in a manner which reduces a symptom of the movement disorder. In
some instances, the movement disorder includes Parkinson's Disease,
Multiple Sclerosis or a Demylenating Movement Disorder. In other
instances, the movement disorder includes Cerebral Palsy, Chorea,
Dystonia, Spasm, Tic disorder or Tremor. It may be appreciated that
other movement disorders may also be treated with the methods and
devices of the present invention,
[0018] In some embodiments, the at least a portion of the spinal
nerve comprises at least a portion of a dorsal root ganglion
associated with the movement disorder. And, in some embodiments,
providing stimulation energy comprises adjusting at least one
signal parameter to reduce the symptom of the movement disorder. In
some instances, adjusting the at least one signal parameter
comprises adjusting a frequency of the stimulation energy. For
example, adjusting a frequency of the stimulation energy may
comprise selecting a frequency less than or equal to approximately
100 Hz. Or, adjusting a frequency of the stimulation energy may
comprise selecting a frequency less than or equal to approximately
50 Hz.
[0019] In a third aspect of the invention, a stimulation system is
provided for treating a patient having a movement disorder. In some
embodiments, the system comprises a lead having at least one
electrode, wherein the lead is configured for implantation so as to
position at least one of the at least one electrode adjacent a
dorsal root ganglion associated with the movement disorder, and a
pulse generator electrically connected to the at least one of the
at least one electrode, wherein the pulse generator provides a
signal to the at least one of the at least one electrode which
stimulates at least a portion of the dorsal root ganglion so as to
reduce a symptom of the movement disorder.
[0020] In some embodiments, the target dorsal root ganglion is
associated with a reflex arc and the signal is configured to
activate the reflex arc. In some instances, activation of the
reflex arc comprises stimulation of at least one sensory neuron so
as to activate at least one soma of an alpha motor neuron. In some
instances, the at least one sensory neuron comprises an Ia sensory
fiber. In other instances, the at least one sensory neuron
comprises an Ib sensory fiber.
[0021] In some embodiments, the at least of the at least one
electrode has a size that selectively stimulates the at least one
sensory neuron. In some embodiments, the at least of the at least
one electrode has a shape that selectively stimulates the at least
one sensory neuron.
[0022] In some embodiments, the signal has at least one parameter
that is programmable to selectively stimulate the at least one
sensory neuron. In some instances, the at least one parameter
comprises frequency. In some instances, the frequency is
programmable with a value up to approximately 100 Hz. In other
instances, the frequency is programmable with a value up to
approximately 50 Hz.
[0023] In some embodiments the stimulation system further comprises
at least one sensor configured to sense an indicator of the
movement disorder. In some embodiments, the at least one sensor
comprises an accelerometer, a strain gauge, or an electrical device
which measures electrical activity in a muscle or nerve. In some
embodiments, the indicator indicates an onset of the symptom of the
movement disorder, and the stimulation signal is provided to reduce
or avoid the onset of the symptom. In some embodiments, the
indicator indicates a status of the symptom of the movement
disorder, and the stimulation signal is provided to treat the
symptom in real time. In some embodiments, the indicator indicates
a position of at least a portion of a body of the patient.
[0024] In some embodiments, the stimulation system further
comprises at least one sensor configured to sense an activity or an
activity level of the patient.
[0025] In a fourth aspect of the invention, a system is provided
for treating a patient having a movement disorder, the system
comprising a lead having at least one electrode, wherein the lead
is configured to be positioned so that at least one of the at least
one electrodes is able to stimulate at least a portion of a target
dorsal root associated with the movement disorder, at least one
sensor configured to sense a symptom of the movement disorder, and
an implantable pulse generator connectable with the lead, wherein
the generator Includes electronic circuitry configured to receive
information from the at least one sensor and provide a stimulation
signal to the lead in response to the sensed symptom of the
movement disorder, wherein the stimulation signal has an energy
below an energy threshold for stimulating a ventral root associated
with the target dorsal root while the lead is so positioned,
[0026] In some embodiments, the at least one sensor senses an onset
of the symptom of the movement disorder, and the stimulation signal
is provided to reduce or avoid the onset of the symptom.
[0027] In some embodiments, the at least one sensor senses a status
of the symptom of the movement disorder, and wherein the
stimulation signal is provided to treat the symptom in real
time.
[0028] In some embodiments, the at least one sensor senses an
activity or an activity level of the patient.
[0029] In some embodiments, the at least one sensor detects a
position of at least a portion of a body of the patient.
[0030] In some embodiments, the at least one sensor comprises an
accelerometer, a strain gauge, or an electrical device which
measures electrical activity in a muscle or nerve.
[0031] Other objects and advantages of the present invention will
become apparent from the detailed description to follow, together
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 illustrates an embodiment of an implantable
stimulation system,
[0033] FIG. 2 illustrates example placement of the leads of the
embodiment of FIG. 1 within a patient anatomy.
[0034] FIG. 3 illustrates an example cross-sectional view of an
individual spinal level showing a lead positioned on, near or about
a target dorsal root ganglion.
[0035] FIGS. 4-5 illustrates example activation of reflex arc in
the treatment of movement disorders.
DETAILED DESCRIPTION
[0036] The present invention provides devices, systems and methods
for the targeted treatment of movement disorders. Such movement
disorders include, among others, [0037] 1) Akathisia [0038] 2)
Akinesia (lack of movement) [0039] 3) Associated Movements (Mirror
Movements or Homolateral Synkinesis) [0040] 4) Athetosis (contorted
torsion or twisting) [0041] 5) Ataxia [0042] 6) Ballismus (violent
involuntary rapid and irregular movements) and Hemiballismus
(affecting only one side of the body) [0043] 7) Bradykinesia (slow
movement) [0044] 8) Cerebral palsy [0045] 9) Chorea (rapid,
involuntary movement), including Sydenham's chorea, Rheumatic
chorea and Huntington's disease [0046] 10) Dystonia (sustained
torsion), including Dystonia muscularum, Blepharospasm, Writer's
cramp, Spasmodic torticollis (twisting of head and neck), and
Dopamine-responsive dystonia (hereditary progressive dystonia with
diurnal fluctuation or Segawa's disease) [0047] 11) Geniospasm
(episodic involuntary up and down movements of the chin and lower
lip) [0048] 12) Myoclonus (brief, involuntary twitching of a muscle
or a group of muscles) [0049] 13) Metabolic General Unwellness
Movement Syndrome (MGUMS) [0050] 14) Multiple Sclerosis [0051] 15)
Parkinson's disease [0052] 16) Restless Legs Syndrome RLS
(WittMaack-Ekboms disease) [0053] 17) Spasms (contractions) [0054]
18) Stereotypic movement disorder [0055] 19) Stereotypy
(repetition) [0056] 20) Tardive dyskinesia [0057] 21) Tic disorders
(involuntary, compulsive, repetitive, stereotyped), including
Tourette's syndrome [0058] 22) Tremor (oscillations) [0059] 23)
Rest tremor (approximately 4-8 Hz) [0060] 24) Postural tremor
[0061] 25) Kinetic tremor [0062] 26) Essential tremor
(approximately 6-8 Hz variable amplitude) [0063] 27) Cerebellar
tremor (approximately 6-8 Hz variable amplitude) [0064] 28)
Parkinsonian tremors (approximately 4-8 Hz variable amplitude)
[0065] 29) Physiological tremor (approximately 10-12 Hz low
amplitude) [0066] 30) Wilson's disease
[0067] The present invention provides for targeted treatment of
such conditions with minimal deleterious side effects, such as
undesired motor responses or undesired stimulation of unaffected
body regions. This is achieved by directly neuromodulating a target
anatomy associated with the condition while minimizing or excluding
undesired neuromodulation of other anatomies. In most embodiments,
neuromodulation comprises stimulation, however it may be
appreciated that neuromodulation may include a variety of forms of
altering or modulating nerve activity by delivering electrical
and/or pharmaceutical agents directly to a target area. For
illustrative purposes, descriptions herein will be provided in
terms of stimulation and stimulation parameters, however, it may be
appreciated that such descriptions are not so limited and may
include any form of neuromodulation and neuromodulation
parameters.
[0068] Typically, the systems and devices are used to stimulate
portions of neural tissue of the central nervous system, wherein
the central nervous system includes the spinal cord and the pairs
of nerves along the spinal cord which are known as spinal nerves.
The spinal nerves include both dorsal and ventral roots which fuse
to create a mixed nerve which is part of the peripheral nervous
system. At least one dorsal root ganglion (DRG) is disposed along
each dorsal root prior to the point of mixing. Thus, the neural
tissue of the central nervous system is considered to include the
dorsal root ganglions and exclude the portion of the nervous system
beyond the dorsal root ganglions, such as the mixed nerves of the
peripheral nervous system. Typically, the systems and devices of
the present invention are used to stimulate one or more dorsal root
ganglia, dorsal roots, dorsal root entry zones, or portions
thereof, while minimizing or excluding undesired stimulation of
other tissues, such as surrounding or nearby tissues, ventral root
and portions of the anatomy associated with body regions which are
not targeted for treatment. However, it may be appreciated that
stimulation of other tissues are contemplated.
[0069] The target stimulation areas of the present invention,
particularly the dorsal root ganglia, are utilized due to their
specialized role in movement. It is in these areas that sensory
fibers are isolated from motor fibers. Sensory fibers are involved
in a variety of reflexes that are involved in movement control, and
these reflexes can be utilized in the treatment of various movement
disorders. Thus, by stimulating sensory fibers in these areas,
fundamental reflexes can be affected to lessen the symptoms of
movement disorders. In addition, such targeted stimulation reduces
undesired side effects, such as painful tingling or unwanted
movements caused by direct stimulation of motor nerves, such as
within the ventral root.
[0070] A variety of motor reflexes are involved in movement
control. A reflex or reflex arc is the neural pathway that mediates
a reflex action. A motor reflex action occurs relatively quickly by
activating motor neurons in the spinal cord without the delay of
routing signals through the brain. Normally, messages from nerve
cells in the brain (upper motor neurons) are transmitted to nerve
cells in the brain stem and spinal cord (lower motor neurons) and
from there to particular muscles. Thus, upper motor neurons direct
the lower motor neurons to produce movements such as walking or
chewing. Lower motor neurons control movement in the arms, legs,
chest, face, throat, and tongue. However, lower motor neurons can
be accessed via a reflex arc to circumvent the involvement of upper
neurons. This is beneficial when responding to a harmful stimulus,
such as a hot surface, wherein speed is critical. And, this is
beneficial when there is damage or disease affecting upper neurons
resulting in a movement disorder.
[0071] The present invention utilizes such reflex arcs to treat
patients presenting with one or more movement disorders. FIG. 1
illustrates an embodiment of an implantable stimulation system 100
for treatment of such patients. The system 100 includes an
implantable pulse generator (IPG) 102 and at least one lead 104
connectable thereto. In preferred embodiments, the system 100
includes four leads 104, as shown, however any number of leads 104
may be used including one, two, three, four, five, six, seven,
eight, up to 58 or more. Each lead 104 includes at least one
electrode 106. In preferred embodiments, each lead 104 includes
four electrodes 106, as shown, however any number of electrodes 106
may be used including one, two, three, four five, six, seven,
eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen,
sixteen or more. Each electrode can be configured as off, anode or
cathode. In some embodiments, even though each lead and electrode
are independently configurable, at any given time the software
ensures only one lead is stimulating at any time. In other
embodiments, more than one lead is stimulating at any time, or
stimulation by the leads is staggered or overlapping.
[0072] Referring again to FIG. 1, the IPG 102 includes electronic
circuitry 107 as well as a power supply 110, e.g., a battery, such
as a rechargeable or non-rechargeable battery, so that once
programmed and turned on, the IPG 102 can operate independently of
external hardware. In some embodiments, the electronic circuitry
107 includes a processor 109 and programmable stimulation
information in memory 108.
[0073] The implantable stimulation system 100 can be used to
stimulate a variety of anatomical locations within a patient's
body. In preferred embodiments, the system 100 is used to stimulate
one or more dorsal roots, particularly one or more dorsal root
ganglions. FIG. 2 illustrates example placement of the leads 104 of
the embodiment of FIG. 1 within the patient anatomy. In this
example, each lead 104 is individually advanced within the spinal
column S in an antegrade direction. Each lead 104 has a distal end
which is guidable toward a target DRG and positionable so that its
electrodes 106 are in proximity to the target DRG. Specifically,
each lead 104 is positionable so that its electrodes 106 are able
to selectively stimulate the DRG, either due to position, electrode
configuration, electrode shape, electric field shape, stimulation
signal parameters or a combination of these. FIG. 17 illustrates
the stimulation of four DRGs, each DRG stimulated by one lead 104.
These four DRGs are located on three levels, wherein two DRGs are
stimulated on the same level. It may be appreciated that any number
of DRGs and any combination of DRGs may be stimulated with the
stimulation system 100 of the present invention. It may also be
appreciated that more than one lead 104 may be positioned so as to
stimulate an individual DRG and one lead 104 may be positioned so
as to stimulate more than one DRG.
[0074] FIG. 3 illustrates an example cross-sectional view of an
individual spinal level showing a lead 104 of the stimulation
system 100 positioned on, near or about a target DRG. The lead 104
is advanced along the spinal cord S to the appropriate spinal level
wherein the lead 104 is advanced laterally toward the target DRG.
In some instances, the lead 104 is advanced through or partially
through a foramen. At least one, some or all of the electrodes 106
are positioned on, about or in proximity to the DRG. In preferred
embodiments, the lead 104 is positioned so that the electrodes 106
are disposed along a surface of the DRG opposite to the ventral
root VR, as illustrated in FIG. 3. It may be appreciated that the
surface of the DRG opposite the ventral root VR may be
diametrically opposed to portions of the ventral root VR but is not
so limited. Such a surface may reside along a variety of areas of
the DRG which are separated from the ventral root VR by a
distance.
[0075] In some instances, such electrodes 106 may provide a
stimulation region indicated by dashed line 110, wherein the DRG
receives stimulation energy within the stimulation region and the
ventral root VR does not as it is outside of the stimulation
region. Thus, such placement of the lead 104 may assist in reducing
any possible stimulation of the ventral root VR due to distance.
However, it may be appreciated that the electrodes 106 may be
positioned in a variety of locations in relation to the DRG and may
selectively stimulate the DRG due to factors other than or hi
addition to distance, such as due to stimulation profile shape and
stimulation signal parameters, to name a few. It may also be
appreciated that the target DRG may be approached by other methods,
such as a retrograde epidural approach. Likewise, the DRG may be
approached from outside of the spinal column wherein the lead 104
is advanced from a peripheral direction toward the spinal column,
optionally passes through or partially through a foramen and is
implanted so that at least some of the electrodes 106 are
positioned on, about or in proximity to the DRG.
[0076] In order to position the lead 104 in such close proximity to
the DRG, the lead 104 is appropriately sized and configured to
maneuver through the anatomy. In some embodiments, such maneuvering
includes atraumatic epidural advancement along the spinal cord S,
through a sharp curve toward a DRG, and optionally through a
foramen wherein the distal end of the lead 104 is configured to
then reside in close proximity to a small target such as the DRG.
Consequently, the lead 104 is significantly smaller and more easily
maneuverable than conventional spinal cord stimulator leads.
Example leads and delivery systems for delivering the leads to a
target such as the DRG are provided in U.S. patent application Ser.
No. 12/687,737, entitled "Stimulation Leads, Delivery Systems and
Methods of Use", incorporated herein by reference for all
purposes.
[0077] FIG. 4 illustrates the lead 104 positioned near a DRG so as
to activate an example reflex arc in the treatment of a movement
disorder. In this example, the reflex arc includes a sensory neuron
SN, which includes a some SA disposed within the DRG and an axon AX
which extends through the dorsal root DR to the dorsal horn of the
spinal cord S. The sensory neuron SN connects with a variety of
motor neurons MN and interconnector neurons IN within the spinal
cord S. In this example, the sensory neuron SN connects with two
motor neurons MN1, MN2 and an interconnector neuron IN which
connects with motor neuron MN3. Motor neuron MN1 (an alpha motor
neuron) includes a some SA1 disposed within the ventral horn of the
spinal cord S and an axon AX1 which extends through the ventral
root VR and innervates a skeletal muscle M1, such as a flexor
muscle. Motor neuron MN2 (a second alpha motor neuron) includes a
soma SA2 disposed within the ventral horn of the spinal cord S and
an axon AX2 which extends through the ventral root VR and
innervates a skeletal muscle M2 which is synergistic with muscle
M1. Motor neuron MN3 (a third alpha motor neuron) includes a soma
SA3 disposed within the ventral horn of the spinal cord S and an
axon AX3 which extends through the ventral root VR and innervates a
skeletal muscle M3 which is antagonistic to muscle M1 and muscle
M2.
[0078] In many movement disorders, improper action potentials are
generated, either from damage to the upper motor neurons or from
other causes. In some instances, such improper action potentials
cause muscles (such as muscle M1) and synergistic muscles (such as
M2) to undesirably contract while causing antagonistic muscles
(such as muscle M3) to undesirably relax. In some embodiments,
treatment of such a condition is achieved by providing selective
stimulation to the dorsal root and/or DRG associated with the
muscles M1, M2, M3, with the use of an appropriately positioned
lead 104, as illustrated in FIG. 4. As mentioned previously, at
least one, some or all of the electrodes 106 are positioned on,
about or in proximity to the target DRG. In some embodiments, the
involved sensory neuron SN, particularly its some SA within the
target DRG, is selectively stimulated so as to inhibit the improper
action potentials causing muscles M1, M2 to contract and muscle M3
to relax. This is particularly the case when the involved sensory
neuron SN is an Ia sensory fiber. Such stimulation reduces the
symptoms of the movement disorder in treatment of the
condition.
[0079] In some embodiments, selective stimulation of the involved
sensory neuron SN is achieved with the choice of the size of the
electrode(s), the shape of the electrode(s), the position of the
electrode(s), the stimulation signal, pattern or algorithm, or any
combination of these. Such selective stimulation stimulates the
targeted neural tissue while excluding untargeted tissue, such as
surrounding or nearby tissue. In some embodiments, the stimulation
energy is delivered to the targeted neural tissue so that the
energy dissipates or attenuates beyond the targeted tissue or
region to a level insufficient to stimulate modulate or influence
such untargeted tissue. In particular, selective stimulation of
tissues, such as the dorsal root, DRG, or portions thereof, exclude
stimulation of the ventral root wherein the stimulation signal has
an energy below an energy threshold for stimulating a ventral root
associated with the target dorsal root while the lead is so
positioned. Examples of methods and devices to achieve such
selective stimulation of the dorsal root and/or DRG are provided in
U.S. patent application Ser. No. 12/607,009, entitled "Selective
Stimulation Systems and Signal Parameters for Medical Conditions",
incorporated herein by reference for all purposes. It may be
appreciated that indiscriminant stimulation of the ventral root,
such as from an electrode which emits stimulation energy which
directly stimulates the ventral root, typically causes unpleasant
sensations for the patient, such as tingling, buzzing or undesired
motions or movements. Therefore, it is desired to stimulate motor
neurons M1, M2 and/or M3 via synapses in the spinal cord rather
than directly via the ventral root.
[0080] It may be appreciated that even though the motor neurons are
stimulated via synapses in the spinal cord, such stimulation is
differentiated from stimulating the spinal cord directly to affect
motor neurons. The spinal cord is a highly innervated portion of
the anatomy; sensory information from receptors throughout most of
the body is relayed to the brain by means of ascending tracts of
fibers that conduct impulses up the spinal cord, and, the brain
directs motor activities in the form of nerve impulses that travel
down the spinal cord in descending tracts of fibers. The white
matter of the spinal cord is composed of ascending and descending
fiber tracts. These are arranged into six columns of white matter
called funiculi. The ascending fiber tracts convey sensory
information from cutaneous receptors, proprioceptors (muscle and
joint senses), and visceral receptors. The descending fiber tracts
convey motor information, and there are two major groups of
descending tracts from the brain: the corticospinal, or pyramidal
tracts, and the extrapyramidal tracts.
[0081] From 80%-90% of the corticospinal fibers decussate in the
pyramids of the medulla oblongata (hence the name "pyramidal
tracts") and descend in the lateral corticospinal tracts, which
decussate in the spinal cord. Because of the crossing of fibers,
the right cerebral hemisphere controls the musculature on the left
side of the body, where the left hemisphere controls the right
musculature. The corticospinal tracts are primarily concerned with
the control of fine movement that requires dexterity.
[0082] Given the high number of fiber tracts within the spinal cord
and the extensive crossing of fibers, direct stimulation of the
spinal cord typically yields highly variable and/or non-specific
generalized results. Slight changes in position of the stimulation
electrodes on the spinal cord causes stimulation of different
tracts which can easily lead to undesired side effects. For
example, given that both sensory and motor information is conveyed
within the spinal cord, attempts at stimulating the motor fiber
tract often causes inadvertent stimulation of the sensory fiber
tract. Likewise, given the interconnectivity of pathways across
various spinal levels within the spinal cord, targeting of a
particular spinal level or a particular pair of opposing muscle
groups is very difficult when applying stimulation to the spinal
cord. Further, a higher frequency signal and a higher level of
power is also typically required in attempts to reach specific
nerve types with stimulation when directly stimulating the spinal
cord.
[0083] By stimulating the motor neurons in the spinal cord via the
dorsal root ganglion, the drawbacks associated with direct
stimulation of the spinal cord are avoided. In particular, since
the dorsal root ganglion houses primarily sensory neurons, rather
than mixed neurons such as in the spinal cord or peripheral nerves,
inadvertent stimulation of unrelated or undesired anatomies is
obviated. In addition, stimulation of a single dorsal root ganglion
only affects muscles that are innervated with motor nerves that
synapse with that dorsal root ganglion. Consequently, a single
muscle, a single muscle group, pair of opposing muscles or muscle
groups or a particular localized area may be precisely targeted by
stimulating a corresponding dorsal root ganglion. Such specificity
and targeting is beneficial for treating localized spasticity or
other such movement disorders, among other conditions. Further,
stimulation of a dorsal root ganglion requires less power than
comparative stimulation on the spinal cord. And, stimulation of the
dorsal root ganglion involves a lower frequency than comparative
stimulation of the spinal cord. In some embodiments, a low
frequency signal is used, particularly a frequency less than or
equal to approximately 100 Hz, more particularly less than or equal
to approximately 80 Hz, and more particularly 4-80 Hz. In some
embodiments, the signal has a frequency of approximately less than
or equal to 70 Hz, 80 Hz, 50 Hz, 40 Hz, 30 Hz, 20 Hz, 10 Hz, or 5
Hz. It may be appreciated that typically the desired frequency used
to treat a movement disorder varies from patient to patient. For
example, in one patient a symptom of a movement disorder is reduced
with the use of a stimulation signal having a given frequency, such
as 100 Hz, by stimulating a particular dorsal root ganglion. And,
in another patient having the same or similar movement disorder, a
symptom of the movement disorder is reduced with the use of a
stimulation signal having a different frequency, such as 50 Hz, by
stimulating a corresponding particular dorsal root ganglion. Such
variations may be due to slight differences in anatomy between the
patients and differences in disease pathology, to name a few.
However, it may be appreciated that the frequency is typically in
the low frequency range.
[0084] In other instances, improper action potentials due to
movement disorders cause muscles (such as muscle M1) and
synergistic muscles (such as M2) to undesirably relax while causing
antagonistic muscles (such as muscle M3) to undesirably contract.
In some embodiments, treatment of such a condition is achieved by
providing selective stimulation to the dorsal root and/or DRG
associated with the muscles M1, M2, M3, with the use of an
appropriately positioned lead 104, as illustrated in FIG. 5. In
this example, the reflex arc again includes a sensory neuron SN,
which includes a soma SA disposed within the DRG and an axon AX
which extends through the dorsal root DR to the dorsal horn of the
spinal cord S. The sensory neuron SN connects with a variety of
Interconnector neurons IN1, IN2, IN3 within the spinal cord S.
Interconnector neuron IN1 connects with motor neuron MN1 (an alpha
motor neuron) which innervates a skeletal muscle M1, such as a
flexor muscle. Interconnector neuron IN2 connects with motor neuron
MN2 (a second alpha motor neuron) which innervates a skeletal
muscle M2 which is synergistic with muscle M1. Interconnector
neuron IN3 connects with motor neuron MN3 to third alpha motor
neuron) which innervates a skeletal muscle M3 which is antagonistic
to muscle M1 and muscle M2. As mentioned previously, at least one,
some or all of the electrodes 106 are positioned on, about or in
proximity to the target DRG. In some embodiments, the involved
sensory neuron SN, particularly its soma SA within the target DRG,
is selectively stimulated so as to inhibit the improper action
potentials causing muscles M1, M2 to relax and muscle M3 to
contract. This is particularly the case when the involved sensory
neuron SN is an Ib sensory fiber. Such stimulation reduces the
symptoms of the movement disorder in treatment of the
condition.
[0085] In some embodiments, the implantable pulse generator (IPG)
102 comprises circuitry which initiates or modifies the electrical
stimulation in response to one or more sensors. Example sensors
include, among others, accelerometers, strain gauges, electrical
devices which measure electrical activity in muscles and/or nerves,
or other devices capable of measuring physiological parameters
indicative of symptoms of the movement disorder under treatment. In
some embodiments, the one or more sensors sense the onset of
symptoms of the movement disorder, transmitting such information to
the electronic circuitry 107 of the IPG 102 so that electrical
stimulation is provided to the patient to counteract, reduce and/or
avoid the onset of symptoms of the movement disorder. For example,
in patients suffering from tremors, such tremors may be sudden hi
onset and remission. Some have increased incidence with stress or
decreased incidence when the patient is distracted. This is
particularly the case with psychogenic tremors. In such patients,
the tremor activity may be sensed with a sensor, such as on a
bracelet or anklet worn on the affected limb or limbs. The sensor
may sense a change in acceleration of the limb, frequency of
movement of the limb, position of the limb, or a combination of
these, to name a few. It may be appreciated that such sensors may
also be used on other affected areas of the body, such as the head,
neck, shoulder, torso, etc. When the tremor activity is sensed as
increased, such as an onset or increase in activity, the electrical
stimulation is changed to inhibit or diminish the increase in
tremor activity. This may be achieved by increasing or decreasing
one or more signal parameters, such as amplitude, frequency, pulse
width or a combination of these. Likewise, it may be appreciated
that when the tremor activity is sensed as decreased, such as a
remission or decrease in activity, the electrical stimulation may
be changed, such as to more appropriately match the stimulation to
the tremor activity, in other instances, stimulation may be changed
during remission or decrease in tremor activity to conserve power,
prolong battery life, or reduce any side effects or symptoms
related to unnecessary or undesired stimulation, to name a few. It
may be appreciated that tremor has been used merely as an example
and other movement disorders or symptoms related to movement
disorders may be similarly sensed. For example, some patients with
movement disorders experience jerks or twitches in some part of the
body. These jerky movements may be triggered by pain, certain
lighting, or even loud noises. The occurrence of these symptoms may
be sensed and counteracted in a manner as described above.
[0086] In some embodiments, the one or more sensors sense the
status of the symptoms of the movement disorder, such as the extent
of contraction or limb movement. Such status information is
utilized to modify the electrical stimulation to a level which is
appropriate to counteract or treat the symptoms of the movement
disorder in real time. For example, patients suffering from
spasticity have altered skeletal muscle performance in muscle tone
involving hypertonia. It is often referred to as an unusual
tightness, stiffness, and/or pull of muscles. Spasticity is found
in conditions where the brain and/or spinal cord are damaged or
fail to develop normally; these include cerebral palsy, multiple
sclerosis, spinal cord injury and acquired brain injury including
stroke. In some instances, the level of spasticity may increase or
decrease, such as over time or with stimulation. In some
embodiments, the status of the symptom, such as spasticity, is
sensed to determine if a change has occurred. When the symptom is
sensed as changed, the electrical stimulation is changed to inhibit
or diminish the change in symptom. This may be achieved by
increasing or decreasing one or more signal parameters, such as
amplitude, frequency, pulse width or a combination of these. Again,
it may be appreciated that spasticity has been used merely as an
example and other movement disorders or symptoms related to
movement disorders may be similarly sensed.
[0087] In other embodiments, the one or more sensors sense a
specific activity or an activity level of the patient. Some
movement disorders are correlated to certain activities, such as
walking. For example, functional movement disorders often cause
problems in coordinated locomotion or walking. These problems could
involve dragging one foot or difficulty balancing while walking. An
activity or activity level sensor may be used to detect the type of
activity (such as walking) and/or amount or degree of activity
(such as slow walk or fast walk). The sensed information could be
an input to dynamically modify the stimulation program to determine
the appropriate level of stimulation. Alternatively or
additionally, different pre-programmed stimulation algorithms may
be designed for an individual patient based on that specific
patient's pattern of activity. Pre-programmed stimulation
algorithms may be stored in an appropriate medium for use by a
stimulation system described herein. Conventional transcutaneous
programming techniques may also be used to update, modify or remove
stimulation algorithms.
[0088] In other embodiments, the one or more sensors comprise a
position sensor which may be used to detect position of the
patient. The position of the patient could be an input to the
stimulation control system to dynamically modify the stimulation
program to determine the appropriate level of stimulation. One
example of such a sensor is a multi-axis accelerometer. A
conventional 3 or 4 axis accelerometer could be implanted into a
patient or maintained on the patient to provide position, activity,
activity level, activity duration or other indications of patient
status. The detected indications of patient status could in turn be
used in determining stimulation level and pattern. The position
sensor can be set up or calibrated once positioned or implanted on
or in a person. The calibration aids the sensor in correctly
recognizing the persons orientation and activity levels.
[0089] In some embodiments, the sensor senses when a patient has
lowered to laying or sleeping position. Since most movement
disorders rarely occur during sleep, stimulation may be reduced or
ceased during sleep to reduce power consumption and extend battery
life.
[0090] In some embodiments, the sensor senses when a patient has
risen to a standing position and stimulation is provided to
counteract a symptom of a movement disorder related to standing.
For example, orthostatic tremor is characterized by fast (>12
Hz) rhythmic muscle contractions that occur in the legs and trunk
immediately after standing. Cramps are felt in the thighs and legs
and the patient may shake uncontrollably when asked to stand in one
spot. No other clinical signs or symptoms are present and the
shaking ceases when the patient sits or is lifted off the ground.
The high frequency of the tremor often makes the tremor look like
rippling of leg muscles while standing. In such patients,
stimulation is provided upon sensing of standing wherein the
patient immediately feels relief of such symptoms. When the patient
moves to a different position, such as sifting, the stimulation is
ceased or reduced to a desired level.
[0091] In some embodiments, the sensor senses a particular movement
pattern and stimulation is provided to counteract a symptom of a
movement disorder related to that particular movement pattern. For
example, cerebellar tremor is a slow, broad tremor of the
extremities that occurs at the end of a purposeful movement, such
as trying to press a button or touching a finger to the tip of
one's nose. When such a movement patterns is sensed, stimulation is
then provided to counteract the symptom of the movement disorder
that follows. Cerebellar tremor is caused by lesions in or damage
to the cerebellum resulting from stroke, tumor, or disease such as
multiple sclerosis or some inherited degenerative disorder. It can
also result from chronic alcoholism or overuse of some medicines.
In classic cerebellar tremor, a lesion on one side of the brain
produces a tremor in that same side of the body that worsens with
directed movement. Cerebellar damage can also produce a
"wing-beating" type of tremor called rubral or Holmes' tremor--a
combination of rest, action, and postural tremors. The tremor is
often most prominent when the affected person is active or is
maintaining a particular posture. Thus, a variety of sensors may be
used in a complex array of decision making processes as to when and
how stimulation is provided or changed for a particular
patient.
[0092] Optionally, a position sensor is located within the same
physical housing as the IPG 102. If desired, the position sensor
may be located elsewhere on the body in an implanted location or
may be worn externally by the person. Position information from the
position and/or activity sensor is provided to the IPG 102 using
suitable means including direct connections or percutaneous
transmission. Although a number of embodiments are suitable, the
preferred mode employs, by way of example and not to be construed
as limiting of the present invention, one or more accelerometers to
determine patient state including, at least, the ability to sense
whether the person is erect or recumbent. Additionally, the
position sensor could be adapted to provide an indication of
activity or level of activity such as the difference between
walking and running. In another embodiment, a position sensor may
be positioned to sense specific motion such as activity of a
particular part of the body to detect specific movement of a body
part or limb that, for example, is being treated for a movement
disorder. Using this position sensor embodiment, when the person
started activity related to a movement disorder, the sensor would
detect such activity and provide the appropriate stimulation. In
additional alternatives, the position and/or activity sensor
includes one or more multi-axis accelerometers.
[0093] In some embodiments, the implantable pulse generator (IPG)
102 comprises circuitry which initiates or modifies the electrical
stimulation in response to a timer or clock. Thus, stimulation may
be reduced or eliminated during times in which the patient is
sleeping or times in which it is determined that the patient
desires reduced or no treatment of the movement disorder. Such
periods of reduced usage may extend the life of the power supply
110.
[0094] As mentioned previously, it may be appreciated that
neuromodulation may include a variety of forms of altering or
modulating nerve activity by delivering electrical and/or
pharmaceutical agents directly to a target area. For illustrative
purposes, descriptions herein were provided in terms of stimulation
and stimulation parameters, however, it may be appreciated that
such descriptions are not so limited and may include any form of
neuromodulation and neuromodulation parameters, particularly
delivery of agents to the dorsal root ganglion. Methods, devices
and agents for such delivery are further described in U.S. patent
application Ser. No. 13/309,429 entitled, "Directed Delivery of
Agents to Neural Anatomy", incorporated herein by reference.
[0095] Although the foregoing invention has been described in some
detail by way of illustration and example, for purposes of clarity
of understanding, it will be obvious that various alternatives,
modifications, and equivalents may be used and the above
description should not be taken as limiting in scope of the
invention which is defined by the appended claims.
* * * * *