U.S. patent application number 11/797408 was filed with the patent office on 2007-09-06 for surface stimulation for tremor control.
This patent application is currently assigned to International Rehabilitative Sciences, Inc.. Invention is credited to William J. Carroll, Richard M. Terrell.
Application Number | 20070208385 11/797408 |
Document ID | / |
Family ID | 32393374 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070208385 |
Kind Code |
A1 |
Carroll; William J. ; et
al. |
September 6, 2007 |
Surface stimulation for tremor control
Abstract
Apparatus and methods for non-invasive electrical stimulation of
the brain through skin surface stimulation of the peripheral
nervous system as a treatment for movement disorders. Skin surface
electrodes are positioned at predetermined peripheral surface
stimulation sites on the skin surface using a variety of neural
imaging techniques. A pulsatile electrical current is generated at
the stimulation sites through a variety of standard electrical
stimulation devices. Stimulation of the peripheral surface
stimulation sites translates to electrical stimulation of a
specific area of the brain.
Inventors: |
Carroll; William J.; (La
Center, WA) ; Terrell; Richard M.; (Vancouver,
WA) |
Correspondence
Address: |
BLANK ROME LLP
600 NEW HAMPSHIRE AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
International Rehabilitative
Sciences, Inc.
|
Family ID: |
32393374 |
Appl. No.: |
11/797408 |
Filed: |
May 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10717925 |
Nov 21, 2003 |
7228178 |
|
|
11797408 |
May 3, 2007 |
|
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|
60428281 |
Nov 22, 2002 |
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Current U.S.
Class: |
607/2 |
Current CPC
Class: |
A61N 1/36025 20130101;
A61N 1/323 20130101 |
Class at
Publication: |
607/002 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Claims
1. A system for tremor control, comprising: a stimulator,
including: a pulse generator for generating digital signal pulses,
a digital signal processor connected to said pulse generator for
generating an approximate sine wave output that is further
processed in first and second circuits, and at least two pairs of
surface electrodes connected to said digital signal processor and
positioned at predetermined peripheral surface stimulation sites on
a subject's skin surface; and at least one neural image, wherein
said at least two pairs of surface electrodes stimulate the
subject's brain, and wherein the predetermined peripheral surface
stimulation sites are determined based at least in part on the at
least one neural image.
2. The system of claim 1, wherein said at least two pairs of
surface electrodes connected to said digital signal processor
produce an interferential current output waveform from said first
and second circuits.
3. The system of claim 2, wherein said interferential current
output waveform includes a base medium frequency of at least 1 KHz
but no more than 100 KHz.
4. The system of claim 2, wherein said interferential current
output waveform includes a resultant beat frequency of no more than
250 Hz.
5. The system of claim 1, wherein said at least two pairs of
surface electrodes connected to said digital signal processor are
positioned on the subject's skin surface using positron emission
tomography and neural imaging devices to identify the peripheral
surface stimulation sites.
6. The system of claim 1, wherein said at least two pairs of
surface electrodes connected to said digital signal processor are
positioned on the subject's skin surface using dermatome maps to
identify the peripheral surface stimulation sites.
7. A system for tremor control, comprising: a stimulator,
including, a pulse generator for generating digital signal pulses,
a field-programmable gate array connected to said pulse generator
for processing the digital signal pulses to approximate a sine-wave
output waveform that is further processed in first and second
circuits, and at least two pairs of surface electrodes connected to
said field-programmable gate array and positioned at predetermined
peripheral surface stimulation sites on a subject's skin surface;
and at least one neural image, wherein said at least two pairs of
surface electrodes stimulate the subject's brain, and wherein the
predetermined peripheral surface stimulation sites are determined
based at least in part on the at least one neural image.
8. The system of claim 7, wherein said at least two pairs of
surface electrodes connected to said field-programmable gate array
produce an interferential current output waveform from said first
and second circuits.
9. The system of claim 8, wherein said interferential current
output waveform includes a base medium frequency of at least 1 KHz
but no more than 100 KHz.
10. The system of claim 8, wherein said interferential current
output waveform includes a resultant beat frequency of no more than
250 Hz.
11. The system of claim 7, wherein said at least two pairs of
surface electrodes connected to said field-programmable gate array
are positioned on the subject's skin surface using positron
emission tomography and neural imaging devices to identify the
peripheral surface stimulation sites.
12. The system of claim 7, wherein said at least two pairs of
surface electrodes connected to said field-programmable gate array
are positioned on the subject's skin surface using dermatome maps
to identify the peripheral surface stimulation sites.
13. A system for tremor control, comprising: a stimulator,
including, a pulse generator for generating electrical pulses, and
at least one pair of surface electrodes connected to said pulse
generator and positioned at predetermined peripheral surface
stimulation sites on a subject's skin surface; and at least one
neural image, wherein said at least one pair of surface electrodes
stimulate the subject's brain, and wherein the predetermined
peripheral surface stimulation sites are determined based at least
in part on the at least one neural image.
14. The system of claim 13, wherein said at least one pair of
surface electrodes connected to said pulse generator produce a
pulsatile current with a square wave output.
15. The system of claim 14, wherein said pulsatile current includes
an amplitude range from 0-150 mA and a pulse width of 1-500
.mu.sec.
16. The system of claim 13, wherein said pulsatile current includes
a frequency range from 1 pps to 2500 pps.
17. The system of claim 13, wherein said at least one pair of
surface electrodes connected to said pulse generator are positioned
on the subject's skin surface using positron emission tomography
and neural imaging devices to identify the peripheral surface
stimulation sites.
18. The system of claim 13, wherein said at least one pair of
surface electrodes connected to said pulse generator are positioned
on the subject's skin surface using dermatome maps to identify the
peripheral surface stimulation sites.
19. The system of claim 1, wherein said at least two pairs of
surface electrodes stimulate the subject's brain
transcutaneously.
20. The system of claim 1, wherein said at least two pairs of
surface electrodes stimulate the subject's brain
percutaneously.
21. The system of claim 7, wherein said at least two pairs of
surface electrodes stimulate the subject's brain
transcutaneously.
22. The system of claim 7, wherein said at least two pairs of
surface electrodes stimulate the subject's brain
percutaneously.
23. The system of claim 13, wherein said at least one pair of
surface electrodes stimulates the subject's brain
transcutaneously.
24. The system of claim 13, wherein said at least one pair of
surface electrodes stimulates the subject's brain percutaneously.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of the U.S.
application Ser. No. 10/717,925, filed Nov. 23, 2003, which claims
priority to Provisional Patent Application No. 60/428,281, filed
Nov. 22, 2002, whose disclosure is hereby incorporated by reference
in its entirety into the present disclosure.
FIELD OF THE INVENTION
[0002] The present invention is generally related to tremor
control, and more particularly, is related to an apparatus and
methods for the electrical stimulation of the brain through skin
surface stimulation of the peripheral nervous system for the
treatment of movement disorders.
BACKGROUND OF THE INVENTION
[0003] In the last decade, the use of deep brain stimulation (DBS)
has demonstrated dramatic improvement in symptoms associated with
movement disorders, including symptoms from Parkinson's disease
(PD), Essential Tremor (ET) and dystonia.
[0004] Essential Tremor is an involuntary movement, such as a
shaking movement that is repeated over and over. Essential Tremor
usually affects the hands and head, although occasionally the feet
or torso may also be affected. Essential tremor, which sometimes
runs in families, is one of the most common types of tremor. It
causes shaking that is most noticeable when a person is performing
a task like lifting a cup or pointing at an object. The shaking
does not occur when the person is not moving. The tremor may also
affect the person's voice. Medication can help reduce the shaking.
Tremors can also be caused by conditions or medications that affect
the nervous system, including Parkinson's disease, liver failure,
alcoholism, mercury or arsenic poisoning, lithium, and certain
antidepressants.
[0005] Instead of destroying the overactive cells that cause
symptoms from PD, for example, DBS instead temporarily disables the
cells by firing rapid pulses of electricity between four electrodes
at the tip of a lead. The lead is permanently implanted and
connected to a pacemaker controller installed beneath the skin of
the chest.
[0006] DBS utilizes electrodes that are usually implanted in one of
three regions of the brain: the thalamic nucleus ventralis
intermedius (Vim), the internal globus pallidus (GPi), and the
subthalamic nucleus (STN) (FIG. 1). Some studies have shown that
DBS has the best effect on tremors, when the Vim is stimulated.
Rigidity and gait disturbances have shown improvements with
stimulation of GPi and STN. The parameters of 130-185 Hz, 60 ms
pulse width and 2.5 to 3.5 volts are most commonly utilized for DBS
stimulation. DBS stimulation is typically pulsed intermittent
stimulation having an on cycle of about a few seconds up to a
minute, then an off cycle for about 30 seconds to several
minutes.
[0007] The challenge of DBS is the obvious drawback of having to
undergo a neuro-surgical procedure and also to have the result of
one or two electrodes implanted deep within the structures of the
brain.
[0008] The present invention achieves tremor control through brain
stimulation without the use of the invasive DBS electrodes.
Stimulation of peripheral nerves results in the excitation of some
area of the brain (Thalmus, sub-cortical and Cortical areas). The
stimulation of sites on the surface of the skin produces effects of
tremor control which are similar to the effects achieved by DBS for
limited amounts of time. Surface stimulation is achieved through
the use of surface electrodes that are currently used for Muscle
Stimulation or TENS. Following a 30-60 minute stimulation time,
there is a residual decrease in tremor of at least 30-60 minutes.
The device can be worn under the clothing and activated while the
decreased tremor period is desired.
[0009] PET (Positron Emission Tomography) scans, a molecular
medical imaging procedure that uses small amounts of radioactive
pharmaceuticals to make images of the body's metabolic activity,
Magnetoencephalography (MEG) scans and fMRI scans can be used to
identify appropriate peripheral surface stimulation sites. Various
types of stimulation can be used including TENS, Neuro-Muscular
Stimulation, Ultra Sound, Interferential Stimulation, PEMF, EMF,
and various types of mechanical stimulation.
[0010] Thus, a heretofore unaddressed need exists in the industry
to address the aforementioned deficiencies and inadequacies
associated with a neuro-surgical procedure and the implantation of
at least one electrode deep within the structures of the brain.
SUMMARY OF THE INVENTION
[0011] Embodiments of the present invention provide an apparatus
and methods for surface electrical stimulation of the peripheral
nervous system at predetermined peripheral stimulation sites for
the treatment of movement disorders.
[0012] In a preferred embodiment, the peripheral stimulation sites,
which are linked to specific areas of the brain, are initially
traced using dermatome maps and then verified using PET scans, MEG
scans, fMRI or other neural imaging devices. The electrical
stimulator may utilize an interferential current that has a base
medium frequency alternating current between 1 KHz and 100 KHz. An
interferential current is set up between two circuits that are
arranged in a cross-pattern on the subject's targeted area of
stimulation. Where the circuits superimpose in a cross-pattern, the
resultant beat frequency will be the difference between the
frequencies of the two circuits and will usually range between
0-250 Hz and can be dynamic, and the amplitude will be additive and
greater than either circuit alone.
[0013] Digital signal processors (DSPs) are used for improving the
accuracy and reliability of digital signals that are used
extensively in the communications field. Digital signal processing
works by standardizing or clarifying the output of a digital
signal. In this embodiment, the digital signal processor is used to
shape multiple pulsatile waveforms to approximate the output of a
sine-wave generator. In another embodiment of the invention, the
digital signal processor is replaced with a field-programmable gate
array (FPGA). A FPGA is an integrated circuit that can be
programmed in the field after it is manufactured and therefore
allows users to adjust the circuit output as the needs change. Both
the DSP and the FPGA process a digital signal into a
pseudo-sine-wave current waveform from the digital pulses generated
by a pulse generator. The pseudo-sine-wave current waveform is
transmitted through surface electrodes at a targeted area creating
an interferential current.
[0014] The electrical stimulator may also use a standard TENS or
NeuroMuscular stimulation waveform. Such devices produce a
pulsatile current with a square wave output, an amplitude range
from 0-150 mA and a phase duration (pulse width) range of 1-500
.mu.sec. The frequency of such devices can range from 1 pulse per
second (pps) to 2500 pps. The devices can be set to various duty
cycles (on and off times) from as little as 1 second to 30 minutes
on, and an off time as little as 1 second to as long as several
minutes. The device can also be set to a continuous output without
a duty cycle. The device may utilize as little as one pair of
electrodes, or multiple sets may be more effective depending on the
condition of the patient.
[0015] Once identified, the peripheral stimulation sites are
stimulated with the surface electrical stimulation device.
[0016] Other systems methods, features and advantages of the
present invention will be or become apparent to one skilled in the
art upon examination of the following drawings and detailed
description. It is intended that all such additional systems,
methods, features and advantages be included within this
description, be within the scope of the present invention, and be
protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Many aspects of the invention can be better understood with
reference to the following drawings. The components in the drawings
are not necessarily to scale, emphasis instead being placed upon
clearly illustrating the principles of the present invention.
Moreover, in the drawings, like reference numerals designate
corresponding parts throughout the several views.
[0018] FIG. 1 is a drawing of the potential stimulation sites in
the brain for deep brain stimulation for movement disorders;
[0019] FIG. 2 is a drawing of a perspective view of an
interferential current set up by two circuits;
[0020] FIG. 3 is a drawing of a perspective view of an
interferential current pattern indicating the current intensity
level and area of beat frequency formation; and
[0021] FIG. 4 is a drawing of a stimulator with surface electrodes
positioned at peripheral stimulation sites.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] A preferred embodiment of the invention and modifications
thereof will now be described with reference to the drawings.
[0023] FIG. 1 shows the potential stimulation sites in the brain
for deep brain stimulation via surface stimulation of the
peripheral nervous system. Using dermatome maps (not shown) of the
peripheral nervous system, which can then be confirmed by PET scans
(not shown) of the brain, peripheral surface stimulation sites 410
on a subject's skin surface are determined (FIG. 4). The
stimulation of the peripheral surface stimulation sites 410 on the
surface of the skin produces effects of tremor control which are
similar to the effects achieved by DBS for limited amounts of time.
The excited peripheral nerves would in turn excite similar, but not
necessarily, the same areas of the brain that are currently
stimulated by DBS.
[0024] FIG. 2 shows a stimulator 200 for the electrical stimulation
of the peripheral nerves for tremor control at the peripheral
surface stimulation sites utilizing an interferential current 210
that has a base medium frequency alternating current between 1K-100
KHz. Such a stimulator 200 is shown, for example, in U.S. Pat. No.
6,393,328, issued on May 21, 2002 to the assignee of the present
application. Other TENS, Neuromuscular stimulation devices,
Ultrasound, Pulsed Electromagnetic Field generators, EMF generators
and mechanical stimulation devices can also be utilized (not
shown).
[0025] The interferential current 210 is set up between two
circuits 218, 220, 418, 420 that are arranged in a cross-pattern. A
first pair of surface electrodes 208, 209 are positioned on a
subject's skin surface at the peripheral surface stimulation site
410 on one set of diagonal corners of a targeted area 114, 314 (see
FIG. 3). The targeted area is the peripheral nerve and surrounding
area to be stimulated. A second pair of surface electrodes 209,
309, and 408, is then positioned at the other set of diagonal
corners of the targeted area 114, 314. A digital signal processor
202 is connected to the first and second pairs of surface
electrodes 208,209; 308,309; and 408. When a signal-generating
source 204 is connected to the digital signal processor 202, a
sine-wave-like waveform signal output 206 is created. The digital
signal processor 202 improves the accuracy and reliability of the
digital signals. The digital signal processor 202 processes the
multiple pulses from the signal generating source 204 to
approximate a sine-wave (pseudo-sine-wave or sine-wave-like). The
digital signal processor 202 generates individual pulses 206 of
differing widths and resultant amplitudes. When those differing
pulses 206 are driven into a transformer (not shown), the
pseudo-sine-wave is produced.
[0026] A pulse generator 204 is connected to the input of the
digital signal processor 202 and supplies a pulsed digital signal
output 216 to the digital signal processor 202. The digital signal
216 is processed by the digital signal processor 202 to create a
first circuit 218 and a second circuit 220 at the first and second
pairs of surface electrodes 208,209; 308,309; and 408,
respectively. Where the first and second circuits 218, 220
superimpose, the resultant beat frequency (which is preferably
between 1 and 250 beats/second) will be the difference between the
frequencies of the two circuits, and the amplitude will be additive
and greater than either circuit alone (FIG. 3).
[0027] Modulating the outputs of the first and second circuits 218,
410, 220, 420 increases the area of the targeted stimulation (FIG.
4). The depth of modulation can vary from 0 to 100% and depends on
the direction of the currents established by the first and second
circuits 218, 418, 220, 420. When the first and second circuits
218, 418, 220, 420 intersect at 90.degree., the maximum resultant
amplitude and the deepest level of modulation is half-way between
the two circuits (45.degree. diagonally). (See FIG. 3). The area of
stimulation can be augmented by modulation of the amplitudes of the
outputs of the two circuits.
[0028] FIG. 4 shows the stimulator 200, 400 positioned to stimulate
the two pairs of electrodes 208,209; 308,309; and 408, at the
predetermined peripheral surface stimulation sites 410. One pair of
electrodes may be utilized if we are utilizing NMES or TENS outputs
and it is deemed effective due to the condition, and predetermined
with Neural Imaging studies.
[0029] In an alternative embodiment, as described above, the
digital signal processor may be replaced with the FPGA. Whereas DSP
processors typically have only eight dedicated multipliers at their
disposal, a higher end FPGA device can offer up to 224 dedicated
multipliers plus additional logic element-based multipliers as
needed. That allows for complex digital signal processing
applications such as finite impulse response filters, forward error
correction, modulation-demodulation, encryption and applications
such as utilized in the present invention.
[0030] It should be emphasized that the above-described embodiments
of the present invention, particularly, any "preferred"
embodiments, are merely possible examples of implementations,
merely set forth for a clear understanding on the principles of the
invention. Many variations and modifications may be made to the
above-described embodiment(s) of the invention without departing
substantially from the spirit and principles of the invention. All
such modifications and variations are intended to be included
herein within the scope of this disclosure and the present
invention, and protected by the following claims.
* * * * *