U.S. patent application number 14/182884 was filed with the patent office on 2014-06-12 for electrode cuffs.
This patent application is currently assigned to BIO CONTROL MEDICAL (B.C.M.) LTD.. The applicant listed for this patent is BIO CONTROL MEDICAL (B.C.M.) LTD.. Invention is credited to Shai AYAL, Tamir BEN-DAVID, Ehud COHEN.
Application Number | 20140163661 14/182884 |
Document ID | / |
Family ID | 43899081 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140163661 |
Kind Code |
A1 |
BEN-DAVID; Tamir ; et
al. |
June 12, 2014 |
ELECTRODE CUFFS
Abstract
Apparatus is provided for application to a nerve of a subject,
including an electrode cuff, which includes a housing, which is
configured to be placed at least partially around the nerve so as
to define an inner surface of the housing that faces the nerve. A
plurality of insulating elements are coupled to the inner surface
of the housing at respective insulating element longitudinal
positions along the housing, such that the inner surface of the
housing and pairs of the insulating elements define one or more
respective cavities at respective cavity longitudinal positions
along the housing. One or more electrodes are fixed to the housing
in fewer than all of the cavities, such that at least one of the
cavities is an empty cavity that does not have an electrode
positioned therein. Other embodiments are also described.
Inventors: |
BEN-DAVID; Tamir; (Tel Aviv,
IL) ; AYAL; Shai; (Shoham, IL) ; COHEN;
Ehud; (Ganei Tikva, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BIO CONTROL MEDICAL (B.C.M.) LTD. |
Yehud |
|
IL |
|
|
Assignee: |
BIO CONTROL MEDICAL (B.C.M.)
LTD.
Yehud
IL
|
Family ID: |
43899081 |
Appl. No.: |
14/182884 |
Filed: |
February 18, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12947608 |
Nov 16, 2010 |
|
|
|
14182884 |
|
|
|
|
12217930 |
Jul 9, 2008 |
|
|
|
12947608 |
|
|
|
|
11070842 |
Feb 24, 2005 |
8386056 |
|
|
12217930 |
|
|
|
|
10719659 |
Nov 20, 2003 |
7778711 |
|
|
11070842 |
|
|
|
|
PCT/IL03/00431 |
May 23, 2003 |
|
|
|
10719659 |
|
|
|
|
Current U.S.
Class: |
607/118 |
Current CPC
Class: |
A61N 1/36114 20130101;
A61N 1/0556 20130101 |
Class at
Publication: |
607/118 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. Apparatus for application to a nerve of a subject, comprising an
electrode cuff, which comprises: a housing, configured to be placed
at least partially around the nerve so as to define an inner
surface of the housing that faces the nerve; a plurality of
insulating elements coupled to the inner surface of the housing at
respective insulating element longitudinal positions along the
housing, such that the inner surface of the housing and pairs of
the insulating elements define respective cavities at respective
cavity longitudinal positions along the housing; and one or more
electrodes, fixed to the housing in fewer than all of the cavities,
such that at least one of the cavities is an empty cavity that does
not have an electrode positioned therein.
2. The apparatus according to claim 1, further comprising a control
unit, coupled to the electrodes, and configured to drive at least a
portion of the electrodes to apply a current to the nerve.
3. The apparatus according to claim 2, wherein the electrodes
comprise two or more cathode electrodes, and wherein the empty
cavity is between and directly adjacent along the cuff to two
cavities containing two respective ones of the cathode
electrodes.
4. The apparatus according to claim 2, wherein the electrodes
comprise two or more anode electrodes, and wherein the empty cavity
is between and directly adjacent along the cuff to two cavities
containing two respective ones of the anode electrodes.
5. The apparatus according to claim 2, wherein the electrodes
comprise two or more cathode electrodes and one or more anode
electrodes, and wherein the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the cathode electrodes.
6. The apparatus according to claim 2, wherein the electrodes
comprise two or more anode electrodes and one or more cathode
electrodes, and wherein the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the anode electrodes.
7. The apparatus according to claim 2, wherein the plurality of
electrodes comprises at least one cathode electrode, at least one
anode electrode, and two or more passive electrodes, and wherein
the apparatus further comprises a conducting element, which
electrically couples the passive electrodes to one another.
8. The apparatus according to claim 7, wherein the plurality of
insulating elements includes at least seven insulating elements,
which are arranged along the housing such that the inner surface of
the housing and the pairs of insulating elements define first,
second, third, fourth, fifth, and sixth cavities, the first cavity
closest to an end of the housing, the second adjacent to the first,
the third adjacent to the second, the fourth adjacent to the third,
the fifth adjacent to the fourth, and the sixth adjacent to the
fifth, wherein the at least one cathode electrode comprises at
least one first cathode electrode and at least one second cathode
electrode, wherein at least a first one of the passive electrodes
is fixed to the housing in the first cavity, wherein the at least
one anode electrode is fixed to the housing in the second cavity,
wherein the at least one first cathode electrode is fixed to the
housing in the third cavity, wherein no electrodes are fixed to the
housing in the fourth cavity, wherein the at least one second
cathode electrode is fixed to the housing in the fifth cavity, and
wherein at least a second one of the passive electrodes is fixed to
the housing in the sixth cavity.
9. The apparatus according to claim 1, wherein the insulating
elements are shaped so as to define respective contact surfaces,
and wherein the housing and the insulating elements are configured
such that the contact surfaces are suitable for being positioned
less than 0.5 mm from a surface of the nerve when the housing is
placed at least partially around the nerve.
10. The apparatus according to claim 1, wherein the insulating
elements are shaped so as to define respective contact surfaces,
and wherein the housing and the insulating elements are configured
such that the contact surfaces are suitable for at least partially
coming in physical contact with the nerve when the housing is
placed at least partially around the nerve.
11. The apparatus according to claim 1, wherein a length that at
least one of the insulating elements protrudes from the housing
toward a central axis of the cuff is at least 0.5 mm.
12. The apparatus according to claim 1, wherein the electrodes are
fixed to the housing in a number of the cavities, wherein a
difference between the number of the cavities and a total number of
the cavities is an integer between 1 and 3, inclusive, such that
between 1 and 3 of the cavities do not have any of the electrodes
fixed therein.
13. (canceled)
14. The apparatus according to claim 1, wherein at least two of the
electrodes are fixed to the housing in one of the cavities.
15. The apparatus according to claim 1, wherein the electrodes
comprise ring electrodes.
16. (canceled)
17. The apparatus according to claim 1, wherein the one or more
cavities include at least three cavities, and wherein the
electrodes are fixed to the housing in at least two of the
cavities.
18. The apparatus according to claim 17, wherein the one or more
cavities include at least four cavities, and wherein the electrodes
are fixed to the housing in at least three of the cavities.
19. Apparatus for application to a nerve, comprising: a cuff shaped
so as to define along a longitudinal axis thereof cavities at
respective cavity longitudinal positions along the cuff, wherein
the cavities are open to the nerve and closed to an outer surface
of the cuff when the cuff is placed at least partially around the
nerve; and one or more electrodes, fixed to the cuff in fewer than
all of the cavities, such that at least one of the cavities is an
empty cavity that does not have an electrode positioned
therein.
20. The apparatus according to claim 19, wherein the electrodes
comprise ring electrodes.
21. The apparatus according to claim 19, wherein at least two of
the electrodes are fixed to the cuff in one of the cavities.
22. (canceled)
23. The apparatus according to claim 19, further comprising a
control unit, coupled to the electrodes, and configured to drive at
least a portion of the electrodes to apply a current to the
nerve.
24. The apparatus according to claim 23, wherein the electrodes
comprise two or more cathode electrodes, and wherein the empty
cavity is between and directly adjacent along the cuff to two
cavities containing two respective ones of the cathode
electrodes.
25. The apparatus according to claim 23, wherein the electrodes
comprise two or more anode electrodes, and wherein the empty cavity
is between and directly adjacent along the cuff to two cavities
containing two respective ones of the anode electrodes.
26. The apparatus according to claim 23, wherein the electrodes
comprise two or more cathode electrodes and one or more anode
electrodes, and wherein the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the cathode electrodes.
27. The apparatus according to claim 23, wherein the electrodes
comprise two or more anode electrodes and one or more cathode
electrodes, and wherein the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the anode electrodes.
28. A method comprising: placing, at least partially around a
nerve, a cuff shaped so to define along a longitudinal axis thereof
cavities at respective cavity longitudinal positions along the
cuff, the cuff including one or more electrodes fixed to the cuff
in few than all of the cavities, such that at least one of the
cavities is an empty cavity that does not have an electrode
positioned therein; and applying a current to the nerve using at
least a portion of the electrodes, wherein placing the cuff
comprises placing the cuff at least partially around the nerve such
that the cavities are open to the nerve and closed to an outer
surface of the cuff.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 12/947,608, filed Nov. 16, 2010, which is a
continuation-in-part of (a) U.S. application Ser. No. 12/217,930,
filed Jul. 9, 2008, now abandoned, and (b) U.S. application Ser.
No. 11/070,842, filed Feb. 24, 2005, now U.S. Pat. No. 8,386,056,
which is a continuation of U.S. application Ser. No. 10/719,659,
filed Nov. 20, 2003, now U.S. Pat. No. 7,778,711, which is a
continuation-in-part of International Application PCT/IL03/00431,
filed May 23, 2003. All of these applications are assigned to the
assignee of the present application and are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to electrical
stimulation of tissue, and specifically to methods and devices for
regulating the stimulation of nerves.
BACKGROUND OF THE INVENTION
[0003] A number of patents and articles describe methods and
devices for stimulating nerves to achieve a desired effect. Often
these techniques include a design for an electrode or electrode
cuff.
[0004] US Patent Application Publication 2010/0010603 to Ben-David
et al., which is assigned to the assignee of the present
application and is incorporated herein by reference, describes
apparatus for application to a nerve of a subject. The apparatus
includes a housing, which is configured to be placed at least
partially around the nerve so as to define an inner surface of the
housing that faces the nerve. A plurality of insulating elements
are coupled to the inner surface of the housing at respective
insulating element longitudinal positions along the housing, such
that the inner surface of the housing and pairs of the insulating
elements define one or more respective cavities at respective
cavity longitudinal positions along the housing. One or more
electrodes are fixed to the housing in fewer than all of the
cavities. Other embodiments are also described.
[0005] PCT Publication WO 03/099377 to Ayal et al., which is
assigned to the assignee of the present application and is
incorporated herein by reference, describes apparatus for treating
a subject, which includes an electrode device, adapted to be
coupled to a vagus nerve of the subject, and a heart rate sensor,
configured to detect a heart rate of the subject, and to generate a
heart rate signal responsive thereto. The apparatus also includes a
control unit, adapted to receive the heart rate signal, and,
responsive to determining that the heart rate is greater than a
threshold value, which threshold value is greater than a normal
heart rate, drive the electrode device to apply a current to the
vagus nerve, and configure the current so as to reduce the heart
rate of the subject.
[0006] U.S. Pat. No. 6,907,295 to Gross et al., which is assigned
to the assignee of the present application and is incorporated
herein by reference, describes apparatus for applying current to a
nerve. A cathode is adapted to be placed in a vicinity of a
cathodic longitudinal site of the nerve and to apply a cathodic
current to the nerve. A primary inhibiting anode is adapted to be
placed in a vicinity of a primary anodal longitudinal site of the
nerve and to apply a primary anodal current to the nerve. A
secondary inhibiting anode is adapted to be placed in a vicinity of
a secondary anodal longitudinal site of the nerve and to apply a
secondary anodal current to the nerve, the secondary anodal
longitudinal site being closer to the primary anodal longitudinal
site than to the cathodic longitudinal site.
[0007] US Patent Application Publication 2006/0106441 to Ayal et
al., which is assigned to the assignee of the present application
and is incorporated herein by reference, describes apparatus for
applying current to a nerve, including a housing, adapted to be
placed in a vicinity of the nerve, and at least one cathode and at
least one anode, fixed to the housing. The apparatus further
includes two or more passive electrodes, fixed to the housing, and
a conducting element, which electrically couples the passive
electrodes to one another.
[0008] U.S. Pat. No. 4,608,985 to Crish et al. and U.S. Pat. No.
4,649,936 to Ungar et al., which are incorporated herein by
reference, describe electrode cuffs for selectively blocking
orthodromic action potentials passing along a nerve trunk, in a
manner intended to avoid causing nerve damage.
[0009] PCT Patent Publication WO 01/10375 to Felsen et al., which
is incorporated herein by reference, describes apparatus for
modifying the electrical behavior of nervous tissue. Electrical
energy is applied with an electrode to a nerve in order to
selectively inhibit propagation of an action potential.
[0010] U.S. Pat. No. 5,755,750 to Petruska et al., which is
incorporated herein by reference, describes techniques for
selectively blocking different size fibers of a nerve by applying
direct electric current between an anode and a cathode that is
larger than the anode.
[0011] U.S. Pat. No. 5,824,027 Hoffer et al., which is incorporated
herein by reference, describes a nerve cuff having one or more sets
of electrodes for selectively recording electrical activity in a
nerve or for selectively stimulating regions of the nerve. Each set
of electrodes is located in a longitudinally-extending chamber
between a pair of longitudinal ridges which project into the bore
of the nerve cuff. The ridges are electrically insulating and serve
to improve the selectivity of the nerve cuff. The ridges seal
against an outer surface of the nerve without penetrating the
nerve. In an embodiment, circumferential end sealing ridges extend
around the bore at each end of the longitudinal ridges, and are
described as enhancing the electrical and/or fluid isolation
between different ones of the longitudinally-extending
chambers.
[0012] U.S. Pat. No. 4,628,942 to Sweeney et al., which is
incorporated herein by reference, describes an annular electrode
cuff positioned around a nerve trunk for imposing electrical
signals on to the nerve trunk for the purpose of generating
unidirectionally propagated action potentials. The electrode cuff
includes an annular cathode having a circular passage therethrough
of a first diameter. An annular anode has a larger circular passage
therethrough of a second diameter, which second diameter is about
1.2 to 3.0 times the first diameter. A non-conductive sheath
extends around the anode, cathode, and nerve trunk. The anode and
cathode are placed asymmetrically to one side of the non-conductive
sheath.
[0013] As defined by Rattay, in an article entitled, "Analysis of
models for extracellular fiber stimulation," IEEE Transactions on
Biomedical Engineering, Vol. 36, no. 2, p. 676 (1989), which is
incorporated herein by reference, the activation function (AF) of
an unmyelinated axon is the second spatial derivative of the
electric potential along an axon. In the region where the
activation function is positive, the axon depolarizes, and in the
region where the activation function is negative, the axon
hyperpolarizes. If the activation function is sufficiently
positive, then the depolarization will cause the axon to generate
an action potential; similarly, if the activation function is
sufficiently negative, then local blocking of action potentials
transmission occurs. The activation function depends on the current
applied, as well as the geometry of the electrodes and of the
axon.
[0014] For a given electrode geometry, the equation governing the
electrical potential is:
.gradient.(.sigma..gradient.U)=4.pi.j,
[0015] where U is the potential, .sigma. is the conductance tensor
specifying the conductance of the various materials (electrode
housing, axon, intracellular fluid, etc.), and j is a scalar
function representing the current source density specifying the
locations of current injection. The activation function is found by
solving this partial differential equation for U. If an
unmyelinated axon is defined to lie in the z direction, then the
activation function is:
AF = .differential. 2 U .differential. z 2 . ##EQU00001##
[0016] In a simple, illustrative example of a point electrode
located a distance d from the axis of an axon in a
uniformly-conducting medium with conductance .sigma., the two
equations above are solvable analytically, to yield:
AF = I e 1 4 .pi. .sigma. 2 z 2 - d 2 ( z 2 + d 2 ) 2.5 ,
##EQU00002##
[0017] where I.sub.el is the electrode current. It is seen that
when .sigma. and d are held constant, and for a constant positive
T.sub.el (to correspond to anodal current), the minimum value of
the activation function is negative, and is attained at z=0, i.e.,
at the point on the nerve closest to the source of the anodal
current. Thus, the most negative point on the activation function
corresponds to the place on a nerve where hyperpolarization is
maximized, namely at the point on the nerve closest to the
anode.
[0018] Additionally, this equation predicts positive "lobes" for
the activation function on either side of z=0, these positive lobes
peaking in their values at a distance which is dependent on each of
the other parameters in the equation. The positive values of the
activation function correspond to areas of depolarization, a
phenomenon typically associated with cathodic current, not anodal
current. However, it has been shown that excess anodal current does
indeed cause the generation of action potentials adjacent to the
point on a nerve corresponding to z=0, and this phenomenon is
therefore called the "virtual cathode effect." (An analogous, but
reverse phenomenon, the "virtual anode effect" exists responsive to
excess cathodic stimulation.)
[0019] The Rattay article also describes techniques for calculating
the activation function for nerves containing myelinated axons. The
activation function in this case varies as a function of the
diameter of the axon in question. Thus, the activation function
calculated for a 1 micron diameter myelinated axon is different
from the activation function calculated for a 10 micron diameter
axon.
[0020] The following patents, which are incorporated herein by
reference, may be of interest:
[0021] U.S. Pat. No. 6,684,105 to Cohen et al.
[0022] U.S. Pat. No. 5,423,872 to Cigaina
[0023] U.S. Pat. No. 4,573,481 to Bullara
[0024] U.S. Pat. No. 6,230,061 to Hartung
[0025] U.S. Pat. No. 5,282,468 to Klepinski
[0026] U.S. Pat. No. 4,535,785 to van den Honert et al.
[0027] U.S. Pat. No. 5,215,086 to Terry et al.
[0028] U.S. Pat. No. 6,341,236 to Osorio et al.
[0029] U.S. Pat. No. 5,487,756 to Kallesoe et al.
[0030] U.S. Pat. No. 5,634,462 to Tyler et al.
[0031] U.S. Pat. No. 6,456,866 to Tyler et al.
[0032] U.S. Pat. No. 4,602,624 to Naples et al.
[0033] U.S. Pat. No. 6,600,956 to Maschino et al.
[0034] U.S. Pat. No. 5,199,430 to Fang et al.
[0035] The following articles, which are incorporated herein by
reference, may be of interest: [0036] Ungar I J et al., "Generation
of unidirectionally propagating action potentials using a monopolar
electrode cuff," Annals of Biomedical Engineering, 14:437-450
(1986) [0037] Sweeney J D et al., "An asymmetric two electrode cuff
for generation of unidirectionally propagated action potentials,"
IEEE Transactions on Biomedical Engineering, vol. BME-33(6) (1986)
[0038] Sweeney J D et al., "A nerve cuff technique for selective
excitation of peripheral nerve trunk regions," IEEE Transactions on
Biomedical Engineering, 37(7) (1990) [0039] Naples G G et al., "A
spiral nerve cuff electrode for peripheral nerve stimulation," by
IEEE Transactions on Biomedical Engineering, 35(11) (1988) [0040]
van den Honert C et al., "Generation of unidirectionally propagated
action potentials in a peripheral nerve by brief stimuli," Science,
206:1311-1312 (1979) [0041] van den Honert C et al., "A technique
for collision block of peripheral nerve: Single stimulus analysis,"
MP-11, IEEE Trans. Biomed. Eng. 28:373-378 (1981) [0042] van den
Honert C et al., "A technique for collision block of peripheral
nerve: Frequency dependence," MP-12, IEEE Trans. Biomed. Eng.
28:379-382 (1981)
[0043] Rijkhoff N J et al., "Acute animal studies on the use of
anodal block to reduce urethral resistance in sacral root
stimulation," IEEE Transactions on Rehabilitation Engineering,
2(2):92-99 (1994) [0044] Mushahwar V K et al., "Muscle recruitment
through electrical stimulation of the lumbo-sacral spinal cord,"
IEEE Trans Rehabil Eng, 8(1):22-9 (2000) [0045] Deurloo K E et al.,
"Transverse tripolar stimulation of peripheral nerve: a modelling
study of spatial selectivity," Med Biol Eng Comput, 36(1):66-74
(1998) [0046] Tarver W B et al., "Clinical experience with a
helical bipolar stimulating lead," Pace, Vol. 15, October, Part II
(1992) [0047] Hoffer J A et al., "How to use nerve cuffs to
stimulate, record or modulate neural activity," in Neural
Prostheses for Restoration of Sensory and Motor Function, Chapin J
K et al. (Eds.), CRC Press (1st edition, 2000) [0048] Jones J F et
al., "Heart rate responses to selective stimulation of cardiac
vagal C fibres in anaesthetized cats, rats and rabbits," J Physiol
489(Pt 1):203-14 (1995) [0049] Evans M S et al., "Intraoperative
human vagus nerve compound action potentials," Acta Neurol Scand
110:232-238 (2004) [0050] Fitzpatrick et al., "A nerve cuff design
for the selective activation and blocking of myelinated nerve
fibers," Ann. Conf. of the IEEE Eng. in Medicine and Biology Soc,
13(2), 906 (1991) [0051] Rijkhoff N J et al., "Orderly recruitment
of motoneurons in an acute rabbit model," Ann. Conf. of the IEEE
Eng., Medicine and Biology Soc., 20(5):2564 (1998) [0052] Rijkhoff
N J et al., "Selective stimulation of small diameter nerve fibers
in a mixed bundle," Proceedings of the Annual Project Meeting
Sensations/Neuros and Mid-Term Review Meeting on the TMR-Network
Neuros, April 21-23, 1999, pp. 20-21 (1999) [0053] Baratta R et
al., "Orderly stimulation of skeletal muscle motor units with
tripolar nerve cuff electrode," IEEE Transactions on Biomedical
Engineering, 36(8):836-43 (1989)
[0054] The following articles, which are incorporated herein by
reference, describe techniques using cuff electrodes to selectively
excite peripheral nerve fibers distant from an electrode without
exciting nerve fibers close to the electrode: [0055] Grill W M et
al., "Inversion of the current-distance relationship by transient
depolarization," IEEE Trans Biomed Eng, 44(1):1-9 (1997) [0056]
Goodall E V et al., "Position-selective activation of peripheral
nerve fibers with a cuff electrode," IEEE Trans Biomed Eng,
43(8):851-6 (1996) [0057] Veraart C et al., "Selective control of
muscle activation with a multipolar nerve cuff electrode," IEEE
Trans Biomed Eng, 40(7):640-53 (1993) [0058] Lertmanorat Z et al.,
"A novel electrode array for diameter-dependent control of axonal
excitability: a simulation study," IEEE Transactions on Biomedical
Engineering 51(7):1242-1250 (2004)
SUMMARY OF THE INVENTION
[0059] In embodiments of the present invention, an electrode cuff
for applying current to a nerve comprises a housing, which is
configured to placed at least partially around the nerve, and a
plurality of insulating elements arranged at respective
longitudinal positions along the housing such that an inner surface
of the housing and pairs of the insulating elements define
respective cavities (i.e., spaces surrounded by portions of the
cuff) at respective longitudinal positions along the housing. The
cuff further comprises one or more electrodes, fixed to the housing
in fewer than all of the cavities. In other words, at least one of
the cavities defined by a pair of the insulating elements does not
have an electrode positioned therein. The electrode cuff is
typically configured such that, after placement of the cuff,
respective contact surfaces of the insulating elements at least
partially come in physical contact with the nerve, or substantially
in physical contact with the nerve, e.g., are less than about 0.5
mm from the surface of the nerve. As used in the present
application, including in the claims, an "electrode" is an
electrically conductive element that includes at least one surface
that is not electrically insulated.
[0060] Providing the one or more empty cavities results in less
physical contact between the contact surfaces of the insulating
elements and the nerve for a cuff of a given length, than in a cuff
of the same length without such an empty cavity. As a result,
providing the empty cavities tends to reduce constriction of the
nerve by the cuff, which may reduce side-effects of application of
the cuff to the nerve. Providing the empty cavity does not have a
material impact on the activation function achieved by the
electrode cuff.
[0061] For some applications, providing a cuff having an increased
length along the nerve is desirable, e.g., because such an
increased length provides greater space for a distribution of
electrodes that enables achievement of a desired activation
function that could not be achieved with a shorter cuff. Providing
the empty cavity enables the lengthening of the cuff without a
concomitant increase in insulating element contact surface
area.
[0062] There is therefore provided, in accordance with an
embodiment of the present invention, apparatus for application to a
nerve of a subject, including an electrode cuff, which
includes:
[0063] a housing, configured to be placed at least partially around
the nerve so as to define an inner surface of the housing that
faces the nerve;
[0064] a plurality of insulating elements coupled to the inner
surface of the housing at respective insulating element
longitudinal positions along the housing, such that the inner
surface of the housing and pairs of the insulating elements define
one or more respective cavities at respective cavity longitudinal
positions along the housing; and
[0065] one or more electrodes, fixed to the housing in fewer than
all of the cavities, such that at least one of the cavities is an
empty cavity that does not have an electrode positioned
therein.
[0066] For some applications, the apparatus further includes a
control unit, coupled to the electrodes, and configured to drive at
least a portion of the electrodes to apply a current to the nerve.
For some applications, the electrodes include two or more cathode
electrodes, and the empty cavity is between and directly adjacent
along the cuff to two cavities containing two respective ones of
the cathode electrodes. For some applications, the electrodes
include two or more anode electrodes, and the empty cavity is
between and directly adjacent along the cuff to two cavities
containing two respective ones of the anode electrodes. For some
applications, the electrodes include two or more cathode electrodes
and one or more anode electrodes, and the empty cavity is between
and directly adjacent along the cuff to two cavities containing two
respective ones of the cathode electrodes. For some applications,
the electrodes include two or more anode electrodes and one or more
cathode electrodes, and the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the anode electrodes. For some applications, the plurality
of electrodes includes at least one cathode electrode, at least one
anode electrode, and two or more passive electrodes, and the
apparatus further includes a conducting element, which electrically
couples the passive electrodes to one another.
[0067] For some applications,
[0068] the plurality of insulating elements includes at least seven
insulating elements, which are arranged along the housing such that
the inner surface of the housing and the pairs of insulating
elements define first, second, third, fourth, fifth, and sixth
cavities, the first cavity closest to an end of the housing, the
second adjacent to the first, the third adjacent to the second, the
fourth adjacent to the third, the fifth adjacent to the fourth, and
the sixth adjacent to the fifth,
[0069] the at least one cathode electrode includes at least one
first cathode electrode and at least one second cathode
electrode,
[0070] at least a first one of the passive electrodes is fixed to
the housing in the first cavity,
[0071] the at least one anode electrode is fixed to the housing in
the second cavity,
[0072] the at least one first cathode electrode is fixed to the
housing in the third cavity,
[0073] no electrodes are fixed to the housing in the fourth
cavity,
[0074] the at least one second cathode electrode is fixed to the
housing in the fifth cavity, and
[0075] at least a second one of the passive electrodes is fixed to
the housing in the sixth cavity.
[0076] For some applications, the insulating elements are shaped so
as to define respective contact surfaces, and the housing and the
insulating elements are configured such that the contact surfaces
are suitable for being positioned less than 0.5 mm from a surface
of the nerve when the housing is placed at least partially around
the nerve.
[0077] For some applications, the insulating elements are shaped so
as to define respective contact surfaces, and the housing and the
insulating elements are configured such that the contact surfaces
are suitable for at least partially coming in physical contact with
the nerve when the housing is placed at least partially around the
nerve.
[0078] For some applications, a length that at least one of the
insulating elements protrudes from the housing toward a central
axis of the cuff is at least 0.5 mm.
[0079] For some applications, the electrodes are fixed to the
housing in a number of the cavities, and a difference between the
number of the cavities and a total number of the cavities is an
integer between 1 and 3, inclusive, such that between 1 and 3 of
the cavities do not have any of the electrodes fixed therein.
[0080] For some applications, the housing has a length of between
10 mm and 14 mm, an outer radius of between 4 mm and 8 mm, an inner
radius of between 3 mm and 6 mm; the insulating elements have an
outer radius of between 3 mm and 6 mm, and an inner radius of
between 2 mm and 3.5 mm; and the plurality of insulating elements
includes exactly seven insulating elements, respective edges of
which are positioned within the housing at the following respective
distances from one end of the housing: 0.0 mm, between 1.3 and 1.7
mm, between 2.7 and 3.3 mm, between 5.1 and 6.3 mm, between 7.1 and
8.7 mm, between 8.5 and 10.3 mm, and between 10.2 and 12.4 mm, and
the insulating elements having the following respective widths:
between 0.7 and 0.9 mm, between 0.7 and 0.9 mm, between 1.4 and 1.8
mm, between 0.7 and 0.9 mm, between 0.7 and 0.9 mm, between 1.1 and
1.3 mm, and between 0.7 and 0.9 mm.
[0081] For some applications, at least two of the electrodes are
fixed to the housing in one of the cavities.
[0082] For some applications, the electrodes include ring
electrodes.
[0083] For some applications, the electrodes are fixed to the
housing in none of the one or more cavities, such that all of the
one or more cavities are empty of electrodes.
[0084] For some applications, the one or more cavities include at
least three cavities, and the electrodes are fixed to the housing
in at least two of the cavities. For some applications, the one or
more cavities include at least four cavities, and the electrodes
are fixed to the housing in at least three of the cavities.
[0085] There is further provided, in accordance with an application
of the present invention, apparatus for application to a nerve,
including:
[0086] a cuff shaped so as to define along a longitudinal axis
thereof one or more cavities open to the nerve when the cuff is
placed at least partially around the nerve; and
[0087] one or more electrodes, fixed to the cuff in fewer than all
of the cavities, such that at least one of the cavities is an empty
cavity that does not have an electrode positioned therein.
[0088] For some applications, the electrodes include ring
electrodes.
[0089] For some applications, at least two of the electrodes are
fixed to the cuff in one of the cavities.
[0090] For some applications, the electrodes are fixed to the cuff
in none of the one or more cavities, such that all of the one or
more cavities are empty of electrodes.
[0091] For some applications, the apparatus further includes a
control unit, coupled to the electrodes, and configured to drive at
least a portion of the electrodes to apply a current to the nerve.
For some applications, the electrodes include two or more cathode
electrodes, and the empty cavity is between and directly adjacent
along the cuff to two cavities containing two respective ones of
the cathode electrodes. For some applications, the electrodes
include two or more anode electrodes, and the empty cavity is
between and directly adjacent along the cuff to two cavities
containing two respective ones of the anode electrodes. For some
applications, the electrodes include two or more cathode electrodes
and one or more anode electrodes, and the empty cavity is between
and directly adjacent along the cuff to two cavities containing two
respective ones of the cathode electrodes. For some applications,
the electrodes include two or more anode electrodes and one or more
cathode electrodes, and the empty cavity is between and directly
adjacent along the cuff to two cavities containing two respective
ones of the anode electrodes.
[0092] There is still further provided, in accordance with an
application of the present invention, a method including:
[0093] placing, at least partially around a nerve, a cuff shaped so
to define along a longitudinal axis thereof one or more cavities
open to the nerve, the cuff including one or more electrodes fixed
to the cuff in few than all of the cavities, such that at least one
of the cavities is an empty cavity that does not have an electrode
positioned therein; and
[0094] applying a current to the nerve using at least a portion of
the electrodes.
[0095] The present invention will be more fully understood from the
following detailed description of embodiments thereof, taken
together with the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0096] FIG. 1 is schematic, cross-sectional illustration of an
electrode cuff for applying current to a nerve, in accordance with
respective embodiments of the present invention;
[0097] FIG. 2 is a schematic, cross-sectional illustration of
another electrode cuff for applying current to a nerve, in
accordance with an embodiment of the present invention;
[0098] FIGS. 3 and 4 are graphs modeling calculated activation
functions, respectively, when current is applied using electrode
cuffs similar to those shown in FIGS. 1 and 2, respectively, in
accordance with an embodiment of the present invention;
[0099] FIG. 5 is a schematic, longitudinal cross-sectional view of
another electrode cuff for applying current to a nerve, in
accordance with an embodiment of the present invention;
[0100] FIG. 6 is a schematic, cross-sectional illustration of yet
another electrode cuff for applying current to a nerve, in
accordance with an embodiment of the present invention;
[0101] FIG. 7 is a block diagram that schematically illustrates a
vagal stimulation system applied to a vagus nerve of a patient, in
accordance with an embodiment of the present invention;
[0102] FIG. 8A is a simplified cross-sectional illustration of a
multipolar electrode device applied to a vagus nerve, in accordance
with an embodiment of the present invention;
[0103] FIG. 8B is a simplified cross-sectional illustration of a
generally-cylindrical electrode device applied to a vagus nerve, in
accordance with an embodiment of the present invention; and
[0104] FIG. 8C is a simplified perspective illustration of the
electrode device of FIG. 8A, in accordance with an embodiment of
the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0105] FIG. 1 is a schematic, cross-sectional illustration of an
electrode cuff 20 for applying current to a nerve 30, in accordance
with an embodiment of the present invention. Electrode cuff 20
comprises a housing 32 which defines an outer surface of the cuff
when the cuff is placed at least partially around nerve 30. Housing
32 typically comprises an elastic, electrically-insulating material
such as silicone or polyurethane, which may have, for example, a
Shore A of between about 35 and about 70, such as about 40.
[0106] Electrode cuff 20 further comprises a plurality of
insulating elements 34 that are arranged at respective positions
along the housing, and are typically fixed to an inner surface 37
of housing 32 that faces nerve 30 when the electrode cuff is placed
at least partially around the nerve. Insulating elements 34
typically comprise an elastic, electrically-insulating material
such as silicone or silicone copolymer, which, for some
applications, is softer than that of housing 32, for example, a
Shore A of between about 10 and about 30, such as about 10.
Electrode cuff 20 is typically configured such that, after
placement of the cuff on the nerve, respective contact surfaces 36
of insulating elements 34 at least partially come in physical
contact with the nerve, or substantially in physical contact with
the nerve, e.g., are less than about 0.5 mm from the surface of the
nerve. For some applications, a length that at least one of
insulating elements 34 protrudes from housing 32 toward nerve 30 is
at least 0.5 mm, such as at least 1 mm. For some applications,
insulating elements 34 and housing 32 are constructed as separate
elements that are coupled to one another, while for other
applications, the insulating elements and housing are constructed
as a single integrated element that is shaped to define the
insulating elements and housing.
[0107] Insulating elements 34 typically comprise one or more (such
as exactly two) end insulating elements 38 arranged at or near
respective ends of the cuff, and two or more internal insulating
elements 40 arranged at respective positions along the cuff between
the end insulating elements. End insulating elements 38 extend
along nerve 30 in order to electrically isolate a portion of the
nerve within electrode cuff 20 from a portion of the nerve outside
the electrode cuff.
[0108] Inner surface 37 of housing 32 and pairs of insulating
elements 34 define respective cavities 41 along the housing. (It is
noted that some pairs of the insulating elements may not define a
cavity, such as if two or more of the insulating elements are
arranged in contact with one another.)
[0109] Electrode cuff 20 comprises a plurality of electrodes 42,
fixed within housing 32 in respective cavities 41 defined by
respective pairs insulating elements 34 and inner surface 37 of
housing 32. At least one of cavities 41 defined by a pair of the
insulating elements does not have an electrode positioned therein.
For example, in the embodiment shown in FIG. 1, the insulating
elements define six cavities 41, a fourth one 43 of which (counting
from the left in the figure) does not have an electrode positioned
therein. For some applications, at least two, such as least three,
of the cavities do not have electrodes positioned therein.
Electrodes 42 are typically fixed to inner surface 37 of housing
32. For some applications, none of the cavities have electrodes
positioned therein (see, for example, FIG. 6).
[0110] For some applications, at least one of the empty cavities
has a length along the cuff of at least 0.5 mm, such as at least
0.7 mm, e.g., at least 1.4 mm or at least 2 mm, and/or no more than
5 mm, e.g., no more than 2 mm. For some applications, a length
along the cuff of one of the empty cavities is between about 0.5
and about times a length of one of the cavities that has an
electrode therein, such as between about 1 and about 2 times the
length.
[0111] For some applications, at least one of the empty cavities is
directly adjacent along the cuff to two cavities containing an
anode electrode and a cathode electrode, respectively. For some
applications, at least one of the empty cavities is directly
adjacent along the cuff to two cavities containing two respective
anode electrodes, or to two cavities containing two respective
cathode electrodes. Alternatively, at least one of the two endmost
cavities is empty, e.g., one side of at least one of the empty
cavities is defined by one of end insulating elements 38.
[0112] Providing the empty cavity results in less physical contact
between contact surfaces 36 of insulating elements 34 and nerve 30
for a cuff of a given length, than in a cuff of the same length
without such an empty cavity. As a result, providing the empty
cavity tends to reduce constriction of the nerve by the cuff, which
may reduce side-effects of application of the cuff to the nerve.
Providing the empty cavity does not have a material impact on the
activation function achieved by the electrode cuff, as described
hereinbelow with reference to FIGS. 3 and 4.
[0113] Internal insulating elements 40 are arranged so as to
electrically separate electrodes 42, and to guide current from one
of the electrodes towards the nerve prior to being taken up by
another one of the electrodes. Typically (as shown), insulating
elements 34 are closer to nerve 30 than are the electrodes, i.e.,
the electrodes are recessed within the cavities. Alternatively (not
shown), insulating elements 34 are generally flush with the faces
of the electrodes, such that the inner surfaces of insulating
elements and the conductive surfaces of the electrode are
equidistant from the nerve.
[0114] Electrodes 42 comprise at least one active, i.e.,
stimulating and/or sensing, electrode 44, such as one or more
cathode electrodes 46, one or more anode electrodes 48, or at least
one cathode electrode 46 and at least one anode electrode 48.
Active electrodes 44 are coupled to an implantable or external
control unit 50 by leads 52 and 54. For some applications, active
electrode configurations and/or stimulation techniques are used
which are described in one or more of the patent applications
incorporated by reference hereinbelow. For some applications, two
or more of the active electrodes are shorted to one another inside
or outside of the cuff, such as shown for cathode electrodes 46 in
FIG. 1.
[0115] In an embodiment of the present invention, electrode cuff 20
further comprises two or more passive electrodes 60, fixed within
housing 32, and a conducting element 62, typically a wire, which
electrically couples the passive electrodes to one another. A
"passive electrode," as used in the present application including
the claims, is an electrode that is electrically "device-coupled"
to neither (a) any circuitry that is electrically device-coupled to
any of the cathode electrodes or anode electrodes, nor (b) an
energy source. "Device-coupled" means coupled, directly or
indirectly, by components of a device, and excludes coupling via
tissue of a subject. (It is noted that the passive electrodes may
be passive because of a software-controlled setting of the
electrode assembly, and that the software may intermittently change
the setting such that these electrodes are not passive.) To
"passively electrically couple," as used in the present application
including the claims, means to couple using at least one passive
electrode and no non-passive electrodes. Passive electrodes 60 and
conducting element 62 create an additional electrical path for the
current, such as an additional path for the current that would
otherwise leak outside electrode cuff 20 and travel around the
outside of the housing through tissue of the subject. For some
applications, conducting element 62 comprises at least one passive
element 64, such as a resistor, capacitor, and/or inductor. In this
embodiment, end insulating elements 38 help direct any current that
leaks from active electrodes 44 through the electrical path created
by passive electrodes 60 and conducting element 62. For some
applications, active electrodes 44 are positioned within housing 32
longitudinally between the two or more passive electrodes 60 (as
shown in FIG. 1). Alternatively, at least one of the passive
electrodes is positioned between the at least one cathode electrode
and the at least one anode electrode (configuration not shown).
[0116] In an embodiment of the present invention, electrode cuff 20
comprises one or more passive electrodes 60 which are not
electrically device-coupled to one another. For some applications,
the electrode cuff comprises exactly one passive electrode 60. A
separate conducting element, typically a wire, is coupled to each
passive electrode at a first end of the conducting element. The
second end of the conducting element terminates at a
relatively-remote location in the body of the subject that is at a
distance of at least 1 cm, e.g., at least 2 or 3 cm, from electrode
cuff 20. The remote location in the body thus serves as a ground
for the passive electrode. For some applications, an electrode is
coupled to the remote end of the conducting element, so as to
increase electrical contact with tissue at the remote location.
[0117] For some applications, housing 32 has a length of between
about 10 and about 14 mm, e.g., about 12.1 mm; an outer radius of
between about 4 and about 8 mm, e.g., about 5.9 mm; and an inner
radius of between about 3 and about 6 mm, e.g., about 4.5 mm. For
some applications, insulating elements 34 have an outer radius of
between about 3 and about 6 mm, e.g., about 4.5 mm (the outer
radius of the insulating elements is typically equal to the inner
radius of the housing), and an inner radius of between about 2 and
about 3.5 mm. For some applications in which cuff 20 comprises
exactly two end insulating elements 38 and exactly five internal
insulating elements 40, respective edges of insulating elements 34
are positioned within cuff 32 at the following distances from one
end of the cuff: 0.0 mm, between 1.3 and 1.7 mm (e.g., 1.5 mm),
between 2.7 and 3.3 mm (e.g., 3.0 mm), between 5.1 and 6.3 mm
(e.g., 5.7 mm), between 7.1 and 8.7 mm (e.g., 7.9 mm), between 8.5
and 10.3 mm (e.g., 9.4 mm), and between 10.2 and 12.4 mm (e.g.,
11.3 mm), and the insulating elements having the following
respective widths: between 0.7 and 0.9 mm (e.g., 0.8 mm), between
0.7 and 0.9 mm (e.g., 0.8 mm), between 1.4 and 1.8 mm (e.g., 1.6
mm), between 0.7 and 0.9 mm (e.g., 0.8 mm), between 0.7 and 0.9 mm
(e.g., 0.8 mm), between 1.1 and 1.3 mm (e.g., 1.2 mm), and between
0.7 and 0.9 mm (e.g., 0.8 mm). For some applications, electrodes 42
comprise Pt/Ir. For some applications, as shown in FIG. 1,
electrodes 42 are shaped as rings (e.g., reference numeral 60 and
leftmost reference numeral 42 in FIG. 1 refer to a single ring
electrode). The rings may have an outer radius that equals, or is
slightly greater or less than, the inner radius of housing 32.
[0118] In an embodiment of the present invention, at least some of
the electrodes do not comprise ring electrodes. Instead, each of at
least one of non-empty cavities 41 has fixed therein a plurality of
electrodes positioned at least partially circumferentially around a
central axis of the cuff. In other words, electrodes 42 are first
electrodes 42, fixed within housing 32 in respective cavities 41,
and cuff 20 comprises at least one second electrode 42, fixed
within housing 32 in one of the cavities 41 in which one of the
first electrodes 42 is fixed. For some applications, the plurality
of electrodes within a single cavity are circumferentially
separated from one another by one or more circumferentially
arranged insulating elements.
[0119] In an embodiment of the present invention, at least one of
the one or more of cavities 41 which are empty in the embodiments
described hereinabove, instead has fixed therein one or more
electrodes that are not electrically device-coupled (as defined
hereinabove) to any elements of the device outside of the cavity.
These electrodes thus do not serve the normal function of
electrodes in an electrode cuff, i.e., conducting current to and/or
from tissue.
[0120] In an embodiment of the present invention, nerve 30 is a
vagus nerve, and electrode cuff 20 is configured to be placed at
least partially around the vagus nerve such that anode electrode 48
is more proximal to the brain than are cathode electrodes 46.
[0121] FIG. 2 is a schematic, cross-sectional illustration of an
electrode cuff 120 for applying current to nerve 30, in accordance
with an embodiment of the present invention. Electrode cuff 120 is
identical to electrode cuff 20, described hereinabove with
reference to FIG. 1, except that cuff 120 lacks cavity 43 of cuff
20, which, as mentioned above, does not have one of electrodes 42
positioned therein. Instead of the two internal insulating elements
40 that define cavity 43 in cuff 20, cuff 120 has a single,
elongated insulating element 130, having a length along the housing
equal to the sum of the lengths along the cuff of cavity 43 and the
two internal insulating elements 40 that define cavity 43 in cuff
20.
[0122] Reference is made to FIGS. 3 and 4, which are graphs
modeling calculated activation functions 200 and 202, respectively,
when current is applied using electrode cuffs similar to those
shown in FIGS. 1 and 2, respectively, in accordance with an
embodiment of the present invention. These activation functions
model myelinated nerve fibers having a diameter of 1 micrometer,
over a portion of the length of nerve 30, at a radius of 1.2 mm
from the axis of the nerve. For the purposes of modeling these
activation functions, (a) two cathode electrodes 46 are placed at
longitudinal sites on the nerve labeled z=2.25 mm and z=-1.65 mm,
respectively, (b) anode electrode 48 is placed at a longitudinal
site z=-4.15 mm, and (c) two passive electrodes 60 are placed at
longitudinal sites z=4.15 mm and z=-5.65 mm, respectively. All of
the electrodes are placed at a radius of R=2.5 mm from the axis of
nerve 30, which has a radius of 1.35 mm. The cavity of activation
function 200 (FIG. 3) is at z=0.4 mm. The inner surfaces of all of
the insulating elements (i.e., the surfaces closest to the nerve)
are placed at a radius R=1.5 mm from the axis of nerve 30.
[0123] A comparison of activation functions 200 and 202 shows that
the two activation functions are nearly identical, which
demonstrates that providing empty cavity 43 does not have a
material impact on the activation function achieved by the
electrode cuff.
[0124] For some applications, electrode cuff 20 is configured to
selectively stimulate fibers of the nerve having certain diameters,
such as by using techniques described in one or more of the patent
applications incorporated by reference hereinbelow. For example,
control unit 50 may drive cathode electrode 46 to apply to nerve 30
a stimulating current, which is capable of inducing action
potentials in a first set and a second set of nerve fibers of the
nerve, and drive anode electrode 48 to apply to the nerve an
inhibiting current, which is capable of inhibiting the induced
action potentials traveling in the second set of nerve fibers, the
nerve fibers in the second set having generally larger diameters
than the nerve fibers in the first set.
[0125] For some applications, electrode cuff 20 is configured to
apply unidirectional stimulation to the nerve, such as by using
techniques described in one or more of the patent applications
incorporated by reference hereinbelow. For example, control unit 50
may drive anode electrode 48 to apply an inhibiting current capable
of inhibiting device-induced action potentials traveling in a
non-therapeutic direction in nerve 30. For some applications,
electrode cuff 20 comprises primary and secondary anode electrodes,
the primary anode electrode located between the secondary anode
electrode and the cathode electrode. The secondary anode electrode
is typically adapted to apply a current with an amplitude less than
about one half an amplitude of a current applied by the primary
anode electrode.
[0126] Reference is made to FIG. 5, which is a schematic,
cross-sectional view of an electrode cuff 320 for applying current
to nerve 30, in accordance with an embodiment of the present
invention. Electrode cuff 320 comprises a housing 332 which defines
an outer surface of the cuff when the cuff is placed at least
partially around nerve 30. Housing 332 typically comprises an
elastic, electrically-insulating material such as silicone or
polyurethane, which may have, for example, a Shore A of between
about 35 and about 70, such as about 40. Electrode cuff 20 further
comprises a plurality of m insulating elements 334 which are
arranged at respective circumferential positions around the
housing, and which extend longitudinally along at least a portion
of a length of the housing. Insulating elements 334 typically
comprise an elastic, electrically-insulating material such as
silicone or silicone copolymer, which, for some applications, is
softer than that of housing 332, for example, a Shore A of between
about 10 and about 30, such as about 10. Electrode cuff 320 is
typically configured such that, after placement of the cuff on the
nerve, respective contact surfaces 336 of insulating elements 334
come in physical contact with the nerve, or substantially in
physical contact with the nerve, e.g., are less than about 0.5 mm
from the surface of the nerve. For some applications, a length that
at least one of insulating elements 334 protrudes from housing 332
toward nerve 330 is at least 0.5 mm, such as at least 1 mm. For
some applications, insulating elements 334 and housing 332 are
constructed as separate elements that are coupled to one another,
while for other applications, the insulating elements and housing
are constructed as a single integrated element that is shaped to
define the insulating elements and housing.
[0127] Together, insulating elements 334 define a plurality of n
cavities 341 around housing 332, wherein n is less than or equal to
m (the number of insulating elements, as mentioned above).
Typically, n equals m. Alternatively, n is less than m, such as if
two or more of the insulating elements are arranged in contact with
one another. It is noted that the cavities 341 of electrode cuff
320 are oriented in a direction that is generally perpendicular to
that of cavities 41 of electrode cuff 20 of FIG. 1. Insulating
elements 334 of electrode cuff 320 run along the nerve in a
direction parallel with a longitudinal axis of the nerve, while
insulating elements 34 of electrode cuff 20 surround all or a
portion of the nerve.
[0128] Electrode cuff 320 comprises a plurality of p electrodes
342, fixed within housing 332 in respective cavities 341 defined by
two of insulating elements 334, wherein p is less than n. In other
words, at least one of cavities 341 defined by a pair of the
insulating elements does not have an electrode positioned therein.
For example, in the embodiment shown in FIG. 5, the insulating
elements define twelve cavities 341, half of which do not have an
electrode positioned therein. For some applications, p equals a
fraction of n, such as 2/3, 1/2, 1/3, or 1/4.
[0129] For some applications, electrode cuff 320 comprises elements
described hereinabove with reference to FIG. 1, such active and/or
passive electrodes, and/or a control unit coupled to the cuff with
leads.
[0130] FIG. 6 is a schematic, cross-sectional illustration of an
electrode cuff 420 for applying current to nerve 30, in accordance
with an embodiment of the present invention. Electrode cuff 420
comprises a housing 432 which defines an outer surface of the cuff
when the cuff is placed at least partially around nerve 30. Housing
432 typically comprises an elastic, electrically-insulating
material such as silicone or polyurethane, which may have, for
example, a Shore A of between about 35 and about 70, such as about
40.
[0131] Electrode cuff 420 further comprises at least two, e.g.,
exactly two, insulating elements 434 that are arranged at
respective positions along the housing, and are typically fixed to
an inner surface 437 of the housing that faces nerve 30 when the
cuff is placed at least partially around the nerve. Insulating
elements 434 typically comprise an elastic, electrically-insulating
material such as silicone or silicone copolymer, which, for some
applications, is softer than that of housing 432, for example, a
Shore A of between about 10 and about 30, such as about 10.
Electrode cuff 420 is typically configured such that, after
placement of the cuff on the nerve, respective contact surfaces 436
of insulating elements 434 come in physical contact with the nerve,
or substantially in physical contact with the nerve, e.g., are less
than about 0.5 mm from the surface of the nerve. For some
applications, a length that at least one of insulating elements 434
protrudes from housing 432 toward nerve 30 is at least 0.5 mm, such
as at least 1 mm. For some applications, insulating elements 434
and housing 432 are constructed as separate elements that are
coupled to one another, while for other applications, the
insulating elements and housing are constructed as a single
integrated element that is shaped to define the insulating elements
and housing.
[0132] Insulating elements 434 extend along nerve 30 in order to
electrically isolate a portion of the nerve within electrode cuff
420 from a portion of the nerve outside the electrode cuff.
[0133] Insulating elements 434 are positioned along housing 432
such that end portions 456 of housing 432 extend beyond the
insulating elements toward respective longitudinal ends 458 of the
housing. In other words, the insulating elements are longitudinally
recessed from ends 458 of the housing. In addition, insulating
elements 434 are positioned along housing 432 such that inner
surface 437 of housing 432 and one or more pairs of the insulating
elements define one or more respective cavities 441 along the
housing. In the exemplary configuration shown in FIG. 6, the inner
surface of the housing and exactly one pair of the insulating
elements define exactly one cavity.
[0134] Cuff 420 comprises at least two electrodes 442, each of
which is fixed to inner surface 437 of housing 432 at at least a
portion of one of end portions 456 of housing 432. At least one of
cavities 441, e.g., all of cavities 441 and/or exactly one of the
cavities, does not have an electrode positioned therein. In other
words, the electrodes are fixed to the housing in fewer than all of
the cavities, e.g., in none of the cavities. For some applications,
at least one of the empty cavities has a length along the cuff of
at least 0.5 mm, such as at least 0.7 mm, e.g., at least 1.4 mm or
at least 2 mm, and/or no more than 5 mm, e.g., no more than 3 mm or
no more than 3 cm.
[0135] Providing the empty cavity results in less physical contact
between contact surfaces 436 of insulating elements 434 and nerve
30 for a cuff of a given length, than in a cuff of the same length
without such an empty cavity. As a result, providing the empty
cavity tends to reduce constriction of the nerve by the cuff, which
may reduce side-effects of application of the cuff to the nerve.
Providing the empty cavity does not have a material impact on the
activation function achieved by the electrode cuff.
[0136] Electrodes 442 comprise at least one active, i.e.,
stimulating and/or sensing, electrode, such as at least one cathode
electrode 446 and at least one anode electrode 448. The active
electrodes are coupled to an implantable or external control unit
450 by leads 452 and 458. For some applications, active electrode
configurations and/or stimulation techniques are used which are
described in one or more of the patent applications incorporated by
reference hereinbelow. For some applications, two or more of the
active electrodes are shorted to one another inside or outside of
the cuff, such as shown for cathode electrodes 46 in FIG. 1. For
some applications, cuff 420 comprises one or more passive
electrodes, as described hereinabove with reference to FIG. 1.
[0137] In an embodiment of the present invention, at least some of
electrodes 442 comprise ring electrodes. Alternatively, the
electrodes do not comprise ring electrodes. Instead, fixed to at
least a portion of each of end portions are a plurality of
electrodes positioned at least partially circumferentially around a
central axis of the cuff. In other words, electrodes 442 are first
electrodes 442, and cuff 420 comprises at least one second
electrode 442. For some applications, the plurality of electrodes
are circumferentially separated from one another by one or more
circumferentially arranged insulating elements.
[0138] In an embodiment of the present invention, at least one of
the one or more of cavities 441 which are empty in the embodiment
described hereinabove, instead has fixed therein one or more
electrodes that are not electrically device-coupled (as defined
hereinabove) to any elements of the device outside of the cavity.
These electrodes thus do not serve the normal function of
electrodes in an electrode cuff, i.e., conducting current to and/or
from tissue.
[0139] In an embodiment of the present invention, insulating
elements 434 are not positioned so as to define any cavities 441.
For example, insulating elements 434 may comprise exactly one
insulating element, which may have a length of at least 0.5 mm,
such as at least 1 mm.
[0140] It is noted that although electrode cuffs 20, 320 and 420
and their elements are generally shown in the figures and described
herein in a cylindrical configuration, other geometrical
configurations, such as non-rotationally symmetric configurations,
are also suitable for applying the principles of the present
invention. In particular, housings 32, 332 or 432 of the electrode
cuffs (and the electrodes themselves) may form a complete circle
around nerve 30, or they may define an arc between approximately 0
and 90 degrees, between 90 and 180 degrees, between 180 and 350
degrees, or between 350 and 359 degrees around the nerve. For some
applications, electrode cuff 20 or 420 comprises electrodes that
form rings around the nerve, such that housing 32 surrounds the
electrodes.
[0141] In an embodiment of the present invention, techniques
described herein are practiced in combination with techniques
described with reference to FIGS. 2, 3, and/or 6 of U.S. patent
application Ser. No. 11/280,884 to Ayal et al., filed Nov. 15,
2005, which published as US Patent Application Publication
2006/0106441, and which is assigned to the assignee of the present
application and is incorporated herein by reference. For example:
[0142] for some applications, a closest distance between cathode
electrodes 46 (i.e., the distance between the respective cathode
electrodes' edges that are closest to one another) is equal to at
least a radius R of nerve 30, e.g., at least 1.5 times the radius
of the nerve, as described with reference to FIG. 2 of the '441
publication; and/or [0143] for some applications, end insulating
elements 38 are elongated, as described with reference to FIG. 6 of
the '441 publication.
[0144] As used in the present patent application, including in the
claims, "longitudinal" means along the length of, and does not mean
"around" or "circumferential." For example, "longitudinal
positions" along the housing means positions along the length of
the housing, rather than positions arranged circumferentially
around a longitudinal axis of the housing or the nerve. Such
longitudinal positions might be measured in mm from one end of the
housing.
[0145] FIG. 7 is a block diagram that schematically illustrates a
vagal stimulation system 518 comprising a multipolar electrode
device 540, in accordance with an embodiment of the present
invention. Electrode device 540 is applied to a portion of a vagus
nerve 536 (either a left vagus nerve 537 or a right vagus nerve
539), which innervates a heart 530 of a patient 531. Typically,
system 518 is utilized for treating a heart condition such as heart
failure and/or cardiac arrhythmia. Vagal stimulation system 518
further comprises an implanted or external control unit 520, which
typically communicates with electrode device 540 over a set of
leads 542. Control unit 520 drives electrode device 540 to (i)
apply signals to induce the propagation of efferent nerve impulses
towards heart 530, and (ii) suppress artificially-induced afferent
nerve impulses towards a brain 534 of the patient, in order to
minimize unintended side effects of the signal application. The
efferent nerve pulses in vagus nerve 536 are induced by electrode
device 540 in order to regulate the heart rate of the patient.
[0146] For some applications, control unit 520 is adapted to
receive feedback from one or more of the electrodes in electrode
device 540, and to regulate the signals applied to the electrode
device responsive thereto.
[0147] Control unit 520 is typically adapted to receive and analyze
one or more sensed physiological parameters or other parameters of
the patient, such as heart rate, electrocardiogram (ECG), blood
pressure, indicators of decreased cardiac contractility, cardiac
output, norepinephrine concentration, or motion of the patient. In
order to receive these sensed parameters, control unit 520 may
comprise, for example, an ECG monitor 524, connected to a site on
the patient's body such as heart 530, for example using one or more
subcutaneous sensors or ventricular and/or atrial intracardiac
sensors. The control unit may also comprise an accelerometer 522
for detecting motion of the patient. Alternatively, ECG monitor 524
and/or accelerometer 522 comprise separate implanted devices placed
external to control unit 520, and, optionally, external to the
patient's body. Alternatively or additionally, control unit 520
receives signals from one or more physiological sensors 526, such
as blood pressure sensors. Sensors 526 are typically implanted in
the patient, for example in a left ventricle 532 of heart 530. In
an embodiment, control unit 520 comprises or is coupled to an
implanted device 525 for monitoring and correcting the heart rate,
such as an implantable cardioverter defibrillator (ICD) or a
pacemaker (e.g., a bi-ventricular or standard pacemaker). For
example, implanted device 525 may be incorporated into a control
loop executed by control unit 520, in order to increase the heart
rate when the heart rate for any reason is too low.
[0148] FIG. 8A is a simplified cross-sectional illustration of a
generally-cylindrical electrode device 540 applied to vagus nerve
536, in accordance with an embodiment of the present invention.
Electrode device 540 comprises a central cathode 546 for applying a
negative current ("cathodic current") in order to stimulate vagus
nerve 536, as described below. Electrode device 540 additionally
comprises a set of one or more anodes 544 (544a, 544b, herein:
"efferent anode set 544"), placed between cathode 546 and the edge
of electrode device 540 closer to heart 530 (the "efferent edge").
Efferent anode set 544 applies a positive current ("efferent anodal
current") to vagus nerve 536, for blocking action potential
conduction in vagus nerve 536 induced by the cathodic current, as
described below. Typically, electrode device 540 comprises an
additional set of one or more anodes 545 (545a, 545b, herein:
"afferent anode set 545"), placed between cathode 546 and the edge
of electrode device 540 closer to brain 534. Afferent anode set 545
applies a positive current ("afferent anodal current") to vagus
nerve 536, in order to block propagation of action potentials in
the direction of the brain during application of the cathodic
current.
[0149] For some applications, the one or more anodes of efferent
anode set 544 are directly electrically coupled to the one or more
anodes of afferent anode set 545, such as by a common wire or
shorted wires providing current to both anode sets substantially
without any intermediary elements. Typically, coatings on the
anodes, shapes of the anodes, positions of the anodes, sizes of the
anodes and/or distances of the various anodes from the nerve are
regulated so as to produce desired ratios of currents and/or
desired activation functions delivered through or caused by the
various anodes. For example, by varying one or more of these
characteristics, the relative impedance between the respective
anodes and central cathode 546 is regulated, whereupon more anodal
current is driven through the one or more anodes having lower
relative impedance. In these applications, central cathode 546 is
typically placed closer to one of the anode sets than to the other,
for example, so as to induce asymmetric stimulation (i.e., not
necessarily unidirectional in all fibers) between the two sides of
the electrode device. The closer anode set typically induces a
stronger blockade of the cathodic stimulation.
[0150] Reference is now made to FIG. 8B, which is a simplified
cross-sectional illustration of a generally-cylindrical electrode
device 640 applied to vagus nerve 536, in accordance with an
embodiment of the present invention. Electrode device 640 comprises
exactly one efferent anode 644 and exactly one afferent anode 645,
which are electrically coupled to each other, such as by a common
wire 650 or shorted wires providing current to both anodes 644 and
645, substantially without any intermediary elements. The cathodic
current is applied by a cathode 646 with an amplitude sufficient to
induce action potentials in large- and medium-diameter fibers
(e.g., A- and B-fibers), but insufficient to induce action
potentials in small-diameter fibers (e.g., C-fibers).
[0151] Reference is again made to FIG. 8A. Cathodes 546 and anode
sets 544 and 545 (collectively, "electrodes") are typically mounted
in an electrically-insulating cuff 548 and separated from one
another by insulating elements such as protrusions 549 of the cuff.
Typically, the width of the electrodes is between about 0.5 and
about 2 millimeters, or is equal to approximately one-half the
radius of the vagus nerve. The electrodes are typically recessed so
as not to come in direct contact with vagus nerve 536. For some
applications, such recessing enables the electrodes to achieve
generally uniform field distributions of the generated currents
and/or generally uniform values of the activation function defined
by the electric potential field in the vicinity of vagus nerve 524.
Alternatively or additionally, protrusions 549 allow vagus nerve
524 to swell into the canals defined by the protrusions, while
still holding the vagus nerve centered within cuff 548 and
maintaining a rigid electrode geometry. For some applications, cuff
548 comprises additional recesses separated by protrusions, which
recesses do not contain active electrodes. Such additional recesses
accommodate swelling of vagus nerve 524 without increasing the
contact area between the vagus nerve and the electrodes. For some
applications, the distance between the electrodes and the axis of
the vagus nerve is between about 1 and about 4 millimeters, and is
greater than the closest distance from the ends of the protrusions
to the axis of the vagus nerve. Typically, protrusions 549 are
relatively short (as shown). For some applications, the distance
between the ends of protrusions 549 and the center of the vagus
nerve is between about 1 and 3 millimeters. (Generally, the
diameter of the vagus nerve is between about 2 and 3 millimeters.)
Alternatively, for some applications, protrusions 549 are longer
and/or the electrodes are placed closer to the vagus nerve in order
to reduce the energy consumption of electrode device 540.
[0152] In an embodiment of the present invention, efferent anode
set 544 comprises a plurality of anodes 544, typically two anodes
544a and 544b, spaced approximately 0.5 to 2.0 millimeters apart.
Application of the efferent anodal current in appropriate ratios
from a plurality of anodes generally minimizes the "virtual cathode
effect," whereby application of too large an anodal current
stimulates rather than blocks fibers. In an embodiment, anode 544a
applies a current with an amplitude equal to about 0.5 to about 5
milliamps (typically one-third of the amplitude of the current
applied by anode 544b). When such techniques are not used, the
virtual cathode effect generally hinders blocking of
smaller-diameter fibers, as described below, because a relatively
large anodal current is generally necessary to block such
fibers.
[0153] Anode 544a is typically positioned in cuff 548 to apply
current at the location on vagus nerve 536 where the virtual
cathode effect is maximally generated by anode 544b. For
applications in which the blocking current through anode 544b is
expected to vary substantially, efferent anode set 544 typically
comprises a plurality of virtual-cathode-inhibiting anodes 544a,
one or more of which is activated at any time based on the expected
magnitude and location of the virtual cathode effect.
[0154] Likewise, afferent anode set 545 typically comprises a
plurality of anodes 545, typically two anodes 545a and 545b, in
order to minimize the virtual cathode effect in the direction of
the brain. In certain electrode configurations, cathode 546
comprises a plurality of cathodes in order to minimize the "virtual
anode effect," which is analogous to the virtual cathode
effect.
[0155] As appropriate, techniques described herein are practiced in
conjunction with methods and apparatus described in U.S. patent
application Ser. No. 10/205,474 to Gross et al., filed Jul. 24,
2002, entitled, "Electrode assembly for nerve control," which
published as US Patent Publication 2003/0050677 and issued as U.S.
Pat. No. 6,907,295, is assigned to the assignee of the present
patent application, and is incorporated herein by reference.
Alternatively or additionally, techniques described herein are
practiced in conjunction with methods and apparatus described in
U.S. patent application Ser. No. 10/205,475 to Gross et al., filed
Jul. 24, 2002, entitled, "Selective nerve fiber stimulation for
treating heart conditions," which published as US Patent
Publication 2003/0045909, is assigned to the assignee of the
present patent application, and is incorporated herein by
reference. Further alternatively or additionally, techniques
described herein are practiced in conjunction with methods and
apparatus described in U.S. Provisional Patent Application
60/383,157 to Ayal et al., filed May 23, 2002, entitled, "Inverse
recruitment for autonomic nerve systems," which is assigned to the
assignee of the present patent application and is incorporated
herein by reference.
[0156] FIG. 8C is a simplified perspective illustration of
electrode device 540 (FIG. 8A), in accordance with an embodiment of
the present invention. When applied to vagus nerve 536, electrode
device 540 typically encompasses the nerve. As described, control
unit 520 typically drives electrode device 540 to (i) apply signals
to vagus nerve 536 in order to induce the propagation of efferent
action potentials towards heart 530, and (ii) suppress
artificially-induced afferent action potentials towards brain 534.
The electrodes typically comprise ring electrodes adapted to apply
a generally uniform current around the circumference of the nerve,
as best shown in FIG. 8C.
[0157] The scope of the present invention includes embodiments
described in the following applications, which are assigned to the
assignee of the present application and are incorporated herein by
reference. In an embodiment, techniques and apparatus described in
one or more of the following applications are combined with
techniques and apparatus described herein: [0158] U.S. Provisional
Patent Application 60/383,157 to Ayal et al., filed May 23, 2002,
[0159] International Patent Application PCT/IL02/00068 to Cohen et
al., filed Jan. 23, 2002, entitled, "Treatment of disorders by
unidirectional nerve stimulation," and U.S. patent application Ser.
No. 10/488,334, in the national stage thereof, now U.S. Pat. No.
7,734,355, [0160] U.S. patent application Ser. No. 09/944,913 to
Cohen and Gross, filed Aug. 31, 2001, entitled, "Treatment of
disorders by unidirectional nerve stimulation," which issued as
U.S. Pat. No. 6,684,105, [0161] U.S. patent application Ser. No.
09/824,682 to Cohen and Ayal, filed Apr. 4, 2001, entitled "Method
and apparatus for selective control of nerve fibers," now U.S. Pat.
No. 6,600,954, [0162] U.S. patent application Ser. No. 10/205,475
to Gross et al., filed Jul. 24, 2002, entitled, "Selective nerve
fiber stimulation for treating heart conditions," now U.S. Pat. No.
7,778,703, [0163] U.S. patent application Ser. No. 10/205,474 to
Gross et al., filed Jul. 24, 2002, entitled, "Electrode assembly
for nerve control," which issued as U.S. Pat. No. 6,907,295, [0164]
International Patent Application PCT/IL03/00431 to Ayal et al.,
filed May 23, 2003, entitled, "Selective nerve fiber stimulation
for treating heart conditions," which published as PCT Publication
WO 03/099377, [0165] International Patent Application
PCT/IL03/00430 to Ayal et al., filed May 23, 2003, entitled,
"Electrode assembly for nerve control," and U.S. patent application
Ser. No. 10/529,149, in the national stage thereof, which published
as US Patent Application Publication 2006/0116739, [0166] U.S.
patent application Ser. No. 10/719,659 to Ben David et al., filed
Nov. 20, 2003, entitled, "Selective nerve fiber stimulation for
treating heart conditions," now U.S. Pat. No. 7,778,711, [0167]
U.S. patent application Ser. No. 11/022,011 to Cohen et al., filed
Dec. 22, 2004, entitled, "Construction of electrode assembly for
nerve control," now U.S. Pat. No. 7,561,922 [0168] U.S. patent
application Ser. No. 11/234,877 to Ben-David et al., filed Sep. 22,
2005, entitled, "Selective nerve fiber stimulation," now U.S. Pat.
No. 7,885,709, and [0169] U.S. patent application Ser. No.
11/280,884 to Ayal et al., filed Nov. 15, 2005, entitled,
"Techniques for nerve stimulation," which published as US Patent
Application Publication 2006/0106441.
[0170] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. Rather, the scope of the present
invention includes both combinations and subcombinations of the
various features described hereinabove, as well as variations and
modifications thereof that are not in the prior art, which would
occur to persons skilled in the art upon reading the foregoing
description.
* * * * *