U.S. patent application number 11/494057 was filed with the patent office on 2008-01-31 for multi-electrode assembly for an implantable medical device.
Invention is credited to Bryan P. Byerman, Steven E. Maschino.
Application Number | 20080027524 11/494057 |
Document ID | / |
Family ID | 38695579 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080027524 |
Kind Code |
A1 |
Maschino; Steven E. ; et
al. |
January 31, 2008 |
Multi-electrode assembly for an implantable medical device
Abstract
A method, system, and apparatus are provided for an electrode
assembly comprising a plurality of electrodes for use with an
implantable medical device for conducting an electrical signal
between the implantable medical device and a target tissue. The
electrode assembly includes a helical member and first and second
electrodes formed upon the helical member. The first and second
electrodes are adapted to deliver the electrical signal. The
electrode assembly also includes a first conductive element formed
upon the helical member and operatively coupled to the first
electrode. The electrode assembly also includes a second conductive
element formed upon the helical member and operatively coupled to
the second electrode.
Inventors: |
Maschino; Steven E.;
(Seabrook, TX) ; Byerman; Bryan P.; (League City,
TX) |
Correspondence
Address: |
Timothy L. Scott
100 Cyberonics Blvd.
Houston
TX
77058
US
|
Family ID: |
38695579 |
Appl. No.: |
11/494057 |
Filed: |
July 26, 2006 |
Current U.S.
Class: |
607/118 |
Current CPC
Class: |
Y10T 29/49218 20150115;
A61N 1/0551 20130101; A61N 1/0553 20130101 |
Class at
Publication: |
607/118 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Claims
1. An electrode assembly for conducting a first electrical signal
between an implantable medical device and a target tissue,
comprising: a helical member; a first electrode and a second
electrode formed upon said helical member, said first and second
electrodes to deliver said first electrical signal; a first
conductive element formed upon said helical member and operatively
coupled to said first electrode, said first conductive element to
carry said first electrical signal to said first electrode; and a
second conductive element formed upon said helical member and
operatively coupled to said second electrode.
2. The electrode assembly of claim 1, wherein said first and second
conductive elements are conductive wires that are positioned in at
least a partially parallel configuration along the length of at
least a portion of said helical member.
3. The electrode assembly of claim 1, further comprising a third
electrode formed upon said helical member, wherein said first,
second, and third electrodes form an electrode array.
4. The electrode assembly of claim 3, wherein said first electrode
is adapted to carry said first electrical signal, said second
electrode is adapted to carry a second electrical signal different
from said first electrical signal, and said third electrode is
adapted to carry a third electrical signal different from said
first and second electrical signals.
5. The electrode assembly of claim 1, further comprising a first
lead wire operatively coupled to said first conductive element and
a second lead wire operatively coupled to said second conductive
element.
6. The electrode assembly of claim 5, further comprising a lead
interface operatively coupled to said helical member, said first
and second lead wires being operatively coupled to said first and
second conductive elements via said lead interface.
7. The electrode assembly of claim 1, wherein said first electrode
and said second electrode comprise an electrode pair, and wherein
said electrode pair is a sensing electrode adapted to sense
electrical activity in a target tissue.
8. The electrode assembly of claim 1, wherein said helical material
comprises a material selected from the group consisting of siloxane
polymers, polydimethylsiloxanes, silicone rubbers, polyurethane,
polyether urethane, polyetherurethane urea, polyesterurethane,
polyamide, polycarbonate, polyester, polypropylene, polyethylene,
polystyrene, polyvinyl chloride, polytetrafluoroethylene,
polysulfone, cellulose acetate, polymethylmethacrylate,
polyethylene, and polyvinylacetate, and said first and second
electrodes comprises a material selected from the group consisting
of platinum, iridium, and platinum/iridium alloys.
9. The electrode assembly of claim 1, wherein said first conductive
element comprises a first conductive strip and a first conductive
interface, and said second conductive element comprises a second
conductive strip and a second conductive interface.
10. The electrode assembly of claim 1, wherein said helical member
further comprises a at least a third electrode operatively coupled
to a third conductive element.
11. The electrode assembly of claim 1, wherein said helical member
is capable of being wrapped around a nerve, wherein said first and
second electrodes come into electrical contact with said nerve to
deliver a stimulation signal in a cascading manner.
12. The electrode assembly of claim 1, wherein said first
electrical signal is delivered to said first and second electrodes,
said helical member further comprises a third electrode operatively
coupled to a third conductor, a fourth electrode operatively
coupled to a fourth conductor, and wherein a second electrical
signal is delivered to said third and fourth electrodes.
13. The electrode assembly of claim 1, wherein said first electrode
is located at a first position on the helical member and said
second electrode is located at a second position on the helical
member.
14. A method for forming a helical electrode assembly for carrying
an electrical signal associated with an implantable medical device,
comprising: forming a first layer on a generally flat substrate;
forming a first conducting structure as a second layer upon said
first layer, said first conducting structure comprising a first
electrode and a first conductive strip operatively coupled to said
first electrode; forming a third, non-conductive layer above said
first and second layers; forming a second conducting structure as a
fourth layer upon said third layer, said second conducting
structure comprising a second electrode and a second conductive
strip operatively coupled to said second electrode; and forming
said generally flat substrate into a helical structure.
15. The method of claim 14, wherein forming said first and second
conducting structures comprises: performing a photolithography
process to imprint said first conducting structure upon said first
layer and said second conducting structure upon said third layer;
and performing an etch process to control at least one dimension
relating to each of said first and second conducting structures
within respective predetermined tolerances.
16. The method of claim 15, further comprising performing a
chemical-mechanical polishing process.
17. The method of claim 14, further comprising forming a fifth,
non-conducting layer above said third and fourth layers, and
forming a third conducting structure as a sixth layer upon said
fifth layer, said third conducting structure comprising a third
electrode and a third conductive strip operatively coupled to said
third electrode, wherein forming said fifth layer comprises
performing a deposition process.
18. The method of claim 14, wherein forming said first and second
conducting structures comprises: performing a metal deposition
process to deposit a conductive material for forming said first and
second conducting structures; and performing an etch process to
control at least one dimension relating to each of said first and
second conducting structures within predetermined tolerances.
19. The method of claim 14, wherein forming said first and second
conducting structures comprises offsetting said first conducting
structure from said second conducting structure such that said
first and second electrodes are exposed on the surface of said
electrode assembly.
20. The method of claim 14, further comprising: forming a fifth,
non-conducting layer above said third and fourth layers, and
forming a third conducting structure as a sixth layer upon said
fifth layer, said third conducting structure comprising a third
electrode and a third conducting strip operatively coupled to said
third electrode; and forming a seventh non-conducting layer above
said fifth and sixth layers, and forming a fourth conducting
structure as an eighth layer upon said seventh layer, said fourth
conducting structure comprising a fourth electrode and a fourth
conducting strip operatively coupled to said fourth electrode.
21. The method of claim 14, further comprising: forming a first
connection pad on the surface of said electrode assembly, said
first connection pad being electrically coupled to said first
conductive strip; and forming a second connection pad on the
surface of said electrode assembly, said second connection pad
being electrically coupled to said second conductive strip.
22. The method of claim 14, further comprising: forming a first via
to electrically couple said first conductive strip to said first
electrode; and forming a second via to electrically couple said
second conductive strip to said second electrode.
23. A method for forming a helical electrode assembly for carrying
a signal associated with an implantable medical device, comprising:
forming a first layer on a generally flat substrate; forming a
first conducting structure and a second conducting structure upon
said first layer, said first conducting structure comprising a
first electrode and a first conductive strip operatively coupled to
said first electrode, and said second conducting structure
comprising a second electrode and a second conducting strip
operatively coupled to said second electrode; forming a second,
non-conductive layer such that said first and second conductive
strips are substantially covered by said second layer and said
first and second electrodes remain exposed; and forming said
generally flat substrate and first and second layers into a helical
structure.
24. An implantable medical system for providing a therapeutic
electrical signal to a target tissue using a helical electrode
assembly, comprising: an implantable medical device for generating
a therapeutic electrical signal; a lead assembly operatively
coupled to said implantable medical device and adapted to carry
said therapeutic electrical signal, said lead assembly comprising
first and second lead elements; and an electrode assembly
operatively coupled to said lead assembly and adapted to deliver
said therapeutic electrical signal to a target tissue, said
electrode assembly comprising: a helical member; a first electrode
and a second electrode formed upon said helical member; a first
conductive element formed upon said helical member and operatively
coupled to said first electrode and to said first lead element; and
a second conductive element formed upon said helical member and
operatively coupled to said second electrode and to said second
lead element.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to implantable electrode
assemblies, and more particularly to an electrode assembly
comprising a plurality of electrodes organized into a helical
structure. The electrodes may be operatively coupled to an
implantable medical device (IMD).
[0003] 2. Description of the Related Art
[0004] As used herein, "stimulation" or "stimulation signal" refers
to the application of an electrical, mechanical, magnetic,
electro-magnetic, photonic, audio and/or chemical signal to a
neural structure in the patient's body. The signal is an exogenous
signal that is distinct from the endogenous electrical, mechanical,
and chemical activity (e.g., afferent and/or efferent electrical
action potentials) generated by the patient's body and environment.
In other words, the stimulation signal (whether electrical,
mechanical, magnetic, electro-magnetic, photonic, audio or chemical
in nature) applied to the nerve in the present invention is a
signal applied from an artificial source, e.g., a
neurostimulator.
[0005] A "therapeutic signal" refers to a stimulation signal
delivered to a patient's body with the intent of treating a
disorder by providing a modulating effect to neural tissue. The
effect of a stimulation signal on neuronal activity is termed
"modulation"; however, for simplicity, the terms "stimulating" and
"modulating", and variants thereof, are sometimes used
interchangeably herein. In general, however, the delivery of an
exogenous signal itself refers to "stimulation" of the neural
structure, while the effects of that signal, if any, on the
electrical activity of the neural structure are properly referred
to as "modulation." The effect of delivery of the stimulation
signal to the neural tissue may be excitatory or inhibitory and may
potentiate acute and/or long-term changes in neuronal activity. For
example, the "modulating" effect of the stimulation signal to the
neural tissue may comprise one or more of the following effects:
(a) changes in neural tissue to initiate an action potential
(afferent and/or efferent action potentials); (b) inhibition of
conduction of action potentials (whether endogenous or exogenously
induced) or blocking the conduction of action potentials
(hyperpolarizing or collision blocking), (c) affecting changes in
neurotransmitter/neuromodulator release or uptake, and (d) changes
in neuro-plasticity or neurogenesis of brain tissue.
[0006] Thus, electrical neurostimulation or modulation of a neural
structure refers to the application of an exogenous electrical
signal (as opposed to mechanical, chemical, photonic, or another
mode of signal delivery) to the neural structure. Electrical
neurostimulation may be provided by implanting an electrical device
underneath the skin of a patient and delivering an electrical
signal to a nerve such as a cranial nerve. In one embodiment, the
electrical neurostimulation involves sensing or detecting a body
parameter, with the electrical signal being delivered in response
to the sensed body parameter. This type of stimulation is generally
referred to as "active," "feedback," or "triggered" stimulation. In
another embodiment, the system may operate without sensing or
detecting a body parameter once the patient has been diagnosed with
a medical condition that may be treated by neurostimulation. In
this case, the system may periodically apply a series of electrical
pulses to the nerve (e.g., a cranial nerve such as a vagus nerve)
intermittently throughout the day, or over another predetermined
time interval. This type of stimulation is generally referred to as
"passive," "non-feedback," or "prophylactic," stimulation. The
stimulation may be applied by an implantable medical device that is
implanted within the patient's body. In another alternative
embodiment, the signal may be generated by an external pulse
generator outside the patient's body, coupled by an RF or wireless
link to an implanted electrode.
[0007] Generally, neurostimulation signals that perform
neuromodulation are delivered by the implantable device via one or
more leads. The leads are generally coupled at a distal end to
electrodes, which are coupled to a tissue in the patient's body.
Multiple leads/electrodes may be attached to various points of a
nerve or other tissue inside a human body for delivery of
neurostimulation. Generally, each lead is associated with a
separate electrode, particularly when each of the electrodes is
intended to perform a different function (e.g., deliver a first
electrical signal, deliver a second electrical signal, sense a body
parameter, etc.).
[0008] Generally, a single electrode is associated with each lead
originating from the IMD. The number of leads that originate from
the IMD is limited due to the size constraints of the IMD and of
the patient's body. Therefore, a limited number of electrodes using
state-of-the-art technology can be used to deliver electrical
stimulation from an IMD.
[0009] Further, state-of-the-art medical systems call for
performing a stimulation during a time period that is separate from
a time period of performing a sensing function for sensing the
patient's biological signals. Further, a first lead associated with
a first electrode may deliver a therapeutic electrical signal,
while a second lead associated with a second electrode may perform
data acquisition for sensing of various biometric parameters in the
patient's body. This process may be inefficient since the
state-of-the-art generally lacks a system for simultaneously
delivering an electrical signal to a neural structure and sensing
electrical activity, particularly where associated with the neural
structure to which the signal is applied. Further, problems with
the state-of-the-art also include a limitation on the number of
electrodes that may be employed by an IMD to deliver various stages
of therapy and/or sensing functions.
[0010] The present invention is directed to overcoming, or at least
reducing, the effects of one or more of the problems set forth
above.
SUMMARY OF THE INVENTION
[0011] In one aspect, the present invention provides an electrode
assembly comprising a plurality of electrodes for use with an
implantable medical device for conducting an electrical signal
between the implantable medical device and a target tissue. The
electrode assembly includes a helical member having a first and a
second electrode formed upon the helical member. The first and
second electrodes are adapted to deliver the electrical signal. The
electrode assembly also includes a first conductive element formed
upon the helical member and operatively coupled to the first
electrode. The first conductive element is adapted to carry the
electrical signal to the first electrode. The electrode assembly
also includes a second conductive element formed upon the helical
member and operatively coupled to the second electrode.
[0012] In yet another aspect, the present invention includes a
method for forming a helical electrode assembly for carrying an
electrical signal associated with an implantable medical device. A
first layer is formed on a generally flat substrate. In one
embodiment, the substrate is generally planar. A first conducting
structure is formed upon the first layer. The first conducting
structure includes a first electrode and a first lead operatively
coupled to the first electrode. A second, non-conductive layer is
formed above the first layer. A second conducting structure is
formed upon the second, non-conductive layer. The second conducting
structure includes a second electrode and a second lead operatively
coupled to the second electrode. The method further includes the
step of forming the generally flat substrate into a helical
structure.
[0013] In another aspect, the present invention includes another
method for forming a helical electrode assembly for carrying a
signal associated with an implantable medical device. A first layer
is formed on a generally flat substrate. A first conducting
structure and a second conducting structure are formed upon the
first layer. The first conducting structure includes a first
electrode and a first lead operatively coupled to the first
electrode. The second conducting structure includes a second
electrode and a second lead operatively coupled to the second
electrode. A second, non-conductive layer is formed such that the
first and second leads are substantially covered by the second
layer and the first and second electrodes remain exposed. The
method also comprises the step of forming the generally flat
substrate and first and second layers into a helical structure.
[0014] In yet another aspect, the present invention provides an
implantable medical system for providing a therapeutic electrical
signal to a target tissue using a helical electrode assembly. The
system of the present invention includes an implantable medical
device for generating a therapeutic electrical signal. The system
also includes a lead assembly operatively coupled to the
implantable medical device and adapted to carry the therapeutic
electrical signal. The lead assembly comprises first and second
lead elements. The system also includes an electrode assembly
operatively coupled to the lead assembly. The electrode assembly
includes a helical member having first and second electrodes formed
thereon. The electrode assembly also includes a first conductive
element formed upon the helical member and operatively coupled to
the first electrode and to the first lead element. The electrode
assembly also includes a second conductive element formed upon the
helical member and operatively coupled to the second electrode and
to the second lead element. The first and second electrodes are
adapted to deliver the electrical signal to tissue of a patient
when coupled thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention may be understood by reference to the
following description taken in conjunction with the accompanying
drawings, in which like reference numerals identify like elements,
and in which:
[0016] FIG. 1 is a stylized diagram of an implantable medical
device implanted into a patient's body for providing stimulation to
a portion of the patient's body, in accordance with one
illustrative embodiment of the present invention;
[0017] FIG. 2 illustrates a stylized isometric illustration of an
electrode assembly in accordance with one embodiment of the present
invention;
[0018] FIG. 3 illustrates another isometric depiction of the
electrode assembly and an electrode in accordance with one
illustrative embodiment of the present invention;
[0019] FIG. 4 illustrates a stylized depiction of the electrode
assembly of FIGS. 2 and 3 during fabrication, in accordance with
the illustrated embodiment of the present invention;
[0020] FIG. 5 illustrates a flowchart associated with a method for
providing the electrode assembly of FIGS. 2-4, in accordance with
an illustrative embodiment of the present invention, is
provided;
[0021] FIG. 6 illustrates a stylized depiction of the electrode
assembly of the present invention in a staggered multi-layered
configuration, in accordance with an illustrative embodiment of the
present invention;
[0022] FIG. 7 illustrates a stylized side view of a flexible
material upon which a first through third layers and corresponding
conductive structures are formed, in accordance with an
illustrative embodiment of the present invention; and
[0023] FIG. 8 illustrates an alternative stylized depiction of the
electrode assembly of the present invention in a multi-layered
configuration, in accordance with an illustrative embodiment of the
present invention.
[0024] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0025] Illustrative embodiments of the invention are described
herein. In the interest of clarity, not all features of an actual
implementation are described in this specification. In the
development of any such actual embodiment, numerous
implementation-specific decisions must be made to achieve the
design-specific goals, which will vary from one implementation to
another. It will be appreciated that such a development effort,
while possibly complex and time-consuming, would nevertheless be a
routine undertaking for persons of ordinary skill in the art having
the benefit of this disclosure.
[0026] Certain terms are used throughout the following description
and claims refer to particular system components. This document
does not intend to distinguish between components that differ in
name but not function. In the following discussion and in the
claims, the terms "including" and "includes" are used in an
open-ended fashion, and thus should be interpreted to mean
"including, but not limited to." Also, the term "couple" or
"couples" is intended to mean either a direct or an indirect
electrical connection. "Direct contact," "direct attachment," or
providing a "direct coupling" indicates that a surface of a first
element contacts the surface of a second element with no
substantial attenuating medium therebetween. The presence of
substances, such as bodily fluids, that do not substantially
attenuate electrical connections does not vitiate direct contact.
The word "or" is used in the inclusive sense (i.e., "and/or")
unless a specific use to the contrary is explicitly stated.
[0027] As used herein, "stimulation" or "stimulation signal" refers
to the application of an electrical, mechanical, and/or chemical
signal to a neural structure in the patient's body. In one
embodiment, the stimulation comprises an electrical signal. The
stimulation signal may induce afferent and/or efferent action
potentials on the nerve, may block native afferent and/or efferent
action potentials, or may be applied at a sub-threshold level that
neither generates action potentials nor blocks native action
potentials.
[0028] The stimulation signal applied to the neural structure in
embodiments of the present invention refers to an exogenous signal
that is distinct from the endogenous electrical, mechanical, and
chemical activity (e.g., afferent and/or efferent electrical action
potentials) generated by the patient's body and environment. In
other words, the stimulation signal (whether electrical, mechanical
or chemical in nature) applied to the nerve in the present
invention is from an artificial source, e.g., a
neurostimulator.
[0029] The term "electrode" or "electrodes" described herein may
refer to one or more stimulation electrodes, one or more sensing
electrodes, and/or to one or more electrodes that are capable of
delivering a stimulation signal as well as performing a sensing
function. Stimulation electrodes may refer to an electrode that is
capable of delivering a stimulation signal to a tissue of a
patient's body. A sensing electrode may refer to an electrode that
is capable of sensing a physiological indication of a patient's
body. "Electrode" and/or "electrodes" may also refer to one or more
electrodes capable of delivering a stimulation signal as well as
sensing a physiological indication.
[0030] The terms "stimulating" and "stimulator" may generally refer
to delivery of a stimulation signal to a neural structure. The
effect of such stimulation on neuronal activity is termed
"modulation"; however, for simplicity, the terms "stimulating" and
"modulating", and variants thereof, are sometimes used
interchangeably herein. In general, however, the delivery of an
exogenous signal refers to "stimulation" of the neural structure,
while the effects of that signal, if any, on the electrical
activity of the neural structure are properly referred to as
"modulation." In one embodiment of the present invention, methods,
apparatus, and systems are provided involving a helical electrode
to stimulate an autonomic nerve, such as a cranial nerve, e.g., a
vagus nerve, using an electrical signal to treat a medical
condition such as epilepsy and other movement disorders, mood and
other neuropsychiatric disorders, dementia, coma, migraine
headache, obesity, eating disorders, sleep disorders, cardiac
disorders (such as congestive heart failure and atrial
fibrillation), hypertension, endocrine disorders (such as diabetes
and hypoglycemia), and pain, among others. A generally suitable
form of neurostimulator for use in the method and apparatus of the
present invention is disclosed, for example, in U.S. Pat. No.
5,154,172, assigned to the same assignee as the present
application. The neurostimulator may be referred to a
NeuroCybernetic Prosthesis (NCP.RTM., Cyberonics, Inc., Houston,
Tex., the assignee of the present application). Certain parameters
of the electrical stimulus generated by the neurostimulator are
programmable, such as be means of an external programmer in a
manner conventional for implantable electrical medical devices.
[0031] Embodiments of the present invention provide for an
electrode assembly comprising a plurality of individual electrodes
or an array of electrodes. The electrode assembly may be formed as
a helical structure, wherein the electrode assembly may comprise a
plurality of electrodes and associated conductive elements for
delivering various electrical stimulation signals. One or more of
the plurality of electrodes associated with the electrode assembly
may also provide for the capacity to perform sensing. Therefore,
substantially simultaneous delivery of stimulation and the
acquisition of sensing signals may be performed utilizing the
electrode array of the electrode assembly of the present invention.
The term "electrode array" may refer to two or more electrodes
residing on a single electrode assembly.
[0032] Embodiments of the present invention provide a flexible
"ribbon-type" material upon which various electrodes may be
provided in a variety of configurations to provide efficient
delivery of therapy and/or sensing functions. For example,
electrodes may be positioned on a helical member such that
successive electrodes are generally linear along an axis of a
nerve, such as the vagus nerve. Alternatively, various electrodes
on the electrode assembly of the present invention may be
positioned in a staggered fashion to deliver a signal in a
particular geometry or configuration to target portions of a nerve.
An electrode assembly may be employed using a state-of-the-art IMD
such that a number of electrodes may be substantially
simultaneously activated, or alternatively, activated in a
staggered or sequential fashion.
[0033] Embodiments of the present invention also provide for a
method for manufacturing an electrode assembly that comprises a
plurality of electrodes. A non-conductive material may be coated
with various layers of conductive and non-conductive films or
layers to create various conductive structures, such as electrodes,
strips of conductive materials that provide electrical signals to
the electrodes, and interfaces that provide connection between the
various electrodes on the electrode assembly and lead(s) that are
in operative communication with the IMD. For example,
photolithography processes may be used on a plurality of layers
formed on a substrate to provide various electrodes that are
situated at desirable or strategic locations on a single electrode
assembly, which may be formed into a helical configuration. This
helical configuration may be used to wrap the electrode assembly
around various portions of a patient's body, such as a nerve, such
that the multiple electrodes may come into contact at desired
locations of a particular nerve in a desired geometry or
configuration. One or more of the multiple electrodes may be
energized in a strategically timed fashion to provide desired
stimulation to a portion of a patient's body. This may provide the
ability to direct or steer current flow to a pre-determined
position and direction, through a portion of a patient's body, such
as a nerve. Utilizing embodiments of the present invention more
efficient and effective delivery of stimulation may be
realized.
[0034] Although not so limited, a system capable of implementing
embodiments of the present invention is described below. FIG. 1
depicts a stylized implantable medical system 100 for implementing
one or more embodiments of the present invention. FIG. 1
illustrates an electrical signal generator 110 having main body 112
comprising a case or shell 121 with a header 116 for connecting to
leads 122. The generator 110 is implanted in the patient's chest in
a pocket or cavity formed by the implanting surgeon just below the
skin (indicated by a dotted line 145), similar to the implantation
procedure for a pacemaker pulse generator.
[0035] A nerve electrode assembly 125, preferably comprising a
plurality of electrodes, is conductively connected to the distal
end of an insulated, electrically conductive lead assembly 122,
which preferably comprises a plurality of lead wires (one wire for
each electrode). Each electrode in the electrode assembly 125 may
operate independently or alternatively, may operate in conjunction
with each other to form a cathode and an anode. The electrode
assembly 125 illustrated in FIG. 1 may be formed into a helical
structure that comprises a plurality of electrodes on an inside
surface of the helical structure to deliver electrical signals via
the plurality of electrodes in a simultaneous or time-delayed
fashion, as well as perform efficient sensing of electrical signals
in a patient's body.
[0036] Lead assembly 122 is attached at its proximal end to
connectors on the header 116 on case 121. The electrode assembly
125 at the distal end of lead assembly 122 may be surgically
coupled to a target tissue such as vagus nerve 127. The electrical
signal may also be applied to other cranial nerves. The electrode
assembly 125 preferably comprises a bipolar stimulating electrode
pair, or may comprise three, four or even more electrodes. The
electrode assembly 125 is preferably wrapped around the target
tissue, such as a vagus nerve. Prior art electrodes have been
provided that wrap around a target tissue, such as the electrode
pair described in U.S. Pat. No. 4,573,481. In the prior art
structures, however, a separate helical element is provided for
each electrode. In contrast, the present invention involves a
plurality of electrodes on a single helical element. Varying
lengths of the helical element may be provided, depending upon the
pitch of the helix and the number of electrodes thereon. Lengths
may range from 3 mm to 50 mm, although even small or longer helices
may be employed in particular applications. Lead assembly 122 may
be secured, while retaining the ability to flex with movement of
the chest and neck, by a suture connection to nearby tissue.
[0037] In one embodiment, the open helical design of the electrode
assembly 125 is self-sizing and flexible, minimizes mechanical
trauma and allows body fluid interchange with the target tissue.
The electrode assembly 125 preferably conforms to the shape of the
target tissue, providing a low stimulation threshold by allowing a
large stimulation contact area. Structurally, the electrode
assembly 125 comprises a plurality of electrode ribbons (not
shown), of a conductive material such as precious metals and/or
alloys and oxides thereof, including platinum, iridium,
platinum-iridium alloys, and/or oxides of the foregoing. The
electrode ribbons are individually bonded to an inside surface of
an elastomeric body portion, which may comprise a helical assembly.
The lead assembly 122 may comprise two distinct lead wires or a
multi-wire cable whose conductive elements are respectively coupled
to one of the conductive electrode ribbons. The elastomeric body
portion is preferably composed of silicone rubber, or another
biocompatible, durable polymer such as siloxane polymers,
polydimethylsiloxanes, polyurethane, polyether urethane,
polyetherurethane urea, polyesterurethane, polyamide,
polycarbonate, polyester, polypropylene, polyethylene, polystyrene,
polyvinyl chloride, polytetrafluoroethylene, polysulfone, cellulose
acetate, polymethylmethacrylate, polyethylene, and
polyvinylacetate.
[0038] The electrical signal generator 110 may be programmed with
an external computer 150 using programming software of the type
copyrighted by the assignee of the instant application with the
Register of Copyrights, Library of Congress, or other suitable
software based on the description herein, and a programming wand
155 to facilitate radio frequency (RF) communication between the
computer 150 and the signal generator 110. The wand 155 and
software permit non-invasive communication with the generator 110
after the latter is implanted, according to means known in the
art.
[0039] A variety of stimulation therapies may be provided in
implantable medical systems 100 of the present invention. Different
types of nerve fibers (e.g., A, B, and C fibers being different
fibers targeted for stimulation) have different conduction
velocities and stimulation thresholds and, therefore, differ in
their responsiveness to stimulation. Certain pulses of an
electrical stimulation signal, for example, may be below the
stimulation threshold for a particular fiber and, therefore, may
generate no action potential in the fiber. Thus, smaller or
narrower pulses may be used to avoid stimulation of certain nerve
fibers (such as C fibers) and target other nerve fibers (such as A
and/or B fibers, which generally have lower stimulation thresholds
and higher conduction velocities than C fibers). Additionally,
techniques such as pre-polarization may be employed wherein
particular nerve regions may be polarized before a more robust
stimulation is delivered, which may better accommodate particular
electrode materials. Furthermore, opposing polarity phases
separated by a zero current phase may be used to excite particular
axons or postpone nerve fatigue during long term stimulation.
[0040] Turning now to FIG. 2, a stylized isometric illustration of
a helical electrode assembly 210 in accordance with one embodiment
of the present invention is illustrated. The electrode assembly may
be formed into a helical configuration and may be made of a
flexible material, such as a silicone polymer substrate with
semiconductor layers imprinted thereon using photolithography
techniques. The electrode assembly may also comprise an end member
220 that provides an interface to a lead wire in electrical
communication with the IMD. The helical structure of FIG. 2 may be
wrapped around a portion of the patient's body, such as a nerve,
e.g., the vagus nerve, and anchored thereupon.
[0041] Turning now to FIG. 3, another isometric depiction of the
electrode assembly 210, in accordance with one illustrative
embodiment of the present invention, is provided. An electrode 330
may be formed on the surface of the inside portion of the electrode
assembly 210. The electrode assembly 210 may be wrapped around a
target portion of the patient's body, e.g., a nerve, such that the
electrode 330 contacts the target portion at a predetermined
location. The electrode 330 illustrated in FIG. 3 may comprise a
plurality of electrodes formed on the inside surface of various
portions of the electrode assembly 210. The electrodes 300 may
comprise a conductive material such as platinum, iridium, and/or
platinum/iridium alloys and/or oxides. Further details as to the
position of the electrodes on the electrode assembly 210 are
provided in subsequent drawings and accompanying description
below.
[0042] Turning now to FIG. 4, a stylized depiction is provided of
the electrode assembly 210 during fabrication in accordance with an
embodiment of the present invention. The electrode assembly 210
comprises a substrate material on which various electrodes may be
formed. Flexible substrate materials 440 upon which a plurality of
electrodes may be formed may comprise various materials, such as
silicone rubbers, siloxane polymers, and other materials previously
noted.
[0043] Various conductive structures in a variety of manners may be
formed upon the flexible material 440. The conductive structures
may include one or more electrodes 410, which are capable of being
in contact with a portion of a patient's body, e.g., a nerve, and
provide an electrical signal from the signal generator 110 or
detect electrical signals in the patient's body. The conductive
structures may also include various conductive strips 420 and a
plurality of connection pads 430. Each of the electrodes 410 may be
respectively coupled electrically to one of a plurality of
conductive strips 420 that are capable of carrying electrical
signals to or from the electrodes 410. Further, each of the
conductive strips 420 may be respectively coupled electrically to
one of the plurality of connection pads 430. The connection pads
430 may then be used as an interface to a wire or a lead structure
that may contain several electrical components that may each
respectively attach or connect to the set of connection pads 430
illustrated in FIG. 4.
[0044] Connection pads 430 may be formed at the edge of the helical
structure or on the end portion 220 of FIG. 2. In one embodiment,
the end portion 220 may be part of the flexible material 440 (as
depicted in FIG. 4), upon which various processes described herein
may be used to form the connection pads 430. In an alternative
embodiment, the end portion 220 may be a separate structure that is
coupled to the helical structure, as indicated in FIGS. 2 and 3.
The end portion may house a plurality of connection pads 410.
Continuing referring to FIG. 4, in one embodiment, the portion of
the flexible material 440 that contains the electrodes 410 may be
shaped into a helical form, while the portion of the flexible
material 440 that comprises the conductive strips 420 may be shaped
into an undulated form, and the portion of the flexible material
440 that comprises the connection pads 430 may formed in a
generally flat configuration. In this manner, a connector may be
coupled to the connection pads 430, wherein a lead assembly that
comprises a plurality of electrical wires may be operatively
coupled to connection pads 430. Therefore, electrical connections
between a plurality of electrical wires in a lead assembly may be
respectively operatively coupled to a plurality of electrodes
410.
[0045] Various methods may be used to form the conductive elements
illustrated in FIG. 4 upon the flexible material 440 in a flat or
generally planar initial configuration. Semiconductor processing
techniques, such as photolithography processes, copper deposition
processes, single and/or dual damascene processes, etc., known to
those skilled in the art having benefit of the present disclosure,
may be employed to form the conductive structures (e.g., 410, 420,
430) upon the flexible material 440. The flexible material 440 may
then be formed into a helical structure, wherein the electrodes 410
are located on an inner surface of the helical structure such that
the electrodes would be in electrical communication with a
patient's body when the electrode assembly 210 is wrapped around a
target structure.
[0046] In one embodiment, the flexible material 440 is formed into
a helical structure after creating conductive structures 410, 420,
430, e.g., on the material 440 while the material 440 is in a flat
or generally planar configuration. The flat substrate material 440
is then formed into a helical configuration. In an alternative
embodiment, the flexible material 440 is first formed into a
helical structure, which is then unfurled into a flat or generally
planar configuration. The conductive structures are then created on
the unfurled, flat material, and thereafter a restraining force on
the unfurled structure is released to allow it to return to a
helical configuration. Further, a portion of the flexible material
440 may be shaped in an undulated form. In one embodiment, a
portion of the flexible material 440 that comprises conductive
structures may be shaped into an undulated form. Known fabrication
techniques may be used to form the flexible material into a helical
structure and/or into an undulated structure, such as heat treating
and/or annealing techniques, and scoring and/or etching portions of
the substrate to urge the substrate into a helical
configuration.
[0047] Turning now to FIG. 5, a flowchart associated with a method
for providing the electrode assembly 210 in accordance with an
illustrative embodiment of the present invention, is provided.
Initially, a substrate is provided comprising a flexible material
(block 605). In one embodiment, the substrate is generally flat. In
another embodiment, the substrate is generally planar. A base layer
or first layer may be formed on the substrate that is part of the
flexible material 440 of FIG. 4 (block 610). Numerous types of
deposition techniques known to those skilled in the art having
benefit of the present disclosure may be used to generate the base
layer. Such techniques may include, without limitation, chemical
plating, plasma ion deposition, vapor deposition and sputtering. In
one embodiment, the base layer is a substantially non-conductive
film of material, such as a dielectric material.
[0048] A conductive structure may then be formed over the first
layer to form a second layer (block 620). The conductive structure
may include the electrode 410, the conductive strip 420, the
connection pads 430, etc. Various techniques may be used to form
the conductive structures on the second layer. The formation of the
conductive structure may include various semiconductor processing
steps, such as performing a photolithography process (block 622).
The photolithography process may use a mask and a light source to
provide for deposition of material in a predetermined desired
formation to form one or more electrodes 410, conductive strips
420, and/or connection pads 420. An etch process may also be
performed on the second layer (block 624). The etch process may be
used to etch away excessive deposition material in order to conform
the various conductive structures into predetermined shapes and
sizes. In one embodiment, an excimer laser may be used to remove
excessive deposition material, e.g., removing excessive polymer
deposition material to expose a precisely defined surface area for
an electrode 410. For example, the dimensions of the electrode may
be precisely controlled to provide a width of from about 0.1 mm to
about 2.0 mm, with a typical width of about 1.0 mm, and a length of
from about 0.1 mm to about 10 mm, typically about 7 mm. The widths
of the conductive strips may range from about 20 .mu.m to about 100
.mu.m (0.1 mm), with lengths thereof varying as necessary for a
particular application. The connection pads may be provided with
dimensions sufficient to allow good electrical connection to a lead
wire, which will vary according the application. In one embodiment,
the connection pads may be provided with major dimensions ranging
from about 20 .mu.m to about 3 mm. Further, a chemical-mechanical
polishing (CMP) process may also be performed on the second layer
(block 626). Various semiconductor processing techniques may be
performed to form the conductive structures over the first layer.
Alternatively, a copper deposition process, such as a damascene
process or a dual damascene process, may be performed to form the
conductive structures on the second layer (block 628).
[0049] Upon forming one or more conductive structures on the second
layer, a non-conductive layer may then be formed over the second
layer, resulting in a third layer (block 630). Another set of
conductive structures may then be formed over the third layer to
form the fourth layer that contains additional conductive
structures (block 640). This set of processes (i.e., forming
alternating non-conducting and conducting layers) may then be
repeated until a desired number of electrodes, as well as
associated conductive strips and connection pads, are formed on the
flexible material 440 (block 650). Additionally, upon completion of
the formation of the conductive portions on the flexible material,
additional coating steps may be performed. The coating steps may
include coating the electrode assembly with a non-conductive,
flexible coating while masking off the electrodes. Optionally, a
lead assembly having a plurality of lead elements may be provided,
and the lead elements may be coupled to the electrodes using the
connection pads (block 660). In this manner, an electrode assembly
210 with a helical electrode portion comprising a plurality of
electrodes, conductive strips, and connection pads is provided. The
electrode assembly may be coupled to a lead assembly, which may
have an undulated form, using the connection pads. At least a
portion of the substrate may be formed into a helical shape (block
670). In one embodiment, the portion of the substrate containing
the electrodes may be formed into a helical shape.
[0050] Turning now to FIG. 6, a stylized depiction of the electrode
assembly of the present invention in a staggered, multi-layered
configuration is provided in accordance with an illustrative
embodiment of the present invention. The flexible material 440 may
comprise a first layer upon which a first electrode 710 and an
associated conductive strip 720 are formed into a second layer
using the various techniques described above. The conductive strip
runs along at least a portion of the length of the flexible
material 440 and is illustrated as dotted lines under subsequent
layers that are formed on the connector strip 440, such as a third
layer, and a fourth layer.
[0051] Upon forming of the first layer and the second layer (which
includes the first electrode 710 at a predetermined location, and
associated conductive strip 720 that runs along the length of the
flexible material 440), a third layer is formed. The third layer is
formed at an offset position on the second layer such that the
third layer does not overlap the region in which the first
electrode 710 resides. Upon the third layer, a fourth layer
comprising a second electrode 730 and an associated second
conductive strip 740 may be formed. The second conductive strip 740
may run along a portion of the length of the flexible material
440.
[0052] Further, offset slightly from the third and fourth layers, a
fifth layer may be formed over the fourth layer. The fifth layer
does not overlap the portion of the first and second or third and
fourth layers upon which first electrode 710 or the second
electrode 730 reside. Upon the fifth layer, sixth layer comprising
a third electrode 750 and an associated third conductive strip 760
are formed. The third conductive strip 760 runs along a portion of
the length of the flexible material 440. In this manner, a "stair
step" of layers that contain electrodes and conductive strips are
generated on a single flexible material 440 until a desired number
of electrodes are formed. Further, each layer upon which an
electrode is formed may also contain a respective connection pad
for coupling the electrode and its associated conductive strip to a
lead element.
[0053] Upon forming the flexible material 440 into a helical
structure, and subsequently wrapping the helical structure around a
portion of the patient's body, such as a nerve, the first through
third electrodes 710, 730, 750, come into contact with respective
portions of the patient's body without contacting the conductive
strips 720, 740, 760 associated with another electrode. Different
electrical signals can be applied to different regions of the
patient's body. Further, the first electrode 710 may deliver a
therapeutic stimulation signal, whereas the second electrode 730
may acquire resultant electrical data, e.g., by sensing the
activity on the nerve. In this manner, the IMD is capable of
independently controlling the electrical activities of each of the
electrodes.
[0054] Referring simultaneously to FIGS. 7 and 8, a stylized side
view of the flexible material 440 upon which the first through
sixth layers are formed, is illustrated in FIG. 7. FIG. 8
illustrates the first through eighth layers that are formed above
the substrate on the flexible material 440. As depicted in FIG. 7,
a first layer is formed above the substrate. Above the first layer,
the second layer comprising the first electrode 710 and the first
conductive strip 720 are formed. Without overlapping the first
electrode 710, the third layer is formed upon which the fourth
layer comprising the second electrode 730 and the second conductor
strip 740 are formed. The third layer is capable of electrically
isolating the conductive structures in the second layer. Similarly,
upon forming the conductive structures into a fourth layer above
the third layer, the fifth layer is formed above a portion of the
conductive strip portion of the third and fourth layers without
overlapping the second electrode 730. Upon the fifth layer, a sixth
layer comprising the third electrode 750 and the associated third
conductive strip 730 are formed. Therefore, the thickness of the
overall electrode assembly 210 will depend on the number of
electrodes that are formed on the flexible material 440. In this
manner, each of the first through third electrodes 710, 730, 750,
or additional electrodes that may be formed on the flexible
material 440, operate independently. Although only six layers and
three electrodes are illustrated for clarity and ease of
description, those skilled in the art having benefit of the present
invention would readily appreciate that various additional layers
may be similarly added and remain within the spirit and scope of
the present invention.
[0055] Referring to FIG. 9, an alternative embodiment of providing
the electrode assembly in accordance with one alternative
illustrative embodiment of the present invention, is provided. FIG.
8 illustrates a substrate associated with the flexible material
440. Upon the substrate, a first layer may be formed. Upon the
first layer, a second layer comprising a first conductive strip 920
is formed. The first conductive strip 920 may be connected to a
corresponding electrode that will be formed on another layer.
[0056] Subsequently, a third layer is formed above the first and
second layers. The third layer overlaps the first layer as well as
the first conductive strip 920 which comprises the second layer. A
channel may be grooved into the second layer to provide for the
formation of a first via 915. A fourth layer comprising a second
conductive strip 920 is formed above the third layer to be
connected to a corresponding electrode to be formed on a subsequent
layer. Subsequently, a fifth, non-conductive layer is formed above
the conductive fourth layer. The fifth layer may also comprise a
groove formation to accommodate the first via 915 as well as a
second via 935 to be formed. Further, a sixth layer, comprising a
third conductive strip 960 for electrical coupling with a
corresponding electrode. A seventh, non-conductive layer is formed
above this sixth layer. Three grooves are formed in the seventh
layer to accommodate the first via 915, the second via 935 and a
third via 955 to be formed.
[0057] Upon the seventh layer, a first electrode 910, a second
electrode 930, and a third electrode 950 are formed. However,
before the formation of the first through third electrodes, 910,
930, 950, corresponding vias 915, 935, 955 are formed. The first
via 915 that interconnect the first electrode 910 to the first
conductive strip 920 is formed above the second layer and into the
grooves that already exist in all of the layers below the
electrode. Similarly, the second via 935 is formed over the fourth
layer to interconnect the second electrode 930 with the second
conductive strip 940. Further, the third via 955 is formed above
the sixth layer and in the grooves of the layers below the third
electrode. The third via 955 is capable of connecting the third
electrode 950 to the third conductive strip 960. Therefore, all
three electrodes 910, 930, 950, are respectively electrically
coupled to the corresponding conductive strips 920, 940, 960.
Further, similar techniques may be used to generate corresponding
connection pads that interconnect each electrode to the connection
pads for electrical communications with an IMD.
[0058] The surface of the electrode assembly 210 only exposes
conductive electrodes that come into contact with a portion of the
patient's body, therefore, independent signals may be sent to and
from the electrodes 910, 930, 950 via the electrode assembly 210.
In this manner, staggering of the time period relating to the
delivery of stimulation signal is made possible. Further,
independent acquisition of biometric data and delivery of an
electrical signal may be performed substantially simultaneously.
Utilizing the structure described in FIG. 9, the electrodes 910,
930, 950 are capable of operating independently. Although only
three electrodes are illustrated in FIG. 9, those skilled in the
art would appreciate that any number of electrodes may be
implemented using the technique disclosed in FIG. 9 while still
remaining within the spirit and scope of the present invention.
[0059] Utilizing embodiments of the present invention, an electrode
assembly that comprises an array of electrodes may be deployed to
perform various therapy delivery functions and/or sensing
functions. Therefore, current steering and targeted delivery of
therapeutic electrical signals to different portions of a
particular nerve may be performed using the multi-electrode
assembly described by embodiments of the present invention.
Additionally, electrode assemblies provided by the embodiments of
the present invention may be manufactured in a more uniform,
dimensionally-controlled, and efficient manner utilizing process
methods described herein and known to those skilled in the art of
semiconductor manufacturing having benefit of the present
disclosure. Embodiments of the present invention provides for more
effective therapy and greater efficacy while delivering targeted
therapy delivery to various portions of the patient's body.
[0060] All of the methods and apparatus disclosed and claimed
herein may be made and executed without undue experimentation in
light of the present disclosure. While the methods and apparatus of
this invention have been described in terms of particular
embodiments, it will be apparent to those skilled in the art that
variations may be applied to the methods and apparatus and in the
steps or in the sequence of steps of the methods described herein
without departing from the concept, spirit, and scope of the
invention, as defined by the appended claims. It should be
especially apparent that the principles of the invention may be
applied to selected cranial nerves other than the vagus nerve to
achieve particular results.
[0061] The particular embodiments disclosed above are illustrative
only as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations
are intended to the details of construction or design herein shown
other than as described in the claims below. It is, therefore,
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
* * * * *