U.S. patent application number 13/230410 was filed with the patent office on 2012-03-08 for collapsible/expandable tubular electrode leads.
This patent application is currently assigned to BOSTON SCIENTIFIC SCIMED, INC.. Invention is credited to Robert J. Garabedian, Michael P. Wallace.
Application Number | 20120059446 13/230410 |
Document ID | / |
Family ID | 34920481 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120059446 |
Kind Code |
A1 |
Wallace; Michael P. ; et
al. |
March 8, 2012 |
COLLAPSIBLE/EXPANDABLE TUBULAR ELECTRODE LEADS
Abstract
A medical lead and method of treating a patient are provided.
The medical lead comprises an electrically insulative tubular
membrane, a resilient spring element associated with the insulative
membrane, and at least one electrode associated with the insulative
membrane. The medical lead is configured to be collapsed into a
compact form for percutaneous delivery into the patient, thereby
obviating the need to perform an invasive surgical procedure on the
patient. The body formed by these elements, when expanded, can be
sized to fit within the epidural space of a patient. The patient
can be treated by placing the medical lead into a collapsed state
by applying a compressive force to the medical lead, percutaneously
delivering the collapsed medical lead into the patient adjacent
tissue to be treated, and placing the medical lead into an expanded
state by releasing the compressive force.
Inventors: |
Wallace; Michael P.;
(Fremont, CA) ; Garabedian; Robert J.; (Mountain
View, CA) |
Assignee: |
BOSTON SCIENTIFIC SCIMED,
INC.
Maple Grove
MN
|
Family ID: |
34920481 |
Appl. No.: |
13/230410 |
Filed: |
September 12, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11459618 |
Jul 24, 2006 |
8019441 |
|
|
13230410 |
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|
10799295 |
Mar 12, 2004 |
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11459618 |
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Current U.S.
Class: |
607/117 ;
607/115; 607/116 |
Current CPC
Class: |
A61N 1/0553
20130101 |
Class at
Publication: |
607/117 ;
607/115; 607/116 |
International
Class: |
A61N 1/375 20060101
A61N001/375; A61N 1/36 20060101 A61N001/36 |
Claims
1-6. (canceled)
7. A medical lead, comprising: an electrically insulative membrane
having a first stiffness; a resilient skeletal spring layer
associated with the insulative membrane, wherein the spring layer
wraps around onto itself and has a second stiffness greater than
the first stiffness; and at least one electrode associated with the
insulative membrane.
8. The medical lead of claim 7, wherein the insulative membrane is
flaccid.
9. The medical lead of claim 7, wherein the insulative membrane is
tube-shaped.
10. The medical lead of claim 7, wherein the spring layer is
configured to urge the insulative membrane into a curviplanar
geometry.
11. The medical lead of claim 7, wherein the insulative membrane
has two opposing surfaces, the spring layer is associated with one
of the two surfaces, and the at least one electrode is associated
with the other of the two surfaces.
12. The medical lead of claim 7, wherein the insulative membrane
has two opposing surfaces, and the spring layer and the at least
electrode are associated with the same one of the two surfaces.
13. The medical lead of claim 7, wherein the insulative membrane
has an inner surface and an outer surface, and the spring layer is
associated with the outer surface of the insulative membrane.
14. The medical lead of claim 7, wherein the insulative membrane
has an inner surface and an outer surface, and the spring layer is
associated with the inner surface of the insulative membrane.
15. The medical lead of claim 7, wherein the insulative membrane,
spring layer, and at least one electrode form a body that is
configured to inhibit tissue growth.
16. The medical lead of claim 7, wherein the insulative membrane,
spring layer, and at least one electrode form a body that is
configured to be collapsed into a compact form for percutaneous
delivery into a patient.
17. The medical lead of claim 7, wherein the insulative membrane,
spring layer, and at least one electrode form an expanded body that
is sized to fit within the epidural space of a patient.
18. The medical lead of claim 7, wherein the insulative membrane
insulative membrane has a normally non-cylindrical shape.
19. The medical lead of claim 7, wherein the spring layer is a
discrete element.
20. The medical lead of claim 7, wherein the spring layer is a mesh
or braid.
21. The medical lead of claim 7, wherein the spring layer is
configured to expand the insulative membrane.
22. A method of treating a patient, comprising: placing the medical
lead of claim 7 into a collapsed state by applying a compressive
force to the medical lead; percutaneously delivering the collapsed
medical lead into the patient adjacent tissue to be treated; and
placing the medical lead into an expanded state by releasing the
compressive force, whereby the resilient spring layer facilitates
expansion of the medical lead.
23. The method of claim 22, further comprising stimulating the
tissue with the medical lead.
24. The method of claim 22, wherein the tissue is spinal cord
tissue.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of copending U.S. patent
application Ser. No. 10/799,295, filed on Mar. 12, 2004, which is
related to U.S. patent application Ser. No. 10/799,270, filed on
Mar. 12, 2004, both of which are expressly incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to the implantation of electrode leads
within a patient, and in particular, the implantation of
stimulation electrode leads within a patient's spine to treat
disorders, such as chronic pain.
BACKGROUND OF THE INVENTION
[0003] It is known to treat chronic pain by electrically
stimulating the spinal cord, spinal nerve roots, and other nerve
bundles. Although not fully understood, the application of
electrical energy to particular regions of the spinal cord induces
parasthesia (i.e., a subjective sensation of numbness or tingling)
in the afflicted body regions associated with the stimulated spinal
regions. This parasthesia effectively masks the transmission of
chronic pain sensations from the afflicted body regions to the
brain. Since each body region is associated with a particular
spinal nerve root, it is important that stimulation be applied at
the proper longitudinal position along the spinal cord to provide
successful pain management and avoid stimulation of unaffected
regions of the body. Also, because nerve fibers extend between the
brain and the nerve roots along the same side of the spine as the
body regions they control, it is equally important that stimulation
be applied at the proper lateral position of the spinal cord. For
example, to treat unilateral pain (i.e., pain sensed only on one
side of the body), electrical stimulation is applied to the
corresponding side of the spinal cord. To treat bilateral pain
(i.e., pain sensed on both sides of the body), electrical
stimulation is either applied directly to the midline of the spinal
cord or applied to both lateral sides of the spinal cord.
[0004] In a typical procedure, one or more stimulation leads are
introduced through the patient's back into the epidural space under
fluoroscopy. The specific procedure used to implant the stimulation
lead will ultimately depend on the type of stimulation lead used.
Currently, there are two types of commercially available
stimulation leads: a percutaneous lead and a surgical lead.
[0005] A percutaneous lead comprises a cylindrical body with ring
electrodes, and can be introduced into contact with the affected
spinal tissue through a Touhy-like needle, which passes through the
skin, between the desired vertebrae, and into the spinal cavity
above the dura layer. For unilateral pain, a percutaneous lead is
placed on the corresponding lateral side of the spinal cord. For
bilateral pain, a percutaneous lead is placed down the midline of
the spinal cord, or two percutaneous leads are placed down the
respective sides of the midline.
[0006] A surgical lead has a paddle on which multiple electrodes
are arranged in independent columns, and is introduced into contact
with the affected spinal tissue using a surgical procedure, and
specifically, a laminectomy, which involves removal of the laminar
vertebral tissue to allow both access to the dura layer and
positioning of the lead.
[0007] After the stimulation lead(s) (whether percutaneous or
surgical) are placed at the target area of the spinal cord, the
lead(s) are anchored in place, and the proximal ends of the
lead(s), or alternatively lead extensions, are passed through a
tunnel leading to a subcutaneous pocket (typically made in the
patient's abdominal area) where a neurostimulator is implanted. The
lead(s) are connected to the neurostimulator, which is then
operated to test the effect of stimulation and adjust the
parameters of the stimulation for optimal pain relief. During this
procedure, the patient provides verbal feedback regarding the
presence of paresthesia over the pain area. Based on this feedback,
the lead position(s) may be adjusted and re-anchored if necessary.
Any incisions are then closed to fully implant the system.
[0008] Various types of stimulation leads (both percutaneous and
surgical), as well as stimulation sources and other components, for
performing spinal cord stimulation are commercially available from
Medtronic, Inc., located in Minneapolis, Minn., and Advanced
Neuromodulation Systems, Inc., located in Plano, Tex.
[0009] The use of surgical leads provides several functional
advantages over the use of percutaneous leads. For example, the
paddle on a surgical lead has a greater footprint than that of a
percutaneous lead. As a result, an implanted surgical lead is less
apt to migrate from its optimum position than is an implanted
percutaneous lead, thereby providing a more efficacious treatment
and minimizing post operative procedures otherwise required to
reposition the lead. As another example, the paddle of a surgical
lead is insulated on one side. As a result, almost all of the
stimulation energy is directed into the targeted neural tissue. The
electrodes on the percutaneous leads, however, are entirely
circumferentially exposed, so that much of the stimulation energy
is directed away from the neural tissue. This ultimately translates
into a lack of power efficiency, where percutaneous leads tend to
exhaust a stimulator battery supply 25%-50% greater than that
exhausted when surgical leads are used. As still another example,
the multiple columns of electrodes on a surgical lead are well
suited to address both unilateral and bilateral pain, where
electrical energy may be administered using either column
independently or administered using both columns.
[0010] Although surgical leads are functionally superior to
percutaneous leads, there is one major drawback--surgical leads
require painful surgery performed by a neurosurgeon, whereas
percutaneous leads can be introduced into the epidural space
minimally invasively by an anesthesiologist using local
anesthesia.
[0011] There, thus, remains a need for a minimally invasive means
of introducing stimulation leads within the spine of a patient,
while preserving the functional advantages of a surgical lead.
SUMMARY OF THE INVENTION
[0012] In accordance with a first aspect of the present inventions,
a medical lead is provided. The medical lead comprises an
electrically insulative tubular membrane having an inner surface
and an outer surface, a resilient spring element, and at least one
electrode mounted. The spring element is associated with the
membrane, e.g., by forming or mounting the spring element onto the
membrane, or embedding the spring element into the membrane, and
the electrode(s) is associated with the outer surface of the
membrane, e.g., by forming or mounting the electrode(s) onto the
outer surface, or embedding the springelement into the outer
surface. The spring element can be associated with the inner
surface or the outer surface of the insulative membrane.
[0013] The insulative membrane can be, e.g., continuous, porous, or
meshed. The insulative membrane can take on a variety of tubular
shapes. For example, the tubular shape can exhibit a circular,
rectangular, triangular, or irregular geometry. In one embodiment,
the insulative membrane is allowed to be flaccid and has a
relatively low-stiffness, so that it can be made as thin as
possible to facilitate collapsing of the medical lead into a
low-profile geometry. The spring element is configured to expand
the insulative membrane. The spring element can be, e.g., a
discrete element or can be formed of a mesh or braid.
[0014] In one embodiment, the medical lead is configured to inhibit
tissue growth. If associated with the inner surface of the
insulative membrane, the spring element can be formed of any
suitable resilient material, since it is not exposed to tissue. If
associated with the outer surface of the insulative membrane,
however, the spring element is preferably formed of a material that
inhibits tissue growth. For example, in this case, the spring
element can be formed of a continuous layer of material. In this
manner, the implanted medical lead can be more easily retrieved
from the patient's body, if necessary. The medical lead is
preferably configured to be collapsed into a compact form for
percutaneous delivery into the patient, thereby obviating the need
to perform an invasive surgical procedure on the patient. The
medical lead, when expanded, can be sized to fit within the
epidural space of a patient.
[0015] In accordance with a second aspect of the present
inventions, another medical lead is provided. The medical lead
comprises a resilient tubular structure having a normally
non-circular cross-sectional shape (e.g., a rectangle, oval, or
crescent), and at least one electrode associated with the tubular
structure. The tubular structure may comprise, e.g., a discrete
element or can be formed of a mesh or braid. In one embodiment, the
medical lead is configured to inhibit tissue growth. The medical
lead is preferably configured to be collapsed into a compact form
for percutaneous delivery into the patient, thereby obviating the
need to perform an invasive surgical procedure on the patient. The
medical lead, when expanded, can be sized to fit within the
epidural space of a patient. In this case, the non-cylindrical
geometry of the tubular structure allows the tubular structure to
conform to the non-cylindrical shaped epidural space, so that, when
expanded, painful tissue displacement is minimized.
[0016] In accordance with a third aspect of the present inventions,
a method of treating a patient with one of the previously described
medical leads is provided. The method comprises placing the medical
lead into a collapsed state by applying a compressive force to the
medical lead, percutaneously delivering the collapsed medical lead
into the patient adjacent tissue to be treated, and placing the
medical lead into an expanded state by releasing the compressive
force. In one preferred method, the medical lead is used to
stimulate tissue, such as spinal cord tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The drawings illustrate the design and utility of preferred
embodiment(s) of the invention, in which similar elements are
referred to by common reference numerals. In order to better
appreciate the advantages and objects of the invention, reference
should be made to the accompanying drawings that illustrate the
preferred embodiment(s). The drawings, however, depict the
embodiment(s) of the invention, and should not be taken as limiting
its scope. With this caveat, the embodiment(s) of the invention
will be described and explained with additional specificity and
detail through the use of the accompanying drawings in which:
[0018] FIG. 1 is a plan view of a stimulation lead kit arranged in
accordance with a preferred embodiment of the present
invention;
[0019] FIG. 2 is a cross-sectional view of a stimulation paddle
used in the kit of FIG. 1, particularly shown in a low-profile
collapsed geometry;
[0020] FIG. 3 is a cross-sectional view of the stimulation paddle
used in the kit of FIG. 1, particularly shown in another
low-profile collapsed geometry;
[0021] FIG. 4 is a cross-sectional view of the stimulation paddle
used in the kit of FIG. 1, particularly shown in still another
low-profile collapsed geometry;
[0022] FIG. 5 is a cross-sectional view of a planar stimulation
paddle that can be used in the kit of FIG. 1, taken along the line
5-5;
[0023] FIG. 6 is a cross-sectional view of a curviplanar
stimulation paddle that can be used in the kit of FIG. 1, taken
along the line 6-6;
[0024] FIG. 7 is a top view of the stimulation paddle used in the
kit of FIG. 1;
[0025] FIG. 8 is a top view of another stimulation paddle that can
be used in the kit of FIG. 1;
[0026] FIG. 9 is a top view of still another stimulation paddle
that can be used in the kit of FIG. 1;
[0027] FIG. 10 is a top view of yet another stimulation paddle that
can be used in the kit of FIG. 1;
[0028] FIG. 11 is a top view of yet another stimulation paddle that
can be used in the kit of FIG. 1;
[0029] FIG. 12 is a top view of yet another stimulation paddle that
can be used in the kit of FIG. 1;
[0030] FIG. 13 is a top view of yet another stimulation paddle that
can be used in the kit of FIG. 1;
[0031] FIG. 14 is a perspective view of a stimulation tube that can
be used in the kit of FIG. 1;
[0032] FIG. 15 is a cross-sectional view of the stimulation tube of
FIG. 14, particularly showing its cross-sectional rectangle shape
when placed in an expanded geometry;
[0033] FIG. 16 is a cross-sectional view of an alternative
stimulation tube, particularly showing its cross-sectional oval
shape when placed in an expanded geometry;
[0034] FIG. 17 is a cross-sectional view of another alternative
stimulation tube, particularly showing its cross-sectional crescent
shape when placed in an expanded geometry;
[0035] FIG. 18 is a cross-sectional view of the stimulation tube of
FIG. 14, particularly shown in a low-profile collapsed
geometry;
[0036] FIG. 19 is a perspective view of another stimulation tube
that can be used in the kit of FIG. 1;
[0037] FIG. 20 is a cross-sectional view of the stimulation tube of
FIG. 19, taken along the line 20-20; and
[0038] FIGS. 21A-21D are various views illustrating the
installation of the kit of FIG. 1 into a patients spine.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Referring now to FIG. 1, a spinal cord stimulation lead kit
100 arranged in accordance with one preferred embodiment of the
present invention is shown. In its simplest form, the stimulation
kit 100 generally comprises a stimulation lead 102, which is
configured to be percutaneously delivered and implanted into the
epidural space of a patient's spine, an implantable electrical
stimulation source 104 configured for delivering stimulation energy
to the stimulation lead 102, and an optional extension lead 106
configured for connecting the stimulation lead 102 to the remotely
implanted stimulation source 104.
[0040] It should be noted that although the kit 100 illustrated in
FIG. 1 is described herein as being used in spinal cord stimulation
(SCS) for the treatment of chronic pain, the kit 100, or a
modification of the kit 100, can be used in an SCS procedure to
treat other ailments, or can used in other applications other than
SCS procedures, such as peripheral nervous system stimulation,
sacral root stimulation, and brain tissue stimulation, including
cortical and deep brain stimulation. In the latter case, the
stimulation lead 102 can be delivered through a miniature cranial
burr hole into the brain tissue.
[0041] The stimulation lead 102 comprises an elongated sheath body
108 having a proximal end 110 and a distal end 112. The sheath body
108 is composed of a suitably flexible material (such as
polyurethane, silicone, etc.), which may either be resilient or
non-resilient, and may be formed via an extrusion process or by any
other suitable means. In the illustrated embodiment, the sheath
body 108 is cylindrically-shaped and sized to fit through a
Touhy-like needle (not shown). In this case, the diameter of the
sheath body 108 is preferably less than 5 mm to allow it to be
percutaneously introduced through a needle. More preferably, the
diameter of the sheath body 108 is within the range of 1 mm to 3
mm, so that the stimulation lead 102, along with the secondary
stimulation leads 104 described below, can comfortably fit within
the epidural space of the patient. The sheath body 108 may have
other cross-sectional geometries, such as oval, rectangular,
triangular, etc. If rectangular, the width of the stimulation lead
102 can be up to 5 mm, since the width of an epidural space is
greater than its height. The sheath body 108 may have an optional
lumen (not shown) for receiving an obturator (not shown) that
axially stiffens the sheath body 108 to facilitate percutaneous
introduction of the stimulation lead 102 within the epidural space
of the patient's spine, as will be described in further detail
below.
[0042] The stimulation lead 102 further comprises a plurality of
terminals 114 (in this case, four) mounted on the proximal end 110
of the sheath body 108. The terminals 114 are formed of ring-shaped
elements composed of a suitable biocompatible metallic material,
such as platinum, platinum/iridium, stainless steel, gold, or
combinations or alloys of these materials, and can be mounted to
the sheath body 108 in an interference fit arrangement.
[0043] The stimulation lead 102 further comprises a stimulation
paddle 116 suitably mounted to the distal end 112 of the sheath
body 108. In this embodiment, the stimulation paddle 116 is
laterally centered on the sheath body 108, but as will be discussed
below, the electrode paddle 116 can alternatively be laterally
offset from the sheath body 108. As will be described in further
detail below, the stimulation paddle 116 is configured to be placed
into a compact, low-profile geometry by, e.g., rolling (see FIG. 2)
or folding (see FIGS. 3 and 4) the paddle 116, and maintained in
this low-profile geometry by applying a radial compressive force to
the paddle 116, such as the force that would be applied by the
lumen of a delivery device. Upon release of the radial compressive
force, such as when the paddle 116 exits the delivery device, the
paddle 116 springs open into its normally expanded geometry. In the
illustrated embodiment, the paddle 116 expands into a planar
geometry, as illustrated in FIG. 5. Alternatively, the paddle 116
can expand into a curviplanar geometry (i.e., a plane existing in
three-dimensional space, e.g., a plane having an arcuate, curved,
or undulating shape), as illustrated in FIG. 6.
[0044] Referring further to FIG. 7, the stimulation paddle 116
comprises a paddle-shaped membrane 118 having a surface 124, an
array of electrodes 120 mounted on the membrane surface 124, and a
skeletal spring element 122 mounted on the membrane surface 124
between the electrodes 120. Alternatively, the electrodes 120 and
skeletal spring element 122 can be respectively formed onto
oppositely disposed surfaces of the membrane 118, so that the
routing of the spring element 122 can be accomplished independently
of the electrodes 120. To prevent or inhibit tissue growth after
the stimulation lead 102 is implanted, the surface of the
stimulation paddle 116 is preferably smooth and free of
discontinuities that would otherwise be found in tissue growth
exhibiting surfaces, such as mesh or braided material. In this
manner, the implanted lead 102 can be more easily and
percutaneously removed if necessary.
[0045] The electrodes 120 can be formed onto the membrane 118 using
known deposition processes, such as sputtering, vapor deposition,
ion beam deposition, electroplating over a deposited seed layer, or
a combination of these processes. Alternatively, the electrodes 120
can be formed onto the membrane 118 as a thin sheet or foil of
electrically conductive metal. Or, the electrodes 120 can be
discrete elements that are embedded into the membrane 118, such
that they lie flush with the surface 124 of the membrane 118. The
electrodes 120 can be composed of the same electrically conductive
and biocompatible material as the terminals 114, e.g., platinum,
platinum/iridium, stainless steel, gold, or combinations or alloys
of these materials. In the embodiment illustrated in FIG. 7, the
electrodes 120 are arranged in a single column of four elements
extending along the midline of the membrane 118. As will be
described in further detail below, the electrodes 120 can have
other configurations. In the illustrated embodiment, the electrodes
120 are circular, but can be formed as other geometric shapes, such
as rectangular or ellipsoidal.
[0046] The stimulation lead 102 further comprises a plurality of
conductors (not shown) extending through the sheath body 108 and
membrane 118 and connecting each electrode 120 with a respective
terminal 114. The conductors 122 are composed of a suitably
electrically conductive material that exhibits the desired
mechanical properties of low resistance, corrosion resistance,
flexibility, and strength.
[0047] In the illustrated embodiment, the membrane 118 is composed
of a continuous layer of material, although alternatively, the
membrane 118 may be porous, meshed, or braided. Whether continuous
or not, the material from which the membrane 118 is composed is
relatively thin (e.g., 0.1 mm to 2 mm, although 1 mm or less is
most preferred) and has a relatively low-stiffness. Exemplary
materials are low-stiffness silicone, expanded
polytetrafluoroethylene (ePTFE), or urethane. Due to these
properties, the stimulation paddle 116 can be more easily collapsed
into a low-profile geometry. For example, the stimulation paddle
116 can be rolled (see FIG. 2), or folded along one or more fold
lines (see FIGS. 3 and 4). Although these properties allow the
stimulation paddle 116 to be more easily collapsed into a
low-profile geometry, thereby facilitating percutaneous delivery of
the lead 102, these same properties also cause the membrane 118 to
be too flaccid to easily spring open from the low-profile geometry.
Radio-opaque markers (not shown) may optionally be provided on the
membrane 118, so that the stimulation paddle 116 may be more easily
navigated and placed into the epidural space of the patient under
fluoroscopy.
[0048] The skeletal spring element 122, however, advantageously
provides this necessary spring force. In particular, the spring
element 122 is composed of a relatively high-stiffness and
resilient material, such as stainless steel, a metallic and polymer
material, or a high-stiffness urethane or silicone, that is shaped
into a normally planar (curviplanar) geometry. In alternative
embodiments, the spring element 122 may be composed of a shape
memory material, such as nitinol, so that it assumes a planar (or
curviplanar) geometry in the presence of a defined temperature,
such as, e.g., body temperature. Thus, it can be appreciated that
the normally planar (or curviplanar) geometry of the spring element
122 will cause the stimulation paddle 116 to likewise assume a
planar (curviplanar) geometry in the absence of an external force
(in particular, a compressive force). In the illustrated
embodiment, the spring element 122 is formed of a thin layer of
material that is laminated onto the membrane 118. In effect, the
spring element 122 has a two-dimensional geometry in that it has a
length and a width, but a minimal thickness. As a result,
protrusions from the membrane 118 are avoided, thereby allowing the
stimulation paddle 116 to be placed into a lower collapsed profile.
Alternatively, the spring element 122 can be made from wire, which
is cylindrical in nature, and thus, can be said to have a
three-dimensional geometry. Whether formed from a layer of material
or a wire, the spring element 122 may alternatively be embedded
into the membrane 118, so that the surface of the spring element
122 is flush with the surface 124 of the membrane 118.
[0049] As can be seen in FIG. 7, the spring element 122 is formed
of a single linear element that longitudinally extends along the
membrane 118 in a meandering fashion between the electrodes 120. In
this case, the laterally extending curves of the meandering spring
element 122 act as cross-supports that provide the necessary spring
force to urge the stimulation paddle 116 from its low-profile
collapsed geometry into its expanded geometry. Notably, the end of
the spring element 122 is beaded to prevent inadvertent perforation
of the membrane 118 when the stimulation paddle 116 is mechanically
stressed.
[0050] The spring element 122 can have other geometries. For
example, FIG. 8 illustrates a stimulation paddle 126 that comprises
a skeletal spring element 132 that includes a main spring segment
134 that is similar to the spring element 122 illustrated in FIG.
7, and additional secondary spring segments 135 that extend
longitudinally from the apexes of the main spring segment curves.
The longitudinally extending secondary spring segments 135 provide
additional axial stiffness to the stimulation paddle 126, thereby
facilitating axial movement (i.e., the pushability) of the expanded
stimulation paddle 126 by minimizing axial buckling of the membrane
118. To prevent inadvertent perforation of the insulative membrane
118, the distal ends of the secondary spring segments 135 are
beaded.
[0051] As another example, FIG. 9 illustrates a stimulation paddle
136 having a skeletal spring element 122 that includes a main
spring segment 144 that extends longitudinally along the centerline
of the membrane 118, and a plurality of lateral spring segments 145
that branch off of the main spring segment 144 between the
electrodes 120. As can be seen in FIG. 9, the electrodes 120 are
arranged as two columns of four elements each extending down the
lateral sides of the membrane 118. Besides providing a structure
from which the lateral spring segments 144 are supported, the main
spring segment 144 provides axial stiffness to the stimulation
paddle 146, thereby facilitating axial movement (i.e., the
pushability) of the expanded stimulation paddle 146 by minimizing
axial buckling of the membrane 118. To this end, the main spring
segment 144 is somewhat wider than the lateral spring segments 145.
The lateral spring segments 145 act as cross-members that urge the
membrane 118 into its normally expanded state, thereby providing
the spring force that transforms the collapsed membrane 118 into
the expanded geometry in the absence of a compressive force.
[0052] FIG. 10 illustrates a stimulation paddle 146 that comprises
a skeletal spring element 152, which is similar to the previously
described spring element 152, with the exception that it comprises
lateral staggered spring segments 155 that are not linear, but are
rather formed into two dimensional shapes--in this case a leaf
shape. This increased size of the lateral spring segments 155
provides increased lateral spring force to the stimulation paddle
146. In this case, the number of lateral segments 155 are
decreased, and the electrodes 120 are arranged into two columns of
two elements each.
[0053] FIG. 11 illustrates a stimulation paddle 156 that comprises
a skeletal spring element 162 with a plurality of diamond-shaped
elements 164 longitudinally extending down the midline of the
membrane 118 and a plurality of innerconnecting segments 165
between the respective diamond-shaped elements 164. The electrodes
120 are arranged in a single column of four electrodes 120 that
extend down the midline of the membrane 118 between the respective
diamond-shaped elements 164. The interconnecting segments 165 are
curved in alternating left and right lateral directions in order to
accommodate the centered electrodes 120.
[0054] FIG. 12 illustrates a stimulation paddle 166 that comprises
a skeletal spring element 172 with a trunk segment 173, two main
spring segments 174 that longitudinally extend from the trunk
segment 173 along the left and right lateral sides of the membrane
118, and lateral spring segments 175 that branch off of the main
spring segments 174 towards the midline of the membrane 118. Like
the main spring segment 144 of the stimulation paddle 136
illustrated in FIG. 9, the main spring segments 174 provide axial
rigidity to the stimulation paddle 166, while providing a structure
supporting the lateral spring segments 175. Like the lateral spring
segments 175 of the stimulation paddle 166 illustrated in FIG. 11,
the lateral spring segments 175 act as cross members that
facilitate transformation of the stimulation paddle 166 from its
collapsed geometry into its expanded geometry. To prevent
inadvertent perforation of the insulative membrane 118, the distal
ends of the main spring segments 174 and secondary spring segments
175 are beaded. The electrodes 120 are arranged in a single column
of four electrodes 120 extending down the midline of the membrane
118 between the respective secondary spring segments 175.
[0055] FIG. 13 illustrates a stimulation paddle 176 that comprises
a membrane 118 that is laterally offset from the distal end 112 of
the elongated sheath 108, and a skeletal spring element 182 with a
main spring segment 184 that longitudinally extends along the
membrane 118 and lateral spring segments 185 that laterally branch
off from the main spring segment 184 towards the other lateral side
of the membrane 118. The main spring segment 184 and lateral spring
segments 185 function in the same manner as the main spring segment
144 and lateral spring segments 145 of the spring element 132
illustrated in FIG. 9. To prevent inadvertent perforation of the
insulative membrane 118, the distal ends of the secondary spring
segments 185 are beaded. The electrodes 120 are arranged in a
single column of four elements that longitudinally extend down the
midline of the membrane 118 between the lateral spring segments
185.
[0056] Although all of the stimulation paddles illustrated in FIGS.
7-13 have single spring elements, stimulation paddles with multiple
spring elements can also be provided. In addition, tubular designs,
which are, in effect, stimulation paddles that are wrapped around
onto themselves, can be formed, in order to provide a more stable
and snug engagement within the epidural space.
[0057] In particular, FIGS. 14 and 15 illustrate a stimulation lead
202 that can alternatively be used in the kit 100 of FIG. 1. The
stimulation lead 202 is similar to the stimulation 102 described
above, with the exception that it comprises a stimulation tube 216,
rather than a stimulation paddle. The stimulation tube 216
comprises a tubular, and specifically, rectangular cross-sectional
shaped, membrane 218 having an outer surface 224, an array of
electrodes 220 mounted on the outer surface 224, and skeletal
spring elements 222 mounted on, the outer surface 224 between the
electrodes 220. Alternatively, the electrodes 220 can be mounted on
the outer surface 224, and the spring elements 222 can be mounted
on an inner surface of the tubular membrane 218, so that the
routing of the spring element 222 can be accomplished independently
of the electrodes 220. To prevent or inhibit tissue growth after
the stimulation lead 202 is implanted, the outer surface 224 of the
stimulation tube 216 is preferably smooth and free of
discontinuities that would otherwise be found in tissue growth
exhibiting surfaces, such as mesh or braided material. In this
manner, the implanted lead 202 can be more easily and
percutaneously removed if necessary.
[0058] The electrodes 220 can be composed of the same material,
shaped, and formed onto the membrane 218 in the same manner as the
electrodes 120. In the embodiment illustrated in FIG. 14, the
electrodes 220 are arranged in a single column of four elements
longitudinally extending along one side of the membrane 218. Like
the paddle membrane 118, the tubular membrane 218 is formed of a
relatively thin (e.g., 0.1 mm to 2 mm, although 1 mm or less is
most preferred), and is composed of a relatively low-stiffness
material, such that it can be collapsed into a low-profile
geometry, as shown in FIG. 18. Also, like the paddle membrane 118,
the tubular membrane 218, by itself, is too flaccid to easily
spring open from the low-profile geometry. Again, the skeletal
spring elements 222 provide this necessary spring force, so that
the stimulation tube 216 can expand outward in the absence of an
external compressive force. The spring elements 222 can be composed
of the same material and can be formed onto the membrane 218 in the
same manner as the previously described spring element 122. In the
embodiment illustrated in FIG. 14, each of the spring elements 222
extends around the circumference of the tubular membrane 218 in a
meandering fashion. Of course, other spring element configurations
can be used.
[0059] Although the membrane 218 is illustrated as having a
normally expanded rectangular geometry, as best shown in FIG. 15,
the membrane 218 can alternatively have other non-cylindrical
tube-like shapes. For example, FIG. 16 illustrates an alternative
tubular membrane 216' that has an oval cross-sectional shape, and
FIG. 17 illustrates another tubular membrane 216'' that has a
crescent cross-sectional shape. The crescent-shaped tubular
membrane 216'' lends itself particular well to spinal cord
stimulation, since the spinal cord can be comfortably seated within
a concave region 216 of the tubular membrane 216''.
[0060] FIGS. 19 and 20 illustrate another stimulation tube 236 that
is similar to the stimulation tube 216, with the exception that,
rather than having discrete spring elements, it comprises a
resilient spring element 242 formed of a mesh or braid that may be
composed of the same base material as the previously described
spring elements. The tube 236 also has an oval cross-sectional
shape, rather than a rectangular cross-sectional shape. The spring
element 242 is formed on an inner surface of the tubular membrane
218, so that the mesh or braid material is not in contact with
tissue, and therefore does not inhibit tissue growth. Like the
spring element 222, the spring element 242 serves to urge the
tubular membrane 218 from a low-profile collapsed geometry to an
expanded geometry. As shown in FIG. 19, the distal and proximal
ends of the stimulation tube 236 are tapered to allow for a safer
deployment and, if necessary, retrieval of the device.
[0061] Referring back to FIG. 1, the implantable stimulation source
104 is designed to deliver electrical pulses to the stimulation
lead 102 in accordance with programmed parameters. In the preferred
embodiment, the stimulation source 104 is programmed to output
electrical pulses having amplitudes varying from 0.1 to 20 volts,
pulse widths varying from 0.02 to 1.5 milliseconds, and repetition
rates varying from 2 to 2500 Hertz. In the illustrated embodiment,
the stimulation source 104 takes the form of a totally
self-contained generator, which once implanted, may be activated
and controlled by an outside telemetry source, e.g., a small
magnet. In this case, the pulse generator has an internal power
source that limits the life of the pulse generator to a few years,
and after the power source is expended, the pulse generator must be
replaced. Generally, these types of stimulation sources 106 may be
implanted within the chest or abdominal region beneath the skin of
the patient.
[0062] Alternatively, the implantable stimulation source 104 may
take the form of a passive receiver that receives radio frequency
(RF) signals from an external transmitter worn by the patient. In
this scenario, the life of the stimulation source 104 is virtually
unlimited, since the stimulation signals originate from the
external transmitter. Like the self-contained generators, the
receivers of these types of stimulation sources 106 can be
implanted within the chest or abdominal region beneath the skin of
the patient. The receivers may also be suitable for implantation
behind the ear of the patient, in which case, the external
transmitter may be worn on the ear of the patient in a manner
similar to that of a hearing aid. Stimulation sources, such as
those just described, are commercially available from Advanced
Neuromodulation Systems, Inc., located in Plano, Tex., and
Medtronic, Inc., located in Minneapolis, Minn.
[0063] The optional extension lead 106 comprises an elongated
sheath body 109 having a proximal end 111 and a distal end 113,
much like the sheath body 108 of the stimulation lead 102, a
proximal connector 115 coupled to the proximal end 113 of the
sheath body 109, a distal connector 117 coupled to the distal end
111 of the sheath body 109, and a plurality of electrical
conductors (not shown) extending through the sheath body 109
between the proximal and distal connectors 115/117. The length of
the extension lead 102 is sufficient to extend from the spine of
the patient, where the proximal end of the implanted stimulation
lead 102 protrudes from to the implantation site of the stimulation
source 104--typically somewhere in the chest or abdominal region.
The proximal connector 115 is configured to be coupled with to the
stimulation source 104, and the distal connector 117 is configured
to mate with the proximal end of the stimulation lead 102.
[0064] Having described the stimulation lead kit 100, its
installation and use in treating chronic pain will now be described
with reference to FIGS. 21A-21D. After the patient has been
prepared (which may involve testing the efficacy of spinal cord
stimulation on the patient, and, once determining that the patient
can be effectively treated with spinal cord stimulation,
identifying and marking the appropriate vertebral intervals on the
patient's skin and applying a local anesthetic to this region), a
needle 10, such as, e.g., a Touhy needle, is inserted through the
patient's skin 12 between the desired vertebrae 14, and into the
epidural space 16 within the spine at a position inferior to target
stimulation site 18 (FIG. 21A). In the illustrated method, the
Touhy needle 10 will serve as the primary delivery mechanism for
the stimulation lead 102. Alternatively, if an optional introducer
(not shown) is used, a guide wire (not shown) is introduced through
the needle 10 and advanced to or near the target stimulation site
18. The needle 10 is removed, the introducer is then introduced
over the guide wire and advanced to the target stimulation site 18,
and the guide wire is then withdrawn. In this case, the introducer
will serve as the primary delivery mechanism for the stimulation
lead 102.
[0065] After the deliver mechanism is in place, the stimulation
lead 102, with the stimulation paddle 116 collapsed into a
low-profile geometry (see FIGS. 2-4), is then inserted through the
needle or the introducer (whichever is in place), and positioned in
the epidural space 16 at the target stimulation site 18 (FIGS. 21B
and 21C). The stimulation tubes 216/236 can be inserted through the
needle or the introducer in the same manner. If the stimulation
lead 102 has an obturator lumen, an obturator can be used to
provide additional axial stiffness and to facilitate control. Once
the compressive radial force applied by the delivery device is
released, the stimulation paddle 116 expands into its normally
planar geometry, with the electrodes 120 facing the dural layer 20
and spanning the midline of the spinal cord 22 (FIG. 21D). If
stimulation tubes 216/236 are used, their two-dimensional expansion
will provide a more secure engagement within the epidural space.
Notably, the use of non-cylindrical stimulation tubes, when
expanded, conform better to the non-cylindrical epidural space 16,
thereby minimizing painful tissue displacement.
[0066] Next, the needle 10 or introducer is removed, and the
proximal end of the stimulation lead 102 is connected to a tester
(not shown), which is then operated in a standard manner to confirm
proper location of the stimulation lead 102 and to adjust the
stimulation parameters for optimal pain relief. Once this
optimization process has been completed, the tester is disconnected
from the stimulation lead 102, which is then anchored in place
using standard lead anchors (not shown). In the case of stimulation
tubes 216/236, anchors may not be necessary, since they self-anchor
themselves within the epidural space when expanded. Next, the
stimulation lead 102 is coupled to the stimulation source 104 and
implantation is completed (not shown). In particular, a
subcutaneous pocket is created in the patients abdominal area for
implantation of the stimulation source 104, and a tunnel is
subcutaneously formed between the spine region and the subcutaneous
pocket. The optional lead extension 106 is passed through the
tunnel, after which the adapter 154 of the extension 106 is
connected to the proximal end of the stimulation leads 102 and the
connector 156 of the lead extension 106 is connected to the
stimulation source 104. The stimulation source 104 is programmed
and tested, and then placed within the subcutaneous pocket, after
which all incisions are closed to effect implantation of the
stimulation lead 102 and stimulation source 104. The stimulation
source 104 can then be operated to convey stimulation energy from
the stimulation source 104 to the electrodes 120 of the stimulation
lead 102, where it is, in turn, conveyed into the neural tissue for
pain relief.
[0067] It can be appreciated that the relatively large footprint
made by the stimulation lead 102, much like a prior art surgical
lead, provides a more stable platform for the electrodes 120. Also,
like a prior art surgical lead, the electrodes 120 face in a single
direction, thereby focusing the stimulation energy into the
affected neural tissue where it is needed. Unlike a surgical lead,
however, the stimulation lead 102 can be percutaneously delivered
into the patient's spine in a minimally invasive and relatively
pain-free manner, without requiring extensive patient recovery.
[0068] Although particular embodiments of the present invention
have been shown and described, it should be understood that the
above discussion is not intended to limit the present invention to
these embodiments. It will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present invention. Thus,
the present invention is intended to cover alternatives,
modifications, and equivalents that may fall within the spirit and
scope of the present invention as defined by the claims.
* * * * *