U.S. patent application number 12/827435 was filed with the patent office on 2010-10-21 for implantable medical electrical stimulation lead, such as pne lead, and method of use.
This patent application is currently assigned to MEDTRONIC, INC.. Invention is credited to Eric H. Bonde, Eric M. Stetz, Carole A. Tronnes.
Application Number | 20100268310 12/827435 |
Document ID | / |
Family ID | 38649316 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100268310 |
Kind Code |
A1 |
Bonde; Eric H. ; et
al. |
October 21, 2010 |
IMPLANTABLE MEDICAL ELECTRICAL STIMULATION LEAD, SUCH AS PNE LEAD,
AND METHOD OF USE
Abstract
An implantable medical electrode lead for stimulation of bodily
tissue. The lead is adapted for use with a needle lumen diameter of
not greater than 0.05 inch, and includes a lead body and a tine
assembly. The lead body has a distal section forming at least one
exposed electrode surface. The tine assembly includes a plurality
of tines each having a base end coupled to an exterior of the lead
body immediately adjacent the exposed electrode surface and a free
end that is movable relative to the lead body to inhibit axial
migration of the lead body upon implantation into a patient. In one
embodiment, the lead body is a PNE lead and provides two electrode
surfaces for bipolar operation.
Inventors: |
Bonde; Eric H.; (Victoria,
MN) ; Stetz; Eric M.; (Coon Rapids, MN) ;
Tronnes; Carole A.; (Stillwater, MN) |
Correspondence
Address: |
CAMPBELL NELSON WHIPPS, LLC
HISTORIC HAMM BUILDING, 408 SAINT PETER STREET, SUITE 240
ST. PAUL
MN
55102
US
|
Assignee: |
MEDTRONIC, INC.
Minneapolis
MN
|
Family ID: |
38649316 |
Appl. No.: |
12/827435 |
Filed: |
June 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11413301 |
Apr 28, 2006 |
|
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|
12827435 |
|
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Current U.S.
Class: |
607/116 |
Current CPC
Class: |
A61N 1/0558
20130101 |
Class at
Publication: |
607/116 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
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34. An implantable medical electrode lead for applying electrical
stimulation to bodily tissue of a patient, the lead comprising: a
lead body having a proximal section adapted to be electronically
coupled to a power source and a distal section forming at least one
exposed electrode surface; and a first tine assembly associated
with the lead body and including a plurality of tines each having a
base end and a free end, wherein the base end of at least one of
the tines is coupled to an exterior of the lead body immediately
adjacent the exposed electrode surface such that the free end is
movable relative to the lead body; wherein the tine assembly is
adapted to inhibit axial migration of the lead body, and wherein
the lead is adapted to be introduced through, and released into,
bodily tissue via a needle having a needle lumen defining an inner
diameter of not greater than 0.05 inch.
35. The implantable lead of claim 34, wherein the exposed electrode
surface defines a proximal end and a distal end, the at least one
tine being coupled to the lead body immediately adjacent the
proximal end.
36. The implantable lead of claim 34, wherein the exposed electrode
surface defines a proximal end and a distal end, the at least one
tine being coupled to the lead body immediately adjacent the distal
end.
37. The implantable lead of claim 34, wherein the at least one tine
is coupled to the lead body distal the exposed electrode
surface.
38. The implantable lead of claim 34, wherein the distal section
forms a plurality of longitudinally spaced exposed electrode
surfaces, and further wherein the first tine assembly is coupled to
the lead body longitudinally between two of the exposed electrode
surfaces.
39. The implantable lead of claim 34, further comprising: a second
tine assembly coupled to the lead body and longitudinally spaced
from the first tine assembly in a proximal direction.
40. The implantable lead of claim 34, wherein the tine assembly is
formed of a non-conductive material.
41. The implantable lead of claim 34, wherein the tine assembly
further includes a band interconnecting the tines, and further
wherein the band is bonded to the lead body.
42. The implantable lead of claim 34, wherein the tine assembly is
assembled to the lead body such that in a natural state, the free
end of each of the tines extends generally proximally relative to
the corresponding base end.
43. The implantable lead of claim 34, wherein each of the tines are
highly pliable.
44. The implantable lead of claim 34, wherein the tine assembly is
configured such that in a natural state, extension of each of the
tines relative to a central axis of the lead body defines an angle
of not more than 15.degree..
45. The implantable lead of claim 34, wherein the lead body
includes a wire wound to form a first coil defining an internal
passage and a non-conductive material disposed over at least a
portion of the coil to define a covered region and an uncovered
region, and further wherein the exposed electrode surface is
defined by the uncovered region.
46. The implantable lead of claim 45, wherein the lead body further
includes a second wire wound to form a second coil, the first and
second coils being co-axially wound to one another with a distal
end of the second coil terminating proximal a distal end of the
first coil, and further wherein the second coil forms a second
exposed electrode surface proximal the exposed electrode surface
formed by the first coil such that the lead body is capable of
bipolar operation.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to systems and methods for
providing electrical stimulation to bodily tissue, such as a
portion of a patient's nervous system. More particularly, it
relates to temporarily implantable electrical leads, such as a
peripheral nerve evaluation lead used to stimulate a sacral nerve,
that resist migration and, in some embodiments, are bipolar.
[0002] A number of human bodily functions are affected by the
nervous system. For example, bodily disorders, such as urinary
incontinence, urinary urge/frequency, urinary retention, pelvic
pain, bowel dysfunction (constipation, diarrhea, etc.), erectile
dysfunction, etc., are all bodily functions influenced by the
sacral nerves. As a point of reference, urinary incontinence is the
involuntary loss of control over the bladder. Incontinence is
primarily treated through pharmaceuticals and surgery. Many
pharmaceuticals do not adequately resolve the issue and can cause
unwanted side effects; further, a number of surgical procedures
have a low success rate and/or are not reversible. Similar
treatment insufficiencies have likewise been noted for many of the
other maladies previously mentioned.
[0003] As an alternative to conventional pharmaceuticals and/or
invasive surgical procedures, neurostimulation has more recently
been recognized as a viable treatment approach for many patients.
By way of background, the organs involved in bladder, bowel, and
sexual function receive much of their control via the second,
third, and fourth sacral nerves, commonly referred to as S2, S3,
and S4, respectively. Electrical stimulation of these various
nerves has been found to offer some control over these functions.
Several electrical stimulation techniques have been suggested,
including stimulation of nerve bundles within the sacrum.
Regardless, in order to consistently deliver electrical stimulation
to the sacral nerve(s), certain anatomical obstacles must be
addressed. The sacrum is a large, triangular bone situated at the
lower part of the vertebral column, and at the upper and back part
of the pelvic cavity. The spinal canal runs through the greater
part of the sacrum. Further, the sacrum is perforated by the
anterior and posterior sacral foramina though which the sacral
nerves pass.
[0004] With the above anatomical description in mind, partial
control over one or more of the functions (or dysfunctions)
previously mentioned has been achieved by implanting a
neurostimulation lead at or near the sacral nerves. As a point of
reference, other nerve(s) or tissue can similarly be electrically
stimulated to produce different effects. Relative to sacral nerve
stimulation, however, the neurostimulation lead, having several
stimulation electrodes, can be permanently implanted within and/or
anteriorly beyond the sacral foramen at which the sacral nerve in
question is anatomically located. Because the lead, and in
particular the stimulation electrodes, must remain in operative
proximity to the sacral nerve, the permanent lead (sometimes
referred to as a "chronic lead") can be sutured within the
patient's body to resist migration. In light of the invasive nature
associated with this approach, minimally invasive neurostimulation
leads have been developed, incorporating features proximal the
electrodes that inhibit migration and/or retrograde dislodgement.
Permanent leads of this type are typically somewhat sizable to not
only present a sufficient number of electrodes, but to also better
resist migration. Regardless, wire cabling from the lead is
implanted within a subcutaneously-formed tunnel and connected to a
subcutaneously-implanted pulse generator. One example of such a
system is available from Medtronic, Inc., of Minneapolis, Minn.
under the trade name InterStim.RTM.. Other chronic leads/systems
are further described in U.S. Pat. Nos. 6,999,819; 6,971,393; and
6,847,849, each commonly assigned to the assignee of the present
invention and the teachings of all of which are incorporated herein
by reference.
[0005] Some patients may view the permanent neurostimulation lead
and related pulse generator implantation described above as being a
fairly traumatic procedure. Thus, efforts are conventionally made
to ascertain in advance whether the patient in question is likely
to receive benefit from sacral nerve stimulation. In general terms,
the test stimulation procedure entails the temporary implantation
of a neurostimulation lead in conjunction with an externally
carried pulse generator or other power source. Once in place, the
patient is exposed to neurostimulation over a trial period (e.g.,
3-7 days) during which the patient can experience the sensation of
nerve stimulation during various everyday activities, as well as
record the changes, if any, in the bodily dysfunction of concern
(e.g., a patient experiencing urinary incontinence can maintain a
voiding diary to record voiding behavior and symptoms with the
stimulation). The record of events is then compared with a base
line and post-test stimulation diaries to determine the effect, if
any, of sacral nerve stimulation on the symptoms being experienced
by the patient. If the test stimulation is successful, the patient
and his/her clinician can make a better informed decision as to
whether permanent implantation and long-term sacral nerve
stimulation is a viable therapy option.
[0006] Temporary implantation of the neurostimulation lead is
normally done in one of two manners. With one approach, sometimes
referred to as a "staged implantation," a conventional, permanent
or chronic neurostimulation lead is implanted at the desired sacral
location, with the cable carrying the coiled conductor wiring being
externally extended through the patient's skin and coupled to the
pulse generator. While viable, this technique entails the use of
surgical equipment normally employed to permanently implant the
stimulation lead. By way of background, implantation of a permanent
sacral nerve stimulation lead normally requires the use of a fairly
large introducer (e.g., an elongated, 13 gauge tube), and the
chronic stimulation lead has a fairly large diameter. While local
and/or general anesthesia is available, some patients may be
apprehensive to participate in a short-term test of this type in
view of the size of the instrument(s)/stimulation lead.
[0007] To better address the reluctance of some patients to
participate in the stimulation test procedure described above, a
second technique has been developed that entails the use of a
smaller diameter, more simplified neurostimulation lead intended to
be implanted on only a temporary basis. In general terms, the
temporary stimulation lead (sometimes referred to as a peripheral
nerve evaluation lead or "PNE" lead) has a single electrode and is
of sufficiently small diameter so as to be percutaneously inserted
using a small diameter needle (e.g., a 20 gauge needle). Many
patients are not overly threatened by a small diameter needle and
thus are more likely to participate in the trial stimulation. The
percutaneous test stimulation is similar to an epidural nerve
block, except that the temporary lead is inserted and left in the
patient's back during the trial. The end of the lead that remains
on the outside of the patient's body is secured to the patient's
skin with, for example, surgical tape. Upon conclusion of the trial
stimulation, the lead is removed from the patient.
[0008] While generally preferred by patients, the percutaneous, PNE
lead technique may have certain drawbacks. For example, while the
temporary simulation lead is highly capable of delivering the
necessary stimulation energy throughout the evaluation period, it
is possible that the lead may migrate. For example, any pulling or
tugging on the proximal end of the lead body (from outside of the
patient's body) could be directly communicated to the lead's
electrode, thus creating a higher likelihood of electrode
dislodgement and poor stimulation. Efforts have been made to
address this concern, for example as described in U.S. Pat. No.
6,104,960, the teachings of which are incorporated herein by
reference and assigned to the assignee of the present invention. In
particular, a temporary neurostimulation lead is described as
having a coiled configuration that better accommodates axial forces
placed onto the lead body (e.g., tugging or pulling on the proximal
end of the lead body). Any additional efforts to further minimize
migration of the temporary neurostimulation lead would be well
received, not only in the one exemplary context of peripheral
sacral nerve electrical stimulation, but also for any other
procedure in which an implantable medical electrical stimulation
lead is used. Further, conventional PNE-type leads incorporate only
one electrode (i.e., a unipolar lead electrode), such that a return
electrode (or ground pad) is typically applied to the patient's
skin. The ground pad may cause the patient some discomfort, and in
some instances can become dislodged or disconnected during the test
period, thus preventing the test stimulation therapy from
occurring.
[0009] In light of the above, a need exists for a medical
electrical lead which may be safely and effectively implanted in a
minimally invasive manner, but which better inhibits axial
migration of dislodgement of the lead body from the stimulation
site, such as a sacral location. Other needs exist for bipolar
PNE-type leads.
SUMMARY OF THE INVENTION
[0010] Aspects in accordance with principles of the present
invention relate to an implantable medical electrode lead for
applying electrical stimulation to bodily tissue. The implantable
medical electrode lead is adapted to be introduced through and
released into bodily tissue via a needle having a needle lumen
defining a diameter of not greater than 0.05 inch. With this in
mind, the lead includes a lead body and a tine assembly. The lead
body has a proximal section adapted to be electronically coupled to
a power source and a distal section forming at least one exposed
electrode surface. The tine assembly includes a plurality of tines
each having a base end and a free end. The tine assembly is
associated with the lead body such that the base end of at least
one of the tines is coupled to an exterior of the lead body
immediately adjacent the exposed electrode surface. With this
configuration, the free end of the at least one tine is movable
relative to the lead body. With this construction, the tines are
adapted to inhibit axial migration of the lead body upon
implantation into a patient. In one embodiment, the tines are
highly pliable. In other embodiments, the lead body is configured
to provide two, longitudinally spaced and electrically isolated
electrode surfaces such that the lead can be operated as a bipolar
lead.
[0011] Other aspects in accordance with principles of the present
invention relate to a system for providing temporary medical
electrical stimulation to bodily tissue of a patient. The system
includes a hollow needle and a flexible lead. The hollow needle
defines a lumen having a diameter of not more than 0.05 inch. The
flexible lead is slidably disposed within the lumen, and includes a
lead body and a tine assembly. The lead body includes a proximal
section adapted to be electrically coupled to a power source (e.g.,
an external pulse generator), and a distal section forming at least
one exposed electrode surface. The tine assembly is associated with
the lead body and includes a plurality of tines each having a base
end and a free end. With this in mind, the base end of at least one
of the tines is coupled to an exterior of the lead body immediately
adjacent the exposed electrode surface such that the free end
thereof is movable relative to the lead body. With this
configuration, the system is adapted to promote minimally invasive
insertion of the flexible lead, with the tine assembly inhibiting
migration of the exposed electrode surface following insertion. In
one embodiment, the lead body includes one or more coiled wires
combining to define a central passage, with the system further
including a stylet slidably disposed within the passage.
[0012] Yet other aspects in accordance with principles of the
present invention relate to a method of providing temporary
electrical stimulation to bodily tissue of a patient at a
stimulation site. The method includes providing a flexible lead
including a lead body and at least one tine assembly. The lead body
has a proximal section and a distal section, with the distal
section forming at least one electrode surface. The tine assembly
includes a plurality of tines each having a base end and a free
end. The tine assembly is associated with the lead body such that
the base end of at least one of the tines is coupled to an exterior
of the lead body immediately adjacent the exposed electrode
surface, with the free end thereof being moveable relative to the
lead body. Further, a hollow needle having a proximal end, distal
end, and lumen is provided, with the needle lumen having a diameter
not greater than 0.05 inch. The flexible lead is slidably inserted
within the needle lumen. The needle is percutaneously directed
toward the stimulation site, and the lead body is deployed and
implanted at the stimulation site. To this end, the exposed
electrode surface and the tine assembly are located at or within
the stimulation site. A stimulation energy is applied to the
exposed electrode surface via a power source electrically coupled
to the lead body. In this regard, the tine assembly inhibits axial
migration of the lead body. In one embodiment, the method is
performed as part of a sacral nerve stimulation procedure, with the
stimulation site being a sacral foramen. In a related embodiment,
the method is characterized by the tine assembly interfacing with
sacral bone. In other embodiments, energies are applied to the
distal section of the lead body in a bipolar mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a simplified plan view of a system for providing
electrical stimulation to bodily tissue of a patient, including an
implantable medical electrical lead in accordance with principles
of the present invention;
[0014] FIG. 2A is an enlarged, perspective view of a portion of one
embodiment of the lead of FIG. 1;
[0015] FIG. 2B is a cross-sectional view of the distal end of the
lead of FIG. 2A;
[0016] FIG. 3A is an enlarged, perspective view of an alternative
embodiment lead in accordance with principles of the present
invention;
[0017] FIG. 3B is a cross-sectional view of a portion of the lead
of FIG. 3A;
[0018] FIG. 4A is an enlarged, perspective view of an alternative
embodiment lead in accordance with principles of the present
invention;
[0019] FIG. 4B is a partial, cross-sectional view of the lead of
FIG. 4A;
[0020] FIG. 5A is a posterior view of a spinal column of a patient,
showing a location of a sacrum relative to an outline of a
body;
[0021] FIG. 5B is a simplified sectional view of a human anatomy in
a region of the sacrum;
[0022] FIG. 6 is a flow diagram relating to a method of evaluating
a peripheral nerve of a patient in accordance with principles of
the present invention; and
[0023] FIG. 7A-7C illustrate temporary implantation of the
neurostimulation lead using the system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0024] One embodiment of a medical electrical lead 20 in accordance
with principles of the present invention is shown in simplified
form in FIG. 1 as part of a system 22 useful for delivering
stimulation energy to a patient (not shown) via a power source 23
(that may or may not be considered part of the system 22). The
system 22 can assume a variety of forms, and can include components
apart from those shown in FIG. 1. In one embodiment, however, the
system 22 includes the lead 20, as well as a needle 24 and a stylet
26. Details on the various components are provided below. In
general terms, however, the lead 20 forms at least one exposed
electrode surface 30, and is sized to be slidably received within
the needle 24. The stylet 26 is sized to be slidably received
within the lead 20. Finally, the power source 23 is electrically
coupled to the lead 20 for providing electrical stimulation to the
exposed electrode surface(s) 30. As described in greater detail
below, the lead 20 is of a reduced size, amenable to being
introduced to a delivery site (e.g., sacral foramen) through a
relatively small-diameter needle 24 (for example, and as described
below, a 20 gauge needle or other needle having an inner diameter
no greater than 0.05 inch). Further, the lead 20 includes one or
more tine assemblies 32 that inhibit migration of the lead 20 once
implanted.
[0025] One embodiment of the lead 20 is shown in greater detail in
FIGS. 2A and 2B. The lead 20 includes a lead body 40 having a
proximal section 42 (referenced generally in FIG. 2B; shown in
greater detail in FIG. 1) and a distal section 44. The proximal
section 42 is adapted to be electrically connected to the power
source 23 (FIG. 1) for example via one or more connector pins 46
(FIG. 1). Conversely, the distal section 44, with the one
embodiment of FIGS. 2A and 2B, forms a plurality of the exposed
electrode surfaces 30, including the electrode surfaces 30a and 30b
(referenced generally). As described in greater detail below, by
providing the two exposed electrode surfaces 30a and 30b in a
longitudinally spaced and electrically isolated arrangement, the
lead 20 of FIGS. 2A and 2B is operable in a bipolar mode (e.g., the
second exposed electrode surface 30b serves as a return or ground
path for electrical current applied at the first exposed electrode
surface 30a). Regardless, the lead 20 further includes a plurality
of the tine assemblies 32, including a first tine assembly 32a and
a second tine assembly 32b.
[0026] The lead body 40 is, in one embodiment, akin to a PNE lead
having a relatively small maximum outer diameter (e.g., not greater
than 0.05 inch, more preferably not greater than 0.04 inch, even
more preferably not greater than 0.03 inch, and in one embodiment
on the order of 0.025 inch, although other dimensions are also
acceptable), such that the lead 20 can be implanted using a small
diameter needle (e.g., the needle 24 (FIG. 1) can have a lumen
diameter corresponding with the outer diameters specified above,
for example as found with conventional 20 gauge or 19 gauge foramen
needles). With this in mind and with specific reference to FIG. 2B,
in one embodiment the lead body 40 includes first and second wires
50, 52 that are each wound in coil form (along at least the distal
section 44), combining to form a lumen 54. In one embodiment, the
first and second wires 50, 52 are co-axially inter-wound relative
to one another, with a distal end 56 of the first wire/coil 50
extending distal a distal end 58 of the second wire/coil 52. Both
of the wires 50, 52 can be closely wound as shown; in other
embodiments, one or both of the wires 50, 52 can have a slight
spacing between individual windings. Further, the coiled nature of
the wires 50, 52 can be continued along the proximal section 42;
alternatively, the wires 50, 52 can be straight or non-coiled
proximal the distal section 44. Regardless, each of the wires/coils
50, 52 are formed of an electrically conductive material (e.g.,
stainless steel such as SST 316L stainless steel multi filament
wire, MP35N alloy, etc.) such that electrical energy applied to the
proximal section 42 readily conducts to the distal section 44 along
each of the wires 50, 52. The coiled configuration of the wires 50,
52 along the distal section 44 imparts a longitudinal strain relief
attribute to the lead body 40 such that any tugging or pulling on
the proximal section 42 will not automatically be translated to the
electrode(s) 30a and/or 30b.
[0027] Portions of each of the wires/coils 50, 52 are coated or
exteriorly covered by an electrically non-conductive or insulative
material 60. In one embodiment, the non-conductive material 60 is
ETFE (a polymer of tetrafluoroethylene and ethylene), although
other materials such as PTFE, polyurethane, fluoropolymers,
silicone rubber, polyester, etc., are also useful. Further, while
FIG. 2B illustrates the non-conductive material 60 as encircling or
encompassing a circumference of the wires 50, 52, in other
embodiments, the non-conductive material 60 can be applied to a
lesser extent.
[0028] Regardless of the material and manufacturing technique
selected, at least one region 62 (referenced generally) of the
first wire/coil 50 and at least one region 64 (referenced
generally) of the second wire/coil 52 are not covered by the
non-conductive material 60, thus defining the exposed electrode
surfaces 30a, 30b. For example, in one embodiment, the uncovered
region 62 of the first wire/coil 50 is defined by simply not
coating the non-conductive material 60 to that region (e.g., the
non-conductive material 60 is applied to a portion of a length of
the wire 50 prior to coiling), whereas the uncovered region 64 of
the second wire/coil 52 can be formed by first coating an entirety
of the second wire/coil 52 with the non-conductive material 60, and
then removing (e.g., etching) the non-conductive material 60 from a
portion of the second wire/coil 52 so as to define the uncovered
region 64. Alternatively, a wide variety of other manufacturing
techniques are also available.
[0029] The tine assemblies 32a, 32b are associated with the lead
body 40 with at least one of the tine assemblies 32a and/or 32b
being in close proximity to at least one of the exposed electrode
surfaces 30a and/or 30b. In one embodiment, the tine assemblies
32a, 32b are highly similar in construction, such that the
following description of the tine assembly 32a applies equally to
the second tine assembly 32b. With this in mind, the tine assembly
32a includes, in one embodiment, a plurality of tines 70 and a band
72. Each of the tines 70 defines a length from a base end 74 to a
free end 76 (as a point of reference, the base end 74 and the free
end 76 are identified for one of the tines 70 in each of FIGS. 2A
and 2B). The base end 74 of each the tines 70 is connected to the
band 72 that in turn is coupled or affixed to the lead body 40.
With this configuration, then, the tines 70 are movable relative to
the lead body 40 whereby the free end 76 of each of the tines 70 is
capable of splaying or extending radially outwardly relative to a
central axis A defined by the distal section 44.
[0030] As a point of reference, the tines 70 are shown in FIG. 2A
as being splayed away from the lead body 40 for purposes of
illustration. In one embodiment, however, the tine assemblies 32,
and in particular the tines 70, are highly pliable due to one or
both of a material selection and/or thickness. In one embodiment,
the highly pliable nature of the tines 70 is a function of the
material selected; in one embodiment, the tine assemblies 32 are
formed of a soft polymeric material such as polyurethane, silicone,
PTFE, polyester, etc. With this configuration, then, apart from
having an initial orientation in which the free end 76 of each of
the tines 70 is positioned proximal the corresponding base end 74,
the tines 70 do not have a predetermined spatial orientation in the
absence of an external force. In other words, the tines 70 do not,
in one embodiment, have shape memory or other attributes that would
otherwise cause the tines 70 to automatically or self-revert to the
orientation reflected in FIG. 2A. Stated otherwise, in the absence
of an external force directing the free end 76 away from the lead
body 40 (e.g., where the free end 76 is in contact with bodily
tissue and the lead body 40 is pulled or forced in a proximal
direction) extension of the tine 70 from the lead body 40 relative
to the central axis A defines an angle of no more than 15.degree.,
more preferably no more than 10.degree., in a natural state of the
lead 20. In other embodiments, however, the tine 70 can have a
shape memory attribute otherwise causing the tines 70 to extend in
a generally radially outward fashion relative to the lead body
40.
[0031] In one embodiment, at least one of the tine assemblies 32a
and/or 32b is assembled to the distal section 44 of the lead body
40 in highly close proximity to one of the exposed electrode
surfaces 30a, 30b. For example, with the one embodiment of FIGS. 2A
and 2B, the first tine assembly 32a is positioned in highly close
proximity to the first exposed electrode surface 30a, whereas the
second tine assembly 32b is in highly close proximity to the second
exposed electrode surface 30b. With specific reference to the tine
assembly 32a, the band 72 is coupled to the uncovered region 62 of
the first wire/coil 50, it being understood that where the tine
assembly 32a/band 72 is formed of an electrically non-conductive
material (e.g., akin to the non-conductive material 60), the band
72 effectively serves as a short extension of the non-conductive
material 60, resulting in the exposed electrode surface 30a as
shown (i.e., a longitudinal length of the exposed electrode surface
30a is less than a longitudinal length of the uncovered region 62).
Where the tine assembly 32a is formed of a polymeric material, the
exposed metal wire associated with the uncovered region 62 provides
a surface highly amenable to bonding with the band 72 (otherwise
formed of a polymeric material) via an appropriate adhesive.
[0032] Regardless, the base end 74 of at least one, preferably all,
of the tines 70 is thus coupled to the lead body 40 immediately
adjacent the first exposed electrode surface 30a (i.e., the base
end 74 is longitudinally spaced from the exposed electrode surface
30a by a distance of no more than 0.125 inch; more preferably no
more than 0.065 inch; even more preferably no more than 0.03125
inch). In fact, in some embodiments, the base end 74 of at least
one, preferably all, of the tines 70 can be affixed onto the first
exposed electrode surface 30a (along a length thereof), for example
where the band 72 is not included. Further, while with the one
embodiment of FIGS. 2A and 2B the first tine assembly 32a is
located proximal the first exposed electrode surface 30a, in other
embodiments, one or more of the tine assemblies 32 can be
positioned distal, preferably immediately distal, the first exposed
electrode surface 30a. For example, the second tine assembly 32b is
formed distal the second exposed electrode surface 30b, with the
base end 74 of each of the tines 70 associated with the second tine
assembly 32b being coupled to the distal section 44 immediately
adjacent the second exposed electrode surface 30b as previously
described. As described in greater detail below, positioning of the
tine assemblies 32 in accordance with this one embodiment enhances
an ability of the lead 20 to resist migration following
implantation.
[0033] While the tine assemblies 32 are shown in FIG. 2A as each
including four of the tines 70, any other number, either greater or
lesser, can be provided. Further, while the tine 70 associated with
each of the tine assemblies 32 are illustrated as being
approximately equidistantly spaced about a circumference of the
lead body 40, a non-equidistant spacing can also be employed.
[0034] The tine assemblies 32 can be formed in a wide variety of
fashions. In one embodiment, for example, the tine assemblies 32
are formed from an extruded tubing that is then cut to define the
tines 70 (with the uncut portion forming the band 72).
Alternatively, the tine assemblies 32 can be formed by capturing a
plurality of strands (e.g., sutures strands) under a small section
of tubing that is otherwise assembled to the lead body 40. With
this configuration, then, the strands define the tines 70, whereas
the small section of tubing forms the band 72. Other construction
techniques, such as providing the tine assembly 32 as a molded
component, are also acceptable. Regardless, the tine assemblies 32
can be assembled to the lead body 40 as previously described (i.e.,
use of an adhesive to bond the band 72 to metal associated with the
respective uncovered regions 62, 64 of the first and second wires
50, 52). Alternatively, one or more of the tine assemblies 32 can
be adhered to the non-conductive material 60 with an appropriate
adhesive; shrink-fitting the tine assemblies 32 over the lead body
40 (e.g., at or along the respective uncovered regions 62 or 64,
and/or over the non-conductive material 60); etc.
[0035] While the lead 20 has been described as including a
plurality of the exposed electrode surfaces 30 and a plurality of
the tine assemblies 32, in other embodiments, a single one of the
exposed electrode surfaces 30 and/or the tine assemblies 32 can be
provided. For example, FIGS. 3A and 3B illustrate an alternative
embodiment lead 90 in accordance with principles of the present
invention. The lead 90 includes a lead body 92 and a tine assembly
94. The lead body 92 defines a proximal section (not shown) and a
distal section 96, with the distal section 96 forming an exposed
electrode surface 98. Similar to previous embodiments, the tine
assembly 94 includes a plurality of tines 100 each having a base
end 102 and a free end 104. The tine assembly 94 is coupled to the
lead body 92 such that the base end 102 of at least one, preferably
all, of the tines 100 are immediately adjacent the exposed
electrode surface 98.
[0036] As best shown in FIG. 3B, the lead body 92 is defined by a
wire 110 wound as a coil (at least along the distal section 96) to
define a lumen 112. Once again, the lumen 112 is sized to slidably
receive the stylet 26 (FIG. 1). With the one embodiment of FIG. 3B,
the lead 90 further includes a core 114 comprised of, in one
embodiment, a solid cylindrical stainless steel material (or other
materials such as MP35N, PtIr, etc. The wire/coil 110 is crimped to
the core 114; to this end, a crimp skirt (not shown) can be
employed at an exterior of the wire/coil 110 to ensure assembly of
the core 114. The core 114 closes the lumen 112 so as to inhibit
passage of the stylet 26 distally through the lead body 92. In one
embodiment, the core 114 can be configured to elute a therapeutic
substance (e.g., a pharmacologic agent, such as the steroid
dexamethasone). In yet other embodiments, the core 114 can be
eliminated.
[0037] Regardless of whether the core 114 is provided, a portion of
the wire/coil 110 is encompassed by an electrically non-conductive
material 116 (akin to the non-conductive material 60 (FIGS. 2A and
2B) previously described) so as to define the exposed electrode
surface 98. The resultant lead body 92 has, in some embodiments, a
relatively small outer diameter (e.g., in accordance with the
dimensions recited above with respect to the lead body (FIG. 2B)),
such that the lead body 92 is akin to a convention PNE lead,
appropriately sized for deployment via a small diameter needle
(e.g., a 19 or 20 gauge foramen needle). Further, by forming only
the one electrode surface 98, the lead 90 of FIGS. 3A and 3B is a
unipolar lead. In alternative constructions, the lead body 92 can
be comprised of two or more components that combine to define the
exposed electrode surface 98, whereas a remainder of the lead body
92 does not conduct energy from an external surface thereof.
[0038] As previously described, the tine assembly 94 can assume any
of the configurations previously provided with respect to the tine
assemblies 32a, 32b (FIGS. 2A and 2B). Regardless, with the one
embodiment of FIGS. 3A and 3B, the tine assembly 94 is associated
with the lead body 92 such that at least one, preferably all, of
the tines 100 are positioned distal (and/or immediately adjacent)
at least a portion of the exposed electrode surface 98.
[0039] Yet another alternative embodiment lead 130 in accordance
with principles of the present invention is shown in FIGS. 4A and
4B. Once again, the lead 130 includes a lead body 132 and a
plurality of tine assemblies 134 (referenced generally in FIG. 4A).
The lead body 132 includes a proximal section (not shown) and a
distal section 136 otherwise providing an exposed electrode surface
138. Similar to the embodiment of FIGS. 3A and 3B, the lead body
132 of FIGS. 4A and 4B provides one exposed electrode surface 138,
and thus is suited for operation in a unipolar manner (that might
otherwise require a separate return electrode (not shown)).
Regardless, the plurality of tine assemblies 134 are similar to
previous embodiments, and include first-third tine assemblies
134a-134c (identified in FIG. 4B), each including a plurality of
tines 140.
[0040] The first or distal-most tine assembly 134a is associated
with the lead body 132 such that at least one, preferably all, of
the tines 140 associated therewith are positioned immediately
adjacent the exposed electrode surface 138 as previously described.
The second and third tine assemblies 134b, 134c are longitudinally
spaced from the exposed electrode surface 130. With this one
embodiment, then, at least one of the tine assemblies 134 (i.e.,
the first tine assembly 134a) is positioned immediately adjacent
the exposed electrode surface 138, whereas one or more of the tine
assemblies 134 (e.g., the third tine assembly 134c) is not
immediately adjacent the exposed electrode surface 138, but instead
is longitudinally spaced therefrom (e.g., by a longitudinal
distance of at least 0.125 inch).
[0041] Returning to FIG. 1, the system 22, and in particular the
lead 20 (or the lead 90 (FIGS. 3A and 3B) or the lead 130 (FIGS. 4A
and 4B)), in accordance with principles of the present invention
can be utilized to provide medical electrical stimulation from the
external power source 23 to a wide variety of bodily structures via
a percutaneous approach. For example, the system 22 can be deployed
to stimulate one or more nerves of the nervous system.
Alternatively, the system 22 can be used in other applications
requiring electrical stimulation, such as procedures to
rehabilitate muscle dysfunction by neuromodulation (e.g.,
functional electrical stimulation) of muscular behavior. In one
embodiment, however, the system 22 is employed to provide
electrical stimulation to a sacral nerve(s), for example as part of
a peripheral sacral nerve simulation test or evaluation. With
respect to this one exemplary application, FIG. 5A provides a
posterior view of a spinal column 150 showing a location of a
sacrum 152 relative to an outline of a patient's body 154. As
shown, the sacrum 152 has a series of holes or foramen 156
therethrough. Each foramen 156 provides access to sacral ventral
nerves (not shown). This relationship is further illustrated in
FIG. 5B whereby sacral nerves (a peripheral sacral nerve of which
is illustrated schematically and generally referenced at 158)
extend along the sacrum 152, generally opposite a dorsal surface
160 of the patient's body 154, and through or from a sacral canal
162. FIG. 5B further illustrates a pelvic surface 164 and a dorsal
surface 165 of the sacrum 152.
[0042] With the above anatomical conventions in mind, one method of
evaluating a peripheral sacral nerve 158 in accordance with
principles of the present invention is provided by the flow diagram
of FIG. 6, as well as the illustrations of FIGS. 7A-7C. As a point
of reference, the foregoing description relates to use of the lead
20 of FIGS. 2A and 2B, it being understood that the leads 90, 130
are equally applicable. At step 170, the system 22 is arranged such
that a portion of the lead 20 is slidably received within the
needle 24, and the stylet 26 is slidably received within the lumen
54 (FIG. 2B) of the lead body 40. As previously described, the lead
body 40 has a relatively small diameter such that the needle 24 and
its corresponding needle lumen can also be of a small diameter, for
example, a 19 gauge or 20 gauge thin wall metal needle (e.g., the
needle lumen diameter provided with 20 gauge foramen needles
available from Medtronic, Inc., of Minneapolis, Minn. under product
numbers 041828 or 041829). In one embodiment, the needle 24 is
preferably insulated with a non-conductive coating (e.g., a
parylene coating) along its outer surface except at a distal tip
and a proximal end thereof. This permits the needle tip to
electrically stimulate nerves to assess whether a desired location
has been obtained by the needle tip during the implant procedure.
Regardless, at step 172, the needle 24 is percutaneously delivered
to the sacrum 152, and at step 174, one of the foramen 156 is
located as shown in FIG. 7A, for example using conventional
techniques (e.g., energizing a distal end of the needle 24 and
observing physical reactions by the patient). As a point of
reference, in some embodiment, location of the foramen 156 by the
needle 24 prior to assembling the lead 20/stylet 26 within the
needle lumen. Thus, step 170 can occur after step 174.
[0043] Once the foramen 156 is located, the distal section 44 of
the lead 20 is delivered to and/or through the located foramen at
step 176. In one embodiment, delivery of the distal section 44 of
the lead 20 through the foramen 156 is achieved by distally
advancing the lead 20 relative to the needle 24 as shown in FIG.
7B. To this end, the stylet 26 assists in achieving distal movement
of the lead 20, serving to render the lead body 40 more rigid and
thus capable of pushing through the foramen 156/bodily tissue.
[0044] At step 178, the lead body 40 is positioned at a desired
location or stimulation site 166 (referenced generally) that is
otherwise in operative proximity to one of the sacral nerves, such
as the sacral peripheral nerve 158 in FIG. 7B. The operatively
proximate position is characterized by the patient exhibiting a
physical response to an electrical stimulation applied to the lead
body 40 (and in particular, the exposed electrode surface 30) in a
manner otherwise indicative of a sacral nerve being electrically
stimulated. As a point of reference, precise positioning of the
distal section 44 relative to the sacral nerve 158 in question is
not required so long as once an operatively proximate position is
achieved, the distal section 44 does not overtly migrate (i.e.,
axially migrate or dislodge back through the foramen 156). Thus, as
shown in FIG. 7C, the lead body 40 can be positioned such that the
exposed electrode surface 30 is in close proximity to the sacral
nerve 158; alternatively, a spacing between the exposed electrode
surface 30 and the sacral nerve 158 can be present. Regardless, in
connection with directing the distal section 44 to the desired
location 166, one or more of the tine assemblies 32 (for example,
the distal tine assembly 32a) is inserted anterior beyond the
dorsal surface 165 and can contact and/or nearly contact one or
more of the sacral nerves (e.g., the sacral peripheral nerve 158).
Due to the preferred, highly pliable construction of the tines 70,
the sacral nerves 158 will not be damaged if contacted by the tine
70.
[0045] As shown in FIG. 7C, in the operatively proximate location
166, at least one of the tine assemblies 32 (e.g., the tine
assembly 32a) is located adjacent the pelvic surface 164, with
another of the tine assemblies 32 (e.g., the tine assembly 32b)
being located within the foramen 156 and anteriorly beyond the
dorsal surface 165. Thus, at step 180, whereby the implantation is
completed and the proximal section 42 is secured (e.g., surgically
taped) to an exterior of the patient's body 154, the tine
assemblies 32 resist or impede axial dislodgement of the distal
section 44 of the lead body 40 axially back through the foramen 156
by engaging or contacting the boney surfaces presented by the
sacrum 152. For example, in one embodiment, at least one of the
tines 70 associated with the distal-most tine assembly 32a contacts
or abuts the sacrum 152 at or adjacent the pelvic surface 164, and
in some embodiments is anteriorly beyond the pelvic surface 164.
Further, one or more of the tine assemblies (e.g., the second tine
assembly 32b) contacts the rigid boney material otherwise forming
the foramen 156 within which the tine assembly 32b is located, for
example within the sacral canal 162 and/or anteriorly adjacent the
dorsal surface 165. Thus, by interfacing with rigid, boney
structures, a more complete fixation of the lead 20 in the
operatively proximate location (or stimulation site) 166 can be
achieved. Further, the sacral foramen 156 is covered with a
membraneous connective tissue along the dorsal side thereof; this
tissue can provide an ideal surface to interact with the tines 70
and provide a level of fixation.
[0046] Once implanted, at step 182, the proximal section 42 is
electrically coupled to the power source 23 (FIG. 1) that is
otherwise located external the patient's body 154. The power source
23 can assume a wide variety of forms, but in one embodiment, is a
pulse generator, for example a Model 3625 InterStim.RTM. Test
Stimulator available from Medtronic, Inc., of Minneapolis,
Minn.
[0047] Following the above-described implantation methodology, in
one embodiment the implanted lead 20/external power source 23 is
operated over the course of several or more days at step 184 to
periodically electrically stimulate the sacral nerve 158. With the
one embodiment of FIGS. 7A-7C, the lead 20, and in particular the
lead body 40, provides a bipolar mode of operation via the first
and second exposed electrode surfaces 30a, 30b. In other
embodiments, however, the lead 20 can be of a unipolar design
(i.e., providing only a single exposed electrode surface) such that
a return electrode (not shown) is also provided and secured to the
patient's skin. Following the test period, an evaluation can be
made, based, for example, upon records kept by the patient during
the test period, as to whether a permanently-implanted nerve
stimulation system is a viable option.
[0048] Regardless, at step 186, upon completion of the test period,
the lead 20 is removed from the patient by releasing the proximal
section 42 from the patient's skin, and then applying a slight
pulling or retraction force thereto. This retraction force removes
the distal section 44 from the operatively proximate location 166
and back through the initial point of insertion through the
patient's skin. In this regard, the tine assemblies 32a, 32b do not
overtly resist this removal. For example, the tines 70 readily fold
back over themselves (i.e., the tines 70 associated with the first
tine assembly 32a will fold over onto themselves as the lead 20 is
retracted through the foramen 156).
[0049] The medical electrical lead, and related system and method
of use, of the present invention provides a marked improvement over
previous designs. The lead is readily and temporarily implanted via
a small diameter needle, thus addressing concerns raised by some
patients. In addition, the tine assembly or assemblies inhibit
axial migration of the lead body once implanted while presenting
little or no opportunities for damaging the patient tissue
contacted by the tine assemblies, for example nerves.
[0050] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the present invention. For
example, while the lead has been described as including or
providing one or two electrodes, in other embodiments, a
multiplicity of electrodes are carried by the lead.
* * * * *