U.S. patent application number 11/130000 was filed with the patent office on 2005-09-22 for stimulation/sensing lead adapted for percutaneous insertion.
This patent application is currently assigned to Advanced Neuromodulation Systems, Inc., a Texas corporation. Invention is credited to Daglow, Terry, Drees, Scott F., Erickson, John H., Munson, John Connell JR..
Application Number | 20050209667 11/130000 |
Document ID | / |
Family ID | 34987368 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050209667 |
Kind Code |
A1 |
Erickson, John H. ; et
al. |
September 22, 2005 |
Stimulation/sensing lead adapted for percutaneous insertion
Abstract
The present invention relates to a percutaneous
insertion-capable lead, wherein insertion made through a
percutaneous insertion structure. For one embodiment of such lead,
the electrode-supporting stimulation portion of the lead includes
at least one waisted region, relative to a transverse dimension of
the lead, to facilitate lead steerability.
Inventors: |
Erickson, John H.; (Plano,
TX) ; Drees, Scott F.; (McKinney, TX) ;
Daglow, Terry; (Allen, TX) ; Munson, John Connell
JR.; (McKinney, TX) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
2001 ROSS AVENUE, 6TH FLOOR
DALLAS
TX
75201-2980
US
|
Assignee: |
Advanced Neuromodulation Systems,
Inc., a Texas corporation
|
Family ID: |
34987368 |
Appl. No.: |
11/130000 |
Filed: |
May 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11130000 |
May 16, 2005 |
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09927225 |
Aug 10, 2001 |
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6895283 |
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Current U.S.
Class: |
607/116 |
Current CPC
Class: |
A61B 17/3401 20130101;
A61B 5/287 20210101; A61B 5/6852 20130101; A61N 1/0553 20130101;
A61B 17/3468 20130101 |
Class at
Publication: |
607/116 |
International
Class: |
A61N 001/05 |
Claims
What is claimed is:
1. A percutaneous insertion-capable lead having a plurality of
terminals and a plurality of conductors, such lead being adapted to
pass through a percutaneous introduction structure for insertion
into a human body, the lead further comprising: a body defining a
paddle structure that is substantially defined by two principal
opposing planar surfaces; and a plurality of electrodes, wherein
one of the two planar surfaces incorporates the plurality of
electrodes, and a conductor of the plurality of conductors
electrically couples one terminal of the plurality of terminals
with at least one electrode of the plurality of electrodes, and
wherein a greatest transverse dimension of the body of the lead is
less than a corresponding interior dimension of the percutaneous
introduction structure.
2. A lead in accordance with claim 1, further comprising a channel
extending from a proximal end of the lead to a position within the
body of the lead, wherein the channel is adapted to receive a
stylet.
3. A lead in accordance with claim 2, wherein the body of the lead
has a varying cross-sectional moment of inertia.
4. A percutaneous insertion-capable lead having a distal end
portion and a proximal end portion, such lead being adapted to pass
through a percutaneous introduction structure for insertion into a
human body, the lead further comprising: a plurality of terminals
positioned at the proximal end portion; a paddle-shaped body
positioned at the distal end portion, wherein the body of the lead
includes two principal opposing substantially planar surfaces; a
plurality of electrodes, which are carried on one of the two
principal surfaces of the body of the lead; and a plurality of
conductors, wherein a conductor of the plurality of conductors
electrically couples one terminal of the plurality of terminals
with at least one electrode of the plurality of electrodes, and
wherein the body of the lead has a varying transverse dimension
that enables flexibility in a plane substantially parallel to the
principal surfaces of the body of the lead.
5. A lead in accordance with claim 4, further comprising a channel
extending from the proximal end portion to a position within the
body of the lead, wherein the channel is adapted to receive a
stylet.
6. A percutaneous insertion-capable lead having a distal end
portion and a proximal end portion, such lead being adapted to pass
through a percutaneous insertion structure for insertion into a
human, the lead further comprising: a plurality of terminals
positioned at the proximal end portion; a paddle-shaped body
positioned at the distal end portion, wherein the body includes two
principal opposing substantially planar surfaces and at least one
waisted region; a plurality of electrodes, which are carried on one
of the two principal surfaces of the body; and a plurality of
conductors, wherein a conductor of the plurality of conductors
electrically couples one terminal of the plurality of terminals
with at least one electrode of the plurality of electrodes.
7. A lead in accordance in claim 6, wherein the at least one
waisted region is formed by a narrowing of the body in a transverse
direction.
8. A lead in accordance with claim 6, further comprising a channel
extending from the proximal end portion of the lead to a position
within the body, wherein the channel is adapted to receive a
stylet.
Description
TECHNICAL FIELD
[0001] The present invention relates to an epidural stimulation
lead, and in particular, to an epidural stimulation lead adapted
for percutaneous insertion.
BACKGROUND
[0002] Application of specific electrical fields to spinal nerve
roots, spinal cord, and other nerve bundles for the purpose of
chronic pain control has been actively practiced since the 1960s.
While a precise understanding of the interaction between the
applied electrical energy and the nervous tissue is not fully
appreciated, it is known that application of an electrical field to
spinal nervous tissue (i.e., spinal nerve roots and spinal cord
bundles) can effectively mask certain types of pain transmitted
from regions of the body associated with the stimulated tissue.
More specifically, applying particularized electrical energy to the
spinal cord associated with regions of the body afflicted with
chronic pain can induce paresthesia, or a subjective sensation of
numbness or tingling, in the afflicted bodily regions. This
paresthesia can effectively mask the transmission of non-acute pain
sensations to the brain.
[0003] It is known that each exterior region, or each dermatome, of
the human body is associated with a particular spinal nerve root at
a particular longitudinal spinal position. The head and neck
regions are associated with C2-C8, the back regions extend from
C2-S3, the central diaphragm is associated with spinal nerve roots
between C3 and C5, the upper extremities correspond to C5 and T1,
the thoracic wall extends from T1 to T11, the peripheral diaphragm
is between T6 and T11, the abdominal wall is associated with T6-L1,
the lower extremities are located from L2 to S2, and the perineum
from L4 to S4. By example, to address chronic pain sensations that
commonly focus on the lower back and lower extremities, a specific
energy field can usually be applied to a region between bony level
T8 and T10. As should be understood, successful pain management and
the avoidance of stimulation in unafflicted regions necessarily
requires the applied electric field to be properly positioned
longitudinally along the dorsal column.
[0004] Positioning of an applied electrical field relative to a
physiological midline is equally important. Nerve fibers relating
to certain peripheral areas extend between the brain and a nerve
root along the same relative side of the dorsal column as the
corresponding peripheral areas. Pain that is concentrated on only
one side of the body is "unilateral" in nature. To address
unilateral pain, electrical energy is applied to neural structures
on the side of a dorsal column that directly corresponds to a side
of the body subject to pain. Pain that is present on both sides of
a patient is "bilateral." Accordingly, bilateral pain is addressed
through either an application of electrical energy along a
patient's physiological midline or an application of electrical
energy that transverses the physiological midline.
[0005] Pain-managing electrical energy is commonly delivered
through electrodes positioned external to the dura layer
surrounding the spinal cord. The electrodes are carried by two
primary vehicles: a percutaneous catheter and a laminotomy
lead.
[0006] Percutaneous catheters, or percutaneous leads, commonly have
a circular cross-section (.about.0.05 inches) and three or more,
equally-spaced ring electrodes. Percutaneous leads are placed above
the dura layer of a patient using a Touhy-like needle. For
insertion, the Touhy-like needle is passed through the skin,
between desired vertebrae, to open above the dura layer. For
unilateral pain, percutaneous leads are positioned on a side of a
dorsal column corresponding to the "afflicted" side of the body, as
discussed above, and for bilateral pain, a single percutaneous lead
is positioned along the patient midline (or two or more leads are
positioned on each side of the midline).
[0007] Laminotomy leads have a paddle configuration and typically
possess a plurality of electrodes (for example, two, four, eight,
or sixteen) arranged in one or more columns. An example of a
sixteen-electrode laminotomy lead is shown in FIG. 1. Using the
laminotomy lead of FIG. 1 as but one example, the paddle portion of
the laminotomy lead is approximately 0.4 inches wide and a
thickness of approximately 0.065 inches. Common to laminotomy
leads, the exposed surface area of the plurality of electrodes is
confined to only one surface of the laminotomy lead, thus
facilitating a more focused application of electrical energy.
[0008] It is typical that implanted laminotomy leads are
transversely centered over the physiological midline of a patient.
In such position, multiple columns of electrodes are well suited to
address both unilateral and bilateral pain, where electrical energy
may be administered using either column independently (on either
side of the midline) or administered using both columns to create
an electric field which traverses the midline. A multi-column
laminotomy lead enables reliable positioning of a plurality of
electrodes, and in particular, a plurality of electrode columns
that do not readily deviate from an initial implantation
position.
[0009] Given the relative dimensions of conventional laminotomy
leads, a surgical procedure is necessary for implantation. The
surgical procedure, or partial laminectomy, requires the resection
and removal of certain vertebral tissue to allow both access to the
dura and proper positioning of a laminotomy lead. The laminotomy
lead offers a more stable platform, which is further capable of
being sutured in place, that tends to migrate less in the operating
environment of the human body.
[0010] Percutaneous leads require a less-invasive implantation
method and, with a plurality of leads, provide a user the ability
to create almost any electrode array. While laminotomy leads are
likely more stable during use, these leads do not offer an
opportunity for electrode array variance as the configuration of
such arrays are fixed.
[0011] To supply suitable pain-managing electrical energy,
stimulation leads are connected to multi-programmable stimulation
systems, or energy sources (not shown). Typically, such systems
enable each electrode of a connected stimulation lead to be set as
an anode (+), a cathode (-), or in an OFF-state. As is well known,
an electric current "flows" from an anode to a cathode.
Consequently, using the laminotomy lead of FIG. 1 as an example, a
range of very simple to very complex electric fields can be created
by defining different electrodes in various combinations of (+),
(-), and OFF. Of course, in any instance, a functional combination
must include at least one anode and at least one cathode.
[0012] Notwithstanding the range of electric fields that are
possible with conventional stimulation leads, in certain instances
it is necessary to concentrate electrical energy at a particular
point, or over a small region. As an example of such occasion,
assume pain-managing electrical energy is applied at or about T8 to
address only localized lower back pain. At T8, however, spinal
nervous tissue corresponding to the patient's lower extremities
commingles with the specific spinal nervous tissue associated with
the lower back. Moreover, it is common that the lower back-related
spinal nervous tissue is deeply embedded within the combined spinal
nervous tissue. It is thus desirable to focus applied electrical
energy to the targeted nervous tissue to (i) reach the deeply
situated target nervous tissue and (ii) avoid undesirable
stimulation of unafflicted regions.
[0013] Accordingly, a need exists for a percutaneously insertable
stimulation lead that facilitates an application of delivered
electrical energy in a manner consistent with that delivered
through conventional laminotomy leads.
SUMMARY OF THE INVENTION
[0014] One aspect of certain embodiments of the present invention
is drawn to a stimulation lead having a plurality of electrodes, a
plurality of terminals, and a plurality of conductors, wherein a
conductor of the plurality of conductors electrically couples one
terminal of the plurality of terminals with at least one electrode
of the plurality of electrodes. Although this lead is adapted to
pass through a percutaneous introduction device for insertion into
a human body, the lead includes a body defining a paddle structure
that is substantially defined by two principal opposing planar
surfaces. One of the two planar surfaces incorporate the plurality
of electrodes; however, a greatest transverse dimension of the body
is less than a corresponding interior dimension of a percutaneous
introduction device used for insertion of the lead into a human
body.
[0015] Another aspect of certain embodiments of the present
invention includes providing the body of the lead with at least one
waisted region that effectively increases the flexibility of the
body.
[0016] Another aspect of certain embodiments of the present
invention is drawn to a method of placing a lead in a human
patient. This method concerns providing a lead, percutaneously
accessing a site proximate to a desired lead placement site through
formation of an access passage, and directing the lead through the
access passage to the desired lead placement site. The lead
includes a body having two principal surfaces arranged opposite to
one another, each of such surfaces being substantially planar, and
at least one waisted region; a plurality of terminals; a plurality
of electrodes positioned relative to one principal surface of the
body; and a plurality of conductors. A conductor electrically
couples one terminal of the plurality of terminals with at least
one electrode.
[0017] An object of certain embodiments of the present invention is
to provide a paddle-type lead, capable of either delivering
stimulation or sensing electrical activity, which includes a
plurality of electrodes but is adapted to be inserted and
positioned within a human body via percutaneous access.
[0018] Another object of certain embodiments of the present
invention is to provide a paddle-type lead that includes certain
features to increase the flexibility of such lead, thus enhancing
the steerability of such lead.
[0019] Other objects and advantages of certain embodiments of the
present invention will be apparent to those of ordinary skill in
the art having reference to the following specification together
with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the drawings, like reference numerals and letters
indicate corresponding parts throughout the several views:
[0021] FIG. 1 is a plan view of a conventional laminotomy spinal
cord stimulation lead;
[0022] FIG. 2 is a plan view of a laminotomy spinal cord
stimulation lead that illustrates the fundamental principle of
construction of one aspect of certain embodiments of the present
invention;
[0023] FIG. 3 is a plan view of a first embodiment of a laminotomy
spinal cord stimulation lead in accordance with one aspect of
certain embodiments of the present invention;
[0024] FIG. 4 is a plan view of a second embodiment of a laminotomy
spinal cord stimulation lead in accordance with one aspect of
certain embodiments of the present invention;
[0025] FIG. 5 is a plan view of a third embodiment of a laminotomy
spinal cord stimulation lead in accordance with one aspect of
certain embodiments of the present invention;
[0026] FIG. 6 illustrates a percutaneous implantation of the
laminotomy spinal cord stimulation lead of FIG. 3;
[0027] FIG. 7A illustrates a lower surface of another embodiment of
a percutaneous laminotomy lead in accordance with certain
embodiments of the present invention, FIG. 7B is a plan view of the
percutaneous laminotomy lead of FIG. 7A, and FIG. 7C is a
perspective view of the percutaneous laminotomy lead of FIGS. 7A
and 7B;
[0028] FIG. 8A illustrates a straight stylet for placement within a
passage formed within the percutaneous laminotomy leads of certain
embodiments of the present invention, and FIG. 8B illustrates a
bent stylet also for placement within a passage formed within the
percutaneous laminotomy leads of certain embodiments of the present
invention;
[0029] FIGS. 9A, 9B, and 9C illustrate a functional relationship
between the bent stylet of FIG. 8A and the percutaneous laminotomy
leads of at least one of FIGS. 7B, 10A, and 11;
[0030] FIG. 10A is a plan view of another embodiment of a
percutaneous laminotomy lead in accordance with certain embodiments
of the present invention, and FIG. 10B is a cross-sectional view of
the percutaneous laminotomy lead of FIG. 10A as taken along line
I-I;
[0031] FIG. 11 is a plan view of another embodiment of a
percutaneous laminotomy lead in accordance with certain embodiments
of the present invention;
[0032] FIG. 12 is a plan view of another embodiment of a
percutaneous laminotomy lead in accordance with certain embodiments
of the present invention;
[0033] FIG. 13A is a plan view of an insertion needle-insertion
stylet combination for facilitating the implantation of a
percutaneous laminotomy lead, FIG. 13B illustrates a side view of
the insertion needle-stylet of FIG. 13A, and FIG. 13C is a partial
perspective view of the insertion needle-stylet combination of
FIGS. 13A and 13B;
[0034] FIG. 14 is a cross-sectional view of the insertion
needle-stylet combination of FIG. 13A as taken along line
II-II;
[0035] FIG. 15 is a cross-sectional view of the insertion
needle-stylet combination of FIG. 13A as taken along line III-III;
and
[0036] FIG. 16 illustrates a potential placement relationship using
multiple percutaneous laminotomy leads, wherein the illustrated
leads are of the form illustrated in FIG. 7A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] Various embodiments, including preferred embodiments, will
now be described in detail below with reference to the
drawings.
[0038] In reference to FIG. 1, the illustrated laminotomy lead 10
includes a proximal end 12 and a distal end 14. The proximal end 12
includes a plurality of electrically conductive terminals 18, and
the distal end 14 includes a plurality of electrically conductive
electrodes 20 arranged within a flat, thin paddle-like structure
16. Typically, each terminal 18 is electrically connected to a
single electrode 20 via a conductor 22; however, a terminal 18 can
be connected to two or more electrodes 20.
[0039] Terminals 18 and electrodes 20 are preferably formed of a
non-corrosive, highly conductive material. Examples of such
material include stainless steel, MP35N, platinum, and platinum
alloys. In a preferred embodiment, terminals 18 and electrodes 20
are formed of a platinum-iridium alloy.
[0040] The sheaths 24 and the paddle structure 16 are formed from a
medical grade, substantially inert material, for example,
polyurethane, silicone, or the like. Importantly, such material
must be non-reactive to the environment of the human body, provide
a flexible and durable (i.e., fatigue resistant) exterior structure
for the components of lead 10, and insulate adjacent terminals 18
and/or electrodes 20. Additional structure (e.g., a nylon mesh, a
fiberglass substrate) (not shown) can be internalized within the
paddle structure 16 to increase its overall rigidity and/or to
cause the paddle structure 16 to assume a prescribed
cross-sectional form (e.g., a prescribed arc along a transverse
direction of the paddle structure 16) (not shown).
[0041] The conductors 22 are carried in sheaths 24. In the
illustrated example, each sheath 24 carries eight (8) conductors
22. Given the number of conductors 22 that are typically carried
within each sheath 24, the cross-sectional area of each conductor
22 is restricted. As but one example, for a sheath 24 in accordance
with certain embodiments of the present invention, having an outer
diameter of approximately 0.055 inches, each conductor 22 would be
approximately 0.0065 inches in diameter.
[0042] Each conductor 22 is formed of a conductive material that
exhibits desired mechanical properties of low resistance, corrosion
resistance, flexibility, and strength. While conventional stranded
bundles of stainless steel, MP35N, platinum, platinum-iridium
alloy, drawn-brazed silver (DBS) or the like can be used, a
preferred embodiment of the present invention uses conductors 22
formed of multi-strands of drawn-filled tubes (DFT). Each strand is
formed of a low resistance material and is encased in a high
strength material (preferably, metal). A selected number of
"sub-strands" are wound and coated with an insulative material.
With regard to the operating environment of certain embodiments of
the present invention, such insulative material would protect each
individual conductor 22 if its respective sheath 24 were to be
breached during use. Wire formed of multi-strands of drawn-filled
tubes to form conductors 22, as discussed here, is available from
Temp-Flex Cable, Inc.
[0043] In addition to providing the requisite strength,
flexibility, and resistance to fatigue, conductors 22 formed of
multi-strands of drawn-filled tubes, in accordance with the above
description, provide a low resistance alternative to other
conventional materials. Specifically, a stranded wire, or even a
coiled wire, having a length of approximately 60 cm and formed of
MP35N or stainless steel or the like would have a measured
resistance in excess of 30 ohms. In contrast, for the same length,
a wire formed of multi-strands of drawn-filled tubes could have a
resistance less than 4 ohms. Accordingly, in a preferred
embodiment, each conductor 22, having a length equal to or less
than 60 cm, has a resistance of less than 25 ohms. In a more
preferred embodiment, each conductor 20, having a length equal to
or less than 60 cm, has a resistance equal to or less than 10 ohms.
In a most preferred embodiment, each conductor 20, having a length
equal to or less than 60 cm, has a resistance of less than 4
ohms.
[0044] While a number of material and construction options have
been discussed above, it should be noted that neither the materials
selected nor a construction methodology is critical to the present
invention.
[0045] The following discussion is directed to a number of examples
illustrated in FIGS. 2-5. While the examples set forth a variety of
variations of the present invention, it may be readily appreciated
that the present invention could take any of a variety of forms and
include any number of electrodes. Importantly, however, certain
embodiments of the present invention are characterized by a first
electrode, or a first electrode array, that substantially
encompasses or circumscribes at least one independently controlled
electrode. The first electrode (or first electrode array) can
operatively form an "anode guard" relative to the substantially
surrounded independently controlled electrode(s). To clarify such
structure, the following examples are provided.
[0046] FIG. 2 illustrates a laminotomy lead 100a featuring the
fundamental principle of construction of certain embodiments of the
present invention. Specifically, the paddle structure 16 includes a
plurality of electrodes 20, wherein one electrode 30 substantially
surrounds another electrode 40. For this embodiment, each electrode
is electrically coupled to an independent terminal (not shown),
which is connectable to a programmable energy source, for example,
a pulse generator (not shown). The construction and arrangement of
the terminals (and related conductors, which establish the desired
electrical coupling) are not in themselves unique but are
consistent with that described hereinabove.
[0047] Depending upon a configuration/programmability of the energy
source connected to the laminotomy lead 100a, either the electrode
30 or the electrode 40 could operatively assume a positive polarity
(with the remaining electrode assuming a negative polarity) during
active delivery of electrical energy therefrom. For purposes of
focusing applied electrical energy, however, the electrode 30
assumes a positive polarity, whereby in such a condition the
electrode 30 forms an "anode guard" relative to the encompassed
electrode 40.
[0048] The electrode 30 can be constructed in a manner and from a
material consistent with that used to form electrode 40.
Alternatively, as longitudinal and transverse flexibility of the
paddle structure 16 are desirable, it is preferred that the
electrode(s) 30 be formed so as to not otherwise significantly
impair the inherent flexibility of the paddle structure 16.
Accordingly, the electrode 30 can be constructed using less
material--in a thickness direction--than an electrode 40, formed
from a conductive film/foil applied to the surface of the paddle
structure 16, formed through deposition of a conductive material,
constructed using a coil (FIG. 3), or formed using other like
processes/techniques that are well known in the art.
[0049] An anode guard functions, in part, to laterally limit an
applied electrical field, which assists in reducing extraneous
stimulation of surrounding neural tissue. In this regard, neural
tissue at or immediately about the cathode electrode(s) is
depolarized, while neural tissue relative to the anode guard is
subject to hyperpolarization. Further, an anode guard in accordance
with that illustrated in FIG. 2 focuses an applied electrical field
from practically every direction to any cathode-electrode(s)
positioned therein. Thus, for any given drive signal from a coupled
energy source, the stimulation lead of certain embodiments of the
present invention can effect a deeper application of applied energy
than stimulation leads of a conventional nature.
[0050] FIG. 3 illustrates a four-channel (a "channel" represents a
controllable electrical output) laminotomy stimulation lead 100b in
accordance with certain embodiments of the present invention. The
stimulation lead 100b is shown having a plurality of electrodes 20,
which includes an electrode 30, formed from a coil, that
substantially circumscribes an electrode array formed of three
electrodes 40a, 40b, and 40c.
[0051] Again, while each of the plurality of electrodes 20 could
individually function as a cathode or an anode, or be placed in an
OFF-state, it is intended that the electrode 30, as an anode guard,
assume a positive polarity. To this end, the form of an electric
field generated using the electrode 30 is altered/controlled
through setting each of the electrodes 40a, 40b, and 40c as a
cathode, an anode, or in an OFF-state. Such control over the
electrodes 40a, 40b, and 40c enables formation of a focused
electrical field with a single electrode 40 as a cathode or a more
diverse electrical field spread over two or more electrodes 40,
whereas each electrode 40 of such plurality functions as a
cathode.
[0052] Furthermore, to the extent that the benefits of an anode
guard are not required, the electrode 30 may be placed in an
OFF-state. In such operative configuration, the laminotomy lead
100b then functions in a manner consistent with conventional
laminotomy stimulation leads.
[0053] The configuration illustrated in at least FIG. 3 enables the
delivery of electrical energy to targeted nervous tissue with fewer
required electrodes. Moreover, it should be noted that the compact
structure (i.e., narrow transverse dimension) of the laminotomy
lead 100b enables such laminotomy lead to be implanted
percutaneously, if so desired, using a special insertion needle 200
(FIG. 6) that accommodates the larger dimensions (relative to a
conventional percutaneous lead) of the laminotomy lead 100b. Of
note, additional embodiments of this variation are described below
in cooperation with FIGS. 7 and 10-12.
[0054] FIG. 4 illustrates a laminotomy stimulation lead 100c in
accordance with certain embodiments of the present invention. The
stimulation lead 100c includes a plurality of electrodes 20, which
includes a first electrode array having a plurality of electrodes
30a-30d that substantially surrounds a second electrode array
having a plurality of electrodes 40.
[0055] Similar to the stimulation lead 100b, the second electrode
array of the stimulation lead 100c is formed of a group of
individual electrodes that can respectively be set as an anode, a
cathode, or in an OFF-state. Although the electrodes 40 of the
stimulation lead 100c are shown in two, staggered columns, the
arrangement of the electrodes 40 of the second electrode array is
not critical to the present invention--the electrodes 40 of the
second electrode array may assume any multiple-column
arrangement.
[0056] Unlike the other embodiments illustrated, the anode guard is
constructed of a first electrode array that includes electrodes
30a-30d. In a preferred embodiment, each electrode of the first
electrode array extends for a length substantially equivalent to a
comparable dimension of at least two of electrodes 40 of the second
electrode array. Further, and generally consistent with the
structures of FIGS. 2, 3, and 5, the collection of electrodes
30a-30d forms an effectively continuous ring that substantially
extends about the second electrode array.
[0057] Although each of the electrodes 30a-30d may be electrically
independent (i.e., coupled to respective conductors/terminals),
allowing each respective electrode to be an anode, a cathode, or
set to an OFF-state, in consideration of practical space
limitations, it may be advisable to electrically couple two or more
of electrodes 30a-30d. In a simplest form, electrodes 30a-30d are
electrically linked so as to maintain the same electrical state
during operation and minimize the number of conductors necessary to
couple the first electrode array to an energy source.
[0058] Depending upon the form/construction of the electrodes
30a-30d, the segmented nature of the illustrated first electrode
array of this embodiment would improve longitudinal flexibility of
the paddle structure 16. As additional segmentation of electrodes
30b and 30d would likewise improve transverse flexibility of the
paddle structure 16, such modification is within the scope of this
embodiment of the present invention.
[0059] To maintain a generally uniform electrical field between an
anode guard and one or more cathode-electrodes, the distance
between the one or more cathode-electrodes and the anode guard
should be largely equidistant. Achieving this optimum arrangement
is typically hindered by both a need that the platform structure 16
fit easily within the narrow confines of the human epidural space
and a desire that the provided electrode array(s) span a
significant vertebral range of spinal nervous tissue.
[0060] While a long electrode array substantially surrounded by a
single anode guard electrode (or a composite anode guard) would not
be operatively ineffective, an alternative to such structure is
illustrated by the stimulation lead 100d of FIG. 5. Specifically,
the electrodes 40 can be divided into groups 40a and 40b, and each
electrode group 40a and 40b is encompassed by its own independently
controlled anode guard electrode 30a and 30b.
[0061] In furtherance of the percutaneous implantation method
illustrated in FIG. 6, another embodiment of a percutaneous lead
100e is illustrated in FIGS. 7a-7c. The percutaneous lead 100e is a
"laminotomy" lead which can have the anode guard construction or it
can be a non-anode guard-bearing percutaneous lead. Consistent with
conventional laminotomy leads, the stimulation lead 100e includes
two principal, substantially planar surfaces, one of which carries
the plurality of electrodes 20. Unique to the percutaneous
insertion-capable lead of certain embodiments of the present
invention, the greatest transverse dimension (i.e., the width
dimension) of the stimulation lead 100e is preferably about 75% of
a width dimension of a conventional laminotomy lead, more
preferably about 50% of a width dimension of a conventional
laninotomy lead, and most preferably about 40% of a width dimension
of a conventional laminotomy lead. Notwithstanding these
preferences, the greatest width dimension of the percutaneous
laminotomy lead of certain embodiments of the present invention can
be between about 20% and 40% of a conventional laminotomy lead.
Further yet, it is preferable that the greatest transverse
dimension of the platform structure 16 is substantially equivalent
to two times (2.times.) the thickness of the same
[0062] The limiting factor for a minimum width dimension of the
percutaneous laminotomy lead of certain embodiments of this
invention is a maximum transverse dimension of any given electrode
20, wherein each electrode must possess adequate surface area to
effectively deliver sufficient electrical energy or sense
environmental conditions.
[0063] The stimulation lead 100e includes necked portions 50, or
"waisted" regions, wherein a transverse dimension at the necked
portions 50 is less than an adjacent (e.g., maximum) transverse
dimension of the platform structure 16. This structural
configuration creates a stimulation lead having a varying
cross-sectional moment of inertia, which enables a predetermined
flexibility in a plane substantially parallel to the principal
planar surfaces of the platform structure 16. Improving the
flexibility of the stimulation leads in this matter enhances the
steerability of such stimulation leads.
[0064] As shown in FIGS. 7A and 10B, a channel 52 longitudinally
extends through stimulation lead 100e (FIGS. 7A and 10B). The
channel 52 is adapted to receive a stylet 54.
[0065] FIGS. 8A and 8B illustrate two configurations for a stylet.
FIG. 8A illustrates a stylet 54 having a straight distal end. If
used with the stimulation lead 100e, this stylet 54 would enable
forward driving of the stimulation lead/stylet combination but
would not offer an optimum structure to readily alter a course of
(i.e., steer) the stimulation lead 100e from a particular course.
Conversely, FIG. 8B illustrates a stylet 54a having a bent (i.e.,
contoured) distal end. If used with the stimulation lead 100e, this
stylet 54a would enable forward driving of the stimulation
lead/stylet combination (FIG. 9B, when the contoured end of the
stylet 54a is oriented substantially perpendicular to the principal
planar surfaces of the stimulation lead 100e) as well as
directional steering. In reference to FIGS. 9A and 9C, when the
contoured end of the stylet 54a is oriented substantially parallel
to the principal planar surfaces of the stimulation lead 100e, the
stimulation lead 100e deforms in a direction consistent with a
predetermined direction of the bent end of the stylet 54a.
Accordingly, through rotation of a bent stylet 54a, a practitioner
can purposely control and direct the stimulation lead being
implanted to a desired site. Thus the combination of the curved
stylet 54a and the stimulation lead 100e provides a stylet
steerable, electric field directional, percutaneous stimulation
lead. With either the straight stylet 54 or the curved stylet 54a,
the insertion of the stylet into the inner lumen the entire length
of the lead provides a stiffening member for handling and placing
the lead.
[0066] While the bent stylet 54 of FIG. 8B is illustrated in one
particular form, it should be readily appreciated that the contour
could take any of a number of forms. In particular, the distal end
of the illustrated stylet 54 could be formed so as to have a gentle
bow (not shown) or include additional angles (not shown) that could
heighten the nature of the deflection of the platform structure 16
when the stylet 54 is properly oriented.
[0067] It is anticipated that the handle 56 of the stylet 54 would
include a marking or the like (not shown) to indicate to the user a
contour direction, if any, of the stylet 54.
[0068] For this embodiment, the stimulation lead 100e includes a
serial arrangement of waisted regions 50 that repeat along
substantially an entire length of the platform structure 16 so as
to maximize the flexibility of the stimulation lead 100e. In
addition to adding flexibility to the platform structure 16, the
scalloped edge of at least the stimulation lead 100e enables
multiple stimulation leads to be operatively positioned relative to
one another (FIG. 16) in close proximity. In this instance,
multiple stimulation leads can be combined to effectively produce a
structure akin to a conventional, non-percutaneous laminotomy lead
like that illustrated in FIG. 1.
[0069] FIG. 10A illustrates a stimulation lead 100f that includes a
single waisted region 50. The stimulation lead 100f would
operatively exhibit performance characteristics like the
stimulation lead 100e; however, the overall flexibility of the
platform structure 16 would be arguably less. Depending upon the
nature of the procedure to be performed or the environment to which
a percutaneous laminotomy stimulation lead is to be inserted, it
may be that the stimulation lead 100f may be more suitable than the
stimulation lead 100e. Moreover, while the stimulation leads 100e
and 100f represent two extremes of this design, it is contemplated
that any number of waisted regions 50 can be used for a stimulation
lead depending upon a desired level of planar flexibility. To this
end, an alternative design 100g is further illustrated in FIG.
11.
[0070] FIG. 12 illustrates a percutaneous laminotomy lead that is
formed of suitable flexible material without any waisted regions
50. Although material selection for or construction of the platform
structure 16 could be used to emulate the flexibility
characteristics otherwise attainable through the use of the waisted
regions 50, it may be desirable to provide a less flexible
structure that simply exploits the valuable attribute of a
percutaneously insertable "laminotomy" lead.
[0071] While not shown, it is contemplated that a waisted region(s)
50 could be formed in the principal planar surfaces of a platform
structure of a laminotomy lead between two or more electrodes 20 so
as to form thinner regions in a thickness direction. Functionally,
when the contoured end of the stylet 54 of Figure BB is then
oriented substantially perpendicular to the principal planar
surfaces of a stimulation lead, at least a portion of the platform
structure 16 would be caused to deform outside a non-deflected
plane otherwise defined by the platform structure 16. Accordingly,
a stimulation lead having this feature would facilitate relative
upward and downward movement of the platform structure 16 during
insertion. While the environment of an epidural space may not
require such feature, other regions of the human body or other
environments may benefit from such feature. Further yet, this
feature could be combined with the earlier-described, transversely
oriented waisted regions 50 to enable such a lead to be steered in
two dimensions. Steering control could be accomplished with
multiple stylets, each stylet including a unique contour to address
a corresponding waisted region, or a single stylet "keyed" to
corresponding waisted regions.
[0072] Notwithstanding the plurality of configurations of the
percutaneous insertion-capable stimulation leads of the present
invention, FIGS. 13A and 13B illustrate one embodiment of the
insertion needle 200 (FIG. 6) usable to insert and place anyone of
the above-discussed stimulation leads. The needle 200 defines an
interior path 202 that ultimately receives and guides a stimulation
lead 100.times. into an epidural space. However, at least
initially, the path 202 receives a stylet 204, wherein the needle
200 and the stylet 204 combination facilitates penetration through
human tissue into the patient's epidural space.
[0073] As but one example of an implantable procedure, a small
incision is first made in a patient's skin using a scalpel at the
desired site of insertion. Making an initial incision prevents the
application of excess force to the tip of the needle 200 and
further avoids the undesirable introduction of dermal matter into
the epidural space. The needle 200 and the stylet 204 combination
is introduced through the incision at an angle that allows passage
of the needle 200 between vertebral bodies. Once the distal end of
the needle 200 is positioned within and opens into the epidural
space, the stylet 204 is removed to allow insertion of the platform
structure 16 of a stimulation lead 100.times..
[0074] Given the increased surface area of the cross-section of the
needle 200 and the stylet 204 combination (FIG. 14), it is
important that the stylet 204 efficiently integrate with the needle
200 (FIG. 15) to provide a largely "unitary" surface that
facilitates penetration through the tissue that encompasses an
epidural space.
[0075] A lamitrode epidural needle needle having a generally
rectangular passageway can be employed for the insertion of the
percutaneous stimulation lead, as an example, the generally
rectangular passageway can have a height in the range of one to two
millimeters and a width in the range of two to four millimeters,
with the width to height ratio being approximate 2:1. While a
needle is one type of percutaneous introduction device, there are
other know percutaneous introduction devices and methods available,
e.g., a dilating catheter can be employed in the form of a silicone
sleeve surrounding a needle for the initial insertion through the
skin, with removal of the needle after the insertion of the sleeve
through the skin, followed by insertion of a dilator into the
hollow sleeve to expand the sleeve. The dilator can have a hollow
passage for the insertion of the stimulation lead of certain
embodiments of the present invention.
[0076] While the invention has been described herein relative to a
number of particularized embodiments, it is understood that
modifications of, and alternatives to, these embodiments, such
modifications and alternatives realizing the advantages and
benefits of this invention, will be apparent to those of ordinary
skill in the art having reference to this specification and its
drawings. It is contemplated that such modifications and
alternatives are within the scope of this invention as subsequently
claimed herein, and it is intended that the scope of this invention
claimed herein be limited only by the broadest interpretation of
the appended claims to which the inventors are legally entitled
* * * * *