U.S. patent application number 09/862104 was filed with the patent office on 2001-09-20 for apparatus and method for expanding a stimulation lead body in situ.
Invention is credited to King, Gary W., Rise, Mark T., Schallhorn, Richard, Schendel, Michael J..
Application Number | 20010023367 09/862104 |
Document ID | / |
Family ID | 22093367 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010023367 |
Kind Code |
A1 |
King, Gary W. ; et
al. |
September 20, 2001 |
Apparatus and method for expanding a stimulation lead body in
situ
Abstract
An implantable lead is provided with at least one extendable
member to position therapy delivery elements, which may be
electrodes or drug delivery ports, after the lead has been inserted
into the body. The lead may formed as a resilient element which is
contained in a retainer tube that may be removed to permit the lead
to deploy. Alternatively, a non-resilient lead may be provided with
a slotted retainer tube. A series of mechanical linkages for
expanding and retracting the lead within the human body may be
actuated with various mechanisms. A control system may be provided
for closed-loop feedback control of the position of the extendable
members. The invention also includes a method for expanding an
implantable lead in situ.
Inventors: |
King, Gary W.; (Fridley,
MN) ; Rise, Mark T.; (Monticello, MN) ;
Schendel, Michael J.; (Andover, MN) ; Schallhorn,
Richard; (Lake Elmo, MN) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE
SUITE 3000
CHICAGO
IL
60606
US
|
Family ID: |
22093367 |
Appl. No.: |
09/862104 |
Filed: |
May 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09862104 |
May 21, 2001 |
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09584572 |
May 31, 2000 |
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09584572 |
May 31, 2000 |
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09070136 |
Apr 30, 1998 |
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6161047 |
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Current U.S.
Class: |
607/117 |
Current CPC
Class: |
A61M 2209/045 20130101;
A61N 1/056 20130101; A61M 2210/1003 20130101; A61M 5/1723 20130101;
A61M 2210/0693 20130101; A61N 1/0551 20130101; A61N 1/05 20130101;
A61N 1/0558 20130101; A61M 5/14276 20130101 |
Class at
Publication: |
607/117 |
International
Class: |
A61N 001/05 |
Claims
What is claimed is:
1. An implantable lead for providing therapy to a body comprising:
an elongate central portion; and at least one extendable member
having an end, the extendable member depending from the central
portion and being adapted to assume a compact position, in which
the end is disposed in close proximity to the central portion, and
an extended position, in which the end is disposed at a location
distal from the central portion; at least one therapy delivery
element disposed on the extendable member for delivering therapy to
the body.
2. The implantable lead according to claim 1, wherein the
extendable member is a span adapted to coil around the central
portion when the span is in the compact position.
3. The implantable lead according to claim 2, wherein the span
incorporates a resilient material to urge the span towards the
extended position.
4. The implantable lead according to claim 3, further comprising
therapy delivery elements disposed on the span for delivering
therapy to the body.
5. The implantable lead according to claim 2, further comprising a
central passage in the central portion for accommodating a
centering stylet to stabilize and center the lead.
6. The implantable lead according to claim 2, further comprising a
retainer tube having a notch for guiding the span to its extended
position.
7. The implantable lead according to claim 2, wherein the span is
adapted to be folded in such a manner that the therapy delivery
elements are disposed one on top of the other in the compact
position.
8. The implantable lead according to claim 1, wherein the
extendable member is formed as a coaxial accessory tube mounted
over a distal end of the central portion, the accessory tube
including a central slot forming at least two flexible leaf
portions.
9. The implantable lead according to claim 8, wherein a lower end
of the accessory tube is adapted to slide with respect to the
central portion, the flexible leaf portions adapted to extend
outward as the lower end slides.
10. The implantable lead according to claim 1, wherein the
extendable member is formed as a series of telescoping
elements.
11. The implantable lead according to claim 10, wherein the
telescoping elements are provided with therapy delivery elements
thereon.
12. The implantable lead according to claim 1, wherein the
extendable member is formed as a resilient transverse span adapted
to bend to a compact position in which the extendable member
extends in a direction substantially parallel to an axis of the
lead and wherein the extendable member is adapted to extend in an
extended position at an angle of 90 degrees or less to the axis of
the lead.
13. The implantable lead according to claim 1, further comprising a
linkage assembly for expanding the lead.
14. The implantable lead according to claim 13, wherein the linkage
assembly comprises a first and second actuating members adapted to
move in a direction substantially parallel to an axis of the
lead.
15. The implantable lead according to claim 14, further comprising
a mechanism for adjusting the relative positions of the first and
second actuating members.
16. The implantable lead according to claim 15, wherein the
mechanism comprises a rotatable circular component cooperatively
associated with the first and second actuating members.
17. The implantable lead according to claim 15, wherein the
mechanism comprises a rack gear and pinion gear, the rack gear
being cooperatively associated with one of the first and second
actuating members.
18. The implantable lead according to claim 15, wherein the
mechanism comprises a hydraulic cylinder adapted to adjust the
relative positions of the first and second actuating members.
19. The implantable lead according to claim 13, wherein the linkage
assembly comprises a rotatable shaft.
20. The implantable lead according to claim 19, further comprising
a gear mechanism for imparting rotational movement to the
shaft.
21. An implantable lead for providing therapy to a body comprising:
an elongate central portion; and at least one extendable member
having an end, the extendable member depending from the central
portion and being adapted to assume a compact position, in which
the end is disposed in close proximity to the central portion, and
an extended position, in which the end is disposed at a location
distal from the central portion; at least one therapy delivery
element disposed on the extendable member for delivering therapy to
the body; and a linkage assembly for permitting adjustment of the
position of the extendable member in situ.
22. The implantable lead according to claim 21, wherein the
extendable member is a span adapted to coil around the central
portion when the span is in the compact position.
23. The implantable lead according to claim 22, wherein the span is
adapted to be folded in such a manner that the therapy delivery
elements are disposed one on top of the other in the compact
position.
24. The implantable lead according to claim 21, wherein the
extendable member is formed as a coaxial accessory tube mounted
over a distal end of the central portion, the accessory tube
including a central slot forming at least two flexible leaf
portions.
25. The implantable lead according to claim 24, wherein a lower end
of the accessory tube is adapted to slide with respect to the
central portion, the flexible leaf portions adapted to extend
outward as the lower end slides.
26. The implantable lead according to claim 25, further comprising
a screw mechanism for adjusting the position of the lower end of
the accessory tube.
27. The implantable lead according to claim 21, wherein the
extendable member is formed as a series of telescoping
elements.
28. The implantable lead according to claim 21, wherein the linkage
assembly comprises a first and second actuating members adapted to
move in a direction substantially parallel to an axis of the
lead.
29. The implantable lead according to claim 28, further comprising
a mechanism for adjusting the relative positions of the first and
second actuating members.
30. The implantable lead according to claim 29, wherein the
mechanism comprises a rotatable circular component cooperatively
associated with the first and second actuating members.
31. The implantable lead according to claim 29, wherein the
mechanism comprises a rack gear and pinion gear, the rack gear
being cooperatively associated with one of the first and second
actuating members.
32. The implantable lead according to claim 29, wherein the
mechanism comprises a hydraulic cylinder adapted to adjust the
relative positions of the first and second actuating members.
33. The implantable lead according to claim 21, wherein the linkage
assembly comprises a rotatable shaft.
34. The implantable lead according to claim 33, further comprising
a gear mechanism for imparting rotational movement to the
shaft.
35. An implantable lead system for providing therapy to a body
comprising: an elongate central portion; at least one extendable
member having an end, the extendable member depending from the
central portion and being adapted to assume a compact position, in
which the end is disposed in close proximity to the central
portion, and an extended position, in which the end is disposed at
a location distal from the central portion; at least one therapy
delivery element disposed on the extendable member for delivering
therapy to the body; an actuating assembly for permitting
adjustment of the position of the extendable member in situ; a
sensor for sensing a stimulation parameter; a closed-loop feedback
controller for operating the actuating assembly to maintain the
stimulation parameter at a predetermined value.
36. A method for expanding an implantable lead in situ in the body,
the lead including an expandable member having therapy delivery
elements thereon, the method comprising the steps of: inserting the
lead into the body; expanding the lead while the lead is in the
body to thereby expand the expandable member such that the relative
positions of the therapy delivery elements may be adjusted.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to implantable leads for delivering
therapy, in the form of electrical stimulation or drugs, to the
human body. Specifically, this invention relates to implantable
leads that may be expanded, retracted or adjusted after
implantation in the human body. This invention also relates to
mechanisms for accomplishing such expansion, retraction or
adjustment of such leads in situ. Further, this invention relates
to control systems for controlling such expansion, retraction or
adjustment of such an implanted lead.
[0002] Recent efforts in the medical field have focused on the
delivery of therapy in the form of electrical stimulation or drugs
to precise locations within the human body. Therapy originates from
an implanted source device, which may be an electrical pulse
generator, in the case of electrical therapy, or a drug pump, in
the case of drug therapy. Therapy is applied through one or more
implanted leads that communicate with the source device and include
one or more therapy delivery sites for delivering therapy to
precise locations within the body. In drug therapy systems,
delivery sites take the form of one or more catheters. In
electrical therapy systems, they take the form of one or more
electrodes wired to the source device. In Spinal Cord Simulation
(SCS) techniques, for example, electrical stimulation is provided
to precise locations near the human spinal cord through a lead that
is usually deployed in the epidural space of the spinal cord. Such
techniques have proven effective in treating or managing disease
and acute and chronic pain conditions.
[0003] Percutaneous leads are small diameter leads that may be
inserted into the human body, usually by passing through a Tuohy
(non-coring) needle which includes a central lumen through which
the lead is guided. Percutaneous leads are advantageous because
they may he inserted into the body with a minimum of trauma to
surrounding tissue. On the other hand, the types of lead structure,
including the electrodes or drug-delivery catheters, that may be
incorporated into percutaneous leads is limited because the lead
diameter or cross-section must be small enough to permit the lead
to pass through the Tuohy needle.
[0004] Recently, the use of "paddle" leads, like Model 3586
Resume.RTM. Lead or Model 3982 SymMix.RTM. Lead of Medtronic, Inc.,
which offer improved therapy control over percutaneous leads, have
become popular among clinicians. Paddle leads include a generally
two-dimensional set of electrodes on one side for providing
electrical therapy to excitable tissue of the body. Through
selective programmed polarity (i.e., negative cathode, positive
anode or off) of particular electrodes, electric current can be
"steered" toward or away from particular tissue within the spinal
cord or other body areas. Such techniques are described by
Holsheimer and Struijk, Stereotact Funct Neurosurg, vol. 56, 199:
pp 234-249; Holsheimer and Wesselink, Neurosurgery, vol. 41, 1997:
pp 654-660; and Holsheimer, Neurosurgery, vol. 40, 1997: pp
990-999, the subject matter of which is incorporated herein by
reference. This feature permits adjustment of the recruitment areas
after the lead has been positioned in the body and therefore
provides a level of adjustment for non-perfect lead placement. Such
techniques are disclosed in U.S. Pat. Nos. 5,643,330, 5,058,584 and
5,417,719, the subject matter of which is incorporated herein by
reference. Additionally, the value of a transverse tripole group of
electrodes has been demonstrated for spinal cord stimulation, as
described by Struijk and Holsheimer, Med & Biol Engng &
Comput, July, 1996: pp 273-276; Holsheimer. Neurosurgery, vol. 40,
1997: pp 990-999; Holsheimer et al., Neurosurgery, vol. 20, 1998.
This approach allows shielding of lateral nervous tissue with
anodes, like the dorsal roots, and steering of fields in the middle
under a central cathode by use of two simultaneous electrical
pulses of different amplitudes.
[0005] One disadvantage recognized in known paddle leads is that
their installation, repositioning and removal necessitates
laminectomies, which are major back surgeries involving removal of
part of the vertebral bone. Laminectomies are required because
paddle leads have a relatively large transverse extent compared to
percutaneous leads. Thus, implantation, repositioning and removal
require a rather large passage through the vertebral bone.
[0006] Another disadvantage with paddle leads is that optimal
positioning is often difficult during implant. For example, the
transverse tripole leads described above work optimally if the
central cathode is positioned coincident with the physiological
midline of the spinal cord. Such placement is difficult since the
doctor cannot see the spinal cord thru the dura during implant.
Moreover, lead shifting may occur subsequent to implant, thereby
affecting the to efficacy of the therapy delivered from the
lead.
[0007] Yet another disadvantage recognized with paddle leads is
that the lead position may change merely with patient movement. For
example, when a patient lies down, the spacing between an epidural
lead and the spinal cord decreases to a large extent, so that it is
often necessary to lower the amplitude of the stimulation by half.
It is reasonable to assume that steering effects of a tripole lead
might also be affected if the CSF width changes dramatically, or if
due to patient twisting or activity, the orientation between the
lead and spinal cord changes.
[0008] While the prior art has attempted to provide deformable
leads, which may provide improved insertion characteristics or
enhanced stability once inside the body, they have not succeeded in
providing a device which remedies the aforementioned problems. For
example, U.S. Pat. No. 4,285,347 to Hess discloses an implantable
electrode lead having a distal end portion with a laterally
extending stabilizer, preferably in the form of curved loops.
Similarly, and U.S. Pat. No. 4,519,403 to Dickhudt discloses an
inflatable lead for enhanced contact of the electrode with the dura
of the spinal cord. U.S. Pat. No. 5,121,754 to Mullett discloses a
device to allow electrodes to move to more lateral positions after
insertion, when a stiffening guidewire used during insertion is
removed. In Mullett's device, only one electrode can be found at
any particular longitudinal location, since only gentle curves of
the lead were designed, and the curves are not adjustable after
implant of the lead. Similar problems apply to the device disclosed
by O'Neill in U.S. Pat. No. 4,154,247.
[0009] Patent Cooperation Treaty (PCT) Publication No. WO 93/04734
to Galley discloses a lead tip that has four spans that will bulge
into four different directions when a confining outer catheter is
drawn proximally back over the lead body. The publication describes
one electrode on the middle of each span. In situ in the epidural
space, these four electrodes will form a to square or rectangular
cross-sectional shape. Two of them might be pressed into the dura
(at lateral positions) and the other two would be dorsal, against
the vertebral bone. Only the electrodes nearest the spinal cord
would be useful for programming. While this could give two
electrodes at the same longitudinal position, their medial to
lateral locations are difficult to control, and their ability to
spread apart depends on the relative stresses in the spans and
tissue-like adhesions that may be present. Other malecot-type lead
tips have been proposed for positioning of electrodes in the heart
(U.S. Pat. No. 4,699,147, Chilson and Smith, 1985; U.S. Pat. No.
5,010,894, Edhag, 1989) or anchoring of lead bodies (U.S. Pat. No.
4,419,819, Dickhudt and Paulson, 1982; U.S. Pat. No. 5,344,439,
Otten, 1992) or positioning of ablation electrodes (Desai, U.S.
Pat. No. 5,215,103, 5,397,339 and 5,365,926). While the
aforementioned prior art devices provide various configurations for
compact insertion or lead stabilization after implant, they do not
offer the advantages and improved efficacy recognized with respect
to paddle lead configurations.
[0010] It would therefore be desirable to provide a lead structure
for stimulation of excitable tissue surfaces which combines the
advantages offered by percutaneous leads with respect to minimized
trauma during insertion, repositioning and removal with the
advantages offered by paddle-type leads with respect to improved
efficacy, ability to provide electrodes in places lateral to the
axis of the lead and tailoring of treatment.
[0011] It would also be desirable to provide a lead structure which
permits adjustment of the lead dimensions and therefore the
delivery site location in situ for enhanced control of the therapy
being applied to the excitable body tissues.
[0012] It would be further desirable to provide a paddle lead which
is capable of automatically adjusting its width or delivery site
spacing automatically in response to patient factors such as body
position or activity or in response to a parameter such as muscle
contraction or action potentials, which may be characteristic of
the stimulation or therapy being applied.
SUMMARY OF THE INVENTION
[0013] The invention combines the advantages of percutaneous leads
with those of paddle leads. In a preferred embodiment, the
invention provides a lead structure including a central core
portion and at least one flexible, semi-flexible or semi-rigid
transversely extending span which may be positioned in a compact
position during insertion in which it is wound around or otherwise
disposed in close proximity to the central core portion. Each span
may also be deployed or shifted to a position in which it extends
outward from the central core portion in a transverse direction.
Each span has disposed on one surface a number of therapy delivery
elements, in the form of electrodes or catheter ports, for
delivering therapy in the respective form of electrical or drug
therapy to the body. In the compact insertion position, the lead
may be easily inserted within a catheter or Tuohy needle. Once the
lead has been positioned at the appropriate place in the body, the
span or spans may be deployed from the compact position to the
extended position in which the therapy delivery elements are
positioned in a fashion similar to a paddle lead. The flexibility
of the spans also permits the lead to be retracted back to the
compact position in the event that the lead must be removed from
the body.
[0014] In a preferred embodiment, the invention provides a lead
which includes a central core portion and at least one flexible
paddle extending therefrom and which may be coiled around the core
portion when the lead is to be compacted for insertion. As the lead
is inserted through a catheter or Tuohy needle, the spans are kept
in the compact position by lead rotation in a direction opposite
their direction of winding around the central core. Also according
to the invention, the spans are deployed by rotating the central
core portion in the same direction in which the spans are coiled
around the central core portion. Because of the flexibility of the
spans, they are caused to move outward, away from the central core
as the lead is uncoiled. In another embodiment of the invention,
the spans can be formed of a resilient material in which resilient
forces develop when the lead is configured in its compact position.
The lead is maintained in its compacted form while inside of the
insertion tool, i.e. Tuohy needle. The resilient forces cause the
spans to extend outward once the lead exits the end of the
insertion tool.
[0015] An outer concentric retainer tube may be provided in
combination with the lead, the outer retainer tube acting to retain
the lead in its compact position during insertion. The retainer
tube may be provided with a pair of notches on its distal end to
aid in the retraction of the lead after deployment. Specifically,
the notches are disposed on the distal end of the retainer tube in
such a manner that the spans will engage the notches when the
central core portion is rotated and pulled toward a proximal end of
the retainer tube. The notches retain the spans in position as the
central core rotates, thus causing the spans to coil around the
central core portion and assume a compact position.
[0016] The present invention also provides a lead which may be
compacted in a different manner than described above. The lead is
comprised of a series of therapy delivery elements which are
attached to a thin backing sheet which permits the sheets to be
disposed one on top of the other in the compact insertion position
and then to expand to a generally planar orientation once the lead
is inserted to the appropriate position in the body.
[0017] The following are exemplary advantages of adjustable leads
constructed according to the preferred embodiments of the
invention:
[0018] 1. The spacing of the sites can be matched to important
dimensions of the tissue affected, e.g., the width of the
Cerebro-Spinal Fluid (CSF) between the dura and the spinal
cord.
[0019] 2. As the dimensions of the lead tip are changed, the
locations of the sites relative to the tissue affected may be
advantageously altered. For example, as a paddle's width is
increased the paddle will move toward the spinal cord in the
semicircular dorsal part of the epidural space.
[0020] 3. In cases where the bones or fluid compartments have large
widths (e.g., CSF depth at spinal level T7 or T8) or are too wide
in a particular patient, the paddle width can be increased
appropriately to ensure effective therapy.
[0021] 4. Changes in paddle width and the accompanying medial and
lateral movement of the sites can have a beneficial effect on the
therapy. For example, the ability to stimulate only the medial
dorsal columns versus the more lateral dorsal roots may provide
enhanced therapeutic results.
[0022] 5. As the patient ages, their pathological condition
changes, their degree of fibrosis or scar tissue changes, or the
effects of the therapy change, adjustments of the paddle
dimension(s) might restore or maintain the benefit.
[0023] 6. If the paddle's dimension(s) can be changed after
implant, it may be possible to optimize the benefits and minimize
undesirable side effects.
[0024] 7. By changing the paddle's dimension(s), it may be possible
to avoid surgery to replace or reposition the lead.
[0025] 8. By changing the paddle's dimension(s), it may be possible
to position the sites optimally relative to important physiological
locations, e.g., the physiological midline of nervous tissue, or
receptors responsive to the drugs being delivered.
[0026] 9. It may be possible to minimize the use of energy by
optimizing efficiency of therapy delivery through adjustment of
paddle width.
[0027] 10. There may be minimal insertion trauma and operating room
time and resources needed if it is possible to place a lead with
percutaneous techniques, and then expand it in situ.
[0028] 11. Repositioning of a paddle lead can be done without
laminectomy. Removal is also made quicker and less traumatic.
[0029] 12. With closed loop feedback control of the paddle's
dimension(s), optimal therapy can be maintained with less
interference with the patient's lifestyle.
[0030] Another preferred embodiment allows automatic changes in at
least one dimension of a paddle lead. Such a system would measure
an effect of the stimulation, e.g., a compound action potential
caused by stimulation/drugs, a muscle contraction, the direction of
gravity, increased activity of the patient, relative motion of
vertebral bones, or other effects. Measurement techniques for
compound action potentials are disclosed in U.S. Pat. No. 5,702,429
the subject matter of which is incorporated herein by reference.
Such a recorded signal should be altered if the lead paddle
dimension that is controlled is changed. Then, after filtering,
amplifying, integrating and comparing the recorded signal to a
previous stored signal, the parts of the lead that control the
dimension in question will be moved or activated, causing a change
in said dimension, which will restore the effect measured to its
original value. This constitutes closed loop feedback control, and
can enable to patient to be less affected by changes in the therapy
caused by his/her position, activity, etc. Of course there should
be governors on the dimensional changes allowed, so that if the
measured parameter is very greatly changed, neither the device nor
the patient will undergo damage or trauma. The described
embodiments show preferred techniques to expand a lead in
directions transverse to the main axis of the lead body. The
invention also contemplates devices for expanding the lead in a
direction substantially parallel to the lead axis.
[0031] Other advantages novel features, and the further scope of
applicability of the present invention will be set forth in the
detailed description to follow, taken in conjunction with the
accompanying drawings, and in part will become apparent to those
skilled in the art upon examination of the following, or may be
learned by practice of the invention. The advantages of the
invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The accompanying drawings which are incorporated into and
form a part of the specification, illustrate several embodiments of
the present invention and, together with the description, serve to
explain the principles of the invention. The drawings are only for
the purpose of illustrating a preferred embodiment of the invention
and are not to be construed as limiting the invention. In the
drawings, in which like numbers refer to like parts throughout:
[0033] FIG. 1 is a plan view of a lead according to the present
invention being inserted through a Tuohy needle near the dura of a
human spine;
[0034] FIGS. 2A-2D are isometric views of a lead according to the
present invention in a compact insertion position;
[0035] FIG. 2E is an isometric view of the lead of FIG. 2A in an
expanded or deployed position;
[0036] FIG. 3 is an isometric view of a lead according to another
embodiment of the invention;
[0037] FIG. 4A is an isometric view of a lead and retainer tube
according to yet another embodiment of the invention;
[0038] FIG. 4B is an isometric view of a lead retainer tube
according to the present invention;
[0039] FIG. 4C is an isometric view of a lead and retainer tube
according to the present invention;
[0040] FIG. 5A is an isometric view of a lead and expansion
mechanism according to another embodiment of the present
invention;
[0041] FIG. 5B is a top view of the lead of FIG. 5A in a compact
position;
[0042] FIG. 6A is a cross section of a lead according to another
embodiment of the invention;
[0043] FIG. 6B is a front view of an expansion mechanism according
to a preferred embodiment of the present invention;
[0044] FIG. 7 is a front view of an expansion mechanism according
to another preferred embodiment of the present invention;
[0045] FIGS. 8A and 8B are front views of an expandable lead
according to another preferred embodiment of the invention;
[0046] FIG. 8C is a front view of the expandable lead of FIGS. 8A
and 8B with an alternative embodiment for the actuating
mechanism;
[0047] FIGS. 9A and 9B are side and front views, respectively, of
another preferred embodiment of the present invention;
[0048] FIGS. 10A and 10B are front views of another preferred
embodiment of the present invention;
[0049] FIGS. 11A and 11B depict yet another preferred embodiment of
the present invention;
[0050] FIG. 12A is a front view of an adjustment mechansim
according to a preferred embodiment of the invention;
[0051] FIG. 12B is a front view of an adjustment mechansism
according to another preferred embodiment of the invention;
[0052] FIG. 12C is a front view of an adjustment mechansim
according to yet another preferred embodiment of the invention;
and
[0053] FIG. 12D is a front view of an adjustment mechansim
according to still another preferred embodiment of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] FIG. 1 illustrates a lead according to a preferred
embodiment of the invention being utilized in an SCS
implementation. In accordance with known techniques, a Tuohy needle
14 is positioned near the dura 12 of spine 10. Lead body 20 is
inserted through the lumen of Tuohy needle 14 and positioned near
the dura 12. A proximal end (not shown) of lead body 20 is
connected to a source device (not shown) which may be a pulse
generator, in the case of electrical stimulation, or a drug pump in
the case of drug therapy. Although the invention will be described
herein with reference to SCS procedures and the embodiments
described in relation to electrical therapy, it will be recognized
that the invention finds utility in applications other than SCS
procedures, including other applications such as Peripheral Nervous
System (PNS) Stimulation, Sacral Root Stimulation, Cortical Surface
Stimulation or Intravecular Cerebral Stimulation. In addition, the
invention finds applicability to SCS procedures where the lead is
placed in the intrathecal (subdural) space. The invention also
finds utility to drug therapy where electrical components are
replaced with conduits and catheters for conducting drug material
to the therapy site. In this case, especially, the lead may be
placed in the intrathecal space.
[0055] FIGS. 2A thru 2D illustrate a lead according to a preferred
embodiment of the present invention. Lead 20 is provided with a
distal tip 30 that may be compacted for insertion and unfolded
after it has been positioned appropriately within the body. Distal
tip 30 includes a central portion 32 which has at least one span 34
depending therefrom. Span 34 is comprised of a flexible, insulative
material, such as polyurethane or silicone rubber. The term
"flexible" as used herein refers to both resilient and
non-resilient materials. Central portion 32 may have a generally
semi-circular cross-section as shown, or may be flat. A central
passage 33 may run axially along the inside of lead 20. A centering
stylet 25 is provided through central passage 33 and extends in a
distal direction through central portion 32 for engaging a part of
the body, such as adhesions in the epidural space, to stabilize
lead tip 30 as it is deployed. Affixed to a surface of spans 34 and
to the central portion 32 is a series of other therapy delivery
elements in the form of electrodes 36A-E. In accordance with the
invention lead 20 may be configured into a compact insertion
position shown in FIG. 2A. As shown in FIG. 2B, spans 34 are coiled
around central portion 32 such that the lateral extent of lead tip
30 is no larger than the lumen of Tuohy needle 14.
[0056] Once in position within the epidural space, lead tip 30 may
be deployed out of the Tuohy needle 14, as shown in FIG. 2C. FIG.
2D shows the view from the side opposite the side illustrated in
FIG. 2C. In the embodiment described in which the spans are flaccid
or semirigid, deployment of lead tip 30 may be implemented by
rotating the lead body 20 in a counterclockwise direction once lead
tip 30 is beyond the end of the Tuohy needle in a desired position.
As spans 34 encounter dura or dorsal bone of spinal canal, they can
uncoil to assume a generally planar shape in which electrodes 36A-E
are disposed on one side of the lead facing the dura, as shown in
FIG. 2E. As shown in phantom in FIG. 2D, electrodes 36A-E
communicate electrically with the source device (not shown) via
conductor paths 39 and 41. Conductor paths 39 and 41 may be
comprised of a flexible electrical conductor or thin wires which
are embedded or molded within lead 20.
[0057] In the case of drug therapy, the electrodes 36A-E
illustrated in FIGS. 2C-E would be replaced by ports which act as
therapy delivery elements to convey drug to the body. Similarly,
conductor paths 39 and 41 would be replaced by conduits formed in
the interior of lead 20 for conveying drug from the source device.
Stylet 25 may be left permanently in the epidural space or may be
withdrawn from the lead 20 after the lead tip 30 is uncoiled. In
the case of a drug delivery device, stylet 25 might remain as a
catheter at some preferred distance
[0058] FIG. 3 illustrates another embodiment of the invention in
which lead 20 is provided with a pair of guide pins 40 which are
affixed to a more proximal removable sheath 41 that surrounds lead
body 20. Alternatively, guide pins may be formed integrally on
Tuohy needle (not shown). Guide pins 40 act to guide spans 34
outward as the lead body 20 is rotated in a counterclockwise and to
guide spans 34 to coil around central portion as lead body 20 is
rotated in a clockwise direction. Guide pins 40 may be comprised of
a rigid, material and may be extended or retracted from sheath 41
or Tuohy needle 14. After spans 34 are deployed, sheath 41 may be
removed.
[0059] FIG. 4A illustrates another embodiment of the invention in
which spans 34 are formed as resilient or elastic elements. The
term "resilient" as used herein refers a tendency to return to an
undeformed state once spans 34 are no longer compressed to lay
beside central part 32. In accordance with this embodiment of the
invention, a retainer tube 50 is provided to retain lead tip 30 in
its compacted position until deployment is desired. Retainer tube
50 includes an inner passage which is sufficient to accommodate the
diameter or lateral extent of lead body 20 and its compact
shape-changing tip 30. The outer diameter of retainer tube 50 is
small enough that retainer tube 50 may also be inserted through the
lumen of Tuohy needle 14 (FIG. 1). Alternatively, tube 50 may
replace the Tuohy needle. Spans 34 are formed in such a manner that
they have a tendency to undertake a position in which they are
extended from central portion 32. Thus, in the compact insertion
position illustrated in FIG. 4A, resilient forces are present in
spans 34 to urge them outward into their extended, uncoiled
position. The resiliency of spans 34 may derive from the polymeric
material used to construct spans 34 or from resilient elements like
wires (not shown) which are incorporated into the interior or onto
the exterior surface of spans 34.
[0060] Referring to FIGS. 4B and 4C, in accordance with yet another
preferred embodiment of the invention, a notch 60 is provided in a
distal end 52 of retainer tube 50 to facilitate retraction of a
deployed lead. Preferably, one notch is provided for each span 34
provided on lead tip 30. In operation, retainer tube 50 is inserted
around a proximal end (not shown) of lead body 20 and pushed
towards lead tip 30 a sufficient distance until retainer tube 50
encounters lead tip 30. Lead body 20 is then pulled in a proximal
direction and simultaneously rotated, in a direction which may be
clockwise or counterclockwise, until lower edges 37 of spans 34
slide into notches 60. Under continued rotation of lead tip 30 and
lead 20, notches 60 function to guide spans 34 into their coiled,
compacted position. Once compacted, lead 20 may be retracted
further into retainer tube 50. Compacted lead 20 and retainer tube
50 may then be repositioned to a higher or lower point along the
spinal cord or may be removed from the body.
[0061] FIGS. 5A and 5B illustrate an expandable lead tip 130
according to another embodiment of the invention. Referring to FIG.
5B, lead tip 130 is comprised of a series of electrodes 136A-E
which are fastened to a flexible insulative backing sheet or span
140. The central portion of lead tip 130 is comprised of middle
electrode 136C. Span 140 may be constructed of polyurethane or
DACRON-reinforced silicone rubber. Electrodes 136A-E are in
electrical communication with source device (not shown) via a
series of conductors 139 incorporated into or onto span 140.
Electrodes 136A-E are embedded in span 140 or fastened by adhesive
or other known means. Ends 142 of span 140 are provided with
eyelets 144 for fastening to an expanding mechanism which will be
described below. This aspect of the invention provides a lead tip
130 which may assume a compacted position, in which electrodes
136A-E are stacked one on top of the other such that the thickness
of lead tip 130 may be reduced to a dimension that is slightly
larger than the collective thicknesses of electrodes 136A-E.
[0062] Referring to FIG. 5A, lead tip 130 may be expanded with the
use of an expansion mechanism 150 according to one aspect of the
invention. Expansion mechanism 150 comprises a series of struts 152
which are pivotally linked to one another such that points A and B
may be caused to move towards and away from one another in order to
compact or expand lead tip 130, respectively. A first linkage 156
is pivotally connected to struts 152A and 152B. A second link 158
is pivotally connected to links 152C and 152D. First and second
links 156 and 158 extend to a proximal end of lead body 10 where
they can be individually actuated by a clinician. By moving first
link 156 with respect to second link 158, points A and B are caused
to move toward or away from one another, thereby contracting or
expanding lead tip 130. By using rigid struts and linkages,
sufficient farces can be applied so that a space may be created for
the expanded size of lead tip 130. Introductory Sheath 170 may be
removed after lead tip 30 is expanded. Or, as another embodiment,
it might remain in the position shown, and a locking mechanism to
keep links 156 & 158 at a constant position might be able to
compress sheath 170 over the two links. A tether 180 sets a limit
on the separation of points A and B, and guarantees that electrodes
are evenly spaced when the length of tether 180 equals the length
of span 140.
[0063] FIGS. 6A and 6B illustrate another embodiment of the
invention. FIG. 6A is a cross-section of a lead tip 230 according
to a preferred embodiment of the invention which comprises a single
span 234 incorporating a series of conductors 236A-F therein. FIG.
6B illustrates a plan view of a mechanism 250 suitable for
deploying lead tip 230 or a stack of electrodes as shown in FIG.
5B. Mechanism 250 comprises a pair of links 252A and 252B pivotally
connected to one another and each pivotally connected to a
respective actuator link 258A and 258B. Through relative movement
of actuator links 258A and 258B, point A is caused to move toward
or away from link 258A, thereby causing contraction or expansion of
lead tip 230 or 130. One eyelet 144 on span 234 is attached to
point A, and the other eyelet may slide on link 258A. With this
embodiment, since the lead tip is pulled in one direction,
mechanism 250 in its initial, collapsed position, should be
positioned toward one side, for example, over the dorsal roots on
one side of the spinal cord. In the expanded position, point A
would advance to the opposite dorsal roots. Once again, a way to
lock point A at a certain expanded position is to have an anchor
along sheath 170 that compresses and holds sheath 170 against links
258A and 258B. Like mechanism 150, by using rigid struts and
linkages, a space can be created for lead tip 230.
[0064] FIG. 7 illustrates an expansion mechanism according to
another preferred embodiment of the invention. Lead tip 130 may be
expanded with the use of mechanism 350, comprised of struts 311 and
310. Linkage 330 is pivotally connected to the end of these struts.
Linkage 340 is pivotally connected to the center of these struts.
As linkages 330 and 340 are moved relative to each other be a
clinician, tips 360 will move together or apart. Eyelets 144 of
lead tip 130 (FIG. 5B) can be connected to tips 360.
[0065] FIGS. 8A and 8B illustrate an expandable lead according to
another preferred embodiment of the present invention. The lead
comprises a flexible outer coaxial accessory tube 802 which is
mounted over the distal end of lead body 801. A stop 806 is affixed
to the distal end of lead body 801 to prevent movement of the upper
end 830 of accessory tube 802 relative to lead body 801. The lower
end 832 of accessory tube 802 is adapted to slide with respect to
lead body 801. Accessory tube 802 includes a central slot 805
forming two flexible leaf portions 820 and 822. A recess 824 is
provided in each leaf portion 820 to form a bending joint therein.
The lower end 832 may be moved upward, thereby causing leaf
portions 820 to bend and deploy outward from the lead body 801. To
accuate the mechanism an actuator 807 is slid over the axial tube
801 by the clinician. While holding onto the axial tube 801, the
clinician pushes the actuator 807 against the accessory tube which
causes the slot 805 to separate and the lead to open as illustrated
in FIG. 8B. A series of ratchet rings 811, 812 and 813 are formed
in lead body 801 to prevent downward movement of lower end 832 of
accessory tube 802 to thereby retain the leaf portions 820 in their
outward, deployed position. These rachet rings will also allow and
hold different amounts of lateral expansion to be chosen by the
clinician. A rigid barrel electrode 803 is mounted on each leaf
portion 820 of the accessory tube 802. In the expanded position of
accessory tube 802, central electrodes 808. 809 and 810 are
exposed. Central electrodes 808, 809 and 810 and barrel electrodes
803 communicate electrically with the source device (not shown)
through electrical conductors (not shown) within the lead body.
[0066] FIG. 8C illustrates an expandable lead according to another
preferred embodiment of the present invention. This embodiment is
the same as that illustrated in FIGS. 8A and 8B except that a screw
actuator is provided for precise adjustment of the outward
deployment of leaf portions 820. The axial lead body 801 has a
threaded portion 811 formed therein. A threaded drive nut 812 is
mounted on the threaded portion of the lead body 811. The drive nut
has multiple indented holes 812a to receive an actuation driver
similar to 813. The drive nut is interlocked by pins (813a) on an
actuation driver 813 and rotated by the driver. This screw
apparatus allows finer adjustment of the expansion and also
adjustment of the expansion after implantation of the lead
device.
[0067] FIGS. 9A and 9B illustrate another embodiment of the
invention. Mechanism 450 can have a central element 410 that may
contain an electrode or catheter port 405. It may house
progressively smaller mobile telescoping parts 420, 430, 440 that
can be pushed outward toward one or more directions. Each mobile
part is provided with a shoulder 422 to limit its outward movement
and to recruit an adjacent mobile part. A tab 424 is provided to
limit inward movement. For an expansion in one plane, element 410
may have inside it one or more mechanisms 150 (FIG. 5A), 250 (FIG.
6B) or 350 (FIG. 7). Alternatively. there might be single, curved
linkage passing along lead 20 and attached to the final electrode
or catheter port site 445. As this linkage is moved by a clinician,
site 445 will move outward or inward, and itermediate sites will
follow if the movement of each site relative to the next site is
limited.
[0068] FIGS. 10A and 10B illustrate another embodiment of the
invention. In FIG. 10A, the lead 20 is in a compacted position,
with elastic and resilient transverse spans 500 bent to remain
inside the lumen of Tuohy needle 14. Spans 500 are adapted to bend
to a position substantially parallel to the axis of lead 20 in the
compact position. Once the lead is pushed beyond the needle, spans
500 will move by their resiliency to their natural position, as
shown in FIG. 10B. Those of ordinary skill will note that the
grouping of central electrode or catheter port 510 and the two
nearest side electrodes or ports 520 form a tripole/triport
arrangement transverse to the longitudinal direction of the lead
20. The clinician may have to place and manipulate a mechanism like
150, 250 or 350 prior to placement of this lead to create a space.
Alternatively, a metal material like NITINOL may be placed inside
span 500 and treated so that its position after removal of the
confinement of needle 14 will be perpendicular to the lead
axis.
[0069] FIGS. 11A and 11B illustrate another embodiment of the
invention. In FIG. 11A, the lead 20 is in a compacted position with
elastic and resilient spans 600 bent to remain inside the lumen of
Tuohy needle 14. There is a central electrode or catheter port 610.
The lateral electrodes/ports 620 are on members that will remain
parallel to the lead axis due to pivot points 630 and equal length
spans 600 above and below.
[0070] In FIG. 11B, the lead tip is beyond the introducing needle.
The spans 600 resume their normal, unstressed positions
perpendicular to the lead body axis. Lateral electrodes/ports 620
are on either side of central electrode/port 610. Removal may be
accomplished by pulling on the lead body with sufficient force to
bend the spans 600 back along the lead body, or by pushing another
catheter or needle over lead 20. It is recommended that there be a
thin, inert and flexible film (not shown) over the space between
spans to help removal by preventing tissue ingrowth. One embodiment
of the invention is to lock linkages as shown in FIGS. 5-7 into a
fixed orientation by using a compressive sleeve to squeeze the lead
body 20 inward against the linkages. This sleeve may be an anchor
to superficial (subcutaneous) tissue. To make a change, minor
surgery can be done to cut down to this anchor, loosen or remove
it, adjust the positions of the linkages, replace the
anchor/compressive sleeve, and resuture the wound. Obviously, the
clinician and patient need to believe that the benefits of such a
procedure out weigh the discomfort and risks.
[0071] FIGS. 12A through 12D illustrate mechanisms that may be used
to operate the linkages illustrated and described with respect to
FIGS. 5A, 6B, 7 and 9 in accordance with preferred embodiments of
the invention. FIG. 12A illustrates an embodiment of the invention
that allows chronic adjustment of the relative positions of two
actuating members 710 and 720. A rigid needle 775 with a sharp
hexagonal tip 785 is passed through the skin and engages a
hexagonal receptacle (possibly via reduction gears) 790 that is
capable of turning a circular component 760 inside of a container
750 beneath the patient skin. On end of this container 750 attaches
to the lead body 20, which contains the two actuating members 710
and 720 and wires/catheters 730 that go to the distal tip of the
lead 20. Another end of the container 750 connects to a lead 721
that conveys the wires/catheters 730 to a source device (not
shown). Actuating members 710 and 720 are connected to the rotating
component 760 are connected to the rotating component 760 by pivot
points 770 and 780. As the needle 775 is rotated, the linkages 710
and 720 will move relative to each other. This device 750 should be
large enough to be palpated under the skin, and the rotating
component 760 should be large enough so that limited rotation of
approximately 60.degree. causes sufficient movement of the
linkages.
[0072] FIG. 12B illustrates another preferred embodiment of a
linkage actuating mechanism according to a preferred embodiment of
the invention. This embodiment allows chronic adjustment of the
position of one linkage 810 relative to the lead body 20 using a
rack gear and pinion gear arrangement. This embodiment may be used
with a two-actuating member configuration as described with respect
to FIG. 12A, where one actuating member is fixed with respect to
lead body 20. As in the embodiment described above with respect to
FIG. 12A, a rigid needle (not shown) with a hex-head sharp tip is
passed through the patient's skin and engages a hexagonal
receptacle 865 that drives an internal gear 860 of subcutaneous
container 850. As gear 860 turns possibly with the aid of reducing
gears, it will move the actuating member 810 back or forth, which
has gear teeth 840 formed on its proximal end. A stop 870 prevents
excessive movement of actuating member 810. A wire/catheter group
830 passes from lead 20 through the container to another lead 821
from the source device. Alternatively, the source device could be
on the back side of the container 850. It will be recognized by
those of ordinary skill that there could be a number of gears
inside container 850 to change the direction of movement of the
actuating member 810, for example, to a rotary direction.
[0073] FIG. 12C illustrates another preferred embodiment of a
linkage actuating mechanism according to a preferred embodiment of
the invention. This embodiment allows chronic adjustment of the
position of linkage 910 relative to the lead body 20. Again, this
embodiment may be used with two linkage configurations where on
linkage is fixed with respect to the lead body 20. This embodiment
utilizes a hydraulic cylinder arrangement to actuate linkage 910.
In this case a noncoring hypodermic syringe needle (not shown) is
passed through the patient's skin and through a compressed rubber
septum 960 provided on the side of container 950. Fluid may be
added or withdrawn from beneath the septum, which is connected to a
syringe 940. The moveable plug of this syringe 920 is connected to
the moveable linkage 910. Again, the wires/catheters 930 from the
proximal tip of lead 20 pass through container 950 and on to the
source device. Alternatively, the source device could be on the
back side of container 950, although, for drug delivery, there
would need to be another system on the front of container 950 for
refilling the drug.
[0074] FIG. 12D illustrates an actuating mechansim according to a
preferred embodiment of the present invention that allows chronic
adjustment of the degree of rotation of linkage 1010 relative to
lead body 20. A rigid needle with a hex-head sharp tip can be
inserted into a hexagonal receptacle 1070 in container 1050.
Rotation of this needle device rotates gear 1020 which causes
rotation of gear 1040 attached to linkage 1010. There may be
restrictions on the movement of gear 1020 to prevent excessive
rotation.
[0075] The embodiments shown in FIGS. 12A-D demonstrate devices to
actuate linkages that pass to the distal tip of the lead and cause
changes in one or more dimensions of the lead paddle. As described,
these involve transmission of force or energy through the skin by
means of a needle that passes through the skin. The same effects
can be achieved by having a small motor implanted into the
container parts shown, or into the power source itself (not shown)
which runs on an electrical battery or transmitted and received
radio frequency signal, such as the motor provided in the totally
implantable, programmable drug device called SynchroMed.RTM.,
manufactured by Medtronic, Inc. of Minneapolis, Minn. Smaller
motors may be acceptable, especially if a sequence of gears may be
used to provide mechanical advantage. If such motors are used,
there should be a mechanical circuit breaker to prevent excess
motion of the linkages.
[0076] Very similar techniques would allow expansion of a lead in a
direction parallel to the lead body. For example, telescoping
elements with electrodes could move parallel to the axis of the
lead body (parallel to the spinal cord), similar to the way a car
antenna can be extended and retracted. By attaching electrodes and
catheter ports to the axial linkages of FIGS. 5 through 8, or
attaching eyelets 144 of compacted groups of electrodes/ports such
as items 130 or 230, it is possible to extend or compact said
groups of electrodes in an axial direction. This is a valuable
feature if one wishes to match the axial spacing of
electrodes/ports to important dimensions of the structure to be
stimulated/affected. For example, Holsheimer (Neurosurgery, vol.
40, 1997: pp 990-999) has shown that there may be preferred
longitudinal spacing of electrodes based upon the recruitment
factors in spinal cord tissue, and also critically dependent upon
the width of the CSF (cerebrospinal fluid) layer between the spinal
cord dorsal surface and the dura mater. Therefore, we wish to
include the ability to increase or decrease the longitudinal
spacing between electrodes/ports by these inventions, and to be
able to make a change in said spacing after initial implant of a
complete therapeutic system.
[0077] Those skilled in the art will recognize that the preferred
embodiments may be altered or amended without departing from the
true spirit and scope of the invention, as defined in the
accompanying claims.
* * * * *