U.S. patent application number 11/591171 was filed with the patent office on 2008-05-01 for implantable medical lead with threaded fixation.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Martin T. Gerber.
Application Number | 20080103572 11/591171 |
Document ID | / |
Family ID | 37966114 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080103572 |
Kind Code |
A1 |
Gerber; Martin T. |
May 1, 2008 |
Implantable medical lead with threaded fixation
Abstract
The disclosure is directed to securing electrodes of a medical
lead adjacent to a target tissue site. The medical lead may include
one or more threaded fixation structures disposed circumferentially
about the outer surface of the lead body, or elongated member, that
resembles a "screw" or "auger." During implantation, a clinician
may rotate the entire lead to "screw" the lead into the tissue of
the patient until electrodes of the lead reside adjacent to a
target tissue. In this manner, the threaded fixation structure
secures the lead within the patient to resist lead migration and
improper therapy and provide a fine adjustment for depth of
placement. The threaded fixation structure may be disposed on a
portion of the lead proximal to or distal to the electrodes of the
lead or over the portion of the lead that includes the
electrodes.
Inventors: |
Gerber; Martin T.; (Maple
Grove, MN) |
Correspondence
Address: |
SHUMAKER & SIEFFERT, P. A.
1625 RADIO DRIVE, SUITE 300
WOODBURY
MN
55125
US
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
37966114 |
Appl. No.: |
11/591171 |
Filed: |
October 31, 2006 |
Current U.S.
Class: |
607/116 |
Current CPC
Class: |
A61N 1/3605 20130101;
A61N 1/0558 20130101; A61N 1/0529 20130101; A61N 1/057 20130101;
A61N 1/0536 20130101; A61N 1/0534 20130101 |
Class at
Publication: |
607/116 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. A medical lead comprising: an elongated member having a proximal
end and a distal end; at least one stimulation electrode disposed
closer to the distal end of the lead than the proximal end of the
lead; and at least one threaded structure extending around a
portion of an outer surface of the elongated member and configured
to engage tissue within a patient to resist migration of the
medical lead.
2. The medical lead of claim 1, wherein the portion of the outer
surface is proximal to the at least one stimulation electrode.
3. The medical lead of claim 1, wherein the portion of the outer
surface is distal to the at least one stimulation electrode.
4. The medical lead of claim 3, further comprising a tapered tip at
the distal end of the elongated member, wherein the tapered tip
includes the portion.
5. The medical lead of claim 1, wherein the portion of the outer
surface includes the at least one stimulation electrode.
6. The medical lead of claim 1, wherein a plurality of threaded
fixation structures are formed around the portion of the outer
surface of the elongated member to simulate a continuous threaded
fixation structure.
7. The medical lead of claim 1, wherein the threaded fixation
structure is foldable in one direction to allow the thread
structure to lay substantially flat against the elongated member
when restrained by a sheath.
8. The medical lead of claim 1, further comprising a helical
reinforcement member disposed within an inner surface of the
elongated member to provide torsional rigidity to the elongated
member.
9. The medical lead of claim 8, wherein the helical reinforcement
member is disposed in a direction different than the direction of
the threaded fixation structure.
10. The medical lead of claim 1, wherein the threaded fixation
structure comprises a pitch between adjacent threads or
approximately 0.5 millimeters (mm) to approximately 3 mm.
11. The medical lead of claim 1, wherein the threaded fixation
structure comprises a thread height between approximately 0.1
millimeters (mm) and approximately 3 mm.
12. The medical lead of claim 1, wherein the threaded fixation
structure comprises at least one of a biocompatible metal alloy and
a biocompatible polymer.
13. A method comprising: inserting a medical lead into a patient,
wherein the lead comprises at least one stimulation electrode and
at least one threaded fixation structure extending around a portion
of an outer surface of the lead; and rotating the lead to engage
the threaded fixation structure with tissue of the patient to
resist migration of the lead.
14. The method of claim 13, further comprising removing a sheath
from the lead to expose the at least one threaded fixation
structure after the lead is inserted into the patient.
15. The method of claim 14, wherein removing the sheath allows the
at least one threaded fixation structure to unfold and extend from
the lead.
16. The method of claim 13, further comprising generating
electrical stimulation with a stimulator and delivering the
electrical stimulation to the patient via the at least one
stimulation electrode of the lead.
17. The method of claim 13, further comprising rotating the lead to
disengage the threaded fixation structure from the tissue in the
patient.
18. The method of claim 13, further comprising sliding a sheath
over the lead to cover the at least one threaded fixation structure
with the sheath.
19. The method of claim 18, further comprising removing the lead
and sheath from the patient
20. The method of claim 13, wherein inserting a medical lead into a
patient comprises forcing the at least one threaded fixation
structure to fold down against the outer surface of the lead in a
first direction.
21. The method of claim 20, further comprising pulling the lead in
the first direction to extend the at least one threaded fixation
structure into the tissue, and wherein rotating the lead causes the
at least one threaded fixation structure to advance the lead in a
second direction opposite the first direction.
22. The method of claim 13, further comprising positioning the at
least one electrode adjacent to at least one of a sacral nerve, a
pudendal nerve, a spinal cord, and an occipital nerve.
23. A system comprising: a medical lead comprising: an elongated
member having a proximal end and a distal end; at least one
stimulation electrode disposed closer to the distal end of the lead
than the proximal end of the lead; and at least one threaded
structure extending around a portion of an outer surface of the
elongated member and configured to engage tissue within a patient
to resist migration of the medical lead; and a stimulator that
delivers electrical stimulation therapy to a patient via the
medical lead within the patient.
24. An apparatus comprising: an elongated member having a proximal
end and a distal end; a conduit disposed within the elongated
member; an exit port disposed on an outer surface of the elongated
member in fluidic communication with the conduit; and at least one
threaded fixation structure extending around a portion of an outer
surface of the elongated member and configured to engage tissue
within a patient to resist migration of the medical lead.
25. The apparatus of claim 24, wherein the exit port is disposed on
an axial outer surface of the distal end of the elongated
member.
26. The apparatus of claim 24, wherein the exit port is disposed on
a longitudinal outer surface of the elongated member.
27. The apparatus of claim 26, wherein the at least one threaded
fixation structure is disposed at least one of proximal to the exit
port and distal to the exit port.
28. The apparatus of claim 24, wherein the at least one threaded
fixation structure is foldable in one direction to allow the thread
structure to lay substantially flat against the elongated member
when restrained by a sheath.
29. The apparatus of claim 24, further comprising a helical
reinforcement member disposed within an inner surface of the
elongated member to provide torsional rigidity to the elongated
member.
30. The apparatus of claim 29, wherein the helical reinforcement
member is disposed in a direction different than the direction of
the at least one threaded fixation structure.
31. The apparatus of claim 24, wherein the threaded fixation
structure comprises a pitch between approximately 0.5 millimeters
(mm) and 3 mm.
32. The apparatus of claim 24, wherein the threaded fixation
structure comprises a thread height between approximately 0.1
millimeters (mm) and 3 mm.
33. The apparatus of claim 24, wherein the threaded fixation
structure comprises at least one of a biocompatible metal alloy and
a biocompatible polymer.
34. The apparatus of claim 24, wherein the conduit delivers a
therapeutic agent to the patient via the exit port.
Description
TECHNICAL FIELD
[0001] The invention relates to stimulation systems and, more
particularly, to stimulation leads in stimulation systems.
BACKGROUND
[0002] Electrical stimulation systems may be used to deliver
electrical stimulation therapy to patients to treat a variety of
symptoms or conditions such as chronic pain, tremor, Parkinson's
disease, multiple sclerosis, spinal cord injury, cerebral palsy,
amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy,
pelvic floor disorders, or gastroparesis. An electrical stimulation
system typically includes one or more stimulation leads coupled to
an external or implantable electrical stimulator. The stimulation
lead may be percutaneously or surgically implanted in a patient on
a temporary or permanent basis such that at least one stimulation
electrode is positioned proximate to a target stimulation site. The
target stimulation site may be, for example, a spinal cord, pelvic
nerve, pudendal nerve, stomach, muscle, or within a brain or other
organ of a patient. The electrodes located proximate to the target
stimulation site may deliver stimulation therapy to the target
stimulation site in the form of electrical signals.
[0003] Electrical stimulation of a sacral nerve may eliminate or
reduce some pelvic floor disorders by influencing the behavior of
the relevant structures, such as the bladder, sphincter and pelvic
floor muscles. Pelvic floor disorders include urinary incontinence,
urinary urge/frequency, urinary retention, pelvic pain, bowel
dysfunction, and male and female sexual dysfunction. The organs
involved in bladder, bowel, and sexual function receive much of
their control via the second, third, and fourth sacral nerves,
commonly referred to as S2, S3 and S4 respectively. Thus, in order
to deliver electrical stimulation to at least one of the S2, S3, or
S4 sacral nerves, a stimulation lead is implanted proximate to the
sacral nerve(s).
[0004] Electrical stimulation of a peripheral nerve, such as
stimulation of an occipital nerve, may be used to induce
paresthesia. Occipital nerves, such as a lesser occipital nerve,
greater occipital nerve or third occipital nerve, exit the spinal
cord at the cervical region, extend upward and towards the sides of
the head, and pass through muscle and fascia to the scalp. Pain
caused by an occipital nerve, e.g. occipital neuralgia, may be
treated by implanting a lead proximate to the occipital nerve to
deliver stimulation therapy.
[0005] In many stimulation applications, including stimulation of a
sacral nerve, it is desirable for a stimulation lead to resist
migration following implantation. For example, it may be desirable
for the electrodes disposed at a distal end of the implantable
medical lead to remain proximate to a target stimulation site in
order to provide adequate and reliable stimulation of the target
stimulation site. In some applications, it may also be desirable
for the electrodes to remain substantially fixed in order to
maintain a minimum distance between the electrode and a nerve in
order to help prevent inflammation to the nerve and in some cases,
unintended nerve damage. Securing the stimulation lead at the
target stimulation site may minimize lead migration.
SUMMARY
[0006] In general, the disclosure is directed toward securing
electrodes of a medical lead adjacent to a target tissue site with
a threaded fixation structure configured to engage tissue within a
patient to resist migration of the medical lead. The medical lead
may be similar to a "screw" or "auger-like." The threaded fixation
structure defines one or more threads disposed circumferentially
about the outer surface of a lead body. Specifically, the threads
of the threaded fixation structure may be arranged in a helical
pattern. During implantation, a clinician may rotate the entire
lead to "screw" the lead into the tissue of the patient until
electrodes of the lead reside adjacent to a target tissue. In this
manner, the threaded fixation structure secures the lead within the
patient to resist lead migration. In addition, the threaded
fixation structure may allow a fine adjustment mechanism for the
depth of the elongated member within the tissue. The threaded
fixation structure may be disposed on a portion of the lead
proximal to or distal to the electrodes of the lead or over the
portion of the lead that includes the electrodes. In some cases,
the entire distal end of the lead may include the threaded fixation
structure to engage a greater area of tissue. In other embodiments,
the threaded fixation structure may be used with drug delivery
catheters instead of electrical stimulation leads.
[0007] In one embodiment, the disclosure is directed to a medical
lead that includes an elongated member having a proximal end and a
distal end, at least one stimulation electrode disposed closer to
the distal end of the lead than the proximal end of the lead, and
at least one threaded structure extending around a portion of an
outer surface of the elongated member and configured to engage
tissue within a patient to resist migration of the medical
lead.
[0008] In another embodiment, the disclosure is directed to method
that includes inserting a medical lead into a patient, wherein the
lead comprises at least one stimulation electrode and at least one
threaded fixation structure extending around a portion of an outer
surface of the lead, and rotating the lead to engage the threaded
fixation structure with tissue of the patient to resist migration
of the lead.
[0009] In an additional embodiment, the disclosure is directed to a
system that includes a medical lead having an elongated member
having a proximal end and a distal end, at least one stimulation
electrode disposed closer to the distal end of the lead than the
proximal end of the lead, and at least one threaded structure
extending around a portion of an outer surface of the elongated
member and configured to engage tissue within a patient to resist
migration of the medical lead. The system also includes a
stimulator that delivers electrical stimulation therapy to a
patient via the medical lead within the patient.
[0010] In another additional embodiment, the disclosure is directed
to an apparatus that includes an elongated member having a proximal
end and a distal end, a conduit disposed within the elongated
member, an exit port disposed on an outer surface of the elongated
member in fluidic communication with the conduit, and at least one
threaded fixation structure extending around a portion of an outer
surface of the elongated member and configured to engage tissue
within a patient to resist migration of the medical lead.
[0011] The disclosure may provide one or more advantages. The
threaded fixation structure may be engaged to the adjacent tissue
of the patient and still allow the clinician to advance or retract
the lead to finely adjust the lead position. A sheath may also be
used to cover the threaded fixation structure until the clinician
desires to expose the threaded fixation structure to the adjacent
tissue, and the sheath may collapse the threaded fixation structure
to reduce the lead diameter until lead fixation is desired. In
addition, the clinician may remove the lead by rotating the lead
and reducing tissue trauma.
[0012] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1A is a schematic perspective view of a therapy system
including an electrical stimulator coupled to a stimulation lead
that has been implanted in a body of a patient proximate to a
target stimulation site.
[0014] FIG. 1B is an illustration of the implantation of a
stimulation lead at a location proximate to an occipital nerve.
[0015] FIG. 2 is a block diagram illustrating various components of
an electrical stimulator and an implantable lead.
[0016] FIGS. 3A and 3B are perspective drawings of a sheath that
covers a lead prior to implantation and is removed after the lead
is correctly positioned in a patient.
[0017] FIGS. 4A-4C are perspective drawings illustrating exemplary
stimulation leads with varying configurations of threaded fixation
mechanisms.
[0018] FIGS. 5A-5B are perspective drawings illustrating exemplary
stimulation leads with varying threaded fixation mechanisms over
electrodes of the lead.
[0019] FIG. 6 is a perspective drawing illustrating an exemplary
stimulation lead with threads from the distal tip to a location
proximal to electrodes.
[0020] FIG. 7 is a perspective drawing illustrating an exemplary
stimulation lead with torsional reinforcement members within the
elongated member.
[0021] FIGS. 8A and 8B are perspective drawings illustrating
exemplary stimulation leads with foldable threads.
[0022] FIG. 9 is a flow diagram illustrating an exemplary process
for securing a threaded lead to a tissue of a patient.
[0023] FIG. 10 is a flow diagram illustrating an exemplary process
for removing a threaded lead from a tissue of a patient.
[0024] FIG. 11 is a flow diagram illustrating an exemplary process
for securing a lead with folding threads to a tissue of a
patient.
[0025] FIGS. 12A and 12B are perspective drawings illustrating
exemplary medical catheters with a helical threaded structure.
[0026] FIGS. 13A and 13B are cross-sectional end views of a keyed
stylet and reciprocally keyed medical lead.
DETAILED DESCRIPTION
[0027] The medical leads described herein include a threaded
fixation mechanism that secures the medical lead within a tissue of
a patient. The threaded fixation mechanism prevents the electrodes
of the lead from migrating away from the target stimulation tissue,
which may lead to a reduction in therapy efficacy. Specifically,
the threaded fixation mechanism includes a thread structure
disposed around the outer surface of the elongated member, such
that the lead resembles a "screw" or "auger" device that advances
or retreats when rotated. The threaded fixation mechanism may allow
the clinician to finely adjust the elongated member location, in
contrast to other medical lead fixation structures such as tines or
adhesives. Generally, the threads may be arranged in a helical
pattern, but other types of thread patterns may also be used to
secure the lead. Hence, the threaded fixation mechanism may be
referred to as a threaded fixation structure for purposes of
illustration. In addition, other non-helical thread patterns may be
used in some embodiments. The thread structure may be disposed
distal to the electrodes, proximal to the electrodes, and/or at the
same axial position of the electrodes. In addition, in some
embodiments, the threaded fixation structure may be disposed on a
tapered tip at the distal end of the elongated member to begin the
engagement and tunneling of the lead through the tissue when the
lead is rotated to secure the threaded fixation structure.
[0028] In some embodiments, the thread structure may not engage the
adjacent tissue until the user, e.g. a clinician, desires the
structure to do so. For example, a sheath may be configured to
cover the elongated member and thread structure for lead insertion
and be removed to allow the threaded fixation structure to contact
the adjacent tissue. In addition, the thread structure may fold
down against the elongated member outer surface when constricted by
the sheath. When the clinician removes the sheath, the threaded
fixation structure extends away from the elongated member and
returns to its original thread shape to secure the lead. In this
case, the thread structure may have elastic, super-elastic, or
shape memory properties that cause it to assume an extended
position when a sheath or other restraint mechanism is removed to
expose the thread structure.
[0029] Alternatively, the medical lead may not include electrodes
on the elongated member. In this case, the medical lead may be a
catheter that delivers a therapeutic agent through one or more
lumens in the elongated member, while the threaded fixation
structure secures the location of the catheter. The lumen may end
at one or more exit ports near the distal end of the elongated
member, and the exit ports may be disposed in an axial or
longitudinal outer surface of the elongated member.
[0030] FIG. 1A a schematic perspective view of therapy system 10,
which includes electrical stimulator 12 coupled to stimulation lead
14, which has been implanted in body 16 of a patient proximate to
target stimulation site 18. Electrical stimulator 12 provides a
programmable stimulation signal (e.g., in the form of electrical
pulses or substantially continuous-time signals) that is delivered
to target stimulation site 18 by stimulation lead 14, and more
particularly, via one or more stimulation electrodes carried by
lead 14. Electrical stimulator 12 may be either implantable or
external. For example, electrical stimulator 12 may be
subcutaneously implanted in the body of a patient 16 (e.g., in a
chest cavity, lower back, lower abdomen, or buttocks of patient
16). Electrical stimulator 12 may also be referred to as a pulse or
signal generator, and in the embodiment shown in FIG. 1A,
electrical stimulator 12 may also be referred to as a
neurostimulator. In some embodiments, lead 14 may also carry one or
more sense electrodes to permit stimulator 12 to sense electrical
signals from target stimulation site 18. Furthermore, in some
embodiments, stimulator 12 may be coupled to two or more leads,
e.g., for bilateral or multi-lateral stimulation.
[0031] Lead 14 further includes a lead body, or elongated member,
and one or more threaded fixation structures (not shown in FIG. 1)
which engage with tissue proximate to target stimulation site 18 to
substantially fix a position of lead 14 proximate to target
stimulation site 18. The threaded fixation structure is rotated
during implantation to engage with tissue adjacent to target
stimulation site 18. Proximal end 14A of lead 14 may be both
electrically and mechanically coupled to connector 13 of stimulator
12 either directly or via a lead extension. In particular, lead 14
may include electrical contacts near proximal end 14A to
electrically connect conductors disposed within the elongated
member to stimulation electrodes (and sense electrodes, if present)
at a position adjacent to distal end 14B of lead 14 to stimulator
12. Lead 14 may be connected directly or indirectly (e.g., via a
lead extension) to stimulator 12.
[0032] In the example embodiment of therapy system 10 shown in FIG.
1A, target stimulation site 18 is proximate to the S3 sacral nerve,
and lead 14 has been introduced into the S3 sacral foramen 22 of
sacrum 24 to access the S3 sacral nerve. Stimulation of the S3
sacral nerve may help treat pelvic floor disorders, urinary control
disorders, fecal control disorders, interstitial cystitis, sexual
dysfunction, and pelvic pain. Therapy system 10, however, is useful
in other stimulation applications. Thus, in alternate embodiments,
target stimulation site 18 may be a location proximate to any of
the other sacral nerves in body 16 or any other suitable nerve in
body 16, which may be selected based on, for example, a therapy
program selected for a particular patient. For example, in other
embodiments, therapy system 10 may be used to deliver stimulation
therapy to pudendal nerves, perineal nerves, or other areas of the
nervous system, in which cases, lead 14 would be implanted and
substantially fixed proximate to the respective nerve. As further
alternatives, lead 14 may be positioned for temporary or chronic
spinal cord stimulation for the treatment of pain, for peripheral
neuropathy or post-operative pain mitigation, ilioinguinal nerve
stimulation, intercostal nerve stimulation, gastric stimulation for
the treatment of gastric mobility disorders and obesity, muscle
stimulation (e.g., functional electrical stimulation (FES) of
muscles), for mitigation of other peripheral and localized pain
(e.g., leg pain or back pain), or for deep brain stimulation to
treat movement disorders and other neurological disorders.
Accordingly, although sacral nerve stimulation will be described
herein for purposes of illustration, a stimulation lead 14 in
accordance with the invention may be adapted for application to a
variety of electrical stimulation applications.
[0033] Migration of lead 14 following implantation may be
undesirable, and may have detrimental effects on the quality of
therapy delivered to a patient 16. For example, migration of lead
10 may cause displacement of electrodes carried by lead 14 to a
target stimulation site 18. As a result, the electrodes may not be
properly positioned to deliver the therapy, possibly undermining
therapeutic efficacy of the stimulation therapy from system 10.
Substantially fixing lead 14 to surrounding tissue may help
discourage lead 14 from migrating from target stimulation site 18
following implantation, which may ultimately help avoid harmful
effects that may result from a migrating stimulation lead 14.
[0034] To that end, the invention provides lead 14 with a thread
structure (not shown in FIG. 1) disposed around the elongated
member of lead 14 to provide fixation between lead 14 and tissue
surrounding lead 14, such as tissue within sacrum 16 in the example
of FIG. 1A. The thread structure may have a helical pattern that
permits lead 14 to be, in effect, screwed into a tissue site. In
comparison to some existing methods of fixing implanted medical
leads, such as suturing lead 14 to surrounding tissue or applying a
cuff electrode, using a threaded fixation structure to secure lead
14 in patient 16 may be beneficial in a minimally invasive surgery,
which may allow for reduced pain and discomfort for patient 16
relative to invasive surgery, as well as a quicker recovery time.
As described in further detail below, the threaded fixation
structure is disposed around the outer surface of the elongated
body near the distal end of lead 14 and configured to engage with
the adjacent tissue to prevent lead 14 movement.
[0035] Implanting lead 14 with the threaded fixation structure may
be completed via a few methods. First, the clinician may rotate
lead 14 to advance lead 14 toward target stimulation sire 18 and
utilize the threaded fixation structure to engage the adjacent
tissue. Second, a sheath (not shown in FIG. 1A) may be used
initially to cover lead 14 and the included threaded fixation
structure to allow the clinician to insert lead 14 into patient 16
until direct insertion is no longer possible. At this point, the
clinician may remove the sheath to expose the threaded fixation
structure and then rotate lead 14 to advance lead 14 the rest of
the distance towards target stimulation site 18.
[0036] The rotation of lead 14 may be achieved directly by rotating
the lead body, or by a stylet or other device that is inserted into
an inner lumen of the lead to engage the lead. In some embodiments,
the stylet may have a keyed structure, such as one or more
longitudinal flanges, ribs, teeth or grooves that engage reciprocal
structure in the inner lumen of the lead. For example, a keyed
stylet may be inserted to engage the distal end of the lead and
lock into interior grooves or teeth to facilitate the rotation of
the lead. In particular, reciprocal teeth or grooves, or the like,
may rotationally bear against each other such that rotation of the
stylet causes rotation of the lead in the same direction.
[0037] In addition, the threaded fixation structure may be foldable
against the elongated member of lead 14 when covered by the sheath.
When the sheath is removed, the threaded fixation structure may
stand up, or extend, away from the elongated member to its original
shape. The clinician may then rotate lead 14 to advance lead 14 to
target stimulation site 18. In either case, the thread tends to
"bite" into the surrounding tissue to resist migration of the lead
from the target stimulation site.
[0038] Therapy system 10 also may include a clinician programmer 26
and a patient programmer 28. Clinician programmer 26 may be a
handheld computing device that permits a clinician to program
stimulation therapy for patient 16, e.g., using input keys and a
display. For example, using clinician programmer 26, the clinician
may specify stimulation parameters for use in delivery of
stimulation therapy. Clinician programmer 26 supports telemetry
(e.g., radio frequency telemetry) with stimulator 12 to download
stimulation parameters and, optionally, upload operational or
physiological data stored by stimulator 12. In this manner, the
clinician may periodically interrogate stimulator 12 to evaluate
efficacy and, if necessary, modifies the stimulation
parameters.
[0039] Like clinician programmer 26, patient programmer 28 may be a
handheld computing device. Patient programmer 28 may also include a
display and input keys to allow patient 16 to interact with patient
programmer 28 and implantable stimulator 12. In this manner,
patient programmer 28 provides patient 16 with an interface for
control of stimulation therapy by stimulator 12. For example,
patient 16 may use patient programmer 28 to start, stop or adjust
stimulation therapy. In particular, patient programmer 28 may
permit patient 16 to adjust stimulation parameters such as
duration, amplitude, pulse width and pulse rate, within an
adjustment range specified by the clinician via clinician
programmer 28, or select from a library of stored stimulation
therapy programs.
[0040] Stimulator 12, clinician programmer 26, and patient
programmer 28 may communicate via cables or a wireless
communication, as shown in FIG. 2. Clinician programmer 26 and
patient programmer 28 may, for example, communicate via wireless
communication with stimulator 12 using radio frequency (RF)
telemetry techniques known in the art. Clinician programmer 26 and
patient programmer 28 also may communicate with each other using
any of a variety of local wireless communication techniques, such
as RF communication according to the 802.11 or Bluetooth
specification sets, or other standard or proprietary telemetry
protocols.
[0041] FIG. 1B is a conceptual illustration of an alternative
implantation site to the implantation of FIG. 1A. Therapy system 10
may also be used to provide stimulation therapy to other nerves of
a patient 16. For example, as shown in FIG. 1B, lead 14 may be
implanted and fixated with the two or more threaded fixation
members proximate to an occipital region 29 of patient 30 for
stimulation of one or more occipital nerves. In particular, lead 14
may be implanted proximate to lesser occipital nerve 32, greater
occipital nerve 34, and third occipital nerve 36. In FIG. 1B, lead
14 is aligned to be introduced into introducer needle 38 and
implanted and anchored or fixated with fixation elements proximate
to occipital region 29 of patient 30 for stimulation of one or more
occipital nerves 32, 34, and/or 36. A stimulator (e.g., stimulator
12 in FIG. 1A) may deliver stimulation therapy to any one or more
of occipital nerve 32, greater occipital nerve 34 or third
occipital nerve 36 via electrodes disposed adjacent to distal end
14B of lead 14. In alternate embodiments, lead 14 may be positioned
proximate to one or more other peripheral nerves proximate to
occipital nerves 32, 34, and 36 of patient 30, such as nerves
branching from occipital nerves 32, 34, and 36, as well as
stimulation of any other suitable nerve, organ, muscle, muscle
group or other tissue site within patient 30, such as, but not
limited to, nerves within a brain, pelvis, stomach or spinal cord
of patient 30.
[0042] Implantation of lead 14 may involve the subcutaneous
placement of lead 14 transversely across one or more occipital
nerves 32, 34, and/or 36 that are causing patient 30 to experience
pain. In one example method of implanting lead 14 proximate to the
occipital nerve, using local anesthesia, a vertical skin incision
33 approximately two centimeters in length is made in the neck of
patient 30 lateral to the midline of the spine at the level of the
C1 vertebra. The length of vertical skin incision 33 may vary
depending on the particular patient. At this location, patient's
skin and muscle are separated by a band of connective tissue
referred to as fascia. Introducer needle 38 is introduced into the
subcutaneous tissue, superficial to the fascia and muscle layer but
below the skin. Occipital nerves 32, 34, and 36 are located within
the cervical musculature and overlying fascia, and as a result,
introducer needle 38 and, eventually, lead 14 are inserted superior
to occipital nerves 32, 34, and 36.
[0043] Once introducer needle 38 is fully inserted, lead 14 may be
advanced through introducer needle 38 and positioned to allow
stimulation of the lesser occipital nerve 32, greater occipital
nerve 34, third occipital nerve 36, and/or other peripheral nerves
proximate to an occipital nerve. Upon placement of lead 14,
introducer needle 38 may be removed. In some embodiments,
introducer needle 38 may be used to remove lead 14 after
stimulation therapy is no longer needed.
[0044] Accurate lead placement may affect the success of occipital
nerve stimulation. If lead 14 is located too deep, i.e., anterior,
in the subcutaneous tissue, patient 30 may experience muscle
contractions, grabbing sensations, or burning. Such problems may
additionally occur if lead 14 migrates after implantation.
Furthermore, due to the location of implanted lead 14 on the back
of patient's 30 neck, lead 14 may be subjected to pulling and
stretching that may increase the chances of lead migration. For
these reasons, lead 14 may employ the threaded fixation structure
to secure lead 14 within patient 16. In locations near the skin of
patient 16, the threaded fixation structure may only extend from
the elongated body of lead 14 a small distance to minimize patient
detection of the threaded fixation structure at superficial implant
locations. In other words, the thread structure may be sized so as
not to protrude excessively into the superficial tissues, thereby
avoiding skin deformations and potential tissue erosion and
damage.
[0045] Although lead 14 has been generally described as an
electrical lead that includes electrodes, lead 14 may, in other
embodiments, be a drug delivery catheter that delivers therapeutic
agents to target stimulation site 18 (FIG. 1A) or occipital nerves
32, 34 or 36. In this case, stimulator 12 is a drug pump that
controls the delivery of therapeutic agent to patient 16. The drug
delivery catheter embodiment of lead 14 may include an exit port
for the therapeutic agent that is disposed on any surface of lead
14, adjacent to or within the threaded fixation structure.
[0046] FIG. 2 is a block diagram illustrating various components of
implantable stimulator 12 and an implantable lead 14. Stimulator 12
includes therapy delivery module 40, processor 42, memory 44,
telemetry module 46, and power source 47. In some embodiments,
stimulator 12 may also include a sensing circuit (not shown in FIG.
2). Implantable lead 14 includes elongated member 48 extending
between proximal end 48A and distal end 48B. Elongated member 48
may also be described as an elongated member. Elongated member 48
may be a cylindrical or may be a paddle-shaped (i.e., a "paddle"
lead). Electrodes 50A, 50B, 50C, and 50D (collectively "electrodes
50") are disposed on elongated member 48 adjacent to distal end 48B
of elongated member 48. In the example of FIG. 2, threaded fixation
structures are omitted from lead 14 for ease of illustration.
[0047] Stimulator 12 delivers stimulation therapy via electrodes 50
of lead 14. In particular, implantable signal generator within
therapy delivery module 40 delivers electrical signals to patient
16 (FIG. 1A) via at least some of electrodes 50 under the control
of a processor 42. The stimulation energy generated by therapy
delivery module 40 may be formulated as stimulation energy, e.g.,
for treatment of any of a variety of neurological disorders, or
disorders influenced by patient neurological response. The signals
may be delivered from therapy delivery module 40 to electrodes 50
via a switch matrix and conductors carried by lead 14 and coupled
to respective electrodes 50.
[0048] In some embodiments, electrodes 50 may be ring electrodes.
In other embodiments, electrodes 50 may be segmented or partial
ring electrodes, each of which extends along an arc less than 360
degrees (e.g., 90-120 degrees) around the circumference of
elongated member 48. In embodiments in which lead 14 is a paddle
lead, electrodes 50 may extend along a portion of the periphery
defined by elongated member 48. Electrodes 50 are electrically
coupled to a therapy delivery module 40 of stimulator 12 via
conductors within elongated member 48.
[0049] Electrodes 50 extending around a portion of the
circumference of lead body 48 or along one side of a paddle lead
may be useful for providing an electrical stimulation field in a
particular direction/targeting a particular therapy delivery site.
For example, in the electrical stimulation application shown in
FIG. 1B, electrodes 50 may be disposed along lead body 48 such that
the electrodes face toward occipital nerves 32, 34, and/or 36, or
otherwise away from the scalp of patient 30. This may be an
efficient use of stimulation because electrical stimulation of the
scalp may provide minimally useful therapy, if any, to patient 30.
In addition, the use of segmented or partial ring electrodes 50 may
also reduce the overall power delivered to electrodes 50 by
stimulator 12 because of the efficient delivery of stimulation to
occipital nerves 32, 34, and/or 36 (or other target stimulation
site) by eliminating or minimizing the delivery of stimulation to
unwanted or unnecessary regions within patient 30. The
configuration, type, and number of electrodes 28 illustrated in
FIG. 2 are merely exemplary.
[0050] In embodiments in which electrodes 50 extend around a
portion of the circumference of lead body 48 or along one side of a
paddle lead, lead 14 may include one or more orientation markers 45
proximate to proximal end 14A that indicate the relative location
of electrodes 50. Orientation marker 45 may be a printed marking on
lead body 48, an indentation in lead body 48, a radiographic
marker, or another type of marker that is visible or otherwise
detectable (e.g., detectable by a radiographic device) by a
clinician. Orientation marker 45 may help a clinician properly
orient lead 14 such that electrodes 50 face the desired direction
(e.g., toward occipital nerves 32, 34, and/or 36) within patient
16. For example, orientation marker 45 may also extend around the
same portion of the circumference of lead body 48 or along the side
of the paddle lead as electrodes 50. In this way, orientation
marker 45 faces the same direction as electrodes, thus indicating
the orientation of electrodes 50 to the clinician. When the
clinician implants lead 14 in patient 16, orientation marker 45 may
remain visible to the clinician.
[0051] Stimulator 12 delivers stimulation therapy via electrodes 50
of lead 14. In one embodiment, an implantable signal generator or
other stimulation circuitry within therapy delivery module 40
delivers electrical signals (e.g., pulses or substantially
continuous-time signals, such as sinusoidal signals) to targets
stimulation site 18 (FIG. 1A) via at least some of electrodes 50
under the control of a processor 42. The stimulation energy
generated by therapy delivery module 40 may be formulated as
stimulation energy, e.g., for treatment of any of a variety of
neurological disorders, or disorders influenced by patient
neurological response. The signals may be delivered from therapy
delivery module 40 to electrodes 50 via a switch matrix and
conductors carried by lead 14 and electrically coupled to
respective electrodes 50. The implantable signal generator may be
coupled to power source 47. Power source 47 may take the form of a
small, rechargeable or non-rechargeable battery, or an inductive
power interface that transcutaneously receives inductively coupled
energy. In the case of a rechargeable battery, power source 47
similarly may include an inductive power interface for
transcutaneous transfer of recharge power.
[0052] Processor 42 may include a microprocessor, a controller, a
DSP, an ASIC, an FPGA, discrete logic circuitry, or the like.
Processor 42 controls the implantable signal generator within
therapy delivery module 40 to deliver stimulation therapy according
to selected stimulation parameters. Specifically, processor 42
controls therapy delivery module 40 to deliver electrical signals
with selected amplitudes, pulse widths (if applicable), and rates
specified by the programs. In addition, processor 42 may also
control therapy delivery module 40 to deliver the stimulation
signals via selected subsets of electrodes 50 with selected
polarities. For example, electrodes 50 may be combined in various
bipolar or multi-polar combinations to deliver stimulation energy
to selected sites, such as nerve sites adjacent the spinal column,
pelvic floor nerve sites, or cranial nerve sites.
[0053] In addition, processor 42 may control therapy delivery
module 40 to deliver each signal according to a different program,
thereby interleaving programs to simultaneously treat different
symptoms or provide a combined therapeutic effect. For example, in
addition to treatment of one symptom such as sexual dysfunction,
stimulator 12 may be configured to deliver stimulation therapy to
treat other symptoms such as pain or incontinence.
[0054] Memory 44 of stimulator 12 may include any volatile or
non-volatile media, such as a RAM, ROM, CD-ROM, NVRAM, EEPROM,
flash memory, and the like. In some embodiments, memory 44 of
stimulator 12 may store multiple sets of stimulation parameters
that are available to be selected by patient 16 or a clinician for
delivery of stimulation therapy. For example, memory 44 may store
stimulation parameters transmitted by clinician programmer 26 (FIG.
1A). Memory 44 also stores program instructions that, when executed
by processor 42, cause stimulator 12 to deliver stimulation
therapy. Accordingly, computer-readable media storing instructions
may be provided to cause processor 42 to provide functionality as
described herein.
[0055] In particular, processor 42 controls telemetry module 170 to
exchange information with an external programmer, such as clinician
programmer 26 and/or patient programmer 28 (FIG. 1A), by wireless
telemetry. In addition, in some embodiments, telemetry module 46
supports wireless communication with one or more wireless sensors
that sense physiological signals and transmit the signals to
stimulator 12.
[0056] In some embodiments, where lead 14 is a drug delivery
catheter, therapy delivery module 40 may include a fluid pump or
other release mechanism to dispense a therapeutic agent through
lead 14 and into patient 16. Therapy deliver module 40 may also, in
this case, include a fluid reservoir which contains the therapeutic
agent. Possible therapeutic agents may include pharmaceutical
agents, insulin, a pain relieving agent or a gene therapy agent.
Refilling the fluid reservoir may be accomplished by inserting the
needle of a syringe through the skin of patient 16 and into a
refill port in the housing of stimulator 12. In addition, more than
one lead may be coupled to therapy delivery module 40.
[0057] FIGS. 3A and 3B are perspective drawings of a sheath that
covers a lead prior to implantation and removed after the lead is
correctly positioned in a patient, which includes a lead that
includes a threaded fixation structure. As shown in FIG. 3A, lead
52 is capable of delivering electrical stimulation to numerous
tissue sites within patient 16. Lead 52 may be an embodiment of any
lead described herein, including lead 14. Prior to delivering
stimulation, elongated member 54 of lead 52 is covered completely
around the longitudinal outer surface with sheath 58. Sheath 58 may
be constructed to protect electrodes 56 and threaded fixation
structure 57 from implantation stresses or damage of adjacent
tissues. In addition, sheath 58 may be a restraint mechanism that
keeps threaded fixation structure 57 from being deployed until the
clinician removed the sheath. Electrodes 56 are typically ring
electrodes, but other types of electrodes may be used. For example,
segmented electrodes, or multiple electrodes around the
circumference of elongated member 54 may be employed.
Alternatively, lead 52 may be in a non-circular shape, such as a
rectangular paddle lead. In some embodiments, lead 52 may also
include one or more radio-opaque markers that allow the clinician
to image the lead in real time to determine the exact position of
the lead within patient after rotating the lead.
[0058] Sheath 58 may be constructed of a flexible polymer that
provides a smooth interface between the sheath and elongated member
54. Sheath 58 may be dimensioned just larger than elongated member
54, or the sheath may be shrunk to fit elongated member 54 snugly
for implantation. In some embodiments, sheath 58 may constructed to
assist the clinician in guiding lead 52 within patient 16. In this
case, sheath 58 may be rigid or semi-rigid and similar to a lead
introducer or a cannula introduction device.
[0059] FIG. 3B shows lead 52 with sheath 58 being removed from
elongated member 54 in the direction of the arrow. Once lead 52 is
positioned such that electrodes 56 are adjacent to a target tissue
for stimulation, the clinician may begin removing lead 52 as shown.
As sheath 58 is removed, threaded fixation structure 57 is exposed
to the adjacent tissue to fix elongated member 54 in position. In
other embodiments, the clinician may remove sheath 58 in sections
as fixation elements need to be deployed or as necessary to ensure
proper fixation within patient 16. As will be described in detail
below, threaded fixation structure 57 may have different
dimensions, sizes, locations, and properties than shown in FIGS. 3A
and 3B.
[0060] FIGS. 4A-4C are perspective drawings illustrating exemplary
stimulation leads with varying configurations of threaded fixation
mechanisms. As shown in FIG. 4A, lead 60 includes elongated member
62, electrodes 64, tapered tip 68, and threaded fixation structure
70. The distal end of lead 60 is shown. Elongated member 62 is
substantially cylindrical in shape, but the elongated member may
also be configured into any other shape. Electrodes 64 are ring
electrodes disposed at the distal end of elongated member 62. At
the distal tip of lead 60, tapered, conical tip 68 is attached to,
or integrally formed with, elongated member 62. Threaded fixation
structure 70 is disposed distal to electrodes 64 and around the
outer surface of tapered tip 68.
[0061] Tapered tip 68 is formed in the shape of a cone to
facilitate the tunneling of lead 60 through tissue in order to
reach the target tissue. Threaded fixation structure 70 is disposed
around the outer surface of tapered tip 68 from adjacent to the
distal end of the tapered tip to the distal end of elongated member
62. In this manner, threaded fixation structure 70 engages with the
adjacent tissue of patient 16 as tapered tip 68 pierces through the
tissue. As a user, e.g., a clinician, rotates lead 60, threaded
fixation structure 70 advances the lead through the adjacent tissue
and moves electrodes 64 increasingly closer to a target tissue with
each turn of the lead. In other embodiments threaded fixation
structure 70 may only be disposed along a portion of tapered tip
68.
[0062] Threaded fixation structure 70 may be constructed of a
material similar to or different from elongated member 62 or
tapered tip 68. The material of threaded fixation structure 70 may
be substantially biologically inert, e.g., biocompatible, and may
include any of metals, metal alloys, composites, or polymers. Some
example materials may include stainless steel, titanium, nitinol,
polypropylene, polyurethane, polycarbonate, polyethylene, nylon,
silicone rubber, or expanded-polytetrafluoroethylene. The material
selection of threaded fixation structure 70 may be based upon
whether the structure is desired to be rigid, semi-rigid, or
flexible properties, which could affect the engagement of the
structure to the adjacent material. In addition, threaded fixation
structure 70 may be a combination of different materials depending
on the implantation site. For example, threaded fixation structure
70 may have a flexible distal portion that changes to a rigid
portion for precise engagement with the adjacent tissue. Threaded
fixation structure 70 may be adhered to tapered tip 68 through a
glue, an epoxy, welding, soldering, or any other attachment
mechanism. In other embodiments, threaded fixation structure 70 may
be an overmold that is fitted to a snug fit around elongated member
62. Alternatively, threaded fixation structure 70 may be formed
with tapered tip 68.
[0063] In addition, threaded fixation structure 70 may have a
cross-sectional shape configured to assist the advancement of lead
60 through the adjacent tissue. The cross-sectional shape of each
thread may generally be a triangle, but other shapes are possible.
For example, the cross-sectional shape of threaded fixation
structure 70 may be a rounded triangle, a semi-circle, a square, a
rectangle, a trapezoid, or any other shape desired by the
clinician. In addition, the cross-sectional shape may be angled in
a direction non-perpendicular to the outer surface of tapered tip
68. For example, threaded fixation structure 70 may be tilted
toward the proximal end of lead 60. In other words, the angle
between the outer surface of tapered tip 68 and the proximal side
of threaded fixation structure 70 may be less than 90 degrees.
Alternatively, the angle between the outer surface of tapered tip
68 and the proximal side of threaded fixation structure 70 may be
greater than 90 degrees.
[0064] Threaded fixation structure 70 may also be configured to
advance through tissue at a predetermined rate or extend into the
tissue a predetermined distance. The pitch of threaded fixation
structure 70 may be defined by the distance lead 60 is advanced
with each full 360 degree rotation of the lead, i.e., the axial
distance between two peaks of the threaded fixation structure.
Threaded fixation structure 70 may have a pitch between
approximately 0.5 millimeters (mm) and 3 mm. The pitch may be less
than approximately 0.5 mm or greater than 3 mm. The height of
threaded fixation structure 70 is the distance between the outer
surface of tapered tip 68 and the top edge of the threaded fixation
structure. Generally, the height is between approximately 0.1 mm
and 3 mm. However, other embodiments of threaded fixation structure
70 may include heights smaller than approximately 0.1 mm or greater
than 3 mm. While threaded fixation structure 70 may have a constant
height, the threaded fixation structure may increase in height as
the threaded fixation structure moves away from the distal end of
tapered tip 68. Generally, elongated member 62 may have an outside
diameter between approximately 0.5 mm and 5 mm. The wall thickness
of elongated member 62 may be between approximately 0.1 mm and 2
mm. In addition, the ratio of diameter to thread height may be
between approximately 1 and 50, depending on the application of
lead 60.
[0065] FIG. 4B shows lead 72, which is an embodiment of lead 60
(FIG. 4A). Lead 72 includes elongated member 74, electrodes 76,
tapered tip 80, and threaded fixation structure 82. Lead 72 differs
from lead 60 in the shape of tapered tip 80. While tapered tip 68
is constructed as a cone shape, tapered tip 80 is a parabolic shape
with an atraumatic, rounded distal end. Tapered tip 80 may be
beneficial if the clinician does not want a tip that may damage
adjacent tissue during extreme bends of elongated member 74. In
other embodiments, tapered tip 80 may be configured into a
different shape. For example, tapered tip 80 may be curved in any
parabolic shape different from that shape of the tapered tip shown
in FIG. 4B. In addition, tapered tip 80 may be asymmetrical or bent
in a predetermined direction to facilitate creating a curved path
for lead 72.
[0066] FIG. 4C illustrates lead 84 with threaded fixation structure
90 disposed proximal to electrodes 88. Lead 84 includes elongated
member 86, electrodes 88 and threaded fixation structure 90.
Threaded fixation structure 90 is disposed around the longitudinal
outer surface of elongated member 86, proximal to the location of
electrodes 88. In other embodiments, threaded fixation structure 90
may be disposed around the longitudinal outer surface of elongated
member 86 at a location distal to electrodes 88. The distal
position of threaded fixation structure 90 may be instead of or in
addition to the proximal position of the threaded fixation
structure.
[0067] Threaded fixation structure 90 may include any number of
turns around elongated member 86. For example, threaded fixation
structure 90 may include 3 complete turns as shown in FIG. 4C.
However, threaded fixation structure 90 may include more than 3 or
less than 3 turns, as desired by the clinician for a particular
implantation site. In addition, threaded fixation structure 90 may
include partial turns, or even continuous structures with less than
one complete turn. In other embodiments, multiple threaded fixation
structures 90 may be disposed proximal to or distal to electrodes
88. In alternative embodiments, lead 84 may include a tip that has
a threaded fixation structure such as tapered tips 68 and 80 of
leads 60 and 72, respectively.
[0068] Threaded fixation structure 90 may be constructed of a
material similar to or different from elongated member 86. The
material of threaded fixation structure 90 may be substantially
biologically inert, e.g., biocompatible, and may include any of
metals, metal alloys, composites, or polymers. Some example
materials may include stainless steel, titanium, nitinol,
polypropylene, polyurethane, polycarbonate, polyethylene, nylon,
silicone rubber, or expanded-polytetrafluoroethylene. The material
selection of threaded fixation structure 90 may be based upon
whether the structure is desired to be rigid, semi-rigid, or
flexible properties. Threaded fixation structure 90 may be adhered
to elongated member 86 through a glue, an epoxy, welding,
soldering, or any other attachment mechanism. In other embodiments,
threaded fixation structure 90 may be an overmold that is fitted to
a snug fit around elongated member 86. Alternatively, threaded
fixation structure 90 may be integrally formed with elongated
member 86, e.g., by injection molding and/or insert molding.
[0069] In addition, threaded fixation structure 90 may have a
cross-sectional shape configured to assist the advancement of lead
84 through the adjacent tissue. The cross-sectional shape may
generally be a triangle, but other shapes are possible. For
example, the cross-sectional shape of threaded fixation structure
90 may be a rounded triangle, a semi-circle, a square, a rectangle,
a trapezoid, or any other shape desired by the clinician. In
addition, the cross-sectional shape may be angled in a direction
non-perpendicular to the outer surface of elongated member 86. For
example, threaded fixation structure 90 may be tilted toward the
proximal end of lead 84. In other words, the angle between the
outer surface of elongated member 86 and the proximal side of
threaded fixation structure 90 may be less than 90 degrees.
Alternatively, the angle between the outer surface of elongated
member 86 and the proximal side of threaded fixation structure 90
may be greater than 90 degrees.
[0070] Threaded fixation structure 90 may also be configured to
advance through tissue at a predetermined rate or extend into the
tissue a predetermined distance. The pitch of threaded fixation
structure 90 may be defined by the distance lead 84 is advanced
with each full 360 degree rotation of the lead, i.e., the axial
distance between two peaks of the threaded fixation structure.
Threaded fixation structure 90 may have a pitch between
approximately 0.5 millimeters (mm) and 3 mm. In some embodiments,
the pitch may be less than approximately 0.5 mm or greater than 3
mm. The height of threaded fixation structure 90 is the distance
between the outer surface of elongated member 86 and the top edge
of the threaded fixation structure. Generally, the height is
between approximately 0.1 mm and 3 mm. However, other embodiments
of threaded fixation structure 90 may include heights smaller than
approximately 0.1 mm or greater than 3 mm. As threaded fixation
structure 90 increases in height, the surface area of the threaded
fixation structure increases as well. A larger surface area of
threaded fixation structure 90 may increase the axial force lead 84
may be able to incur without allowing the lead to migrate in the
direction of the axial force. In other words, a larger height of
threaded fixation structure 90 may be desired in cases where lead
84 is subjected to greater movement. While threaded fixation
structure 90 may have a constant height, the threaded fixation
structure may increase in height as it moves towards the proximal
end of the threaded fixation structure. Elongated member 62 may
have an outside diameter between approximately 0.5 mm and 5 mm. The
wall thickness of elongated member 62 may be between approximately
0.1 mm and 2 mm. In addition, the ratio of diameter to thread
height may be between approximately 1 and 50, depending on the
application of lead 60.
[0071] Implantation of all leads 60, 72, and 84, may vary depending
on the target stimulation site within patient 16 or implant
preferences of the clinician. For example, a sheath (shown in FIGS.
3A and 3B) may be used to cover any threaded fixation structures to
allow insertion of the lead without requiring rotation of the lead.
Upon positioning the lead near the stimulation site, the clinician
may remove the sheath and begin rotating the lead to engage to
recently exposed threaded fixation structure. Alternatively, the
clinician may guide and rotate the lead through a substantial
length of the insertion of the lead without the use of a
sheath.
[0072] FIGS. 5A-5B are perspective drawings illustrating exemplary
stimulation leads with varying threaded fixation mechanisms over
electrodes of the lead. As shown in FIG. 5A, lead 92 includes
elongated member 94, electrodes 96, and threaded fixation structure
98, a fixation structure. Threaded fixation structure 98 is shown
to be disposed around the same portion of elongated member 94 that
includes electrodes 96. In this manner, threaded fixation structure
98 is located over a portion of the surface of each electrode 96 as
the threaded fixation structure rotates from the proximal end of
the threaded fixation structure to the distal end of the threaded
fixation structure. Utilizing threaded fixation structure 98 over
electrodes 96 may provide for reduced movement of electrodes 96
with respect to the target tissue, compared to threaded fixation
structures located elsewhere along the longitudinal outer surface
of lead 92. Threaded fixation structure 98 may be constructed
similar to and have similar physical properties of threaded
fixation structure 90 of FIG. 4C. Threaded fixation structure 98
may attached to electrodes 96 with an adhesive or other bonding
technique, while some embodiments may not have the threaded
fixation structure attached to the electrodes.
[0073] While threaded fixation structure 98 is shown to be
substantially disposed around the entire portion of elongated
member 94 that includes electrodes 96, the threaded fixation
structure may also be disposed further in the proximal or distal
direction along the elongated member. In some embodiments, threaded
fixation structure 98 may only be disposed on a portion of the
surface including electrodes 96. In other words, threaded fixation
structure 98 may not be disposed around all electrodes 96, e.g.,
the threaded fixation structure may only be disposed around the
proximal two electrodes. In other embodiments, lead 92 may include
threaded fixation structure 98 at locations along elongated body
similar to leads 60, 72, or 84 of FIGS. 4A, 4B, and 4C,
respectively.
[0074] FIG. 5B shows lead 100 that is substantially similar to lead
92 of FIG. 5A. Lead 100 includes elongated member 102, electrodes
104, and threaded fixation structures 106A, 106B, 106C, 106D and
106E (collectively "threaded fixation structures 106). Threaded
fixation structures 106 are disposed at the portion of elongated
member 102 which also includes electrodes 104. However, none of
threaded fixation structures 106 are located over the surface of
any of electrodes 104. Instead, each of threaded fixation
structures 106 are only attached to elongated member 102 and stop
before covering any portion of electrodes 104. In other words,
threaded fixation structures 106 may be substantially similar to
threaded fixation structure 98 of FIG. 5B, but have any portion of
the threaded fixation structure over electrodes 96 removed. In this
manner, threaded fixation structures 106 are arranged in sections
to avoid interference with the electrical field produced by
electrodes 104 that provides therapy to the target tissue of
patient 16. Threaded fixation structures 106 may be constructed
similar to and have physical properties similar to threaded
fixation structure 90 of FIG. 4C. In some embodiments, one or more
of threaded fixation structures 106 may be constructed of different
materials to the other threaded fixation structures.
[0075] Threaded fixation structures 106B-D are located between
electrodes 104, threaded fixation structure 106A is disposed
proximal to electrodes 104 and threaded fixation structure 106E is
disposed distal to the electrodes. In some embodiments, threaded
fixation structure 106A may include more turns and be disposed
along a greater proximal portion of elongated member 102.
Alternatively, threaded fixation structure 106E may include more
turns and be disposed along a greater distal portion of elongated
member 102. In other embodiments, one or more of threaded fixation
structures 106 may not be included in lead 100. For example, lead
100 may only include threaded fixation structures 106A-C. In
additional embodiments, lead 100 may include threaded fixation
structures at locations along elongated body similar to leads 60,
72, or 84 of FIGS. 4A, 4B, and 4C, respectively.
[0076] FIG. 6 is a perspective drawing illustrating lead 108 with
threaded fixation structure extending from the distal end of the
lead to a location proximate to electrodes 112. As shown in FIG. 6,
lead 108 includes elongate member 110, electrodes 112, tapered tip
114, and threaded fixation structure 116. Threaded fixation
structure begins at the distal tip of tapered tip 114 and continues
to wrap around elongate member 110 past electrodes 112 to a
location of the electrode member proximal to the electrodes. Lead
108 may be a combination of threaded fixation structures described
with respect to leads 60, 72, 84, 92, or 100 of FIGS. 4 and 5. In
addition, threaded fixation structure 116 may have similar
properties to any of threaded fixation structures 70, 82, 90, 98,
or 106. In other embodiments threaded fixation structure 116 may be
broken into two or more threaded fixation structures at any
location along tapered tip 114 or elongated member 110, including
threaded fixation structures that do not cover the surface of
electrodes 112. In alternative embodiments, lead 108 may include
threaded fixation structures at the proximal and/or intermediate
locations of elongate member 110 instead of or in addition to
threaded fixation structure 116.
[0077] FIG. 7 is a perspective drawing illustrating lead 118 that
includes a reinforcement member. Lead 118 is substantially similar
to lead 108 of FIG. 6 and includes elongate member 120, electrodes
122, tapered tip 124, and threaded fixation structure 126. In
contrast to lead 108, lead 118 includes helical reinforcement
member 128 which resides within elongated member 120. Helical
reinforcement member 128 is provided to add torsional rigidity to
lead 118 which resists twisting of elongated member 120 when the
clinician rotates the lead to engage threaded fixation structure
126.
[0078] Helical reinforcement member 128 may be provided in a
variety of methods. First, helical reinforcement member 128 may be
a metal or polymer wire. Second, helical reinforcement member 128
may be a metal or polymer ribbon that creates a substantially
contiguous cylinder. Other fibers, materials, or members may be
used to construct helical reinforcement member 128, in some
embodiments. While helical reinforcement member 128 is shown as
extending within elongate member 120 in a direction opposite
threaded fixation structure 126, some embodiments may employ the
helical reinforcement member in the same direction as the threaded
fixation structure. Alternatively, helical reinforcement member 128
may include two helical reinforcement members in which one helical
reinforcement member is arranged in one direction and the second
helical reinforcement member is arranged in a second direction
opposite the first direction. Helical reinforcement member 128 may
extend throughout the entire length of lead 118 or only a small
portion of the lead.
[0079] FIGS. 8A and 8B are perspective drawings illustrating
exemplary stimulation leads with foldable threads. FIG. 8A
illustrates lead 130 prior to the removal of sheath 138. Lead 130
includes elongated member 132, electrodes 134, threaded fixation
structure 136, and sheath 138. Lead 130 may be similar to any of
leads 60, 72, 84, 92, 100, 108 or 118; however, threaded fixation
structure 136 is foldable, or compliant, such that sheath 138
prevents the threaded fixation structure from extending away from
elongated member 132. While threaded fixation structure 136 is
shown to be disposed around the portion of elongated member 132
that includes electrodes 134, the threaded fixation structure may
be disposed at any portion of the elongated member as described
herein.
[0080] Sheath 138 is provided to facilitate implantation of lead
130. With sheath 138 covering elongated member 132 and collapsing
threaded fixation structure 136, the diameter of lead 130 is
smaller to allow the clinician to push the lead through a lead
introducer (not shown) or through tissue of patient 16. Once the
clinician inserts lead 130 to the desired position, sheath 138 is
removed to expose threaded fixation structure 136 to the adjacent
tissue. Threaded fixation structure 136 extends away from the outer
surface of elongated member 132 to the originally formed threaded
fixation structure dimensions. Rotating lead 130 may help threaded
fixation structure 136 to extend away from the surface of elongated
member 132 and engage the surrounding tissue. The extended angle of
threaded fixation structure 136 may be less than 90 degrees between
the outer surface of elongated member 132 and the proximal surface
of the threaded fixation structure. While threaded fixation
structure 136 is foldable towards the proximal end of lead 130, the
threaded fixation structure may be foldable towards the distal end
of the lead in other embodiments.
[0081] Threaded fixation structure 136 may be constructed of any
bendable, pliable, elastic, or superelastic material that is
biocompatible. For example, a polymer such as
expanded-polytetrafluoroethylene or a shape memory metal alloy such
as nitinol may be used to construct threaded fixation structure
136. Sheath 138 may be constructed of a thin polymer membrane that
may slide over the surface of elongated member 132 and threaded
fixation structure 136 while maintaining sufficient circumferential
stiffness that retains the threaded fixation structure before
deployment. Sheath 138 may be initially configured to cover
elongated member 132 and threaded fixation structure 136 by sliding
the sheath from the distal end of lead 130 to the proximal end of
the lead. Alternatively, sheath 138 may loosely cover lead 130 and
be heated to shrink the circumference of the sheath and collapse
threaded fixation structure 136.
[0082] FIG. 8B shows lead 130 with sheath 138 being removed in the
proximal direction of arrow 140. The distal portion of threaded
fixation structure 136 has already extended away from elongated
member 132 in the direction of arrow 142. The proximal portion of
threaded fixation structure, indicated by arrow 144, is still
restricted by sheath 138 that has not been fully removed. Once
sheath 138 is fully removed from lead 130, the clinician may rotate
the lead to engage threaded fixation structure 136 with the
adjacent tissue. In addition, once sheath 138 is removed from lead
130, the clinician may not be able to slide the sheath back over
threaded fixation structure 136.
[0083] In alternative embodiments, sheath 138 may not be necessary
for threaded fixation structure 136 to fold down against elongated
member 132. Threaded fixation structure 136 may fold down from
force from adjacent tissue when the clinician inserts lead 130 into
patient 16. When lead 130 is properly positioned, the clinician may
pull back on the lead to cause threaded fixation structure 136 to
engage with the adjacent tissue and extend the threaded fixation
structure away from elongated member 132. The clinician can then
begin to rotate lead 130 to screw the lead into the tissue and
secure electrodes 134 to the desired location.
[0084] FIG. 9 is a flow diagram illustrating an exemplary process
for securing a threaded lead to a tissue of a patient. Any of leads
60, 72, 84, 92, 100, 108 or 118, or 130 may be implanted with this
procedure, but lead 60 will be used as an example. The clinician
beings by inserting the lead introducer into the target stimulation
site of patient 16 (146). Next, the clinician inserts lead 60 into
the lead introducer until the lead is positioned correctly (148).
The clinician then withdraws the sheath that covers lead 60 (150)
and rotates the lead in the direction of threaded fixation
structure 68, e.g., clockwise, to secure the lead at the target
tissue (152). If lead 60 is not correctly placed (154), the
clinician continues to rotate the lead (152). If lead 60 is
positioned correctly (154), the clinician may attach the proximal
end of the lead to the stimulator and proceed with beginning
therapy (156).
[0085] In some embodiments, the clinician may not need to remove a
sheath to expose the threaded fixation structure. In other
embodiments, the clinician may require a keyed stylet or other
device that engages into the distal end of the lead and locks into
interior grooves or teeth to facilitate the rotation of the lead
and engagement of the threaded fixation structure. Alternatively,
the stylet may be inserted through a channel extending within lead
60 that attaches to grooves, slots, or teeth near the proximal end
of the lead to facilitate lead rotation that engages the threaded
fixation structure to the adjacent tissue.
[0086] FIG. 10 is a flow diagram illustrating an exemplary process
for removing a threaded lead from a tissue of a patient. Any of
leads 60, 72, 84, 92, 100, 108 or 118, or 130 may be implanted with
this procedure, but lead 60 will be used as an example. After
stimulation therapy has been completed or lead 60 needs to be
removed for any other reason, the clinician may ready patient 16
for removal of the lead from stimulator 12 (158). If the threaded
fixation structure is foldable (160), the clinician inserts a
sheath down to the proximal end of the threaded fixation structure
(162). If the threaded fixation structure of lead 60 is not
foldable, or the sheath has been inserted to the foldable threads,
the clinician begins to rotate the lead in the opposite direction
of the threaded fixation structure, e.g., counter-clockwise (164).
If the threaded fixation structure is not released from tissue
(166), the clinician continues to rotate lead 60 (164). If the
threaded fixation structure has been released from tissue (166),
the clinician may pull lead 60 from patient 16 (168). Releasing the
threaded fixation structure from the tissue may include either
backing the threaded fixation structure into the sheath such that
the structure folds under the sheath or rotating the lead enough
that the threaded fixation structure is free from being engaged
from any tissue of patient 16.
[0087] Similar to FIG. 9, some embodiments may require that the
clinician use a keyed stylet or other device that engages into the
distal end of the lead and locks into interior grooves or teeth to
facilitate the rotation of the lead and disengagement of the
threaded fixation structure. Alternatively, the stylet may be
inserted through a channel extending within lead 60 that attaches
to grooves, slots, or teeth near the proximal end of the lead to
facilitate lead rotation that disengages the threaded fixation
structure from the adjacent tissue.
[0088] FIG. 11 is a method of implanting a lead in patient 12 with
a different threaded fixation structure than the leads implanted in
with the technique of FIG. 9. Any of leads 60, 72, 84, 92, 100, 108
or 118, or 130 with a foldable threaded fixation structure may be
implanted with this procedure, but lead 130 will be used as an
example. The clinician beings by inserting the lead introducer into
the target stimulation site of patient 16 (169), which causes
threaded fixation structure 136 to fold down against the surface of
lead 130. Next, the clinician inserts lead 130 into the lead
introducer until the lead is positioned correctly (171). The
clinician then removes the lead introducer that covers lead 130
(173) and pulls back on the lead to engage, or extend, the folded
threaded fixation structure with the adjacent tissue (175). The
clinician then rotates the lead in the direction of threaded
fixation structure 136, e.g., clockwise, to secure the lead at the
target tissue (177). If lead 130 is not correctly placed (179), the
clinician continues to rotate the lead (177). If lead 130 is
positioned correctly (179), the clinician may attach the proximal
end of the lead to the stimulator and proceed with beginning
therapy (181).
[0089] In some embodiments, the clinician may be able to insert
lead 130 directly into patient 16 without the use of a lead
introducer. In this case, foldable threaded fixation structure 136
folds down with the force of the adjacent tissue as lead 130 is
inserted into patient 16. In other embodiments, the clinician may
require a keyed stylet or other device that engages into the distal
end of the lead and locks into interior grooves or teeth to
facilitate the rotation of the lead and engagement of the threaded
fixation structure. Alternatively, the stylet may be inserted
through a channel extending within lead 130 that attaches to
grooves, slots, or teeth near the proximal end of the lead to
facilitate lead rotation that engages the threaded fixation
structure to the adjacent tissue.
[0090] FIGS. 12A and 12B are perspective drawings illustrating
exemplary medical catheters with a helical threaded structure.
Threaded fixation structures 174 and 184 may be similar to the
threaded fixation structures of any of leads 60, 72, 84, 92, 100,
108 or 118, or 130. However, a conduit is used to deliver a
therapeutic agent to the tissue instead of electrodes that deliver
stimulation. FIG. 12A shows lead 170 that includes elongated member
172, threaded fixation structure 174, conduit 176, and exit port
178. Threaded fixation structure 174 is disposed about the outer
surface of elongated member 172 at the distal end of the elongated
body. A drug pump may be attached to the proximal end of lead 170
for delivering a therapeutic agent through conduit 176 and out of
exit port 178 into the adjacent target tissue. Conduit 176 resides
within elongated member 172, and may or may not have a common
central axis to the elongated member. In other embodiments, more
than one threaded fixation structure 174 may be provided to secure
the location of lead 170 and ensure that the therapeutic agent is
delivered to the appropriate tissue of patient 16.
[0091] FIG. 12B shows lead 180 which is similar to lead 170 of FIG.
12A. Lead 180 includes elongated body 182, threaded fixation
structure 184, conduit 186, and exit port 188. Exit port 188 is
disposed on a longitudinal outer surface of elongated member 182,
within threaded fixation structure 184. Conduit 186 resided within
elongated member 182, and may or may not have a common central axis
with the elongated member. In other embodiments, exit port 188 may
be located outside of threaded fixation structure 184 either distal
to or proximal to the threaded fixation structure. In alternative
embodiments, conduit 186 may be in fluidic communication with more
than one exit port, where the multiple exit ports are located at
various longitudinal or circumferential positions of elongated
member 182 or in the axial surface of the elongated member. In
addition, lead 180 may include multiple conduits within elongated
member 182.
[0092] FIGS. 13A and 13B are cross-sectional end views of a keyed
stylet 200 and a reciprocally keyed medical lead 202. As discussed
previously, rotational movement of a lead may be accomplished by
simply rotating the lead body. In some embodiments, however, it may
be desirable to rotate the lead body with the aid of a stylet
inserted in an inner lumen of the lead body. For example, a stylet
may provide added structural integrity relative to a flexible lead.
The stylet may be sized to frictionally engaged the inner wall of
the inner lumen such that rotation of the stylet causes rotation of
the lead body. Alternatively, the stylet and the lead body may be
formed with a reciprocal key structure, such as any combination of
slots, grooves, teeth, ribs, rails, or the like.
[0093] In the example of FIGS. 13A and 13B, stylet 200 includes a
stylet body 203 with multiple teeth 204A-204D. The teeth may run
longitudinally substantially the entire length of the stylet body
203, or be provided only near a distal end of the stylet body,
e.g., over the last 2 to 6 centimeters at the distal end of the
stylet. In either case, teeth 204A-204D may be sized and shaped to
engage reciprocal grooves 210A-210D in a lead body 206 of lead 202.
The grooves 210A-210D may be formed by molding, extruding, scribing
or other techniques. In any event, teeth 204A-204D engage
corresponding grooves 210A-210D so that the teeth can bear against
the grooves to transmit rotational force from stylet 200 to lead
202.
[0094] Also shown in FIG. 13B are representative portions 212A,
212B of a threaded fixation structure. Any thread fixation
structure, as described herein, may be combined with a lead 202
including slots, grooves, or the like. Moreover, the number of
slots or grooves may be subject to wide variation. Also, in some
embodiments, lead 202 may include teeth while stylet 200 includes
grooves. The exact combination, arrangement, size, and number of
slots, grooves, teeth or the like is subject to variation provided
the lead 202 and stylet 200 include reciprocal structure to impart
rotational movement from the stylet to the lead.
[0095] Alternative to keyed stylet 200, a cannula device that is
configured to fit around the outside of the lead may be used to
rotate the lead and engage the threaded fixation structure. The
cannula device may be circumferentially locked to the lead via one
or more slots, grooves, teeth, ribs, rails, or the like, disposed
on the outside of the elongated member. In some embodiments, the
cannula device may use a friction fit to lock to the lead. In
either case, the cannula device may be slid down to the proximal
end of the threaded fixation structure or some other location of
the lead that still facilitates rotation of the lead.
[0096] A lead including threaded fixation may be useful for various
electrical stimulation systems. For example, the lead may be used
to deliver electrical stimulation therapy to patients to treat a
variety of symptoms or conditions such as chronic pain, tremor,
Parkinson's disease, multiple sclerosis, spinal cord injury,
cerebral palsy, amyotrophic lateral sclerosis, dystonia,
torticollis, epilepsy, pelvic floor disorders, gastroparesis,
muscle stimulation (e.g., functional electrical stimulation (FES)
of muscles) or obesity. In addition, the helical fixation described
herein may also be useful for fixing a catheter, such as a drug
deliver catheter, proximate to a target drug delivery site.
[0097] The preceding specific embodiments are illustrative of the
practice of the invention. It is to be understood, therefore, that
other expedients known to those skilled in the art or disclosed
herein may be employed without departing from the invention or the
scope of the claims. For example, the present invention further
includes within its scope methods of making and using systems and
leads for stimulation, as described herein. Also, the leads
described herein may have a variety of stimulation applications, as
well as possible applications in other electrical stimulation
contexts, such as delivery of cardiac electrical stimulation,
including paces, pulses, and shocks.
[0098] Many embodiments of the invention have been described.
Various modifications may be made without departing from the scope
of the claims. These and other embodiments are within the scope of
the following claims.
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