U.S. patent application number 10/891834 was filed with the patent office on 2005-04-07 for methods and systems for intracranial neurostimulation and/or sensing.
Invention is credited to Fowler, Brad, Lowry, David Warren, Thompson, Gene.
Application Number | 20050075680 10/891834 |
Document ID | / |
Family ID | 35907867 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050075680 |
Kind Code |
A1 |
Lowry, David Warren ; et
al. |
April 7, 2005 |
Methods and systems for intracranial neurostimulation and/or
sensing
Abstract
Methods and systems for intracranial neurostimulation and/or
sensing are disclosed. An intracranial signal transmission system
in accordance with an embodiment of the invention includes a
generally electrically insulating support body having a head
portion configured to be positioned at least proximate to an outer
surface of a patient's skull, and a shaft portion configured to
extend into an aperture in the patient's skull. The system can
further include at least one electrical contact portion carried by
the support body. The at least one electrical contact portion can
be positioned to transfer electrical signals to, from, or both to
and from the patient's brain via the aperture in the patient's
skull.
Inventors: |
Lowry, David Warren; (Grand
Rapids, MI) ; Fowler, Brad; (Woodinville, WA)
; Thompson, Gene; (Renton, WA) |
Correspondence
Address: |
PERKINS COIE LLP
PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Family ID: |
35907867 |
Appl. No.: |
10/891834 |
Filed: |
July 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10891834 |
Jul 15, 2004 |
|
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10418796 |
Apr 18, 2003 |
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Current U.S.
Class: |
607/45 |
Current CPC
Class: |
A61N 1/0531 20130101;
A61N 1/36025 20130101; A61N 1/0534 20130101; A61N 1/36017 20130101;
A61N 1/0539 20130101 |
Class at
Publication: |
607/045 |
International
Class: |
A61N 001/18 |
Claims
I/We claim:
1. An intracranial signal transmission system, comprising: a
generally electrically insulating support body having a head
portion configured to be positioned at least proximate to an outer
surface of a patient's skull, the support body further having a
shaft portion configured to extend into an aperture in the
patient's skull; and at least one electrical contact portion
carried by the support body, the at least one electrical contact
portion being positioned to transfer electrical signals to, from,
or both to and from the patient's brain via the aperture in the
patient's skull.
2. The system of claim 1 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, and wherein the system further
comprises: a signal transmitter operatively coupled to the first
electrical contact portion to provide stimulation signals to the
patient's brain; and a sensor operatively coupled to the second
electrical contact portion to receive signals from the patient's
brain.
3. The system of claim 1 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion.
4. The system of claim 1, further comprising: an electrical signal
transmitter; and a generally continuous electrical signal path
connected between the electrical signal transmitter and the at
least one electrical contact portion.
5. The system of claim 1, further comprising: an electrical signal
transmitter; and an electrical signal path having a releasable
connection at the electrical signal transmitter and being
continuous between the releasable connection and the at least one
electrical contact portion.
6. The system of claim 1 wherein the at least one electrical
contact portion includes a first electrical contact portion
coupleable to at least one signal transmitter to receive first
electrical signals, and a second electrical contact portion
coupleable to at least one signal transmitter to receive second
electrical signals independent of the first electrical signals.
7. An intracranial signal transmission system, comprising: an
electrical contact portion configured to be positioned in an
aperture of a patient's skull; and an electrical energy transfer
device configured to be releasably positioned external to the
patient's scalp, the energy transfer device being coupleable to a
signal transmitter to transmit signals to the electrical contact
portion while the electrical contact portion is positioned beneath
the patient's scalp and while the energy transfer device is
positioned external to the patient's scalp.
8. The system of claim 7 wherein the electrical energy transfer
device includes: a flexible outer layer; an adhesive gel layer
positioned to contact the patient's scalp; a conductive layer
positioned between the outer layer and the adhesive gel layer; and
a conductive lead connected to the conductive layer.
9. The system of claim 7 wherein the electrical contact portion
includes a first electrical contact portion and wherein the system
further comprises: a second electrical contact portion spaced apart
from the first electrical contact portion; a signal transmitter
operatively coupled to the first electrical contact portion to
provide stimulation signals to the patient's brain; and a sensor
operatively coupled to the second electrical contact portion to
receive signals from the patient's brain.
10. The system of claim 7 wherein the electrical contact portion
includes a first electrical contact portion and wherein the system
further comprises a second electrical contact portion spaced apart
from the first electrical contact portion.
11. The system of claim 7, further comprising: an electrical signal
transmitter; and a generally continuous electrical signal path
connected between the electrical signal transmitter and the at
least one electrical contact portion.
12. The system of claim 7 wherein the electrical contact portion
includes a first electrical contact portion coupleable to at least
one signal transmitter to receive first electrical signals, and
wherein the system further comprises a second electrical contact
portion coupleable to at least one signal transmitter to receive
second electrical signals independent of the first electrical
signals.
13. The system of claim 7 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, the first electrical contact portion
having a first position relative to the support body so as to be
positioned beneath the scalp by a first distance, the second
electrical contact portion having a second position relative to the
support body so as to be positioned beneath the scalp by a second
distance greater than the first distance.
14. An intracranial signal transmission system, comprising: a shaft
configured to extend through an aperture in a patient's skull; a
head connected to the shaft, the head being configured to be
positioned adjacent to an external surface of the patient's skull,
the head being eccentrically positioned relative to the shaft and
having a first portion extending outwardly from the shaft by a
first distance and a second portion extending outwardly from the
shaft by a second distance different than the first distance; and
an electrical contact portion carried by at least one of the shaft
and the head.
15. The system of claim 14, further comprising an insert having an
outer surface and aperture, the aperture being sized to receive the
shaft, the outer surface having at least one securement element
configured to secure the insert to the patient's skull.
16. The system of claim 14, further comprising an insert having an
outer surface and aperture, the aperture being sized to receive the
shaft, the outer surface having threads configured to secure the
insert to the patient's skull.
17. An intracranial signal transmission system, comprising: a shaft
having an external surface configured to extend through an aperture
in a patient's skull; a head connected to the shaft and having a
generally conical shape, with an angle between the external surface
of the shaft and an external surface of the head being obtuse, and
with the external surface of the head being configured to contact
the walls of the aperture in the patient's skull; and an electrical
contact portion carried by at least one of the shaft and the
head.
18. The system of claim 17 wherein the shaft has a first end
surface and the head has a second end surface facing generally
opposite form the first end surface, and wherein the second end
surface is positioned to be flush with an outer surface of the
patient's skull.
19. The system of claim 17 wherein the shaft has a first end
surface and the head has a second end surface facing generally
opposite form the first end surface, and wherein the second end
surface is positioned to project outwardly from an outer surface of
the patient's skull.
20. The system of claim 17 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, and wherein the system further
comprises: a signal transmitter operatively coupled to the first
electrical contact portion to provide stimulation signals to the
patient's brain; and a sensor operatively coupled to the second
electrical contact portion to receive signals from the patient's
brain.
21. The system of claim 17 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion.
22. The system of claim 17, further comprising: an electrical
signal transmitter; and a generally continuous electrical signal
path connected between the electrical signal transmitter and the at
least one electrical contact portion.
23. An intracranial signal transmission system, comprising: a shaft
configured to extend through an aperture in a patient's skull, the
shaft having an external surface with a plurality of surface
features positioned to receive growing bone tissue from the
patient's skull; a head connected to the shaft; and an electrical
contact portion carried by at least one of the shaft and the
head.
24. The system of claim 23 wherein the surface features are
recessed from the external surface of the shaft.
25. The system of claim 23 wherein the surface features include
pores.
26. The system of claim 23 wherein the surface features include
pores recessed from the external surface and, and wherein walls of
the pores are positioned to be out of contact with walls of the
aperture in the patient's skull as the shaft is positioned in the
aperture.
27. The system of claim 23 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, the first electrical contact portion
having a first position relative to the head so as to be positioned
beneath the scalp by a first distance, the second electrical
contact portion having a second position relative to the head so as
to be positioned beneath the scalp by a second distance greater
than the first distance.
28. An intracranial signal transmission system, comprising: a shaft
configured to extend through an aperture in a patient's skull; a
head connected to the shaft; an electrical contact portion carried
by at least one of the shaft and the head; a radio frequency
transponder carried by at least one of the shaft; and at least one
securement feature depending from at least one of the head and the
shaft and being positioned to secure at least one of the head and
the shaft to the patient's skull.
29. The system of claim 28, further comprising: a signal
transmitter coupled to the electrical contact portion with a signal
link; a radio frequency receiver configured to receive signals from
the transponder, the radio frequency receiver being coupled to the
signal transmitter to control signals transmitted to the electrical
contact portion based on signals received from the transponder.
30. The system of claim 28 wherein the shaft and the head are
formed from a generally electrically insulating material.
31. The system of claim 28, further comprising a radio frequency
receiver configured to receive signals from the transponder.
32. A method for installing an electrical contact portion in a
patient's skull, comprising: drilling a hole in a patient's skull;
determining a distance from an outer surface of the patient's skull
to a feature beneath the outer surface of the patient's skill by
inserting an elongated member having graduation makings into the
pilot hole; selecting a size of an intracranial electrode based on
the distance determined with the elongated member; inserting the
intracranial electrode into the hole; and securing the intracranial
electrode to the patient's skull.
33. The method of claim 32 wherein drilling a hole includes
drilling a pilot hole, and wherein the method further comprises
increasing a diameter of the hole prior to inserting the
intracranial electrode into the hole.
34. A method for transmitting intracranial electrical signals,
comprising: positioning a generally electrically insulating support
body proximate to a patient; inserting a shaft portion of the
support body into an aperture in the patient's skull; positioning a
head portion of the support body at least proximate to an outer
surface of a patient's skull; and transmitting electrical signals
to, from or both to and from the patient's brain through the
aperture in the patient's skull via at least one electrical contact
portion carried by the support body.
35. The method of claim 34 wherein transmitting electrical signals
includes transmitting electrical stimulation signals to a first
electrical contact portion carried by the support body and
receiving sensor signals from a second electrical contact portion
carried by the support body, the second electrical contact portion
being spaced apart from the first electrical contact portion.
36. The method of claim 34 wherein transmitting signals via at
least one electrical contact portion includes transmitting signals
via a first electrical contact portion carried by the support body
and a second electrical contact portion carried by the support
body, the second electrical contact portion being spaced apart from
the first electrical contact portion.
37. The method of claim 34 wherein transmitting signals includes
transmitting signals along a generally continuous electrical signal
path connected between an electrical signal transmitter and the at
least one electrical contact portion.
38. The method of claim 34 wherein transmitting signals via at
least one electrical contact portion includes transmitting a first
electrical signal via a first electrical contact portion carried by
the support body and transmitting a second electrical signal via a
second electrical contact portion carried by the support body, the
second electrical contact portion being spaced apart from the first
electrical contact portion, the first signal being independent of
the second signal.
39. The method of claim 34 wherein the support body carries a first
electrical contact portion and a second electrical contact portion,
and wherein inserting a shaft portion of the support body includes
positioning the first electrical contact portion a first distance
beneath the scalp and positioning the second electrical contact
portion a second distance beneath the scalp, the second distance
being greater than the first distance.
40. A method for transmitting intracranial electrical signals,
comprising: disposing an electrode within an aperture in a
patient's skull; releasably positioning an electrical transmission
device at least proximate to an external surface of the patient's
scalp; and transmitting an electrical signal through the patient's
scalp between the electrode and the electrical transmission
device.
41. The method of claim 40, further comprising drilling the
aperture in the patient's skull.
42. The method of claim 40, further comprising adhering the
electrical transmission device to the patient's scalp and wherein
transmitting an electrical signal includes transmitting an
electrical signal from a conductive layer positioned between an
adhesive layer and a flexible outer layer of the electrical
transmission device.
43. The method of claim 40 wherein transmitting an electrical
signal includes transmitting a stimulation signal through the
patient's scalp to the electrode.
44. The method of claim 40 wherein transmitting an electrical
signal includes transmitting a sensor signal from the electrode
through the patient's scalp.
45. A method for installing an intracranial signal transmission
system, comprising: positioning an electrical contact portion of
the system proximate to the patient's head, the electrical contact
portion being carried by a support body having a shaft portion and
a head portion positioned eccentrically relative to the shaft
portion; inserting the shaft portion into an aperture in the
patient's skull; positioning at least some of the head portion
external to the patient's skull; orienting the head portion so that
a first part of the head portion extends outwardly from the shaft
by a first distance and a second part of the head portion extends
outwardly from the shaft by a second distance different than the
first distance; and transmitting an electrical signal via the
electrical contact portion.
46. The method of claim 45 wherein the electrical contact portion
is a first electrical contact portion, the support body is a first
support body, and the aperture is a first aperture, and wherein the
method further comprises: positioning a head portion of a second
support body proximate to the patient's head, the second support
body carrying a second electrical contact portion, the head portion
of the second support body including a first part that extends
outwardly from the shaft by a first distance and a second part that
extends outwardly from the shaft by a second distance different
than the first distance; inserting a shaft of the second support
body into a second aperture in the patient's skull, the second
aperture being spaced apart from the first aperture; and orienting
a head portion of the second support body so that the first part of
the head portion of the second support body is positioned toward
the first part of the head portion of the second support body.
37. The method of claim 45, further comprising: placing an insert
into the aperture in the patient's skull; placing the shaft of the
support body in the an insert; and securing the shaft to the
insert.
48. A method for installing an intracranial signal transmission
system, comprising: forming an aperture in a patient's skull, the
aperture having first generally conical portion with a first
diameter at an external surface of the patient's skull, and a
second portion with a second diameter smaller than the first
diameter beneath the external surface; disposing proximate to the
aperture an electrical contact portion carried by a support body
having a shaft and a head depending from the shaft, the head having
generally conical shape, with an angle between an external surface
of the shaft and an external surface of the head being obtuse; and
inserting the support body into the aperture so that the shaft
extends through the second portion of the aperture and the head
engages a wall of the aperture at the first portion of the
aperture.
49. The method of claim 48 wherein the shaft has a first end
surface and the head has a second end surface facing generally
opposite form the first end surface, and wherein inserting the
support body includes inserting the support body so that the second
end surface is flush with the outer surface of the patient's
skull.
50. The method of claim 48 wherein the shaft has a first end
surface and the head has a second end surface facing generally
opposite form the first end surface, and wherein inserting the
support body includes inserting the support body so that the second
end surface is positioned to project outwardly from the outer
surface of the patient's skull.
51. The method of claim 48 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, and wherein the method further
comprises: transmitting a stimulation signal to the patient's brain
via the first electrical contact portion; and receiving a sensor
signal from the patient's brain via the second electrical contact
portion.
52. The method of claim 48 wherein the at least one electrical
contact portion includes a first electrical contact portion and a
second electrical contact portion spaced apart from the first
electrical contact portion, and wherein the method further
comprises: transmitting a first stimulation signal to the patient's
brain via the first electrical contact portion; and transmitting a
second stimulation signal to the patient's brain via the second
electrical contact portion.
53. The system of claim 48, further comprising transmitting signals
to, from, or both to and from the at least one electrical contact
portion via a generally continuous electrical signal path.
54. A method for installing an intracranial signal transmission
system, comprising: forming an aperture in a patient's skull;
disposing proximate to the aperture an electrical contact portion
carried by a support body, the support body having a shaft and a
head depending from the shaft, the shaft having an external surface
with a plurality of surface features; inserting the shaft into the
aperture; and allowing the patient's bone tissue to grow into
interengagement with the surface features.
55. The method of claim 54 wherein the surface features are
recessed from the external surface of the shaft and wherein
allowing the patient's bone tissue to grow includes allowing the
patient's bone tissue to grow into the recesses.
56. The method of claim 54 wherein the surface features include
pores and wherein allowing the patient's bone tissue to grow
includes allowing the patient's bone tissue to grow into the
pores.
57. A method for installing an intracranial signal transmission
system, comprising: forming an aperture in a patient's skull;
disposing proximate to the aperture an electrical contact portion
carried by a support body having a shaft and a head depending from
the shaft inserting the shaft into the aperture; securing the
support body to the patient's skull; and receiving signals from a
radio frequency transponder carried by at least one of the shaft
and the head.
58. The method of claim 57, further comprising controlling
electrical stimulation signals transmitted to the electrical
contact portion based on a signal received from the transponder.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of pending U.S.
application Ser. No. 10/418,796, filed Apr. 18, 2003, and
incorporated herein in its entirety by reference.
TECHNICAL FIELD
[0002] The present invention relates to intracranial electrodes and
methods for implanting and using intracranial electrodes. These
electrodes and methods may be suited for neurostimulation systems
and may also be used in electroencephalography and other recording
systems, e.g., evoked potential recordings.
BACKGROUND
[0003] A wide variety of mental and physical processes are known to
be controlled or influenced by neural activity in the central and
peripheral nervous systems. For example, the neural functions in
some areas of the brain (e.g., the sensory or motor cortices) are
organized according to physical or cognitive functions. Several
other areas of the brain also appear to have distinct functions in
most individuals. In the majority of people, for example, the areas
of the occipital lobes relate to vision, the regions of the left
inferior frontal lobes relate to language, and the regions of the
cerebral cortex appear to be involved with conscious awareness,
memory, and intellect. Because of the location-specific functional
organization of the brain, in which neurons at discrete locations
are statistically likely to control particular mental or physical
functions in normal individuals, stimulating neurons at selected
locations of the central nervous system can be used to effectuate
changes in cognitive and/or motor functions throughout the
body.
[0004] In several existing applications, neural functions are
treated by electrical or magnetic stimulation powered by a neural
stimulator that has a plurality of therapy electrodes and a pulse
system coupled to the therapy electrodes. The therapy electrodes
can be implanted into the patient at a target site for stimulating
the desired portions of the brain. For example, one existing
technique for masking pain in a patient is to apply an electrical
stimulus to a target stimulation site of the brain.
[0005] The brain can be stimulated in several known fashions. One
type of treatment is referred to as transcranial electrical
stimulation (TES), which involves placing an electrode on the
exterior of the patient's scalp and delivering an electrical
current to the brain through the scalp and the skull. TES, however,
is not widely used because the delivery of the electrical
stimulation through the scalp and the skull causes patients a great
amount of pain and the electrical field is difficult to direct or
focus accurately.
[0006] Another type of treatment is transcranial magnetic
stimulation (TMS), which involves using a high-powered magnetic
field adjacent the exterior of the scalp over an area of the
cortex. TMS does not cause the painful side effects of TES.
Unfortunately, TMS is not presently effective for treating many
patients because the existing delivery systems are not practical
for applying stimulation over an adequate period of time. TMS
systems, for example, are relatively complex and require
stimulation treatments to be performed by a healthcare professional
in a hospital or physician's office. The efficacy of TMS in
longer-term therapies may be limited because it is difficult to (a)
accurately localize the region of stimulation in a reproducible
manner, (b) hold the device in the correct position over the
cranium for the requisite period, and (c) provide stimulation for
extended periods of time.
[0007] Another device for stimulating a region of the brain is
disclosed by King in U.S. Pat. No. 5,713,922, the entirety of which
is incorporated herein by reference. King discloses a device for
cortical surface stimulation having electrodes mounted on a paddle
that is implanted under the skull of the patient. These electrodes
are placed in contact with the surface of the cortex to create
"paresthesia," which is a vibrating or buzzing sensation.
Implanting the paddle typically requires removal of a relatively
large (e.g., thumbnail-sized or larger) window in the skull via a
full craniotomy. Craniotomies are performed under a general
anesthetic and subject the patient to increased chances of
infection.
[0008] A physician may employ electroencephalography (EEG) to
monitor neural functions of a patient. Sometimes this is done
alone, e.g., in diagnosing epileptic conditions, though it may also
be used in conjunction with neurostimulation. Most commonly,
electroencephalography involves monitoring electrical activity of
the brain, manifested as potential differences at the scalp
surfaces, using electrodes placed on the scalp. The electrodes are
typically coupled to an electroencephalograph to generate an
electroencephalogram. Diagnosis of some neurological diseases and
disorders, e.g., epilepsy, may best be conducted by monitoring
neural function over an extended period of time. For this reason,
ambulatory electroencephalography (AEEG) monitoring is becoming
more popular. In AEEG applications, disc electrodes are applied to
the patient's scalp. The scalp with the attached electrodes may be
wrapped in gauze and the lead wires attached to the electrodes may
be taped to the patient's scalp to minimize the chance of
displacement.
[0009] EEG conducted with scalp-positioned electrodes requires
amplification of the signals detected by the electrodes. In some
circumstances, it can be difficult to pinpoint the origin of a
particular signal because of the signal dissipation attributable to
the scalp and the skull. For more precise determinations, EEG may
be conducted using "deep brain" electrodes. Such electrodes extend
through the patient's scalp and skull to a target location within
the patient's brain. Typically, these deep brain electrodes
comprise lengths of relatively thin wire that are advanced through
a bore through the patient's skull to the desired location. If the
electrodes are to be monitored over an extended period of time, the
electrodes typically are allowed to extend out of the patient's
skull and scalp and are coupled to the electroencephalograph using
leads clipped or otherwise attached to the electrodes outside the
scalp. To avoid shifting of the electrodes over time, the
electrodes typically are taped down or held in place with a
biocompatible cementitious material. The patient's head typically
must be wrapped in gauze to protect the exposed electrodes and the
associated leads, and the patient is uncomfortable during the
procedure. This may be suitable for limited testing purposes-deep
brain encephalography typically is limited to tests conducted in
hospital settings over a limited period of time, usually no more
than a few days-but could be problematic for longer-term
monitoring, particularly in nonclinical settings.
[0010] Screws have been used to attach plates or the like to
patients' skulls. FIG. 1, for example, schematically illustrates a
conventional cranial reconstruction to repair a fracture 50 or
other trauma. In this application, a plate 60 is attached to the
outer cortex 12 of the skull 10 by cortical bone screws 62. The
plate 60 spans the fracture 50, helping fix the skull in place on
opposite sides of the fracture 50. As can be seen in FIG. 1, the
screws 62 do not extend through the entire thickness of the skull.
Instead, the screws 62 are seated in the outer cortex 12 and do not
extend into the cancellous 18 or the inter cortex 14. In some
related applications, the screws 62 may be longer and extend into
or even through the cancellous 18. Physicians typically take
significant care to ensure that the screws 62 do not extend through
the entire thickness of the skull, though, because penetrating the
skull can increase the likelihood of trauma to or infection in the
patient's brain.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic illustration of a conventional cranial
reconstruction.
[0012] FIG. 2A is a schematic view in partial cross section of an
intracranial electrode in accordance with one embodiment of the
invention implanted in a patient.
[0013] FIG. 2B is a schematic top elevation view of the implanted
intracranial electrode of FIG. 2A.
[0014] FIG. 3A is a schematic illustration in partial cross section
of an intracranial electrode in accordance with another embodiment
of the invention implanted in a patient.
[0015] FIG. 3B is a schematic top elevation view of the implanted
intracranial electrode of FIG. 3A.
[0016] FIG. 4A is a schematic illustration in partial cross section
of an intracranial electrode in accordance with yet another
embodiment of the invention implanted in a patient.
[0017] FIG. 4B is a side view of a dielectric member of the
electrode of FIG. 4A.
[0018] FIG. 5 is a schematic illustration in partial cross section
of an intracranial electrode in accordance with still another
embodiment of the invention implanted in a patient.
[0019] FIG. 6A is a schematic illustration in partial cross section
of an intracranial electrode in accordance with a further
embodiment of the invention implanted in a patient.
[0020] FIG. 6B is a schematic top elevation view of the implanted
intracranial electrode of FIG. 6A.
[0021] FIG. 7 is a schematic illustration in partial cross section
of an intracranial electrode in accordance with still another
embodiment of the invention implanted in a patient.
[0022] FIG. 8 is a schematic side view of a broken-away portion of
a patient's skull in which an intracranial electrode in accordance
with another embodiment of the invention has been implanted.
[0023] FIG. 9 is a schematic partial cross-sectional view taken
along line 9-9 of FIG. 8.
[0024] FIG. 10 is an isolation view of a portion of the implanted
electrode of FIG. 9.
[0025] FIG. 11 is a perspective view of selected components of the
intracranial electrode of FIGS. 8-10.
[0026] FIG. 12 is a schematic illustration in partial cross section
of an intracranial electrode in accordance with yet another
embodiment of the invention implanted in a patient.
[0027] FIG. 13 is a schematic illustration in partial cross section
of an intracranial electrode in accordance with one more embodiment
of the invention implanted in a patient.
[0028] FIG. 14 is a schematic illustration in partial cross section
of an intracranial electrode in accordance with a further
embodiment of the invention implanted in a patient.
[0029] FIG. 15 is a schematic partial cross-sectional view of the
intracranial electrode of FIG. 13 with a retaining collar of the
electrode in a radially compressed state.
[0030] FIG. 16 is a schematic partial cross-sectional view of the
intracranial electrode of FIG. 14 with the retaining collar in a
radially expanded state.
[0031] FIG. 17 is a schematic illustration in partial cross section
of a deep brain intracranial electrode in accordance with an
alternative embodiment of the invention implanted in a patient.
[0032] FIG. 18 is a schematic illustration in partial cross section
of a deep brain intracranial electrode in accordance with still
another embodiment of the invention implanted in a patient.
[0033] FIG. 19 is a schematic overview of a neurostimulation system
in accordance with a further embodiment of the invention.
[0034] FIG. 20 is a schematic overview of a neurostimulation system
in accordance with another embodiment of the invention.
[0035] FIG. 21 is a schematic illustration of one pulse system
suitable for use in the neurostimulation system of FIG. 17 or FIG.
18.
[0036] FIG. 22 is a schematic top view of the array of electrodes
in FIG. 17.
[0037] FIGS. 23-26 are schematic top views of alternative electrode
arrays in accordance with other embodiments of the invention.
[0038] FIG. 27 is a schematic view in partial cross section of an
intracranial electrode implanted in a patient in accordance with
another embodiment of the invention.
[0039] FIG. 28 is a schematic view in partial cross section of an
intracranial electrode implanted in a patient in accordance with
another embodiment of the invention.
[0040] FIG. 29 is a schematic view in partial cross section of an
intracranial electrode implanted in a patient in accordance with
another embodiment of the invention.
[0041] FIG. 30 is a schematic view in partial cross section of an
intracranial electrode having an adjunct depth-penetrating
electrode implanted in a patient in accordance with another
embodiment of the invention.
[0042] FIG. 31 is a schematic view in partial cross section of
another intracranial electrode having an adjunct depth-penetrating
electrode implanted in a patient in accordance with another
embodiment of the invention.
[0043] FIG. 32 is a schematic view in partial cross section of a
neural stimulation system implanted in a patient in accordance with
an alternative embodiment of the invention.
[0044] FIG. 33 is a schematic view in partial cross section of a
neural stimulation system implanted in a patient in accordance with
yet another embodiment of the invention.
[0045] FIG. 34A is a schematic view in partial cross section of an
intracranial electrode system implanted in a patient in accordance
with another embodiment of the invention.
[0046] FIG. 34B is a schematic illustration of an electrical energy
transfer mechanism in accordance with an embodiment of the
invention.
[0047] FIG. 35 is a schematic view in partial cross section of
portions of intracranial electrode system implanted in a patient in
accordance with an embodiment of the invention.
[0048] FIG. 36 is a schematic overview of an intracranial electrode
system implanted in a patient in accordance with an embodiment of
the invention.
[0049] FIG. 37 is a schematic view in partial cross section of a
set of intracranial electrodes implanted in a patient in accordance
with a further embodiment of the invention.
[0050] FIG. 38 is a schematic view in partial cross section of an
intracranial electrode in accordance with a further embodiment of
the invention.
[0051] FIG. 39 is a schematic view in partial cross section of an
intracranial electrode in accordance with an embodiment of the
invention.
[0052] FIG. 40 is a schematic overview of an intracranial electrode
system having RFID capabilities in accordance with a further
embodiment of the invention.
[0053] FIG. 41 illustrates a depth measurement procedure employing
a depth acquisition stick according to an embodiment of the present
invention.
[0054] FIG. 42 is a flowchart illustrating depth measurement
procedures in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
[0055] A. Overview
[0056] Various embodiments of the present invention provide
intracranial electrodes and methods for implanting and using
intracranial electrodes. It will be appreciated that several of the
details set forth below are provided to describe the following
embodiments in a manner sufficient to enable a person skilled in
the art to make and use the disclosed embodiments. Several of the
details and advantages described below, however, may not be
necessary to practice certain embodiments of the invention.
Additionally, the invention can also include additional embodiments
that are not described in detail with respect to FIGS. 1-42.
[0057] One aspect of the invention is directed to an intracranial
signal transmission system that includes a generally electrically
insulating support body having a head portion configured to be
positioned at least proximate to an outer surface of a patient's
skull. The support body can further have a shaft portion configured
to extend into an aperture in the patient's skull. At least one
electrical contact portion is carried by the support body and can
be positioned to transfer electrical signals to, from, or both to
and from the patient's brain via the aperture in the patient's
skull.
[0058] An intracranial signal transmission system in accordance
with another aspect of the invention includes an electrical contact
portion configured to be positioned in an aperture of a patient's
skull, and an electrical energy transfer device configured to be
releasably positioned external to the patient's scalp. The energy
transfer device can be coupleable to a signal transmitter to
transmit signals to the electrical contact portion while the
electrical contact portion is positioned beneath the patient's
scalp, and while the energy transfer device is positioned external
to the patient's scalp. In particular embodiments, the electrical
energy transfer device can include a flexible outer layer, an
adhesive gel layer positioned to contact the patient's scalp, a
conductive layer positioned between the outer layer and the
adhesive gel layer, and a conductive lead connected to the
conductive layer.
[0059] An intracranial signal transmission system in accordance
with still another aspect of the invention includes a shaft
configured to extend through an aperture in a patient's skull, and
a head connected to the shaft. The head can be configured to be
positioned adjacent to an external surface of the patient's skull
and can be eccentrically positioned relative to the shaft.
Accordingly, the head can have a first portion extending outwardly
from the shaft by a first distance, and a second portion extending
outwardly from the shaft by a second distance different from the
first distance. The system can further include an electrical
contact portion carried by at least one of the shaft and the
head.
[0060] Other aspects of the invention are directed to methods for
installing electrodes and/or transmitting intracranial electrical
signals. A method in accordance with one aspect of the invention
includes drilling a hole in a patient's skull, and determining a
distance from an outer surface of the patient's skull to a feature
beneath the outer surface of the patient's skull by inserting an
elongated member having graduation markings into the pilot hole.
The method can further include selecting a size of an intracranial
electrode based on the distance determined with the elongated
member, and inserting the intracranial electrode into the hole. The
method can still further include securing the intracranial
electrode to the patient's skull.
[0061] A method in accordance with another aspect of the invention
includes forming an aperture in a patient's skull, with the
aperture having a first generally conical portion with a first
diameter at an external surface of the patient's skull, and a
second portion having a second diameter smaller than the first
diameter, located beneath the external surface. The method can
further include disposing proximate to the aperture an electrical
contact portion carried by a support body having a shaft and a head
depending from the shaft. The head can have a generally conical
shape, with an angle between an external surface of the shaft and
an external surface of the head being obtuse. The method can still
further include inserting the support body into the aperture so
that the shaft extends through the second portion of the aperture
and the head engages a wall of the aperture at the first portion of
the aperture.
[0062] A method in accordance with yet another aspect of the
invention includes forming an aperture in the patient's skull,
disposing proximate to the aperture an electrical contact portion
carried by a support body having a shaft and a head depending from
the shaft, with the shaft having an external surface and a
plurality of surface features. The method can still further include
inserting the support body into the aperture so that the shaft
extends into the aperture, and then allowing the patient's bone
tissue to grow into interengagement with the surface features.
[0063] For ease of understanding, the following discussion is
subdivided into three areas of emphasis. The first section
discusses certain intracranial electrodes; the second section
relates to select embodiments of neurostimulation systems; and the
third section outlines methods in accordance with other embodiments
of the invention.
[0064] B. Intracranial Electrodes
[0065] FIGS. 2-15 illustrate intracranial electrodes in accordance
with various embodiments of the invention. Like reference numbers
are used throughout these figures to designate like or analogous
elements.
[0066] FIGS. 2A-B illustrate an intracranial electrode 100 in
accordance with one embodiment of the invention. This electrode 100
includes a head 102 attached to a threaded shaft 110. The head 102
and shaft 110 may be integrally formed of an electrically
conductive material, e.g., titanium or another biocompatible,
electrical conductive metal. The head 102 may include one or more
slots 104, an allen head recess (not shown), or other structure
(e.g., a square drive or TORX.TM. drive recess) adapted to
facilitate turning the electrode 100. As the electrode 100 is
turned, the threads 112 of the threaded shaft 110 will advance a
generally distally positioned contact surface 115 of the electrode
100 toward the dura mater 20. The length of the shaft 110 may be
selected so that the contact surface 115 of the electrode 100
electrically engages the surface of the dura mater 20 without
causing undue harm to the dura mater 20 or the underlying cerebral
cortex. The contact surface 115 may comprise a relatively blunt end
to reduce trauma to the dura mater and the underlying brain tissue
25.
[0067] In one embodiment, the intracranial electrode 100 is adapted
to be electrically connected to a pulse system (1050 in FIG. 18,
for example), as described below. The electrode 100 may be
connected to the pulse system in any desired fashion. In the
illustrated embodiment, the electrode 100 is coupled to such a
pulse system by means of an electrical lead 120. The electrical
lead 120 shown in FIGS. 2A and 2B comprises an elongated,
subcutaneously implantable body 124, which may have an insulative
sheath. An electrically conductive ring or washer 122 may be
attached to an end of the body 124. In one embodiment, an opposite
end of the body 124 is physically attached to a component of the
pulse system. In other embodiments, the leads may be operatively
connected to one or more components of the pulse system without
being physically attached thereto, e.g., using a transmitter and
antenna or a magnetic coupling. Embodiments of pulse systems
incorporating such wireless links are disclosed in U.S. Patent
Application Publication No. US 2002/0087201, the entirety of which
is incorporated herein by reference.
[0068] The head 102 of the electrode 100 is adapted to be implanted
subcutaneously beneath the patient's scalp 30 (shown schematically
in FIG. 2A). As explained below, the electrode 100 may be used to
deliver an electrical signal to the brain tissue 25 adjacent the
contact surface 115. At higher stimulus levels, electrical contact
between the patient's scalp 30 and the head 102 of the electrode
100 may be uncomfortable for the patient. If so desired, the scalp
30 may be electrically insulated from the head 102. This may be
accomplished by applying on the head 102 a quantity of a
dielectric, biocompatible, cementitious material (not shown), which
may be cured or dried in place. In another embodiment, the head 102
may be covered with a separate cap 130 (shown in dashed lines in
FIG. 2A) formed of a dielectric material, e.g., a dielectric,
biocompatible plastic, that may be glued, press-fit, or otherwise
attached to the head 102 and/or the lead 120.
[0069] The dimensions of the electrode 100 can be varied to meet
various design objectives. In one embodiment, however, the
electrode 100 is longer than the thickness of the patient's skull.
More specifically, the head 102 is adapted to be seated at an
extracranial subcutaneous site while the threaded shaft 110 is only
slightly longer than the skull thickness at the intended treatment
site. Lengths on the order of 4-50 mm, for example, may be
appropriate in certain applications. The diameter of the head 102
and the threaded shaft 110 may also be varied. For most
applications, shafts 110 having diameters (typically excluding the
width of the threads 112) of no greater than 4 mm will suffice.
Shaft diameters of about 1-4 mm are likely, with diameters of
1.5-2.5 mm being well suited for most applications. FIGS. 2A-B
illustrate an electrode 100 having a constant diameter shaft 110,
but it should be understood that the shaft diameter may vary. For
example, the shaft 110 may taper distally to improve the ability of
the shaft 110 to be self-tapping. The head 102 typically will have
a larger diameter than an adjoining portion of the shaft 110. (It
should be recognized that FIGS. 2-15 are not drawn to scale. In
particular, the aspect ratio of the electrodes is significantly
reduced to better illustrate certain functional aspects of the
designs.)
[0070] FIG. 3A illustrates an intracranial electrode 150 in
accordance with another embodiment of the invention. This
intracranial electrode 150 is similar in many respects to the
intracranial electrode 100 of FIGS. 2A-B. For example, the
electrode 150 includes an electrically conductive threaded shaft
110 defining a blunt, atraumatic contact surface 115 adjacent a
distal end.
[0071] The connection of the electrode 150 to the lead 160 in FIGS.
3A-B differs somewhat from the connection of the electrode 100 and
lead 120 in FIGS. 2A-B, however. In FIGS. 2A-B, the electrode 100
is electrically coupled to the lead 120 by compressively engaging
the electrically conductive ring 122 of the lead 120 between the
electrode head 102 and the skull 10. In FIGS. 3A-B, the electrode
150 includes a head 152 including slots 154 or other structure for
engaging a screwdriver, wrench, or the like. The head 152 is
adapted to engage a cap 162 carried by the lead 160 that
electrically couples the body 164 of the lead 160 to the head 152
of the electrode 150. In the illustrated embodiment, the cap 162
comprises a dielectric body (e.g., a dielectric plastic material
with some resilience) having an electrically conductive inner
surface 163, which may be provided by coating an interior surface
of the cap 162 with a metal. In one embodiment, the cap 162 is
adapted to resiliently deform to be press-fitted on the head 152.
The body 164 of the lead 160 may be coupled to the electrically
conductive inner surface 163 of the cap 162, thereby providing an
electrical pathway between the electrode 150 and a pulse system
(not shown) operatively coupled to the lead 160.
[0072] In one embodiment, the cap 162 is sized to be subcutaneously
implanted beneath the patient's scalp 30. In the illustrated
embodiment, the head 152 and the cap 162 both extend outwardly
beyond the outer cortex 12 of the patient's skull 10. In another
embodiment (discussed in more detail below with respect to FIGS. 38
and 39) some or all of the length of the head 152 and/or the cap
162 may be countersunk into a recess formed through the outer
cortex 12 and/or an outer portion of the cancellous 18. This can
improve patient comfort, which can be useful if the intracranial
electrode 150 is intended to be implanted permanently or for an
extended period of time.
[0073] FIGS. 4A-B schematically illustrate aspects of an
intracranial electrode 200 in accordance with another embodiment.
The electrode 200 may comprise an electrically conductive inner
portion 205 and an electrically insulative outer portion 206. In
the illustrated embodiment, the electrically conductive portion 205
of the electrode 200 includes a head 202 and a threaded shaft 210
defining a contact surface 215 for electrically contacting the
patient's dura mater 20. These elements of the electrode 200 and
their electrical connection to the lead 120 are directly analogous
to the electrode 100 shown in FIGS. 2A-B. The electrically
insulative outer portion 206 of the electrode 200 shown in FIG. 4A
comprises a dielectric member 240 that is disposed between the
threaded shaft 210 and the patient's skull 10. As shown in FIG. 4B,
this dielectric member 240 may take the form of a tapered sleeve.
The sleeve 240 may have an upper ring-like portion 242 and a
plurality of deformable flanges 244 extending distally therefrom.
The flanges 244 may be adapted to be urged outwardly into
compressive contact with a bore formed in the patient's skull 10
when the threaded shaft 210 is advanced into the interior of the
sleeve 240. Although not shown in FIG. 4B, ribs or teeth may be
provided on the exterior surfaces of the flanges 244 to further
anchor the sleeve 240 in the cancellous 18. In one embodiment, the
sleeve 240 is formed of a dielectric plastic and the threads of the
threaded member 210 may be self-tapping in the inner wall of the
sleeve 240.
[0074] When implanted in a skull 10 as shown in FIG. 4A, the
dielectric sleeve 240 will electrically insulate the skull 10 from
the electrically conductive shaft 210 of the electrode 200. (The
sleeve 240 need not completely electrically isolate the skull and
shaft 210; it merely serves to reduce electrical conduction to the
skull 10.) As explained below, some embodiments of the invention
employ an array comprising a plurality of intracranial electrodes
implanted at various locations in a patient's skull 10. The use of
a dielectric member such as the dielectric sleeve 240 can help
electrically isolate each of the electrodes 200 from other
electrodes 200 in the array (not shown). If so desired, the
electrode 200 may be provided with a dielectric cap 230 sized and
shaped to be implanted subcutaneously beneath the patient's scalp
30 (not shown in FIG. 4A). Much like the cap 130 of FIG. 2A, this
cap 230 may electrically insulate the patient's scalp from the
electrically conductive head 202. This may further improve
electrical isolation of the electrodes 200 in an array.
[0075] FIG. 5 illustrates an intracranial electrode 250 in
accordance with yet another embodiment of the invention. This
electrode 250 includes an electrically conductive shaft 260
electrically coupled to a subcutaneously implantable head 262 and a
distally positioned contact surface 265. The shaft 260 is received
in the interior of an externally threaded dielectric layer 280. The
shaft 260 may be operatively coupled to the dielectric layer 280
for rotation therewith as the electrode is threadedly advanced
through the patient's skull 10. In one embodiment, this may be
accomplished by a spline connection between the shaft 260 and the
dielectric layer 280. In other embodiments, the dielectric layer
280 may be molded or otherwise formed about the shaft 260.
[0076] In one particular embodiment, the dielectric layer 280
comprises an electrically insulative ceramic material. In another
embodiment, the dielectric layer 280 comprises an electrically
insulative plastic or other biocompatible polymer that has
sufficient structural integrity to adequately anchor the electrode
250 to the skull 10 for the duration of its intended use. If so
desired, the dielectric layer 280 may be porous or textured to
promote osseointegration of long-term implants. For shorter-term
applications, the dielectric layer 280 may be formed of or covered
with a material that will limit osseointegration.
[0077] In at least some of the preceding embodiments, the
intracranial electrode 100, 150, 200, or 250 has a fixed length. In
the embodiment shown in FIGS. 2A-B, for example, the distance
between the base of the head 102 and the contact surface 115
remains fixed. When the threaded shaft 110 is sunk into the skull
10 to a depth sufficient to compress the conductive ring 122 of the
lead 120 between the head 102 and the skull 10, this will also fix
the distance from the exterior surface of the outer cortex 12 of
the skull 10 to the contact surface 115. The thickness of the skull
10 can vary from patient to patient and from site to site on a
given patient's skull. Hence, the pressure exerted by the contact
surface 115 against the dura mater 20 will vary depending on the
thickness of the skull. If the electrode 100 is selected to be long
enough to make adequate electrical contact with the dura mater
adjacent the thickest site on a skull, the pressure exerted by the
contact surface 115 against the dura mater 20 may cause undue
damage at sites where the skull is thinner. Consequently, it can be
advantageous to provide a selection of electrode sizes from which
the physician can choose in selecting an electrode 100 for a
particular site of a specific patient's skull.
[0078] FIGS. 6-12 illustrate embodiments of electrodes with
adjustable lengths. FIGS. 6A-B, for example, illustrate an
intracranial electrode 300 that is adapted to adjust a distance
between the outer surface of the skull 10 and a contact surface 315
of the electrode 300. This, in turn, enables the contact force
between the contact surface 315 and the surface of the dura mater
20 to be varied without requiring multiple electrode lengths.
[0079] The intracranial electrode 300 of FIGS. 6A and 6B includes a
probe or shaft 310 that has a blunt distal surface defining the
contact surface 315 of the electrode 300. The shaft 310 has a
proximal end 312 that may include a torque drive recess 314 or the
like to facilitate rotation of the shaft 310 relative to a head 320
of the electrode 300. At least a portion of the length of the shaft
310 is externally threaded. In the illustrated embodiment, the
shaft has an externally threaded proximal length and an unthreaded
surface along a distal length.
[0080] The head 320 of the electrode 300 comprises a body 322 and a
tubular length 324 that extends from the body 322. The body 322 may
be adapted to be rotated by hand or by an installation tool. In one
embodiment the body 322 is generally hexagonal to facilitate
rotation with an appropriately sized wrench. In the particular
embodiment shown in FIGS. 6A-B, the body 322 has a pair of recesses
323 in its outer face sized and shaped to interface with a
dedicated installation tool (not shown) having projections adapted
to fit in the recesses 323. If so desired, the installation tool
may be a torque wrench or other tool adapted to limit the amount of
torque an operator may apply to the head 320 of the electrode 300
during installation. The tubular length 324 may be externally
threaded so the head 320 may be anchored to the skull 10 by
screwing the tubular length 324 into the skull 10.
[0081] The head 320 includes an internally threaded bore 326 that
extends through the thickness of the body 322 and the tubular
length 324. The bore 326 has threads sized to mate with the
external threads on the shaft 310. If so desired, a biocompatible
sealant (e.g., a length of polytetrafluoroethylene tape) may be
provided between the threads of the bore 326 and the threads of the
shaft 310 to limit passage of fluids or infectious agents through
the bore 326.
[0082] Rotation of the shaft 310 with respect to the head 320 will,
therefore, selectively advance or retract the shaft 310 with
respect to the head 320. This will, in turn, increase or decrease,
respectively, the distance between the lower face 323 of the head
body 322 and the contact surface 315 of the shaft 310. As suggested
in FIG. 6A, this may be accomplished by inserting a tip 344 of a
torque driver 340 into the torque drive recess 314 in the shaft 310
and rotating the torque driver 340. The tip 344 of the torque
driver 340 may be specifically designed to fit the torque drive
recess 314. In the embodiment shown in FIGS. 6A-B, the torque drive
recess 314 is generally triangular in shape and is adapted to
receive a triangular tip 344 of the torque driver 340. If so
desired, the torque driver 340 may comprise a torque wrench or the
like that will limit the maximum torque and operator can apply to
the shaft 310 of the electrode 300.
[0083] If so desired, the torque driver 340 may include graduations
342 to inform the physician how far the shaft 310 has been advanced
with respect to the head 320. As noted below, in certain methods of
the invention, the thickness of the skull at the particular
treatment site may be gauged before the electrode 300 is implanted.
Using this information and the graduations 342 on the torque driver
340, the physician can fairly reliably select an appropriate length
for the electrode 300 to meet the conditions present at that
particular site.
[0084] In the embodiment shown in FIGS. 6A-B, the head 320 and the
shaft 310 are both formed of an electrically conductive material.
The conductive ring 122 of the lead 120 may be received in a slot
formed in the lower face 323 of the body 322. Alternatively, the
ring 122 may be internally threaded, permitting it to be threaded
over the external threads of the tubular length 324 before the head
320 is implanted. If so desired, the ring 122 can instead be
compressively engaged by the lower face 323 of the head 320 in a
manner analogous to the engagement of the head 102 with the ring
122 in FIG. 2A, for example.
[0085] In another embodiment, the head 320 is formed of a
dielectric material, such as a dielectric ceramic or plastic. This
may necessitate a different connection between the lead 120 and the
shaft 310, such as by electrically contacting the lead 120 to the
proximal end 312 of the shaft 310. Employing a dielectric head 320
can help electrically insulate the skull 10 from the electrodes
300, improving signal quality and reducing interference between the
various electrodes 300 in an array, as noted above.
[0086] FIG. 7 schematically illustrates an intracranial electrode
350 in accordance with a further embodiment of the invention. The
electrode 350 includes a shaft or probe 360 having a proximal end
362 and a distally located contact surface 365. The shaft 360 may
include a first threaded portion 360a and a second threaded portion
360c. In the embodiment shown in FIG. 7, the first and second
threaded portions 360a and 360c are separated by an unthreaded
intermediate portion 360b. In an alternative embodiment, the two
threaded portions 360a and 360c directly abut one another.
[0087] The intracranial electrode 350 of this embodiment also
includes a head 370 having an internally threaded bore 376
extending through its thickness. The threads of the bore 376 are
adapted to mate with the threads of the first threaded portion
360a. By rotating the shaft 360 with respect to the head 370 (e.g.,
with a screwdriver 340), the distance between the head 370 and the
contact surface 365 can be adjusted in much the same manner
described above in connection with FIGS. 6A-B.
[0088] The head 320 of the electrode 300 in FIGS. 6A-B has an
externally threaded tubular length 324 that extends into the skull
10 and helps anchor the electrode 300 to the skull 10. The shaft
310 may then move with respect to the skull by rotating the shaft
310 with respect to the head 320. In the embodiment shown in FIG.
7, the head 370 is not directly anchored to the skull 10. Instead,
the threads of the second threaded portion 360c are adapted to
threadedly engage the skull 10 to anchor the electrode 350 with
respect to the skull 10 and the head 370 is attached to the first
threaded portion 360a of the shaft 360. In one embodiment, the
shaft 360 may be threaded into a pilot hole in the skull 10. Once
the shaft 360 is positioned at the desired depth, the head 370 may
be screwed onto the first threaded portion 360a of the shaft 360 to
help fix the shaft 360 with respect to the skull and provide a less
traumatic surface to engage the patient's scalp (not shown) when
the scalp is closed over the electrode 350. In another embodiment,
the length of the electrode 350 may first be adjusted by rotating
the shaft 360 with respect to the head 370. Once the electrode 350
has the desired length, the shaft 360 may be advanced into the
skull 10. The shaft 360 may be graduated to facilitate adjustment
to the appropriate length. If so desired, the first threaded
portion 360a may be threaded in a direction opposite the second
threaded portion 360c and/or the pitch of the threads in the first
threaded portion 360a may be different from the pitch of the
threads in the second threaded portion 360c.
[0089] In the embodiment of FIG. 7, the shaft 360 of the electrode
350 extends through the dura mater 20 and the contact surface 365
of the electrode 350 is in direct contact with the cerebral cortex
of the patient's brain. This is simply intended to illustrate one
alternative application. In other embodiments, the length of the
electrode 350 may be selected so that the contact surface 365
electrically contacts the dura mater 20 without extending
therethrough, much as illustrated in FIG. 6A, for example.
[0090] FIGS. 8-11 illustrate an intracranial electrode 400 in
accordance with another embodiment of the invention. The
intracranial electrode 400 includes a shaft or probe 410 that is
slidably received by a head 420. The shaft 410 comprises an
electrically conductive material and defines an electrical contact
surface 415, e.g., on its distal end.
[0091] In the preceding embodiments, some or a majority of the head
of the electrode extends outwardly beyond the outer surface of the
skull 10. In the particular implementation shown in FIGS. 8-10, the
head 420 is received entirely within the thickness of the skull 10.
It should be understood, though, that this is not necessary for
operation of the device, and this is shown simply to highlight that
the position of the head 420 with respect to the skull 10 can be
varied. In another embodiment, at least a portion of the head 420
extends outwardly beyond the outer surface of the skull 10.
[0092] The head 420 includes a base 430 and an actuator 422. The
base 430 includes an externally threaded body 432 and a tubular
length 434 that extends from the body 432. A portion of the tubular
length 434 carries external threads 436. The tubular length 434 may
also include one or more locking tabs 440, each of which includes
an actuating surface 442.
[0093] The actuator 422 has an internally threaded bore 424 that is
adapted to matingly engage the threads 436 on the base 430.
Rotating the actuator 422 with respect to the base 430 in a first
direction will advance the actuator 422 toward the actuating
surface 442 of each of the tabs 440. The actuator 422 may urge
against the actuating surfaces 442, pushing the tabs 440 inwardly
into engagement with the shaft 410. This will help lock the shaft
410 in place with respect to the base 430. Rotating the actuator
422 in the opposite direction will allow the tabs 440 to
resiliently return toward a rest position wherein they do not brake
movement of the shaft 410. The force with which the shaft 410
engages the dura mater 20 (not shown) then can be adjusted to a
desired level by moving the shaft 410 with respect to the base 430.
When the shaft 410 is in the desired position, the actuator 422 may
be moved into engagement with the tabs 440 to hold the shaft 410 in
the desired position.
[0094] FIG. 12 illustrates an adjustable-length intracranial
electrode 450 in accordance with another embodiment. The
intracranial electrode 450 includes an axially slidable probe or
shaft 452 and a head 460. The head 460 includes a body 462 and an
externally threaded tubular length 464. The tubular length 464
includes an axially extending recess 466 sized to slidably receive
a portion of the shaft 452. An O-ring 465 or the like may provide a
sliding seal between the head 460 and the shaft 452.
[0095] The contact surface 455 of the shaft 452 is pushed against
the surface of the dura mater 20 with a predictable force by means
of a spring 454 received in the recess 466. In FIG. 12, the spring
454 is typified as a compressed coil spring formed of a helically
wound wire or the like. In this embodiment, an electrical contact
469 of the lead 468 may be electrically coupled to the wire of the
spring 454. Electrical potential may then be conducted to the shaft
452 by the wire of the spring 454.
[0096] In another embodiment (not shown), the spring 454 comprises
a compressed elastomer, which may take the form of a column that
fills some or all of the diameter of the recess 466. The elastomer
may comprise a biocompatible polymeric material, for example. In
such an embodiment, the elastomer may be electrically conductive,
e.g., by filling a polymeric material with a suitable quantity of a
conductive metal powder or the like. In another embodiment, one or
more wires may be embedded in the elastomeric material to conduct
an electrical signal across the elastomer to the shaft 452.
[0097] In the illustrated embodiment and the alternative embodiment
wherein the spring 454 comprises an elastomer, the head 460 may be
formed of a dielectric material, helping electrically insulate the
skull 10 from the shaft 452. In an alternative embodiment, the head
460 may be formed of an electrically conductive material. Even
though the other structural elements of the electrode 450 may
remain largely the same, this would avoid the necessity of having
the lead 468 extend through the head 460; an electrically conducive
ring 122 or the like instead may be employed in a manner analogous
to that shown in FIG. 6A, for example.
[0098] FIG. 13 depicts and adjustable-length intracranial electrode
475 in accordance with a different embodiment. Some aspects of the
intracranial electrode 475 are similar to the intracranial
electrode 450 shown in FIG. 12. In particular, the intracranial
electrode 475 includes an axially slidable probe or shaft 480 that
is slidably received in an axially extending recess 488 in a
tubular length 492 of a head 490. A proximal face of the body 490
may include a pair of tool-receiving recesses 494, which may be
analogous to the tool-receiving recesses 323 noted above in
connection with FIG. 6A, to aid in the installation of the body
490. If so desired, one or more seals may be provided between the
shaft 480 and the body 490. In the embodiment shown in FIG. 13, the
body 490 carries a first O-ring 493 and the shaft 480 and carries a
second O-ring 484 sealed against the interior of the recess 488.
These O-rings may also serve as abutments to limit axial travel of
the shaft 480 in the recess 488.
[0099] The contact surface 481 of the shaft 480 is pushed against
the surface of the dura mater 20 with a predictable force by means
of a spring 486. The spring 486 may be substantially the same as
the spring 454 shown in FIG. 12, and the various materials
suggested above for the spring 454 may also be employed in the
spring 486 of FIG. 13.
[0100] In FIG. 12, the spring 454 provides the electrical
connection between the lead 468 and the shaft 452. In the
embodiment of FIG. 13, however, the lead 496 may be connected
directly to the shaft 480 through a lumen 495 in the body 490. This
lumen 495 is sized to slidably receive a reduced-diameter neck 482
of the shaft 480. As the body 490 is screwed into the skull 10 and
moves toward the brain 25, contact between the shaft 480 and the
dura mater 20 will urge the shaft 480 upwardly, moving the neck 482
upwardly within the lumen 495.
[0101] The electrode 475 of FIG. 13 may facilitate delivering a
highly reproducible contact force of the contact surface 481 of the
shaft 480 against the dura mater 20. The position of the
reduced-diameter neck 482 of the shaft 480 within the lumen 495
will vary in a fixed relationship with the force exerted on the
spring 486 by the shaft 480. Since the force of the shaft 480
against the spring 486 is essentially the same as the force of the
shaft 480 against the dura mater 20, knowing the position of the
neck 482 within the lumen 495 can give the operator an indication
of the force exerted against the dura mater 20. In one particular
embodiment, the interior of the lumen 495 may be graduated to mark
off the depth of the neck 482 in the lumen 495. In another
embodiment, the body 490 may be driven into the skull 10 until the
height of the neck 482 in the lumen 495 reaches a predetermined
point, e.g., when the top of the neck 482 is flush with the top of
the body 490.
[0102] FIG. 14 illustrates an intracranial electrode 500 in
accordance with still another embodiment of the invention. This
electrode 500 includes an electrically conductive probe or shaft
510 having a head 512 and a contact surface 515. A radially
compressible retaining collar 540 extends along a portion of the
length of the shaft 510. As shown in FIG. 15, the retaining collar
540 may be adapted to assume a radially reduced configuration in
response to a compressive force, indicated schematically by the
arrows F. This compressive force F may be generated by collapsing
the retaining collar 540 and restraining it in the lumen of an
introducing sheath (not shown) sized to be received in a bore
through the skull 10. When this force F is removed (e.g., by
retracting the introducing sheath), the retaining collar 540 may
expand radially outwardly away from the shaft 510, as illustrated
in FIG. 16.
[0103] To implant the electrode 500 in the skull 10, the shaft 510
may be advanced into a bore in the skull until the contact surface
515 exerts the desired contact force against the dura mater 20.
Once the shaft 510 is in the desired position, the compressive
force F on the collar 540 may be released, allowing the collar 540
to expand outwardly into compressive engagement with the lumen of
the bore in the skull 10. This will help hold the electrode 500 in
place with respect to the skull without requiring permanent
anchoring of the shaft 510 to the skull 10.
[0104] The shaft 510 may be electrically coupled to a pulse system
(not shown) by a lead 520. The lead 520 may include a cap 522
having an electrically conductive inner surface 524 coupled to a
body 526 of the lead. The lead 520 may be analogous to the lead 160
shown in FIGS. 3A-B. Any other suitable electrical connection
between the shaft 510 and the pulse system may be employed.
[0105] In one embodiment, the collar 540 comprises a dielectric
material. This will help electrically insulate the skull 10 from
the shaft 510. In another embodiment, the collar 540 is
electrically conductive and the lead 520 may be electrically
coupled to the shaft 510 via the collar 540.
[0106] In the embodiment shown in FIG. 14, the shaft 510 may have a
length only a little longer than the thickness of the patient's
skull 10 and the contact surface 515 may be relatively blunt. Such
a design is useful for relatively atraumatic contact with the dura
mater 20. In another embodiment suggested in dashed lines in FIGS.
15 and 16, the electrode 500 may instead have a substantially
longer shaft 510a and a relatively sharp contact surface 515a. Such
an embodiment may be useful for directly stimulating a particular
location within the cerebral cortex or some other location within
the deeper tissues of the brain.
[0107] FIG. 17 schematically illustrates how certain principles of
the invention can be embodied in a subcortical or deep brain
intracranial electrode 550. The electrode 550 generally includes a
threaded shaft 560 having a head 562. The head 562 may be coupled
to a pulse system or a sensing unit (as described below) via a lead
160 in the same manner lead 160 is attached to the head 152 of
electrode 150 in FIGS. 3A-B. (Like reference numbers are used in
these figures to indicate like elements.) The electrode 550 also
includes an elongate conductive member 570 that extends inwardly
from the skull 10 to a selected target site 28. The conductive
member 570, which may comprise a length of a conductive wire, may
be electrically shielded by a dielectric sheath along much of its
length and have an exposed, electrically conductive tip 574.
[0108] In use, the conductive member 570 may be slid freely through
a pilot hole 11 formed through the skull to position the tip 574 at
the target site 28 in a known manner. The pilot hole 11 may be
larger than the conductive member 570 or be tapped to receive the
threads of the shaft 560. With the conductive member 570 in place,
the shaft 560 may be threaded into the pilot hole 11, crimping the
conductive member 570 against an interior of the pilot hole 11.
This will fix the conductive member 570 in place. If so desired, a
proximal length 572 of the conductive member 570 may extend
outwardly of the skull and be held in place by the head 562. The
threads of the threaded shaft 560 may also cut through the
dielectric sheath of the conductive member 570 as the shaft 560 is
screwed into place, making electrical contact with the conductive
wire therein.
[0109] FIG. 18 schematically illustrates a subcortical or deep
brain intracranial electrode 600 in accordance with an alternative
embodiment of the invention. This electrode 600 includes a head 610
having a threaded shaft 620 with an axially-extending opening 622
extending through the length of the head 610. The head 610 may also
include a gimbal fitting 630 adapted to slidably receive a length
of a conductive member, which may comprise the same type of
elongate conductive member 570 discussed above in connection with
FIG. 17.
[0110] The gimbal fitting 630 is adapted to allow an operator
greater control over the placement of the electrically conductive
tip 574 of the conductive member 570. In use, the tip 574 of the
conductive member 570 will be threaded through an opening in the
gimbal fitting 630. By pivoting the gimbal fitting 630 with respect
to the threaded shaft 620 of the head 610, the angular orientation
of the conductive member 570 with respect to the pilot hole 11 in
the skull 10 can be accurately controlled. Once the operator
determines that the conductive member 570 is at the appropriate
angle, e.g., using a surgical navigation system such as that noted
below, the operator may advance the conductive member 570 to
position the conductive tip 574 at the target site 28. Once the tip
574 is in position, the cap 162 of a lead 160 may be press-fitted
on the body 610 of the electrode 600. This will crimp the proximal
length 572 of the connective member 570 between the body 610 and
the conductive inner surface 163 of the cap 162, providing an
effective electrical connection between the conductive member 570
and the body 164 of the lead 160.
[0111] FIGS. 27-29 schematically illustrate intracranial electrodes
that form portions of signal transmission systems in accordance
with further embodiments of the invention. In FIG. 27, an electrode
700 comprises a body (e.g., a support body) that includes a head
702 coupled to a shaft 710. The body of the electrode 700 may be
integrally formed of an electrically conductive inner core 708 clad
with a biocompatible electrically insulating material 712. In the
illustrated embodiment, the electrically conductive portion 708 of
the electrode 700 extends along the length of both the head 702 and
the shaft 710. An electrical lead 720 may be coupled to the
electrode core 708 to facilitate electrical signal transfer, for
example, for electrical stimulation and/or monitoring. In certain
embodiments, the lead 720 may be coupled to a pulse generator. An
electrical contact or contact portion 704 transmits electrical
signals to and/or from the brain tissue 25. The electrical contact
portion 704 can be integral with or connected to the conductive
inner core 708. In the particular embodiments shown in FIGS. 27-29,
the electrical contact portions are housed within an insulative
body. Electrical contact portions in accordance with other
embodiments of the invention can have other arrangements (e.g.,
they can form part of a larger, generally conductive element).
[0112] FIG. 28 illustrates another intracranial electrode 750 in
accordance with an embodiment of the invention. In this embodiment,
the body of electrode 750 may comprise a biocompatible electrically
insulating material 765 containing a set of biocompatible,
electrically conductive contacts 760a and 760b. The electrically
conductive contacts 760a and 760b may be carried by different
portions of the electrode 750 to facilitate production of
particular types of electric field distributions. In one
embodiment, a first contact 760a may be carried by the head 762,
and a second contact 760b may be carried by a distal portion of the
shaft 755, which may be configured to be in electrical contact with
a stimulation site. A lead 770 may comprise lead wires or links 772
and 774 to provide electrical signal pathways to the contacts 760a
and 760b.
[0113] FIG. 29 illustrates yet another embodiment of an
intracranial electrode 780. In the embodiment shown, the
intracranial electrode 780 may comprise electrical contacts 796 and
798 that are carried by a distal portion of a shaft 785. A head 782
can stabilize the shaft 785 relative to the skull 10. A lead 790
may comprise lead wires or links 792 and 794 that are electrically
coupled to one or more contacts 796 and 798. Such lead wires 792
and 794 may facilitate electrical stimulation and/or monitoring
using one or both contacts 796 and 798.
[0114] In an embodiment shown in FIG. 29, the shaft 785 can carry
two contacts 796, 798, and in other embodiments, the shaft 785 can
carry more or fewer contacts. The diameter of the shaft 785 can be
selected based on factors that include the number of contacts
carried by the shaft 785. In particular embodiments, the shaft 785
can have a diameter of from about 0.5 millimeters to about 3.0
centimeters. In other embodiments, the diameter of the shaft 785
can have other values. The shaft 785 can be inserted into the skull
in a manner that is consistent with the diameter of the shaft 785.
For example, smaller shafts 785 can be inserted through a burr hole
in the skull 10, and larger shafts 785 can be inserted using a
craniotomy procedure.
[0115] FIGS. 30 and 31 schematically illustrate other embodiments
of the invention that may be applicable to cortical, subcortical,
and/or deep brain stimulation and/or monitoring situations. Such
embodiments may facilitate stimulation and/or monitoring involving
surface or cortical tissues and/or subcortical or deep brain
tissues. In FIGS. 30 and 31, like reference numbers may correspond
to identical, essentially identical, or analogous elements. One
embodiment of a combined intracranial electrode assembly 800 is
shown in FIG. 30. The combined intracranial electrode assembly 800
comprises a first electrode 810 and a second electrode 820. The
first and second electrodes 810 and 820 may be configured and
dimensioned for placement relative to physically distinct locations
of the brain. For example, the first electrode 810 may be in
contact with the dura 20, while the second electrode 820 may be
positioned relative to a subcortical or deep brain location.
[0116] In one embodiment, the first electrode 810 comprises at
least one electrical contact 815 carried by a distal portion of a
shaft 816. A first lead wire 830 may be coupled to the first
electrode's contact 815. The second electrode 820 may comprise an
elongate member 822 that carries one or more conductive portions,
sections, segments, and/or contacts 825, in a manner identical,
essentially identical, or analogous to that described above. A
second lead wire 835 may be coupled to the second electrode's
contact(s) 825. The length of the second electrode 820, the
position of one or more contacts 825 carried by the second
electrode 820, and/or the particular contacts 825 that are
electrically active at any given time may depend upon a targeted
tissue type or location and/or establishment of a desired type of
stimulation and/or monitoring configuration. In one embodiment,
each electrode 810, 820 can provide independently controlled
stimulation signals. In another embodiment, one of the electrodes
810, 820 can be coupled to a transmitter to provide stimulation
signals to the patient, and the other can be coupled to a sensor to
receive diagnostic signals from the patient. The electrodes 810,
820 can be coupled to a common ground, or can be coupled to
independent grounds.
[0117] FIG. 31 illustrates an embodiment of an intracranial
electrode assembly 800 wherein a first electrode 810 comprises at
least one electrical contact 817 carried by a head 812. Although
the contact 817 is shown spanning a proximal surface portion of the
head 812, it is to be appreciated that the contact 817 may be
located along, upon, and/or within various portions of the head
812. In one embodiment, the first electrode 810 comprises a shaft
816 that need not touch or rest against neural tissue such as the
dura 20. Rather, the shaft 816 may be shorter than in an embodiment
such as shown in FIG. 30. In another embodiment, a first electrode
810 may include a contact 815 (FIG. 30) carried by the shaft 816 in
addition to the contact 817 carried by the head 812. Such an
embodiment may include an additional lead wire (not shown).
[0118] In a manner identical, essentially identical, or analogous
to other embodiments described herein, a combined electrode
assembly 800 may be comprised of one or more electrically
nonconductive portions along with one or more electrically
conductive portions. In one embodiment, nonconductive portions 814
and 822 of the first and second electrodes 810 and 820,
respectively, may be formed from one or more biocompatible
materials (e.g., plastic, silicone, and/or other materials), and
conductive portions such as the first and second sets of contacts
815 and 825 may be formed from one or more biocompatible conductive
materials (e.g., Titanium, Platinum, and/or other materials).
[0119] Through appropriate electrical coupling, for example, by way
of leads 830 and 835, to an electrical source such as a pulse
generator, one or more contacts 815 may be configured as an anode
or a cathode, while other contacts 825 may respectively be
configured as a cathode or an anode to facilitate bipolar and/or
unipolar stimulation as further described below. For example, a
combined electrode assembly 800 may be implanted into a patient
such that a local contact portion, which may comprise a distal
portion of a shaft 816, resides at, upon, or proximate to a
stimulation site; while a remote contact portion, which may
comprise a distal portion 826 of an elongate member 822, provides a
remote or distant circuit completion site.
[0120] In general, the applicability of one or more intracranial
electrode embodiments to any given neural stimulation and/or
monitoring situation may depend upon the location, depth, and/or
spatial boundaries of target neural structures and/or target neural
populations under consideration, which may depend upon the nature
of a patient's neurological condition or disorder. The extent to
which an electric field reaches, penetrates, and/or travels into
and/or through target neural structures and/or a target neural
population may affect neural stimulation efficiency and/or
efficacy. Various intracranial electrode embodiments in accordance
with the invention, for example, those described above with
reference to FIGS. 27-31, may have conducting portions in various
positions or locations, which may facilitate establishment of
particular types of electric field distributions at one or more
times.
[0121] C. Systems Employing Intracranial Electrodes
[0122] FIG. 19 is a schematic illustration of a neurostimulation
system 1000 in accordance with one embodiment of the invention.
This neurostimulation system 1000 includes an array 1010 of
intracranial electrodes and an internally implantable pulse system
1050. The array 1010 of electrodes may employ one or more
electrodes in accordance with any one or more of the embodiments
described above in connection with FIGS. 2-18 and/or 27-31 and/or
any other suitable design. In the particular implementation
depicted in FIG. 19, the array 1010 (shown schematically in FIG.
20) includes a first implantable intracranial electrode 100a and a
second implantable intracranial electrode 100b, each of which may
be substantially the same as the electrode 100 shown in FIGS. 2A-B.
These electrodes 100b and 100b extend through the skull 10 into
contact with the dura mater 20 at two spaced-apart locations.
[0123] The pulse system 1050 may be implanted in the body of the
patient P at a location remote from the array 1010 of electrodes
100. In the embodiment shown in FIG. 19, the pulse system 1050 is
adapted to be implanted subclavicularly. In the alternative
embodiment shown in FIG. 20, the pulse system 1050 is adapted to be
implanted in a recess formed in the patient's skull 10. In either
embodiment, each of the electrodes 100 in the array 1010 is
electrically coupled to the pulse system 1050 by means of a
separate lead (120 in FIGS. 2A-B) having an elongate,
subcutaneously implantable body 124. Hence, electrode 100a is
coupled to the pulse system 1050 by the elongate body 124a of a
first lead and the other electrode 100b is coupled to the pulse
system 1050 by the elongate body 124b of another lead. In one
embodiment, the elongate bodies 124a-b are combined into a single
subcutaneously implantable cable or ribbon.
[0124] FIG. 21 schematically illustrates one pulse system 1050
suitable for use in the neurostimulation system 1000 shown in FIG.
19. The pulse system 1050 generally includes a power supply 1055,
an integrated controller 1060, a pulse generator 1065, and a pulse
transmitter 1070. The power supply 1055 can be a primary battery,
such as a rechargeable battery or other suitable device for storing
electrical energy. In alternative embodiments, the power supply
1055 can be an RF transducer or a magnetic transducer that receives
broadcast energy emitted from an external power source and converts
the broadcast energy into power for the electrical components of
the pulse system 1050.
[0125] In one embodiment, the controller 1060 includes a processor,
a memory, and a programmable computer medium. The controller 1060,
for example, can be a computer, and the programmable computer
medium can be software loaded into the memory of the computer
and/or hardware that performs the requisite control functions. In
an alternative embodiment suggested by dashed lines in FIG. 21, the
controller 1060 may include an integrated RF or magnetic controller
1064 that communicates with an external controller 1062 via an RF
or magnetic link. In such a circumstance, many of the functions of
the controller 1060 may be resident in the external controller 1062
and the integrated portion 1064 of the controller 1060 may comprise
a wireless communication system.
[0126] The controller 1060 is operatively coupled to and provides
control signals to the pulse generator 1065, which may include a
plurality of channels that send appropriate electrical pulses to
the pulse transmitter 1070. The pulse generator 1065 may have N
channels, with at least one channel associated with each of N
electrodes 100 in the array 1010. The pulse generator 1065 sends
appropriate electrical pulses to the pulse transmitter 1070, which
is coupled to a plurality of electrodes 1080. In one embodiment,
each of these electrodes is adapted to be physically connected to
the body 124 of a separate lead, allowing each electrode 1080 to
electrically communicate with a single electrode 100 in the array
1010 on a dedicated channel of the pulse generator 1065. Suitable
components for the power supply 1055, the integrated controller
1060, the pulse generator 1065, and the pulse transmitter 1070 are
known to persons skilled in the art of implantable medical
devices.
[0127] As shown in FIG. 20, the array 1010 of electrodes 100 in
FIG. 19 comprises a simple pair of electrodes 100a and 100b
implanted in the patient's skull at spaced-apart locations. FIGS.
23-26 illustrate alternative arrays that may be useful in other
embodiments. In FIG. 23, the array 1010a includes four electrodes
100 arranged in a rectangular array. The array 1010b of FIG. 24
includes sixteen electrodes 100, also arranged in a rectangular
array. The array 1010c shown in FIG. 25 includes nine electrodes
100 arranged in a radial array. FIG. 26 illustrates an array 1010d
that includes four electrodes 100.times.arranged in a rectangular
pattern and a fifth electrode 100y at a location spaced from the
other four electrodes 100x. In using such an array, the four
proximate electrodes 100.times.may be provided with the same
polarity and the fifth electrode 100y may have a different
polarity. In some embodiments, the housing (1052 in FIG. 19) of the
pulse system 1050 may serve the function of the fifth electrode
100y. The precise shape, size, and location of the array 1010 and
the number of electrodes 100 in the array 110 can be optimized to
meet the requirements of any particular application.
[0128] One or more electrodes 100 of arrays 1010 such as those
described herein may be provided with electrical signals in a
variety of spatially and/or temporally different manners. In some
circumstances, one electrode 100 or a subset of the electrodes 100
may have one electrical potential and a different electrode 100 or
subset of the electrodes 100 (or, in some embodiments, the housing
1052 of the pulse system 1050) may have a different electrical
potential. U.S. patent application Ser. No. 09/978,134, entitled
"Systems and Methods for Automatically Optimizing Stimulus
Parameters and Electrode Configurations for Neuro-Stimulators" and
filed 15 Oct. 2001 (the entirety of which is incorporated herein by
reference), suggests ways for optimizing the control of the
electrical pulses delivered to the electrodes 100 in an array 1010.
The methods and apparatus disclosed therein may be used to
automatically determine the configuration of therapy electrodes
and/or the parameters for the stimulus to treat or otherwise
effectuate a change in neural function of a patient.
[0129] In general, neural stimulation efficiency and/or efficacy
may be influenced by an extent to and/or manner in which neural
stimulation reaches and/or travels into and/or through target
neural structures and/or a target neural population, which may be
affected by stimulation signal polarity, electrode configuration,
and/or electrical contact configuration considerations. The
particular neural structures and/or neural populations targeted at
any time in a neural stimulation situation, and hence such
considerations, may depend upon the nature, severity, and/or
spatial boundaries of a patient's neurologic dysfunction.
[0130] Various embodiments in accordance with the present invention
may be configured to provide bipolar and/or unipolar stimulation at
one or more times. Neural stimulation in which both an anode and a
cathode are positioned, located, or situated within, essentially
across, or proximate to a stimulation site may be defined as
bipolar stimulation. Neural stimulation in which one of an anode
and a cathode is positioned, located, or situated within or
proximate to a stimulation site while a respective corresponding
cathode or anode is positioned, located, or situated remote from
the stimulation site to provide electrical continuity may be
defined as unipolar, monopolar, or isopolar stimulation. Unipolar
stimulation may alternatively or additionally be characterized by a
biasing configuration in which an anode and a cathode are
positioned, located, or situated in different neurofunctional areas
or functionally distinct anatomical regions. Those skilled in the
art will understand that an anode and a cathode may be defined in
accordance with a first phase polarity of a biphasic or polyphasic
signal.
[0131] In a unipolar configuration, a pulse system 1050 may apply
an identical polarity signal to each electrode or electrical
contact positioned upon or proximate to one or more stimulation
sites. Unipolar stimulation may be defined as anodal unipolar
stimulation when an anode is positioned upon or proximate to a
stimulation site or a target neural population; and as cathodal
unipolar stimulation when a cathode is positioned upon or proximate
to a stimulation site or a target neural population.
[0132] In various situations, neural stimulation having particular
stimulation signal and/or spatial and/or temporal characteristics
(e.g., bipolar stimulation, cathodal or anodal unipolar
stimulation, mixed-polarity stimulation, varying duty cycle
stimulation, varying frequency stimulation, varying amplitude
stimulation, spatially or topographically varying stimulation,
theta burst stimulation, and/or other types of stimulation applied
or delivered in a predetermined, pseudo-random, and/or aperiodic
manner at one or more times and/or locations), possibly in
association or conjunction with one or more adjunctive or
synergistic therapies, may facilitate enhanced symptomatic relief
and/or at least partial recovery from neurologic dysfunction.
[0133] An adjunctive or synergistic therapy may comprise a
behavioral therapy such as a physical therapy activity, a movement
and/or balance exercise, an activity of daily living (ADL), a
vision exercise, a reading task, a speech task, a memory or
concentration task, a visualization or imagination exercise, an
auditory activity, an olfactory activity, a relaxation activity,
and/or another type of behavior, task, or activity; a drug or
chemical substance therapy; and/or another therapy that may be
relevant to a patient's functional state, development, and/or
recovery.
[0134] Neurologic dysfunction to which various embodiments of the
present invention may be directed may correspond to, for example,
motor, sensory, language, visual, cognitive, neuropsychiatric,
auditory, and/or other types of deficits or symptoms associated
with stroke, traumatic brain injury, cerebral palsy, Multiple
Sclerosis, Parkinson's Disease, essential tremor, a memory
disorder, dementia, Alzheimer's disease, depression, bipolar
disorder, anxiety, obsessive/compulsive disorder, Post Traumatic
Stress Disorder, an eating disorder, schizophrenia, Tourette's
Syndrome, Attention Deficit Disorder, a drug addiction, autism,
epilepsy, a sleep disorder, a hearing disorder, and/or one or more
other states, conditions, and/or disorders. Depending upon
embodiment details and/or the nature of a patient's neurologic
dysfunction, at least partial symptomatic relief, functional
recovery, and/or functional development may occur through
mechanisms corresponding or analogous to Long Term Potentiation
(LTP), Long Term Depression (LTD), neuroplastic change, and/or
compensatory processes.
[0135] FIG. 32 is a schematic illustration of an exemplary
implantation configuration for a neural stimulation system 1000
according to an embodiment of the invention. In one embodiment, a
neural stimulation system 1000 may comprise a set of intracranial
electrodes 100c and 100d coupled by lead wires 124c and 124d to a
pulse system 1050. The intracranial electrodes 100c and 100d may be
surgically implanted at or relative to a set of target sites, and
the pulse system 1050 may be implanted beneath the scalp 30 and
adjacent to and/or partially within the skull 10. In certain
configurations, a particular separation between and/or relative
positioning of two or more intracranial electrodes 100c and 100d
may be established, such that target electrode implantation or
stimulation sites may correspond to anatomically remote and/or
distinct regions. This may facilitate unipolar stimulation and/or
stimulation of neural populations in different neural association
areas, for example, different neurofunctional areas associated with
motor skills or abilities; neurofunctional areas associated with
motor and language skills; and/or neurofunctional areas associated
with other skills.
[0136] FIG. 33 is a schematic illustration of another exemplary
implantation configuration for a neural stimulation system 1000
according to an embodiment of the invention. Relative to FIG. 32,
like reference numbers may indicate like, corresponding, and/or
analogous elements. As in FIG. 32, a set of intracranial electrodes
100e and 100f may be implanted or positioned relative to particular
neurofunctional areas. In one embodiment, the set of electrodes
100e and 100f may exhibit multiple types of electrical contact
configurations, orientations, and/or geometries. For example, a
particular electrode 100e may carry an electrical contact C.sub.e
that is distinctly different from one or more contacts C.sub.f
carried by another electrode 100f. Depending upon embodiment
details, differences in contact configuration may facilitate
establishment of particular types of electric field distributions,
which may influence neural stimulation efficiency and/or
efficacy.
[0137] Various portions of the discussion herein focus on use of
intracranial electrodes (e.g., electrodes 100, 150, 200, 250, 300,
350, 400, 450, 475, 500, 550, or 600) in neurostimulation systems.
In certain alternative applications, intracranial electrodes may
additionally or alternatively be used to monitor electrical
potentials, for example, in situations involving
electroencephalography or electrocorticography. A suitable
electroencephalograph may incorporate a system similar to the
neurostimulation system 1000 shown in FIG. 19, but a sensing unit
(not shown) may be used in place of the pulse system 1050. Suitable
components for such a sensing unit are known to those skilled in
the art of electroencephalography.
[0138] FIG. 34A illustrates an intracranial electrode system 900 in
accordance with an embodiment of the invention. In one embodiment,
the electrode system 900 comprises an electrical energy transfer
mechanism (ETM) 910 externally placed adjacent to a patient's scalp
30 to couple electrical energy from a pulse generator 1050 to an
intracranial electrode 920. A lead wire 915 may couple the ETM 910
to the pulse generator 1050. The pulse generator 1050 may be of an
identical, essentially identical, analogous, or different type
relative to a pulse generator 1050 shown in FIGS. 19-21.
[0139] In some embodiments, the ETM 910 may comprise a conventional
adhesive patch electrode commonly used for providing an electrical
coupling to a particular location on a patient. The intracranial
electrode 920 may comprise a head 922 coupled to a shaft 924. The
head 922 and shaft 924 may be integrally formed of an electrically
conductive material forming a conductive core 925 that forms an
electrical energy conduit. The conductive core 925 may extend
throughout a portion or along the entire length of the electrode
920. The conductive core 925 may be carried by or encased in an
electrically insulating material or cladding 921. The conductive
core 925 may extend from an upper or proximal contact surface 925a
to a lower or distal contact surface 925b. Contact surfaces 925a
and 925b provide a signal exchange interface of the conductive core
925. The conductive core 925 and the insulating material 921 may
vary in proportionate dimensions with one another accordingly.
[0140] FIG. 34B is a cross sectional illustration of an ETM 910
according to an embodiment of the invention. In one embodiment, the
ETM 910 comprises an energy transfer patch 912 that may have
several layers. In general, an ETM 910 may comprise an outer
flexible, insulating, and/or articulated layer 916, an electrically
conductive layer 914, and a gel layer 912. The conductive layer 914
may be comprised of a conductive material, such as aluminum for
example, for carrying or conveying an electrical signal. The
conductive layer 914 may be appropriately shaped (e.g., oval or
elliptical) for conforming to a portion of the skull's rounded
surface, and may be coupled to the lead wire 915. The conductive
layer 914 forms a portion of a conductive circuit between the lead
wire 915 and the conductive core 925 (FIG. 34A).
[0141] The outer layer 916 may be comprised of essentially any
appropriate insulating nonconductive material as is known in the
art (e.g., foam). The outer layer 916 may be smooth and flexible to
facilitate contouring to the patient's skin surface 30. The gel
layer 912, which may be placed in contact with scalp 30, may
comprise one or more of an electrically conductive coupling gel
912a (such as a hydrogel or wet gel), an adhesive gel 912b, and/or
an anesthetic gel 912c. Electrical coupling gel 912a may be
comprised of a saline composition for enhancing electrical
conductivity and decreasing losses between the conductive layer 914
and scalp 30. The adhesive gel 912b aids in keeping the ETM 910 in
place. An anesthetic gel 912c may be incorporated to possibly
reduce or retard sensations that may result from the transfer of
electrical signals from the ETM 910 through scalp tissues 30 to the
electrode 920.
[0142] FIG. 35 illustrates yet another embodiment of portions of an
intracranial electrode system 900. In one embodiment, an
intracranial electrode 930 comprises a head 932 and a shaft 934
forming a body of the electrode 930. The electrode 930 may contain
a conductive core 925 having contact surfaces 935a and 935b for
conducting electrical energy through the scalp 30 to a stimulation
site such as the dura 20. The conductive core 935 may be clad with
an electrically insulating material 931. A portion of the
insulating material 931 may form one or more portions of the shaft
934, which may contain threads 935 for tapping into the cancellous
18. As in certain previous embodiments having threads, intracranial
electrode 930 may be tapped into the skull 10 to a desired depth. A
bore, notch or groove 933 may be formed in a proximal portion of
the head 932 to facilitate tapping the electrode 930 into
place.
[0143] FIG. 36 is an illustration of an intracranial electrode
system 900 according to an embodiment of the invention. A set of
intracranial electrodes 920 (shown as electrodes 920a and 920b) may
be implanted relative to one or more target sites within cancellous
18. For purposes of simplicity, only two electrodes 920 are shown;
however, it is to be appreciated that additional or fewer
electrodes 920 may be employed. In some embodiments, ETMs 910
(shown as ETMs 910a, 910b) may be placed proximate to each
electrode 920a and 920b, external to the body and adjacent the
scalp 30. Such a set of ETMs 910 may be coupled to the pulse
generator 1050 via leads 915a and 915b. Depending upon embodiment
details and/or a type of neurologic dysfunction under
consideration, the intracranial electrode system 900 may be
configured to provide bipolar stimulation, as a first electrode
920a may have a first polarity and a second electrode 920b may have
an opposing polarity as determined by electrical signals
transmitted via corresponding lead wires 915a and 915b,
respectively. Alternatively, each of the electrodes 920 may be
biased with the same polarity in a unipolar configuration. In such
a situation, a return electrode (not shown) may be placed in
another location upon the patient's body; or one or more portions
of the pulse generator's case may serve as a return electrode. The
leads 915a, 915b can be generally continuous (e.g., they can extend
from the corresponding ETM 910a, 910b to the pulse generator 1050
without a break, except for an optional releasable connection at
the pulse generator 1050).
[0144] FIG. 37 is an illustration of a set of implanted
intracranial electrodes 940a and 940b according to an embodiment of
the invention. In one embodiment, the intracranial electrodes 940a
and 940b may comprise heads 942a and 942b that are eccentrically
offset relative to a center axis A1 and A2 of an electrode shaft
944a and 944b, respectively. A first offset may be defined for a
first electrode 940a by a first radius L1 and a second radius R1,
where L1>R1. Likewise, a second offset may be defined for a
second electrode 940b having a head 942b with radii L2 and R2 where
R2>L2. The offset radii may facilitate the placement of
intracranial electrodes 940a and 940b in close or generally close
proximity to one another at a distance D, while keeping D at a
minimum due to the shorter radii R1 and L2. The offset radii
provide maximum distancing between the ETMs 910a and 910b. In a
situation wherein several sets of electrodes may be needed for
treatment, having electrodes with off center heads 942a and 942b
may provide better and/or more placement options when a plurality
of electrodes are to be placed in close proximity to one another.
Although a set of two intracranial electrodes 940a and 940b are
shown, it is to be understood that larger sets may be employed
depending on electrode dimensions and/or a number of stimulation
sites under consideration. In any of these embodiments, the
electrodes 940a, 940b can be secured relative to the skull 10 by
inserting each of the electrodes 940a, 940b into a corresponding
collar, e.g., a collar 540 generally similar to that described
above with reference to FIG. 14. The collar can be secured to the
skull with one or more securement elements (e.g., threads).
[0145] FIG. 38 illustrates an intracranial electrode 950 according
to another embodiment of the invention. In one aspect of this
embodiment, electrode 950 comprises a body formed of a head 952 and
shaft 954, wherein the head 952 and the shaft 954 are formed with
an obtuse angle .theta. at their juncture. The obtuse angle .theta.
provides the body of the electrode with a tapered, frustoconical
shape that facilitates a more contoured, conformal implant within
the cancellous 18. The head 952 may also be formed with a
protrusion or protruded upper portion E. The protrusion E may be
rounded for a more contoured abutment with scalp tissues 30 to
enhance patient comfort. The head 952 may be contoured and/or
tapered, and may be at least partially recessed within the skull 10
to facilitate a more conformal positioning within the patient's
skull 10. Furthermore, a recessed, contoured placement within the
skull 10 may provide a more aesthetically pleasing implant.
[0146] An outer portion of the electrode 950 may be comprised of an
insulating cladding 956 disposed around a conductive core 955. The
conductive core 955 can include a first electrical contact portion
955a and a second conductive contact portion 955b. It is to be
appreciated by those of ordinary skill in the art that the cladding
956 may be comprised of any suitable biocompatible electrically
insulating material, such as, but not limited to, polymers and/or
ceramic materials. The cladding 956 may contain a plurality of
pores 957. Pores 957 may encourage bone regeneration within and
about the pores for a more friction enhanced and/or lasting
placement within the skull 10. In lieu of pores 957, an exterior
portion of the cladding 956 in contact with body tissues may also
be formed with a roughened surface (not shown) that may encourage
bone growth and/or regeneration. Such enhanced friction and
intergrowth between the cladding 956 and the cancellous 18 may
provide for a more secure and/or conformal placement, which may
reduce or minimize positional migration of the implanted electrodes
950. Other embodiments (not shown) may include variations of the
cladding 957 having combinations of compatible insulative materials
comprising the exterior; such as for example, an upper proximal
portion of the cladding 967 being comprised of a ring-like polymer
insulator; and/or a distal or generally distal portion of the
cladding 967 being comprised of a ceramic insulator.
[0147] FIG. 39 illustrates yet another intracranial electrode 960
according to an embodiment of the invention. In one embodiment, the
intracranial electrode 960 comprises a body having a head 962 and a
shaft 964. One or more portions of the head 962 and/or the shaft
964 may form a tapered transition region, such that a juncture of
the head 962 and the shaft 964 form an obtuse angle 0. The
intracranial electrode 960 may be surgically implanted within a
patient's skull 10 such that a proximal portion (e.g., an end
surface) of the head 962 is flush or substantially flush with an
outer portion or layer 12 of the skull 10. The entirety of the
electrode 960 may be countersunk into a recess formed through the
outer skull 12 and cancellous 18.
[0148] The intracranial electrode 960 may also comprise a cladding
966 surrounding a conductive core 965. The cladding 966, comprised
of any suitable biocompatible material, may in some embodiments
include recesses 967 which may encourage surrounding cancellous
tissue 18 to grow within and/or around the recesses 967, thus
forming an enhanced bonding between the implanted electrode 960 and
the skull 10. This modified bonding may discourage migration of the
electrode 960.
[0149] FIG. 40 illustrates an intracranial electrode system 900
according to another embodiment of the invention. In one aspect of
this embodiment, the intracranial electrode system 900 comprises at
least one intracranial electrode 970 that includes a radio
frequency identification (RFID) element, tag, or transponder 971
and/or another type of proximity sensing and/or detecting device.
The RFID element 971 may be embedded within or carried by a portion
of the head 972 and/or shaft 974, for example, within an insulating
non-conductive material 973 forming a portion of the head 972.
Insulating material 973 may electrically insulate the RFID element
971 from a conductive core 975. The conductive core 975 may include
contact surface areas 975a and 975b that couple to and/or comprise
a portion of an electrical conduit that facilitates signal transfer
or electrical communication between an ETM 910 and intended target
tissues. The ETM 910 is electrically coupled to a pulse generator
1050. In this embodiment, the pulse generator 1050 may include an
RFID unit 1063 comprising an RFID reader configured to identify one
or more RFID elements 971 to either allow/enable or
disallow/disable electrical signal transmissions to particular
intracranial electrodes 970 at one or more times.
[0150] The RFID unit 1063 may comprise an RFID reader that may
include a transmitter and a receive module, a control unit, and a
coupling element (e.g., an antenna). The reader may have three
functions: energizing, demodulating, and decoding. In addition, a
reader can include or be fitted with an interface that converts RF
signals returned from an RFID element 971 into a form that can be
passed on to and/or processed by other elements (e.g., a controller
1060) associated with the system 900.
[0151] The RFID element 971 may comprise an integrated circuit that
is activated when placed in a transmitting field of the RFID unit
1063. The transmitting field may vary depending on specifications
of the RFID element 971 and/or RFID unit 1063. When an ETM 910 is
placed proximate to the intracranial electrode 970, the RFID unit
1063 may emit an RF signal that may used to power up the
electrode's RFID element 971. In one embodiment, in the event that
an RFID element 971 corresponds to or provides a particular code
and/or other information, electrical signal transmission between
the pulse generator 1050 and the ETM 910, and hence to the
electrode 970, may be allowed. Such an embodiment may facilitate
enhanced security neural stimulation.
[0152] The above descriptions of embodiments of the invention are
not exhaustive and it is to be appreciated that, although not
detailed in every instance, certain characteristics of some
embodiments may be applicable to other embodiments. Various
embodiments may include characteristics that are identical,
essentially identical, or analogous to those described in relation
to other embodiments. For example, regarding various embodiments of
FIGS. 27-40, one or more of the following may be incorporated
therewith in a manner that is identical, essentially identical,
and/or analogous to that described above: an adjunct sleeve may
serve as an anchor surrounding an electrode as discussed with
reference to FIG. 4B; a dielectric member may be included with an
insulating layer as discussed with reference to FIGS. 3A, 4A, and
14; one or more mechanisms for adjusting the overall length of the
electrode as discussed with reference to FIGS. 6-13 may be
included; an electrode may have a compressible retaining collar as
discussed with reference to FIG. 14; an electrode may have a
sharper contact surface as discussed with reference to FIGS. 14 and
15; and/or the second electrode 820 of the intracranial electrode
system of FIGS. 30 and 31 may have a gimbal type fitting, as
discussed with reference to FIG. 18.
[0153] D. Methods
[0154] As noted above, other embodiments of the invention provide
methods of implanting an intracranial electrode and/or methods of
installing a neurostimulation system including an implantable
intracranial electrode. In the following discussion, reference is
made to the particular intracranial electrode 100 illustrated in
FIGS. 2A-B and to the neurostimulation system 1000 shown in FIG.
19. It should be understood, though, that reference to this
particular embodiment is solely for purposes of illustration and
that the methods outlined below are not limited to any particular
apparatus shown in the drawings or discussed in detail above.
[0155] As noted above, implanting conventional cortical electrodes
typically requires a full craniotomy under general anesthesia to
remove a relatively large (e.g., thumbnail-sized or larger) window
in the skull. Craniotomies are performed under a general anesthetic
and subject the patient to increased chances of infection.
[0156] In accordance with one embodiment of the present invention,
however, the diameter of the electrode shaft 110 is sufficiently
small to permit implantation under local anesthetic without
requiring a craniotomy. In this embodiment, a relatively small
(e.g., 4 mm or smaller) pilot hole may be formed through at least
part of the thickness of the patient's skull adjacent a selected
stimulation or monitoring site of the brain. When implanting the
electrode 100 of FIGS. 2A-B, it may be advantageous to extend the
pilot hole through the entire thickness of the skull. Care should
be taken to avoid undue trauma to the brain in forming the pilot
hole. In one embodiment, an initial estimate of skull thickness can
be made from MRI, CT, or other imaging information. A hand-held
drill may be used to form a bore shallow enough to avoid extending
through the entire skull. A stylus may be inserted into the pilot
hole to confirm that it strikes relatively rigid bone. The drill
may then be used to deepen the pilot hole in small increments,
checking with the stylus after each increment to detect when the
hole passes through the thickness of the inner cortex 14 of the
skull 10. If so desired, the stylus may be graduated to allow a
physician to measure the distance to the springy dura mater and
this information can be used to select an electrode 100 of
appropriate length or, if an adjustable-length electrode (e.g.,
electrode 300 of FIGS. 6A-B) is used, to adjust the electrode to an
appropriate length.
[0157] The location of the pilot hole (and, ultimately the
electrode 100 received therein) can be selected in a variety of
fashions. U.S. Patent Application Publication No. US 2002/0087201
and U.S. application Ser. No. 09/978,134 (both of which are
incorporated hereinabove), for example, suggest approaches for
selecting an appropriate stimulation site. When the desired site
has been identified, the physician can bore the pilot hole to guide
the contact surface 115 of the electrode 100 to that site. In one
embodiment, the physician may use anatomical landmarks, e.g.,
cranial landmarks such as the bregma or the sagittal suture, to
guide placement and orientation of the pilot hole. In another
embodiment, a surgical navigation system may be employed to inform
the physician during the procedure. Briefly, such systems may
employ real-time imaging and/or proximity detection to guide a
physician in placing the pilot hole and in placing the electrode
100 in the pilot hole. In some systems, fiducials are positioned on
the patient's scalp or skull prior to imaging and those fiducials
are used as reference points in subsequent implantation. In other
systems, real-time MRI or the like may be employed instead of or in
conjunction with such fiducials. A number of suitable navigation
systems are commercially available, such as the STEALTHSTATION
TREON TGS sold by Medtronic Surgical Navigation Technologies of
Louisville, Colo., US.
[0158] Once the pilot hole is formed, the threaded electrode 100
may be advanced along the pilot hole until the contact surface 115
electrically contacts a desired portion of the patient's brain. If
the electrode 100 is intended to be positioned epidurally, this may
comprise relatively atraumatically contacting the dura mater 20; if
the electrode is to contact a site on the cerebral cortex, the
electrode will be advanced to extend through the dura mater. The
electrodes 100 may also be implanted to a selected depth within the
cerebral cortex or at a deeper location in the brain.
[0159] In one embodiment, the length of the electrode 100 is
selected (or adjusted for electrode 300, for example) to achieve
the desired level of contact and the electrode will be advanced
until a known relationship with the skull is achieved, e.g., when
the head 102 compresses the contact ring 122 of the lead 120
against the exterior of the skull 10. In another embodiment, the
thickness of the skull 10 need not be known to any significant
accuracy before the electrode 100 is implanted. Instead, the
electrode 100 may be connected, e.g., via the lead 120, to an
impedance monitor and the impedance may be monitored as the
electrode 100 is being implanted. It is anticipated that the
measured impedance will change when the electrode 100 contacts the
dura mater 20. Once this contact is detected, the physician may
advance the electrode a small, fixed distance to ensure reliable
electrical contact over time.
[0160] As noted above, the electrode 100 may be coupled to a lead
120. The timing of this coupling may vary with the nature of the
coupling. For a lead 120 employing a contact ring 122 or the like
positioned below the head 102, the lead may be coupled to the
electrode before the electrode is introduced into the skull. In
other embodiments, the lead (e.g., lead 160 of FIGS. 3A-B) may be
coupled to the electrode after the electrode is properly positioned
with respect to the selected site of the brain. The lead, or at
least a length thereof, may be implanted subcutaneously, e.g., by
guiding it through a tunnel formed between the implant site and the
intended site of a subclavicularly implanted pulse system 1050. The
patient's scalp may then be closed over the head 102 of the
electrode 100 so the electrode is completely enclosed. This can
materially improve patient comfort compared to more conventional
systems wherein epilepsy monitoring electrodes or the like extend
through the scalp to an extracorporeal connection.
[0161] Additionally or alternatively, implant depth may be
measured, estimated, or indicated through the use of a depth
measurement device or apparatus. FIG. 41 is a schematic
illustration of a depth measurement apparatus 175 (e.g., a depth
acquisition stick or DAS) and a set of intracranial electrodes
I.sub.1-I.sub.4. In one embodiment, an appropriate electrode length
may be determined by performing a depth measurement procedure using
the device 175. The device 175 may be inserted into a surgically
formed pilot hole 11. The device 175 may contain indicia comprising
a plurality of calibrated indicators d1-d4, which provide linear
measurements as to the depth of the pilot hole 11. The device 175
may have a retainer cuff and/or sleeve 176 that aids in keeping the
device 175 in an upright position for accurate depth
measurements.
[0162] Depending on the depth of the pilot hole 11, intracranial
electrodes 11-14 may have shafts of varying lengths S.sub.1-S.sub.4
that correspond to the demarcated indicators d.sub.1-d.sub.4. For
example, the shaft of intracranial electrode I.sub.1, may have a
length S.sub.1 associated with a distance d, indicated on the
device 175. Likewise, intracranial electrodes I.sub.2, I.sub.3 and
I.sub.4 may be associated with distances d.sub.2, d.sub.3, and
d.sub.4, respectively. The depths of the pilot holes 11 may vary
from patient to patient depending on such variables as the age of
the patient and/or an implant location in the skull 10.
[0163] FIG. 42 is a flowchart illustrating a depth acquisition
procedure 2000 according to an embodiment of the invention. In one
embodiment, a depth acquisition procedure 2000 may comprise an
accessing procedure 2010 that involves surgically accessing an
implantation or stimulation site. An accessing procedure may
utilize a surgical navigational system and/or anatomical landmarks,
as discussed above, to aid in making a pilot hole 11 in one or more
appropriate locations. The depth acquisition procedure 2000 may
further comprise an insertion procedure 2020 that may involve
insertion of a depth acquisition apparatus such as device 175 (FIG.
41) into a pilot hole 11. As discussed above, the device 175 may be
provided with indicia corresponding to demarcations or units of
length (e.g., millimeters). The depth acquisition procedure 2000
may additionally comprise a measurement procedure 2030 that
involves measuring or comparing the depth of a hole 11 relative to
a calibrated indicia on a measurement device, e.g., the device 175.
As discussed above, the device 175 may have calibrations
corresponding to a set of shaft lengths of a series of electrodes.
The depth acquisition procedure 2000 may also comprise a mapping
procedure 2040 that involves mapping or correlating a measurement
depth associated with a pilot hole 11 to a corresponding electrode,
for example, one of intracranial electrodes I.sub.1-I.sub.4. A
depth acquisition procedure 2000 may additionally comprise a
selection procedure 2050 that involves selecting an electrode
characterized by an appropriate length or dimension for
implantation.
[0164] Once an electrode 100 is in place, an electrical stimulus
may be delivered from a pulse system 1050 to the patient's brain
via a lead 120 and the electrode 100. In certain embodiments of the
invention discussed previously, a plurality of electrodes 100 may
be implanted in an array (e.g., array 1010, 1010a, 1010b, or 1010c)
in the patient's skull and each of the electrodes 100 may be
coupled to the pulse system 1050 by an electrically separate lead
120. The precise nature of the stimulus delivered via the
electrode(s) 100 can be varied as desired to diagnose or treat a
variety of conditions. The type, pattern, and/or frequency of
stimulus may be selected in a manner identical, essentially
identical, or analogous to or different from that outlined in U.S.
Patent Application Publication No. US 2002/0087201, for example,
and/or may be optimized in a manner described in U.S. application
Ser. No. 09/978,134.
[0165] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense as opposed
to an exclusive or exhaustive sense, that is to say, in a sense of
"including, but not limited to." Words using the singular or plural
number also include the plural or singular number, respectively.
When the claims use the word "or" in reference to a list of two or
more items, that word covers all of the following interpretations
of the word: any of the items in the list, all of the items in the
list, and any combination of the items in the list.
[0166] The above-detailed descriptions of embodiments of the
invention are not intended to be exhaustive or to limit the
invention to the precise form disclosed above. While specific
embodiments of, and examples for, the invention are described above
for illustrative purposes, various equivalent modifications are
possible within the scope of the invention, as those skilled in the
relevant art will recognize. For example, whereas steps are
presented in a given order, alternative embodiments may perform
steps in a different order. Aspects of the invention described in
the context of particular embodiments can be combined or eliminated
in other embodiments.
[0167] In general, the terms used in the following claims should
not be construed to limit the invention to the specific embodiments
disclosed in the specification, unless the above-detailed
description explicitly defines such terms. While certain aspects of
the invention are presented below in certain claim forms, the
inventors contemplate the various aspects of the invention in any
number of claim forms. Accordingly, the inventors reserve the right
to add additional claims after filing the application to pursue
such additional claim forms for other aspects of the invention.
* * * * *