U.S. patent application number 13/619930 was filed with the patent office on 2013-01-10 for method, system and apparatus for neural localization.
Invention is credited to Jeffery L. Bleich, Eric C. Miller, Gregory P. Schmitz, Michael P. Wallace.
Application Number | 20130012831 13/619930 |
Document ID | / |
Family ID | 39535818 |
Filed Date | 2013-01-10 |
United States Patent
Application |
20130012831 |
Kind Code |
A1 |
Schmitz; Gregory P. ; et
al. |
January 10, 2013 |
METHOD, SYSTEM AND APPARATUS FOR NEURAL LOCALIZATION
Abstract
Described herein are devices, systems and methods for
determining if a nerve is nearby a device or a region of a device.
In general, a device for determining if a nerve is nearby a device
includes an elongate body having an outer surface with one or more
bipole pairs arranged on the outer surface. Bipole pairs may also
be referred to as tight bipoles. The bipole pairs may be arranged
as a bipole network, and may include a cathode and an anode that
are spaced relatively close together to form a limited broadcast
field. In general, the broadcast filed is a controlled or "tight"
broadcast field that extends from the bipole pair(s). Methods of
using these devices and system are also described.
Inventors: |
Schmitz; Gregory P.; (Los
Gatos, CA) ; Wallace; Michael P.; (Pleasanton,
CA) ; Bleich; Jeffery L.; (Palo Alto, CA) ;
Miller; Eric C.; (Los Gatos, CA) |
Family ID: |
39535818 |
Appl. No.: |
13/619930 |
Filed: |
September 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13090944 |
Apr 20, 2011 |
8303516 |
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13619930 |
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12060229 |
Mar 31, 2008 |
7959577 |
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13090944 |
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61020670 |
Jan 11, 2008 |
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61017512 |
Dec 28, 2007 |
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60976029 |
Sep 28, 2007 |
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60970458 |
Sep 6, 2007 |
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Current U.S.
Class: |
600/554 |
Current CPC
Class: |
A61B 2562/043 20130101;
A61B 5/4041 20130101; A61B 5/1104 20130101; A61B 5/0488 20130101;
A61B 5/4893 20130101; A61B 5/6855 20130101; A61B 5/4504 20130101;
A61B 2562/0261 20130101; A61B 2562/046 20130101 |
Class at
Publication: |
600/554 |
International
Class: |
A61B 5/05 20060101
A61B005/05 |
Claims
1. A method of detecting if a nerve is above or below a region of a
device in a tissue, the method comprising: positioning a flexible
elongate device within the tissue, so that an upper region of the
device faces the dorsal side of a patient and a lower region of the
device faces the ventral side of the patient; determining a
threshold amount of energy required to stimulate a response in the
patient while the upper region faces the dorsal side of the patient
by applying increasing levels of energy from the upper region to
determine the first stimulation level at which the nerve responds;
repositioning the device within the tissue so that the lower region
faces the dorsal side of the patient and the upper region faces the
ventral side of the patient; determining a threshold amount of
energy required to stimulate a response in the patient while the
upper region faces the ventral side by applying increasing levels
of energy from upper region to determine the first stimulation
level at which the nerve responds; confirming that the nerve is
ventral to the device by comparing the threshold amounts.
2. The method of claim 1, further comprising positioning a
guidewire after confirming that the nerve is ventral to the
device.
3. The method of claim 2, further comprising removing the device
from the patient with the guidewire in position.
4. The method of claim 3, further comprising using the guidewire to
position a surgical device.
5. A method of detecting if a nerve is above or below a region of a
device in a tissue, the method comprising: positioning a device
within the tissue, wherein the device comprises a flexible elongate
body having a first plurality of anodes and cathodes on a
stimulation region of the device; determining a threshold amount of
energy required to stimulate a response in the patient from the
stimulation region by applying increasing levels of energy to form
a substantially continuous broadcast field in a first direction
from the stimulation region to determine the first stimulation
level at which the nerve responds; determining a threshold amount
of energy required to stimulate a response in the patient from the
stimulation region by applying increasing levels of energy to form
a substantially continuous broadcast field in a second direction
from the stimulation region to determine the second stimulation
level at which the nerve responds; and determining if the nerve is
in the first direction from the device or in the second direction
from the device by comparing the threshold amounts.
6. The method of claim 5, further comprising positioning a
guidewire after confirming that the nerve is ventral to the
device.
7. The method of claim 6, further comprising removing the device
from the patient with the guidewire in position.
8. The method of claim 7, further comprising using the guidewire to
position a surgical device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/090,944, filed on Apr. 20, 2011, titled
"METHOD, SYSTEM AND APPARATUS FOR NEURAL LOCALIATION," now
Publication No. US-2011-0196257-A1, which is a divisional of U.S.
patent application Ser. No. 12/060,229, filed on Mar. 31, 2008,
titled "METHOD, SYSTEM AND APPARATUS FOR NEURAL LOCALIZATION," now
U.S. Pat. No. 7,959,577, which claims priority to U.S. Provisional
Patent Application Nos. 61/020,670, filed on Jan. 11, 2008, titled
"DEVICES AND METHODS FOR TISSUE LOCALIZATION AND IDENTIFICATION;"
61/017,512, filed on Dec. 28, 2007, titled "METHOD, SYSTEM AND
APPARATUS FOR TISSUE LOCALIZATION AND IDENTIFICATION;" 60/976,029,
filed on Sep. 28, 2007, titled "METHOD AND APPARATUS FOR NEURAL
LOCALIZATION;" and 60/970,458, filed Sep. 6, 2007, titled "NERVE
TISSUE LOCALIZATION SYSTEM." Each of these provisional patent
applications is herein incorporated by reference in its
entirety.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
BACKGROUND
[0003] Many types of surgical intervention require manipulation of
one or more medical devices in close proximity to a nerve or
nerves, and therefore risk damage to the nerve tissue. For example,
medical devices may be used to cut, extract, suture, coagulate, or
otherwise manipulate tissue including or near neural tissue. It
would therefore be beneficial to precisely determine the location
and/or orientation of neural tissue when performing a medical
procedure.
[0004] Knowing the location or orientation of a nerve in relation
to a medical device (e.g., a probe, retractor, scalpel, etc.) would
enable more accurate medical procedures, and may prevent
unnecessary damage to nearby nerves. Although systems for
monitoring neural tissue have been described, these systems are
relatively imprecise. Further, many of these systems require large
current densities (which may also damage tissue) and may be
severely limited in their ability to accurately guide surgical
procedures. For example, in many such systems a current is applied
from an electrode (e.g., a needle electrode) in order to evoke an
efferent muscular response such as a twitch or EMG response. Such
systems typically broadcast, via the applied current, from the
electrode and the current passes through nearby tissue until it is
sufficiently near a nerve that the current density is adequate to
depolarize the nerve.
[0005] Because the conductance of biological tissue may vary
between individuals, over time in the same individual, and within
different tissue regions of the same individual, it has been
particularly difficult to predictably regulate the applied current.
Furthermore, the broadcast fields generated by such systems are
typically limited in their ability to spatially resolve nerve
location and/or orientation with respect to the medical device.
[0006] For example, US patent application 2005/0075578 to Gharib
et. al. and US 2005/0182454 to Gharib et al. describe a system and
related methods to determine nerve proximity and nerve direction.
Similarly, U.S. Pat. No. 6,564,078 to Marino et al. describes a
nerve surveillance cannula system and US 2007/016097 to Farquhar et
al. describes a system and method for determining nerve proximity
and direction. These devices generally apply electrical current to
send current into the tissue and thereby depolarize nearby nerves.
Although multiple electrodes may be used to stimulate the tissue,
the devices, systems and methods described are do not substantially
control the broadcast field. Thus, these systems may be limited by
the amount of current applied, and the region over which they can
detect nerves.
[0007] Thus, it may be desirable to provide devices, systems and
methods that controllably produce precise electrical broadcast
fields in order to stimulate adjacent neural tissue, while
indirectly or directly monitoring for neural stimulation (e.g. EMG,
muscle movement, or SSEP), and thereby accurately determine if a
nerve is in close proximity to a specified region of the
device.
SUMMARY OF THE DISCLOSURE
[0008] Described herein are devices, systems and methods for
determining if a nerve is nearby a region of a device. In general,
the devices may include one or more bipole pairs that can be
excited by the application of a current or voltage to produce a
bipole field between the anode(s) and cathode(s). These bipoles may
be referred to as "tight" bipole pairs because the bipole field
produced is limited to the adjacent region relatively near the
surface of the device. In some variations the bipole field is
formed by a bipole network comprising a plurality of anodes and
cathodes arranged along an outer surface of the device. Multiple
bipole pairs or multiple bipole networks maybe arranged in
different regions along the outer surface of the device.
[0009] For example, described herein are devices that are capable
of determining if a nerve is nearby a region of the device. These
devices may include an elongate body having an outer surface, and a
bipole network arranged along the outer surface. The bipole network
typically includes a plurality of anodes and a plurality of
cathodes, wherein the plurality of anodes and the plurality of
cathodes are configured to form an effectively continuous bipole
field along a portion of the device's outer surface.
[0010] In some variations the plurality of anodes are in electrical
communication with a first anodal conductor. For example, the
plurality of anodes may all be positioned in a single region of the
device (e.g., the outer surface of the device) and may all connect
to a single connector. In some variations the plurality of anodes
are effectively formed from a single anode. For example, all of the
anodes in a particular region may be formed from a single anodal
wire. Individual anodes forming the bipole network may be formed as
openings (or uninsulated regions) through the body of the device
electrically exposing the anodal conductor (e.g., wire).
[0011] Similarly, any of the devices described herein may include a
plurality of cathodes that are all in electrical communication with
a first cathodal conductor. As mentioned for the anodes, the
cathodes forming a bipole network may be formed from the same
cathodal conductor, such as a wire having multiple regions that are
exposed (or uninsulated) to form the cathodes.
[0012] Alternatively, in some variations the individual anodes
and/or cathodes forming the bipoles of the devices described herein
(including the bipoles of a bipole network) may be separately
connected to the power supply and/or controller. For example, each
anode and/or cathode may be separately wired back to the
controller, allowing individual control of each anode and/or
cathode.
[0013] The anodes and cathodes forming the bipole network may be
arranged so that the current from a particular cathode or anode
passes substantially to an adjacent cathode or anode rather than
spreading out or broadcasting. Thus, the broadcast field formed
when the bipoles are excited by the application of energy may be
limited or controlled. For example, each anode of a bipole network
may be located less than 2 mm from at least one cathode. In some
variations the anodes and cathodes form an alternating pattern
(e.g., of adjacent anodes/cathode/anode). As used herein, a bipole
network (or a plurality of bipoles) may be formed as a "tripolar"
electrode arrangement, in which an anode is adjacent to two
cathodes, or a cathode is adjacent to two anodes.
[0014] In some variations, the anodes forming a bipole network are
arranged in a line. Similarly, the cathodes may be formed in a
line. For example, when the anodes of a bipole network are formed
from a single anodal conductor such as an insulated wire, the
openings through the electrical insulator that expose the wire may
be arranged in a line (including a curved or straight line). In
some variations, an anodal wire forms the anodes of a bipole
network, and a cathodal wire forms the cathodes of the bipole
network, and the wires are arranged in parallel with each other on
or in the body of the device. In some variations, the anodal and
cathodal wires are arranged in a helical pattern.
[0015] The electrodes forming a bipole may have any appropriate
dimension, particularly relatively smaller dimensions. For example,
the anode and/or cathode may have a surface area of less than 5
mm.sup.2 (or less than 3 mm.sup.2, less than 2 mm.sup.2, less than
1 mm.sup.2, etc.). The cathode may be the same size as the anode,
or the sizes of the cathodes and anodes may be different.
[0016] Some device variations have a plurality of bipole networks
that are arranged in a non-overlapping fashion along the outer
surface. For example, the outer surface of the device may contain
two or more regions that each includes a bipole network.
[0017] Also described herein are devices capable of determining if
a nerve is nearby one or more regions of the device that include an
outer surface having a first region and a second region, a first
bipole network comprising a plurality of anodes and a plurality of
cathodes, wherein the plurality of anodes and the plurality of
cathodes are configured to form an effectively continuous bipole
field along the first region of outer surface, and a second bipole
network comprising a plurality of anodes and a plurality of
cathodes, wherein the plurality of anodes and the plurality of
cathodes are configured to form an effectively continuous bipole
field along the second region of outer surface.
[0018] As described above, the plurality of anodes in the first
bipole network may be formed along a first anodal conductor and the
plurality of cathodes in the first bipole network may be formed
along a first cathodal conductor. Similarly, the plurality of
anodes in the second bipole network may be formed along a second
anodal conductor and the plurality of cathodes in the second bipole
network may be formed along a second cathodal conductor.
[0019] The dimension and arrangement of the anodes and cathodes
within each bipole network may be formed as described above.
[0020] In some variations, the bipole field formed along the first
region of the outer surface does not overlap with the bipole field
formed along the second region of the outer surface. For example,
the substantially continuous bipole filed may be formed by applying
current or voltage simultaneously to all of the anodes and cathodes
so that the bipole filed extends between adjacent anodes and
cathodes to form a region in which the bipole fields connect the
adjacent anodes and cathodes to form a stitched together length.
This substantially continuous bipole filed provides a length along
the surface of the device which may be used to detect a nerve near
this region of the surface. For example, the plurality of anodes of
the first bipole network may be arranged in a line.
[0021] In some variations, a first connector electrically is
connected to the anodes of the first bipole network and a second
connector electrically connected to the cathodes of the first
bipole network. For example, the anodes of the first bipole network
may be formed from a single anodal conductor and the cathodes of
the first bipole network may be formed from a single cathodal
conductor. Similarly a third connector may be electrically
connected to the anodes of the second bipole network and a fourth
connector electrically may be connected to the cathodes of the
second bipole network.
[0022] Also described herein are devices capable of determining if
a nerve is nearby one or more regions of the device that include an
outer surface having a first region and a second region, a first
bipole network in the first region and a second bipole network in
the second region. The first bipole network may include a plurality
of anodes in electrical communication with a first anodal conductor
and a plurality of cathodes in electrical communication with a
first cathodal conductor, wherein the plurality of anodes and the
plurality of cathodes are configured to form an effectively
continuous bipole field along the first region of outer surface.
The second bipole network in the second region may include a
plurality of anodes in electrical communication with a second
anodal conductor, and a plurality of cathodes in electrical
communication with a second cathodal conductor, wherein the
plurality of anodes and the plurality of cathodes are configured to
form an effectively continuous bipole field along the second region
of outer surface.
[0023] As mentioned above, the bipole field formed along the first
region may not overlap with the bipole field formed along the
second region when these bipole fields are excited.
[0024] Also described herein are devices capable of determining if
a nerve is nearby a region of the device that include an elongate
body having an outer surface, wherein the outer surface includes a
first region and a second region, a first bipole network in the
first region, and a second bipole network in the second region. The
first bipole network may include a first anodal conductor forming a
plurality of anodes within the first region, and a first cathodal
conductor forming a plurality of cathodes within the first region.
The plurality of anodes and the plurality of cathodes in the first
region may be configured to form a substantially continuous bipole
field in the first region. Similarly, the second bipole network in
the second region may include a second anodal conductor forming a
plurality of anodes located within the second region and a second
cathodal conductor forming a plurality of cathodes located within
the second region, wherein the plurality of anodes and the
plurality of cathodes in the second region are configured to form a
continuous bipole field in the second region.
[0025] Also described herein are devices capable of determining if
a nerve is nearby a region of the device that include an elongate
body having an outer surface and a plurality of anodes and cathodes
on the outer surface, wherein the anodes and cathodes are arranged
to form a substantially continuous broadcast field between the
plurality of anodes and cathodes such that the broadcast field is
formed by adjacent bipole pairs of anodes and cathodes which share
either an anode or cathode.
[0026] As mentioned, the plurality of anodes may be in electrical
communication with a first anodal conductor, and the plurality of
cathodes may be in electrical communication with a first cathodal
conductor. In this variation, bipole pairs (formed by an anode and
cathode) are arranged adjacent to each other so that they can form
a substantially continuous broadcast field (e.g., bipole filed).
Thus, adjacent bipole pairs share either a cathode or an anode, and
an anode may communicate electrically with one or more adjacent
cathode, and a cathode may communicate with one or more adjacent
anodes. This arrangement allows a single network (in some cases
formed by a single cathodal conductor and a single anodal
conductor) to span a larger region of the surface using a
relatively small exposed electrode area. As described below, there
may also be advantages in the ability to detect adjacent nerves
based on the multiple field orientations.
[0027] In some variations, the device also includes a second,
non-overlapping plurality of anodes and cathodes on the outer
surface configured to form a substantially continuous broadcast
field between the second plurality of anodes and cathodes such that
the broadcast field is formed by adjacent bipole pairs of anodes
and cathodes which share either an anode or cathode. For example,
multiple regions on the surface (including more than two) may each
include a plurality of anodes and cathodes configured to form a
substantially continuous broadcast field.
[0028] For example, a device capable of determining if a nerve is
nearby a region of the device may include an elongate body having
an outer surface, wherein the outer surface includes a first region
and a second region, a plurality of anodes and cathodes in the
first region, wherein the anodes and cathodes are arranged in the
first region to form a substantially continuous broadcast field
between the plurality of anodes and cathodes such that the
broadcast field is formed by adjacent bipole pairs of anodes and
cathodes which share either an anode or cathode, and a plurality of
anodes and cathodes in the second region, wherein the anodes and
cathodes are arranged in the second region to form a substantially
continuous broadcast field between the plurality of anodes and
cathodes such that the broadcast field is formed by adjacent bipole
pairs of anodes and cathodes which share either an anode or
cathode. The broadcast field of the first region does not
substantially overlap with the broadcast field of the second
region.
[0029] For example, also described herein are devices capable of
determining if a nerve is nearby a region of the device that
include an outer surface, a plurality of adjacent bipolar electrode
pairs within a first region of the surface, wherein the bipolar
electrode pairs are formed by alternating anodes and cathodes such
that adjacent bipole pairs share either an anode or a cathode,
wherein the anodes in the first region are electrically continuous
and the cathodes in the first region are electrically continuous
and the adjacent bipole pairs form an angle of less than 180
degrees. This arrangement may also be referred as forming a
"zigzag" pattern of bipole pairs.
[0030] Also described herein are systems capable of determining if
a nerve is nearby one or more regions of a device. The systems may
include any of the variations of the devices described herein as
well as one or more additional elements. For example, a system
capable of determining if a nerve is nearby one or more regions of
a device and a controller. The device may include a device with an
outer surface having a first region and a second region, a first
bipole network including a plurality of anodes and a plurality of
cathodes, wherein the plurality of anodes and the plurality of
cathodes are configured to form an effectively continuous bipole
field along the first region of outer surface, and a second bipole
network including a plurality of anodes and a plurality of
cathodes, wherein the plurality of anodes and the plurality of
cathodes are configured to form an effectively continuous bipole
field along the second region of outer surface. The controller may
be configured to switch between applying energy to form the bipole
field of the first bipole network or applying energy to form the
bipole field of the second bipole network.
[0031] The system may also include a power source connected to the
controller. The power source may be a battery. In some variations
the system includes one or more sensors. In particular, the sensors
may be configured for detecting stimulation of a nerve. For
example, motion detectors, muscle twitch detectors, nerve
depolarization detectors, EMG detectors, etc.
[0032] As already described, in some variations of the device, the
plurality of anodes in the first bipole network may be in
electrical communication with a first anodal conductor and the
plurality of cathodes in the first bipole network may be in
electrical communication with a first cathodal conductor; similarly
the plurality of anodes in the second bipole network may be in
electrical communication with a second anodal conductor and the
plurality of cathodes in the second bipole network may be in
electrical communication with a second cathodal conductor.
[0033] Any of the features or arrangements of the devices described
herein may be part of the systems for determining if a nerve is
nearby one or more regions of a device.
[0034] Also described herein are device for determining if a nerve
is nearby a region of the device that only require a single tight
bipole pair in each region of the outer diameter of an elongate
member. For example, described herein are devices for determining
if a nerve is nearby including an elongate device with an outer
surface having a first circumferential region and a second
circumferential region, a first tight bipole pair within the first
circumferential region, wherein the first tight bipole pair
comprises an anode and a cathode that are separated by a distance
that is less half the length of the first circumferential region,
and a second tight bipole pair within the second circumferential
region, wherein the second tight bipole pair comprises an anode and
a cathode that are separated by a distance that is less than half
the length of the second circumferential region, wherein the
broadcast field of the first bipole pair does not overlap with the
broadcast field of the second bipole pair.
[0035] In some variations, each anode is located less than 2 mm
from at least one cathode. Further, each anode may have a surface
area of less than 5 mm.sup.2, and/or each cathode may have a
surface area of less than 5 mm.sup.2 (e.g., less than 3 mm.sup.2,
less than 2 mm.sup.2, less than 1 mm.sup.2, etc.). In some
variations, the first tight bipole pair is separated from the
second tight bipole pair by a distance that is greater than the
distance separating either the first tight bipole pair or the
second tight bipole pair.
[0036] Also described herein are systems for determining if a nerve
is nearby a region of a probe that include an elongate probe with a
surface having a first region and a second region, a first tight
bipole pair within the first region, a second tight bipole pair
within the second region (wherein the broadcast field of the first
tight bipole pair does not substantially overlap with the broadcast
field of the second tight bipole pair), and a controller configured
to switch between the first or second tight bipole pairs so that
energy may be applied to either the first or second tight bipole
pairs, wherein the system is configured to enable determination of
whether the tissue is detectably closer to the first region or the
second region.
[0037] This system, as with any of the systems described herein,
may include a power supply connected to the controller, wherein the
controller regulates the power applied to the tight bipole pairs.
The system may also include one or more sensors, such as a sensor
for determining stimulation of a nerve.
[0038] Also described herein are devices for determining if a nerve
is nearby the device that includes one or more rotatable bipole
pairs. For example, described herein are devices for determining if
a nerve is nearby the device, the device including an elongate body
having an outer body surface and a plurality of circumferential
regions, a scanning surface that is movable with respect to the
outer body surface, and a bipolar electrode pair connected to the
scanning surface, wherein the bipole pair comprises an anode and a
cathode configured to form a bipole field, wherein the scanning
surface is configured to scan the bipolar electrodes across at
least two of the circumferential regions to determine if a nerve is
near a circumferential region.
[0039] The device may also include a controller configured to
control the scanning of the bipolar electrode pair. In some
variations the devices also include a driver for driving the motion
of the scanning surface. The driver may be a motor or other moving
mechanism that drives the movement of the bipole pair. The device
may also include an output for indicating which circumferential
region the bipolar electrode pair corresponds to. For example, as
the bipole pair is rotated, the output may indicate where around
the circumference of the elongate body the bipole pair is
positioned. This may help coordinate the location of the nerve
relative to the probe.
[0040] The scanning surface (including the bipole pair(s)) may be
movable in any appropriate fashion. For example, in some variations
the scanning surface is rotatable with respect to the outer body
surface.
[0041] In some variations, the scanning surface includes a
plurality of bipolar electrode pairs.
[0042] In operation, any of the devices and systems described
herein may be used to determine if a nerve is nearby the
device.
[0043] For example, a method of determining if a nerve is nearby a
region of a device may include the steps of energizing a first
tight bipole pair within a first circumferential region of the
device to form a first broadcast field, energizing a second tight
bipole pair within a second circumferential region of the device to
form a second broadcast field, and determining if a nerve has been
stimulated by either the first broadcast field or the second
broadcast field.
[0044] The step of energizing the second tight bipole pair may
include forming a second broadcast field that does not
substantially overlap with the first broadcast field. Thus, energy
(e.g., current, voltage) may be applied to the bipole pairs (which
may be a bipole network) of different circumferential regions at
different times in order to determine which region is closer to the
device.
[0045] The method may also include the step of determining whether
a nerve is closer to the first circumferential region or the second
circumferential region. In some variations the method includes the
step of monitoring the output of the nerve, such as muscle twitch,
EMG, SSEP, or other methods for determining depolarization of the
nerve, directly or indirectly. If the nerve is depolarized when
stimulating the bipole pair(s) in one region but not when
stimulating other regions, then the nerve is likely closer to the
region that resulted in stimulation. Alternatively, if the nerve is
stimulated after exciting bipole pairs from more than one region,
the nerve may be relatively near all of these regions, but may be
assumed to be closer to the region that results in the greatest
output response.
[0046] The method may also include switching between the bipole
pairs to apply energy. Thus, the energy may be applied separately
(in time) between different regions.
[0047] Also described herein are methods of determining if a nerve
is nearby a region of a device using a moving bipole pair. For
example, the method may include the steps of energizing a bipolar
electrode pair, scanning the bipolar electrode pair across a
plurality of circumferential regions of the outer surface of an
elongate body, and determining if a nerve has been stimulated. The
method may also include determining which circumferential region
corresponds to the stimulation of a nerve.
[0048] The step of scanning the bipolar electrode pair includes
rotating the bipole pair with respect to the outer surface of the
elongate body. In some variations, the step of energizing a bipolar
electrode pair comprises energizing a plurality of bipolar
electrode pairs.
[0049] Also described herein are methods of determining if a nerve
is nearby a device when the bipole pair forms part of a bipole
network in an outer surface region of a device. For example, a
method of determining if a nerve is nearby a device may generally
include energizing a plurality of bipolar electrodes within a first
region of an outer surface of the device to form a first
substantially continuous broadcast field, and determining if a
nerve has been stimulated by energizing the first substantially
continuous broadcast field.
[0050] The method may also include the steps of energizing a
plurality of bipolar electrodes within a second region of an outer
surface of the device to form a second substantially continuous
broadcast field when not energizing the plurality of electrodes
within the first region, and determining if a nerve has been
stimulated by the second substantially continuous broadcast field.
In some variations, the method includes the steps of determining
whether a nerve is closer to the first region or the second
region.
[0051] Also described herein are methods of determining if a nerve
is nearby a device including the steps of energizing a plurality of
bipolar electrodes within a first region of an outer surface of the
device, energizing a plurality of bipolar electrodes within a
second region of an outer surface of the device, and determining
whether a nerve is closer to the first region or the second region.
The plurality of bipole pairs within the first region may be
substantially simultaneously energized. The plurality of bipole
pairs within the second region may be substantially simultaneously
energized.
[0052] Also described herein are methods of determining if a nerve
is nearby a device including the steps of energizing a plurality of
bipolar electrodes within a first region of an outer surface of the
device to form a first substantially continuous broadcast field,
energizing a plurality of bipolar electrodes within a second region
of an outer surface of the device to form a second substantially
continuous broadcast field, wherein the second broadcast field does
not overlap with the first broadcast field, and determining whether
a nerve is closer to the first region or the second region.
[0053] Another method of determining if a nerve is nearby a device
includes energizing a plurality of bipolar electrodes within a
first region of an outer surface of the device, wherein the
plurality of bipolar electrodes comprise one or more anodes
electrically connected to a first anodal conductor and one or more
cathodes electrically connected to a first cathodal conductor,
energizing a plurality of bipolar electrodes within a second region
of an outer surface of the device, wherein the plurality of bipolar
electrodes comprise one or more anodes electrically connected to a
second anodal conductor and one or more cathodes electrically
connected to a second cathodal conductor, and determining whether a
nerve is closer to the first region or the second region.
[0054] Any of the devices described herein may be used as part of a
treatment method for treating tissue that includes the method of
determining if a nerve is nearby the device. The device may be a
treatment device or a device involved in the procedure. Thus, any
of the devices described herein may be integrated into known
devices or instruments.
[0055] For example, a method of determining if a nerve is nearby a
device may include the steps of positioning a device within a
tissue, wherein the device comprises a plurality of circumferential
regions around the device, wherein each circumferential region
includes a plurality of electrodes comprising at least one bipole
pair, energizing the electrodes in a first circumferential region
to a plurality of stimulation levels, determining a first
stimulation level from the plurality of stimulation levels based on
a response of a nerve, energizing the electrodes in the other
circumferential regions to the first stimulation level, and
determining which circumferential region the nerve is nearest to.
The step of energizing the electrodes in the first circumferential
region may include energizing the electrodes in to a plurality of
increasing stimulation levels. In some variations, the electrodes
within each circumferential region may comprise a plurality of
bipole pairs configured to form a substantially continuous
broadcast field when energized.
[0056] The step of energizing the electrodes in the first
circumferential region may comprises energizing the electrodes to
increasing stimulation levels between 0.001 mV and 100 mV (e.g.,
between 0.01 mV and 10 mV, etc.). In some variations the step of
energizing the electrodes includes applying a ramp of stimulation
at increasing levels (e.g., increasing voltage).
[0057] The step of determining the first stimulation level may
include determining the first stimulation level at which the nerve
responds.
[0058] In some variations, the step of energizing the electrodes in
the other circumferential regions comprises sequentially energizing
the electrodes in the other circumferential regions.
[0059] The step of determining which circumferential region the
nerve is nearest to may include determining which circumferential
region evokes the largest response from the nerve when the
electrodes within that circumferential region are energized to the
first stimulation level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] FIG. 1A shows an example of a generic device including an
elongate body and a bipole pair.
[0061] FIGS. 1B and 1C show a tight bipole pair.
[0062] FIGS. 1D-1F show bipole networks.
[0063] FIGS. 2A-2D are various views of portions of a
neurostimulation device, according to one embodiment of the present
invention.
[0064] FIG. 3 is cross-section through a device showing four
circumferential regions.
[0065] FIG. 4 is another cross-section through a device having four
circumferential regions.
[0066] FIGS. 5A and 5B illustrate side views and cross-sectional
views, respectively, of one variation of a portion of a nerve
localization device.
[0067] FIGS. 6A and 6B illustrate side views and cross-sectional
views, respectively, of another variation of a portion of a nerve
localization device.
[0068] FIGS. 7A and 7B illustrate side views and cross-sectional
views, respectively, of another variation of a portion of a nerve
localization device.
[0069] FIG. 8 is a side view of a nerve localization device showing
multiple current path direction features.
[0070] FIG. 9 is a circuit diagram of one variation of a portion of
a nerve localization device.
[0071] FIG. 10 is a perspective view of a portion of a nerve
localization device having two electrodes with rotating
brushes.
[0072] FIGS. 11A-11C are simplified diagrams of one variation of a
nerve localization device.
[0073] FIG. 11D is a partial, simplified diagram of a rongeur tip
configured as a nerve localization device.
[0074] FIGS. 12A-12C illustrate elongate bodies having a plurality
of regions each including at least one bipole pair.
[0075] FIGS. 13A-13D show partial cross-sections through various
devices having elongate bodies including multiple regions.
[0076] FIGS. 14A-14B illustrate one variations of a device employed
in tissue.
[0077] FIG. 14C illustrates another variation of a device in
tissue.
[0078] FIGS. 14D and 14E show a cross-section and a partial
perspective view, respectively, of a device having an elongate body
including four regions.
[0079] FIG. 14F show a schematic illustration of an electrode that
may form part of a tight bipole pair.
[0080] FIG. 15 is a cross-section through another variation of a
device.
[0081] FIGS. 16A-16D illustrate exemplary signals that may be
applied to one or more bipole pairs or networks within a region of
a device.
[0082] FIG. 17A illustrates a system for determining if a nerve is
nearby applied to a patient.
[0083] FIG. 17B-17D are simplified diagrams of sensors which may be
used as part of a system for determining if a nerve is nearby.
[0084] FIGS. 18A-18B illustrate variations of a device for
determining if a nerve is nearby.
[0085] FIGS. 19A-19C are flow diagrams illustrating method of
determining if a nerve is nearby a region of a device.
[0086] FIG. 20 is a block diagram illustrating components that may
be part of a system for determining if a nerve is nearby a
device.
[0087] FIG. 21 is a cross-sectional view of a spine, showing a top
view of a lumbar vertebra, a cross-sectional view of the cauda
equina, and two exiting nerve roots.
[0088] FIG. 22 is a side view of a lumbar spine.
[0089] FIG. 23 is a cross-sectional view of a spine, illustrating a
minimally invasive spinal decompression device and method including
the use of neural localization as described herein.
[0090] FIG. 24 is a block diagram of one variation of a nerve
tissue localization system.
[0091] FIG. 25 is a perspective view of a nerve tissue localization
system.
[0092] FIGS. 26A-26F are cross-sectional views of a spine,
illustrating one method for using a nerve tissue localization
system.
[0093] FIGS. 27A-27H are cross-sectional views of a spine,
illustrating another method for using a nerve tissue localization
system.
[0094] FIGS. 28A and 28B show variations of devices for determining
if a nerve is nearby.
DETAILED DESCRIPTION
[0095] Described herein are devices, systems and methods for
determining if a nerve is nearby a device or a region of a device.
In general, a device for determining if a nerve is nearby a device
includes an elongate body having an outer surface with one or more
bipoles arranged on the outer surface. These bipoles may also be
referred to as tight bipoles, and include a cathode and an anode
that are spaced relatively close together to form a limited
broadcast field. The broadcast field may be referred to as the
bipole field, or the field formed by the excitation of the bipole
pair. In general, the bipole filed is a controlled or "tight"
broadcast field that extends from the bipole pair(s).
[0096] A device for determining if a nerve is nearby the device may
be referred to as a nerve localization device, a localization
device, or a neurostimulation device. The elongate body region of
the device may be referred to as a probe, although it should be
understood that any appropriate surgical or medical device may be
configured as a device for determining if a nerve is nearby the
device. Particular examples of such devices are described below.
For example, FIG. 1A shows a generic device 1 configured as a nerve
localization device that having an elongate body 5 that may be
configured to determine if a nerve is nearby.
[0097] The outer surface of a device for determining if a nerve is
nearby a region of the device may have two or more regions. In some
variations, each region includes two or more bipole pairs that are
arranged to detect a nearby nerve. The regions may be arranged
around or along the outer surface of the device. For example, the
regions may be circumferential regions that divide the outer
surface up along the circumference. Examples of different regions
are described below. Each region may include one or more bipole
pairs, which may be used to detect a nearby nerve.
[0098] Returning to FIG. 1A, the elongate body 5 has an outer
surface with a blunt (atraumatic) end. In general, the outer body
of the device 5 may be formed of any appropriate material,
including polymeric materials such as PEBAX, PEEK or the like.
Non-conducting and biocompatible materials may be particularly
preferred. In FIG. 1A, a single bipole pair 7 is shown near the
distal end of the device. FIG. 1B illustrates an approximation of
the current lines for a dipole pair, including the cathode 8 and
the anode 6. These current lines reflect the dipole field to
broadcast field for the dipole pair.
[0099] A tight bipole pair may have a very limited broadcast field,
as reflected in FIG. 1C, which shows the bipole pair of FIG. 1B
having only the major current line. In some variations the size of
the anode 6 and cathode 6 forming the bipole pair are relatively
small, particularly (e.g., less than 5 mm.sup.2, less than 3
mm.sup.2, less than 2 mm.sup.2, less than 1 mm.sup.2), and the
anode and cathode are positioned sufficiently nearby so that the
majority of current passes between the anodes and cathodes. For
example, the anode and cathode of a bipole pair may be separated by
less than 5 mm, less than 2 mm, less than 1 mm, etc.
[0100] The limited broadcast field may allow stimulation of only
nerves that are very near the bipole pair. This may enhance
accuracy, and help prevent or limit tissue damage, particularly at
the low stimulation.
[0101] When a region of the outer surface of a device includes more
than one bipole, the bipoles may be arranged as a bipole network. A
bipole network includes at least two bipoles that are formed by at
least three electrodes (e.g., two anodes and a cathode or two
cathodes and an anode). The bipole network is typically arranged so
that all of the bipoles in the network are activated synchronously
to create an effectively continuous bipole field along the outer
surface. For example, FIGS. 1D and 1E illustrates an example of an
effectively continuous bipole filed. In this example, the anodes
and cathodes forming the bipolar network are arranged so that the
current between the two electrodes forms a zigzag pattern. Bipole
pairs are located adjacent to each other and share either an anode
or a cathode. FIG. 1F illustrates another example of a bipole
network, in which adjacent bipole pairs do not share anode or
cathodes. This bipole network also forms an effectively continuous
bipole field along the outer surface of the device. Adjacent bipole
pairs are positioned close to each other.
[0102] In some variation all of the cathodes forming a bipole
network are electrically connected to each other and all of the
anodes forming a bipole network are electrically connected. For
example, the anodes of the bipole network may all be formed from a
single anodal connector, and all of the cathodes of a bipole
network may be formed from a single cathodal connector.
Alternatively, all of the cathodes of the bipole network may be
formed separately and connected distally on the device. For
example, all of the cathodes may be wired to a single connector
that connects to a power source or controller configured to
energize the bipole network in a particular region.
[0103] A device may include multiple bipole networks. For example,
different regions on the surface of the device may include
different bipole networks (e.g., each region may have its own
bipole network). The bipole networks in different regions may be
non-overlapping, and may form effectively non-overlapping
continuous bipole fields. "Effectively non-overlapping bipole
fields" means that the broadcast fields of two or more bipole
networks do not substantially overlap. For example, the component
of a broadcast field (e.g., intensity) due to a second bipole
network is less than 15% (or 10%, or 8% or 5% or 1%) of the
component due to a first bipole network at any position near the
first bipole network, particularly at the excitation ranges
described herein.
[0104] A device for determining if a nerve is nearby may also
include a controller for controlling the application of energy to
the bipoles. In particular, the application of energy to the
bipoles may be coordinated as described in the methods sections
below, so that the activation of a nerve can be correlated to a
particular region of the surface of the device.
[0105] In some variations, the bipole or bipole networks are
movable with respect to the outer surface of the device. Moving the
bipole (e.g., rotating it a around the outer surface) may allow a
bipole field (a tight or narrow broadcast field) to be correlated
with different regions of the device. This is also described in
greater detail below.
Nerve Localization Devices
[0106] FIG. 2A, illustrates the distal portion of one embodiment of
a device capable of determining if a nerve is nearby. This
exemplary device 80 is shown in partial cross-section. For clarity,
FIG. 2A does not show the bipoles, thus showing more clearly the
structure of probe device 80. In this example, the device 80
includes a rigid cannula 82 (or tube or needle) and a curved,
flexible guide 84 that can slide through cannula 82. The guide 84
may include a Nitinol core 86 (or inner tube) having a central
lumen 88 and an atraumatic, rounded tip 87 and may also include a
sheath 89 (or coating or cover) disposed over at least part of
Nitinol core 86. The sheath 89 may comprise, in one embodiment, a
polymeric material such as PEBAX, PEEK or the like, or any other
suitable material, and may form an outer surface having different
regions. Core 86 may be made of Nitinol or may alternatively be
made of one or more other substances, such as spring stainless
steel or other metals. Lumen 88, in some embodiments, may be used
to pass a guidewire.
[0107] FIG. 2B is a perspective view of a portion of the probe 80
of FIG. 2A, in which two electrically conductive members 90 are
visible. One member may be a cathodal conductor and one member may
be an anodal conductor. A probe may include as many electrode pairs
as desired, such as eight, sixteen, thirty-two, etc. In this
example, the probe may have a preformed, curved shape and may be
made of at least one flexible, shape memory material, such as
Nitinol. In this way, guide 84 may be passed through cannula 82 in
a relatively straight configuration and may resume its preformed
curved shape upon exiting a distal opening in cannula 82. This
curved shape may facilitate passage of guide 74 around a curved
anatomical surface, such as through an intervertebral foramen of a
spine.
[0108] The exemplary device shown in FIGS. 2A-2D may include at
least one bipole network, including a plurality of anodes and
cathodes. In this example, anodes of a single bipole network are
all formed from the same anodal conductor, and the cathodes of the
same anodal conductor are all formed from the same cathodal
conductor. FIG. 2C illustrates this. In FIG. 2C a section of probe
sheath 89, including the outer surface region, is shown in more
detail. In one embodiment, sheath 89, which fits directly over at
least a portion of Nitinol core 86 (FIG. 2A), includes multiple,
longitudinal lumen 92, each of which may contain an electrical
conductor 94 forming a plurality of electrodes (e.g., anodes or
cathodes). In some embodiments, conductors 94 may be slideably
disposed inside lumen 92, while in other embodiments they may be
fixedly contained therein. Openings into the sheath 89 form the
plurality of cathodes and anodes. The openings may be pores, holes,
ports, slits, grooves or the like. Each aperture 96 may extend from
an outer surface of sheath 89 to one of conductor lumen 92. As
such, apertures 96 may help direct current along paths from one
electrical conductor (e.g., cathodal conductor) to the other
electrical conductor (e.g., anodal conductor) forming the plurality
of bipolar electrode pairs. In some embodiments the conductor 94
may partially extend through and above of the aperture 96 surface.
This may be achieved by a conductor 94 that has several bends
enabling the apex of the bend to protrude through the aperture 96.
Alternatively, the conductor 94 may have sections of its length
near the aperature 96 that have a larger diameter than other
sections of conductor 94. In a given embodiment, any number of
lumen 92, electrical conductors 94 and apertures 96 forming anodes
or cathodes may be used. In some embodiments, apertures 96 may
extend along a desired length of sheath 89 to approximate, for
example, a length of an area to be treated by a device or
procedure.
[0109] FIG. 2D shows a section of sheath 89 is shown in cross
section, showing an electrical conductor 94 comprising (i.e., a
cathodal conductor) and a current directing aperture 96 (i.e.,
forming a cathode of a bipole). In some embodiments, some or all of
apertures 96 may be filled with a conductive material 97, such as a
conductive gel, solid, matrix or the like. Conductive material 97
may serve the dual purpose of helping conduct electric current
along a path and preventing non-conductive substances from clogging
apertures 96.
[0110] The example shown in FIGS. 2C-2D has four circumferential
regions spaced around the circumference of the outer surface of the
sheath region of the device. In this example, each region includes
a bipole network formed by an anodal and cathodal conductor that
are positioned in parallel. Thus, the bipole network (similar to
that shown in FIGS. 1D and 1E) extends along the length of each
surface region of the device, and may form an effectively
continuous bipolar field along the outer surface.
[0111] FIG. 3 illustrates a similar arrangement having four regions
which each include electrical connectors within the elongate body
that may form the bipole network. For example, in FIG. 3, four
pairs 102 of anodal and cathodal conductors are shown. The
conductors of each pair 102 are close enough together that electric
current is transmitted only between electrodes formed by each pair
102a and not, for example, between electrode pairs formed by other
anodal or cathodal conductors 102b, 102c, 102d. In some
embodiments, the anodal conductor and the cathodal conductor may be
"switched" to change the direction that current is passed between
electrodes formed by the two conductors. For example, one conductor
of each pair 102 may be designated as the transmission conductor
(cathode), and the other electrode of the pair 102 may be
designated as the return electrode (anode). When one of the
conductors forming the anode or cathode is set to ground, this
ground may be isolated from the ground (e.g., an anodal conductor)
in other regions of the device, which may help isolate the current
to the bipolar network in a single region of the device. In various
embodiments, electrodes forming the bipole pair may be spaced at
any suitable distance apart by spacing the electrical conductors
forming the electrodes of the bipole pair. For example, electrodes
of each pair may be spaced about 0.1 mm to about 2 mm apart, or
about 0.25 mm to about 1.5 mm apart, or about 0.5 mm to about 1.0
mm apart.
[0112] FIG. 4 shows another example of a cross-section through a
device having pairs 112 of electrical conductors that may form a
network of bipole pairs on the surface of the device. In this
example, the anodal and cathodal conductors are spaced farther
apart. Farther spaced electrode pairs 112 may allow current to pass
farther into tissue but may also risk dispersing the current
farther and potentially being less accurate. Depending on the
specific use and desired characteristics of the device (e.g.,
sheath 110), the bipole pairs formed may be spaced at any of a
number of suitable distances from one another.
[0113] Alternative arrangements of bipole pairs formed from an
anodal and cathodal conductor are shown in FIGS. 5A-7B. For
example, FIG. 5A is a side-view of a pair of bipole pairs that are
formed by apertures 122, 124 in the body of the device (sheath 120)
which expose portions of the cathodal electrical conductor 126 and
portions of the anodal conductor 128. Apertures forming the
cathodes 122 and anodes 124 are disposed along a length of sheath
120 separated by a distance d. As shown in FIG. 5B, the electrical
conductors (i.e., cathodal conductor 126 and anodal conductor 128)
are embedded in the elongate body and are spaced apart from each
other about a circumferential distance s. In one embodiment, the
distance d may be greater than the distance s, so that current is
more likely to travel circumferentially between positive and
negative electrodes, rather than longitudinally along sheath 120.
As can be appreciated from FIGS. 6A and 7A, current may be directed
along any of a number of different paths in different embodiments
of elongate body (sheath 120), by changing the separation distances
of apertures 122, 124 providing access to the electrical conductors
126, 128.
[0114] For example, in FIGS. 6A and 6B, the cathodal and anodal
conductors are positioned in immediately above and below one
another, and apertures forming the anodes and cathodes of bipole
pairs may be spaced at different distances along the body of the
device 130, such that current is more likely to travel between two
closer spaced apertures (distance d') than between two farther
spaced apertures (distance d).
[0115] In FIGS. 7A and 7B, current may be directed along a distance
d between apertures forming anodes and cathodes of bipole pairs
that are spaced more closely together than the anodal and cathodal
conductors of other bipole pairs. As mentioned above, in various
embodiments of these nerve localization devices, any combination of
anodal or cathodal conductors, apertures forming the anode and
cathode pairs, and/or other current direction path features may be
included.
[0116] FIG. 8 shows a portion of a nerve localization device 150.
This nerve localization device variant includes a sheath 152 having
multiple current directing apertures 154 disposed over a cathodal
conductor and an anodal conductor, forming bipole pairs along the
outer surface of the device. As shown, current may be driven along
multiple paths between pairs of apertures 154a, 154b, 154c, 154d.
Multiple individual currents I1, I2, I3 and I4 add up to the total
current IT transmitted between the anodal and cathodal conductor.
In various embodiments, the bipole pairs formed 154 may be disposed
along any desired length of probe 150. Any number of bipole pairs
may be included. As mentioned above, in some variations the
cathodes and/or anodes formed in a single region of the device may
be formed from multiple (including individual) anodal/cathodal
conductors (e.g., wires).
[0117] FIG. 9 is a circuit diagram 160 for a nerve localization
device having two bipole pairs (e.g., eight electrical conductors).
In this simple form, electric current may be driven between the
electrical conductors along a top, bottom, left and right side,
separately. Each of these side forms a different region of the
device.
[0118] Another example of a nerve localization device is shown in
FIG. 10. In FIG. 10, the nerve localization device includes two
electrical conductors 172, 174 forming at least one bipole pair
(not shown) and two rotating brushes 176, 178. Such an embodiment
may allow different sides, such as top, bottom, left and/or right
sides, to be stimulated with only two electrodes 172, 174, rather
than multiple electrode pairs in different sections.
[0119] The elongate bodies forming part of the nerve localization
devices described above may be used with any appropriate controller
and/or stimulator configured to energize the bipole pairs. Thus,
any of these devices may be used as part of a system including a
controller and/or stimulator. In some variations, the elongate body
may also be referred to as a probe. Examples of elongate bodies,
including elongate bodies having different regions which may each
contain one or more bipole pairs, are shown in FIGS. 11A-13D.
[0120] FIG. 11A is a simplified diagram of one variation of a
device 10. This device 10 may be used to perform one or more
medical procedures when orientation of the device with respect to
an adjacent nerve is desired. Similar to the device shown in FIG.
2A above, this variation 10 includes a cannula 20 and a probe 30.
The device 30 includes a tip 40, a top section 32, and a bottom
section 34. The device 30 may include multiple bipole pairs 76, 78
or bipole networks consisting of multiple bipole pairs. A first
bipole pair or bipole network 76 may be located on a first section
32 and a second bipole pair 78 may be located on a second section
34. In one variation the bipole network or pair 76 may be energized
to determine whether a nerve is located near or adjacent to the
first or top section 32. The second bipole network or pair 78 may
be energized to determine whether a nerve is located near or
adjacent to the second or bottom section 34. The first bipole
network or pair 76 and the second bipole network or pair 78 may be
alternatively energized to independently determine whether a nerve
is located near or adjacent to the first section 32 and/or the
second section 34.
[0121] In some variations a bipole pair or network 76, 78 is
typically energized with one or more electrical signal(s). The
device may monitor the electrical signal applied to the bipole
network (or pair) 76, 78, and may monitor the characteristics of
the electrical signal and determine whether tissue is near or
adjacent the bipole(s) 76, 78 as a function of the monitored
electrical signal characteristics. The electrical signal
characteristics may include amplitude, phase, impedance,
capacitance, and inductance over time or frequency.
[0122] After an electrical signal is applied to the bipole network
or pair 76, 78, an output may be detected. In some variations the
nerve localization device includes a sensor or sensors for
monitoring the nerve response. For example, the device may monitor
one or more sensors anatomically coupled to nerve or afferent
tissue enervated by the nerve whose condition is modified by the
signal(s) applied to the bipolar network or pair 76, 78. For
example, the device may monitor one or more sensors innervated by
the nerve tissue such as limb muscles.
[0123] The nerve localization devices and systems described herein
may include one or more indicators or outputs 22, 24. The detectors
may provide a user-identifiable signal to indicate the location of
the nerve or the status of the system. For example, the nerve
localization devices may include one or more light emitting diodes
(LEDs), buzzers (or other sound output), a video display, or the
like. An LED may be illuminated based on signals generated by,
received by, or generated in response to the energized bipole(s) 76
or 78 as discussed above. In some variations the system or devices
create a vibration or sound that a user manipulating the device 20
may feel or hear. The intensity of the output may vary as a
function of detected signal.
[0124] As shown in FIG. 11B, a nerve localization device may
include a pair of electrical conductors 36 (anodal conductor and
cathodal conductor) which form one or more bipole pairs. The anode
or a cathode of the bipole pair(s) 76, 78 may be formed as
described above via an opening 37 filled with a conductive material
38, such as a conductive gel, solid, matrix, or other conductive
material. An example of this is shown in FIG. 11C. Alternatively,
the bipole pair 36 and the conductive material 38 could be formed
from the same conductive elastic or semi-elastic material. The
elongate body of the device 30 may include a bipole network
comprising bipole pairs that are configured in a coil or zig-zag
pattern along the length of the probe. This arrangement may help
ensure continuous conduction during flexion of the probe 30. In
another variation, the anodal and/or cathodal conductors are formed
of conductive ink (e.g., loaded in an elastomeric matrix) may be
deposited on the outside of the probe. The conductive ink could be
insulated with the exception of discrete points forming the anode
or cathode of the bipole pair. In another embodiment a thin flex
circuit could be wrapped around probe to construct the bipoles.
[0125] FIG. 11D is a partial, simplified diagram of a rongeur jaw
680 configured as a nerve localization device. In this variation
the rongeur jaw forms the elongate body of the device on which at
least one bipole pair is located. The rongeur jaw 680 may include a
lower jaw 682 and an upper jaw 684. The lower jaw 682 may have a
tip 688 and a bipolar network or pair 78 on an inner surface. The
upper jaw 684 may have a tip 686 and a bipolar network or pair 76
on an inner surface. In one variation, the first bipolar network or
pair 78 may be energized to determine whether a nerve is located
near or adjacent to the first or bottom jaw 682. The second bipole
network or pair 76 may be energized to determine whether a nerve is
located near or adjacent to the second or top jaw 684. The first
bipolar network or pair 76 and the second bipolar network or pair
78 may be alternatively energized to independently determine
whether a nerve is located near or adjacent to the first, bottom
jaw 682 and/or the second, upper jaw 684.
[0126] In operation, a user may employ such a device to ensure that
a nerve is located between the lower jaw 682 and upper jaw 684 or
that a nerve is not located between the lower jaw 682 and upper jaw
684. A user may then engage the rongeur jaws 680 to excise tissue
located between the jaws 682, 684. A user may continue to energize
or alternately energize the bipole networks or pairs 76, 78 on
either jaw while excising tissue.
[0127] FIGS. 12A-12C are examples of elongate bodies having regions
which include at least one bipole pair, and may include a bipole
network. Each elongate body in FIGS. 12A-12C (40, 50, and 60,
respectively) may be part of a device or system capable of
determining if a nerve is nearby the device, and may be configured
as part of surgical instrument such as a rongeur 680, or other
instrument. The configuration 40 shown in FIG. 12A includes two
longitudinal regions 42, 44 at the distal end. The distal section
42 has a longitudinal length L1 and a width R, which may also be
referred to as a radial length. The more proximal section 44 has a
longitudinal length L2 and a width of R. Each region 42, 44
includes at least one bipole pair 46, 48. A bipole pair 46, 48
typically includes at least one anode (-) and cathode (+) that can
be excited to create a restricted current pathway between the anode
and cathode 46, 48.
[0128] The distance between the anode and cathode pair of may be
less than the distance between any of the electrodes forming part
of a bipole pair in an adjacent region of the elongate body. For
example, the electrodes forming the bipole pair (or bipole network)
in the first region 42 are closer to each other than to either the
anode or the cathode in the adjacent region 44. Likewise, the
distance between the anode and cathode pair in the second region 44
is less than the distance between the anode and the cathode of the
first region. For example, the distance between the anode and
cathode forming bipole pairs in the first region 42 is labeled D1
and the distance between the anode and cathode in the bipole pair
in the second region is labeled D2. D1 may be less than or equal to
L1 and R and D2 may be less than or equal to L2 and R. Any
appropriate spacing (D1 or D2) may be used between the anodes and
cathodes forming the bipole pairs. For example, D1 and D2 may be
about 0.25 mm to 2.0 mm apart. In one variation D1 and/or D2 are
about 0.50 mm. When a bipole or bipole network in a region 46, 48,
is energized, current may flow between the anode and cathode along
a conductive pathway substantially only within its respective
sections 42, 44. This current flow (and/or the related magnetic
field) may be referred to as the `broadcast field of the bipole
pair or bipolar network. A device including regions having tight
bipoles or bipole networks 40 may be employed to determine whether
a nerve is closer to the first region 42 or the second 44, as
described above. The bipole pairs (or bipole networks) in each
region may be alternatively energized and an external sensor(s) can
be used to monitor and/or determine whether a nerve is closer to
the first region 42 or second region 44.
[0129] The arrangement of the bipole pairs or bipole network may
help determine the sensitivity of the device. For example, D1 may
be less than D2, resulting in the bipole pair in the first region
having a smaller broadcast field (and a shorter conductive pathway)
than the bipole pair 48 in the second region. This may allow
detection of a nerve located further from second region than the
first region, assuming a nearly equivalent energy is applied to the
bipole pairs (or networks) within each region. Of course, the
energy applied may be varied between different regions.
[0130] FIG. 12B shows an example of an elongate member 50 having
two regions 52, 54 separated along the longitudinal (or
circumferential if the member is rounded) axis of the member 50.
Each region 52, 54 may include one or more a bipole pairs 56, 58.
For example, each region may include a bipole network formed of
multiple bipole pairs. The individual bipole pairs may share anodes
and cathodes, as described above. In this example, the width of the
first region is the circumferential or linear distance, R1, and the
length is the distance L. The width of the second region is R2 and
the length is L. The bipole pairs 56, 58 in each region may be
longitudinally oriented, radially oriented, or some combination.
For example, a bipole network may have anodes and cathodes arranged
in a linear pattern (e.g., extending longitudinally) or a zigzag
pattern (also extending generally lineally). Other arrangements are
possible.
[0131] FIG. 12C shows another variation of an elongate member
having three regions, two arranged longitudinally 62, 64, and one
more proximally 63, adjacent to the two distal longitudinal (or
circumferential) regions. Each region 62, 63, 64 may include one or
more bipoles 66, 67, 68 or bipole networks. The spacing between the
electrodes forming the bipoles of a bipole pair or network in one
of the regions may be less than the spacing to electrodes outside
of the region. This may prevent current from passing from an
electrode (e.g., anode, cathode) in one region and electrodes in
another region. In some variations the controller or device is
configured so that the anodes and/or cathodes are electrically
isolated (e.g., do not share a common ground) and may be configured
to electrically float when not being energized.
[0132] FIGS. 13A-13D show partial cross-sections through elongate
members 470, 480, 490, 510 which may be used as part of a device
for determining if a nerve is nearby. Each region includes multiple
(e.g., two or more) regions that each include one or more bipole
pairs (e.g., bipole networks). These examples each have a different
cross-sectional shape, and have circumferential regions that are
oriented differently around the perimeter of the elongate member.
For example, FIG. 13A shows a portion of a device having an outer
surface that includes two regions or sections 472, 474 that are
circumferentially distributed. Each region 472, 474 includes one or
more bipoles 476, 478, having at least one anode (-) and one
cathode (+) that can be powered so that current flows between the
anode and cathode, resulting in a broadcast field. In this
embodiment, the distances between the anode and cathode pairs
forming the bipoles in each region are less than the distance
between the anode of one region and the cathode of the other
region. Region 472 may have a radial length R1 and circumferential
span of L (e.g., a width of R1*pi); the longitudinal distance or
length is not apparent from this cross-section, but may extend for
some distance. In this example, a bipole pair in the first region
may have an anode and cathode 476 that are separated by a distance
(approximately D1) that is less than half the length of the first
circumferential region, and the spacing of the tight bipole pair
(approximately D2) in the second region may be less than half the
length of the second circumferential region. In one variation, D1
and/or D2 may be about 0.50 mm. In some variations the spacing
between the bipole pairs in different regions (and within the same
region for bipole networks) is approximately the same.
[0133] The configuration 480 shown in FIG. 13B may also include two
circumferential regions 482, 484 on the distal end of the elongate
member. Each region 482, 484 may include a bipole pair or network
86, 88, as described above. In this embodiment, the distances
between the anode and cathode pairs of either of region 486 and 488
is less than the distance between the anode of one region and the
cathode of the other region.
[0134] The configuration 490 shown in FIG. 13C includes four radial
regions 492, 494, 502, 504 which may also each have one or more
bipole 496, 498, 506, 508. FIG. 13D has two circumferential regions
512, 514. Each radial region 512, 514 includes at least one bipole
pair 516, 518.
[0135] FIGS. 14A-14C are partial diagrams of a portion of a device
capable of determining if a nerve is nearby. The device includes an
elongate body (shown in cross-section) having to regions with at
least one bipole pair in each region. The device is deployed in
tissue 522, 524. The device 470 shown in FIG. 14A includes two
radially separated regions 472, 474, similar to the device shown in
FIG. 13A. Each region 472, 474 has a bipole network or at least one
bipole pair 476, 478 having an anode (-) and cathode (+). The
device may determine whether the module 476 is near or adjacent a
nerve (e.g., in the tissue 522 or 524) as a function of signals
generated in response to one or more energized bipole pairs in the
regions, as described above. When a bipole pair or network 476 is
energized, the conductive pathway (or bipole field) typically does
not extend substantially into the tissue 524, 522.
[0136] The first region 472 may have a radial length R1 and
longitudinal length, L, and the second region 474 may have a radial
length R2 and longitudinal length, L. An anode and a cathode
forming at least one bipole pair within the first region 472 may be
separated by a distance, D1, and an anode and cathode in the second
region may be separated by a distance D2. In some variations the
energy applied to a bipole pair or network does not project very
far into the tissue. This may be a function of the configuration of
the bipole pair (e.g., the size and spacing) and the energy
applied. For example, the energy projecting in to the tissue from a
bipole pair in the first region 472 may not extend substantially
further than a distance of T1, so that it would not provoke a
response from a neuron located further than T1 from the electrodes.
Similarly, the energy projecting into the tissue from a bipole pair
(or the bipole network) in the second region 474 may not extend
substantially further than a distance of T2 from the electrodes.
The electrodes of the bipole pair or network in the first region
472 may be are separated by a distance, D1 that is less than or
equal to R1, T1, and L, and the bipole pair or network in the
second region 474 may be separated by a distance D2 that is less
than or equal to R2, T2, and L. For example, D1 and D2 may be about
0.25 mm to 2.0 mm apart (e.g., 0.50 mm). The energy applied to the
bipole pair or network may be limited to limit the projection of
energy into the tissue. For example, the current between the bipole
pairs may be between about 0.1 mA to 10 mA.
[0137] The device may be used to determine if a nerve is near one
or more regions of the outer surface of the device, and/or which
region the nerve is closest to. For example, a first electrical
signal may be applied to the bipole pair/network in the first
region 472 for a first predetermined time interval, and a response
(or lack of response) determined. A response may be determined by
using one or more sensors, it may be determined by observing the
subject (e.g., for muscle twitch), or the like. Thereafter a second
electrical signal may be applied to the bipole pair/network in the
second region 474 for a second predetermined time interval, and a
response (or lack of a response) determined. The first
predetermined time interval and the second predetermined time
interval may not substantially overlap, allowing temporal
distinction between the responses to different regions. The device
may include more than two regions, and the bipole network may be of
any appropriate size or length.
[0138] Based on the monitored response generated after the
application of energy during the predetermined time intervals, it
may be determined if a nerve is nearby one or the regions of the
device, or which region is closest. For example, if application of
energy to the bipole pairs/networks in both regions results in a
response, the magnitude of the response may be used to determine
which region is closest. The durations of the predetermined time
intervals may be the same, or they may be different. For example,
the duration of the first predetermined time interval may be longer
than the duration of the second predetermined time interval. The
average magnitude of the electrical signals applied may be the
same, or they may be different. For example, the magnitude of the
signal applied to the bipole pair/network in the first region may
be greater than the average magnitude of the signal applied to the
second region.
[0139] The device 450 shown in FIGS. 14A and 14B includes two
longitudinally separated sections 452, 454. Each section 452, 454
has a bipole pair or bipole network 456, 458 that has at least one
anode (-) and one cathode (+).
[0140] The device 440 shown in FIG. 14C includes two longitudinally
separated regions 442, 444, each including a bipole pair or network
446, 448 including at least one anode (-) and one cathode (+). When
the bipole pair or network in a region is energized, the device may
be used to determine if a nerve is nearby based on the generated
response to the energized bipole pair/network.
[0141] FIG. 14D shows a cross-section through a region of an
elongate body of a device having four regions which each include
bipole pairs or networks. The electrodes forming the bipole pairs
or networks are connected to an electrically conductive element so
that the anode(s) and cathode(s) in a particularly region are all
in electrical communication. For example, as illustrated in FIG.
14D, four cathodal conductors 644, 664, 632, 652 pass through the
body of the device and electrically connect to electrode regions
(not visible in FIG. 14D) on the surface of the device. Similarly,
four anodal conductors 642, 662, 634, 654 pass through the body of
the device and electrically connect to electrode regions (not
visible in FIG. 14D) on the surface. This forms bipole pairs 640,
660, 630, 650. When the cathodal and/or anodal conductors form
multiple electrode regions (electrodes) in each region, they may
form a bipole network 640, 660, 630, 650.
[0142] FIG. 14E is a partial isometric diagram of a device shown in
FIG. 14D, in which each region includes a bipole network formed
along the lengths of the device. Each bipole network includes
anodes formed from a single anodal conductor and cathodes formed
from a single cathodal conductor. FIG. 14F is an exemplary
illustration of an anode or cathode 632. The anode may have any
appropriate shape (e.g., round, oval, square, rectangular, etc.),
and any appropriate surface area (e.g., less than 10 mm.sup.2, less
than 5 mm.sup.2, less than 3 mm.sup.2, less than 2 mm.sup.2, less
than 1 mm.sup.2). For example, in some variations, the height of
the anode or cathode (e.g., Y1) may be about 0.25 mm to 0.75 mm,
and the width of the anode or cathode (e.g., X1) is about 3.times.
the height (e.g., X1=3*Y1). As mentioned previously, the electrode
may be formed of a conductive material (e.g., metal, polymer,
etc.), and may be formed by forming a passage into the body of the
elongate member until contacting the conductive member, then
filling the passage with an electrically conductive material.
[0143] The conductive element may be a conductive wire, gel,
liquid, etc. that may communicate energy to the anodes or
cathodes.
[0144] The elongate body may be any appropriate dimension, and may
be typically fairly small in cross-sectional area, to minimize the
damage to tissue. For example, the outer diameter of elongate
member may be about 1.5 mm to 5 mm (e.g., about 2 mm).
[0145] FIG. 15 illustrates conductive pathways 550 of one example
of a device 490 (similar to the variation shown in FIG. 13C) that
includes four radial regions 492, 494, 502, 504 near the distal
region of the elongate body. Each bipole pair or network 496, 498,
506, 508 includes at least one anode (-) and cathode (+) that, when
energized, creates a limited conductive pathway between the
respective anode(s) and cathode(s) of the bipole or bipole network
496, 498, 506, 508. For example, the current pathways 554, 556,
552, and 558 between the bipoles may broadcast energy about 3 to 5
times the distance between the respective cathodes and anodes
forming the bipole(s). Thus, the current pathways 554, 556, 558,
552 may be substantially confined to the respective regions 492,
494, 502, 504 of the elongate body forming the bipole or bipole
network.
[0146] In operation, each bipole network is stimulated separately
for a predetermined time. For example, one bipole network 496, 498,
506, or 508 may be energized with a first signal for a
predetermined first time interval. Thereafter, another bipole
network 496, 498, 506, or 508 may be energized with a second signal
for a predetermined second time interval. Different energy levels
may be applied, for example, as a function of the tissue 522, 524
that a user is attempting to locate or identify.
[0147] FIGS. 16A-16D are diagrams of electrical signal waveforms
580, 590, 210, 220, 230, 240 that may be applied to one or more
bipole pairs (or bipole networks). Exemplary signal waveforms
include square-wave pulses 582, 584, 586. Each pulse 582, 584, 586
may a have a similar magnitude and envelope. The square-wave pulses
may be idealized (e.g., with square edges, etc.), or rounded (as
shown in FIGS. 16A-16D). The waveforms may be used to energize the
bipole network periodically P1 for a predetermined interval T1
where each pulse 582, 584, 586 has an amplitude A1. For example, A1
may be about 0.1 milliamperes (mA) to 10 mA, the pulse width T1 may
be about 100 microseconds (.mu.s) to 500 .mu.s and the period P1
may from 100 ms to 500 ms. For example, A1 may be about 0.5
milliamperes (mA) to 5 mA, the pulse width T1 may be about 200
microsecond (.mu.s) and the period P1 may about 250 ms as a
function of the energy required to depolarize neutral tissue. The
applied energy may also be expressed as a voltage.
[0148] FIG. 16B illustrates another variation, in which the applied
signal waveform 590 includes square-wave pulses 592, 594, 596 that
have an increasing magnitude but similar pulse width T1. The
waveform 590 may be used to energize a bipole network periodically
P1 for a predetermined interval T1 where pulses 592, 594, 596 have
increasing or ramping amplitudes A1, A2, A3. The waveform 590 may
continue to increase pulse amplitudes in order to identify a nerve
(up to some predetermined limit). For example, stimulation of one
or more bipole pairs may cycle a ramping stimulation. In one
example, A1, A2, and A3 are about 1 milliamps (mA) to 5 mA where
A3>A2>A1, the pulse width T1 may be about 100 microsecond
(.mu.s) to 500 .mu.s and the period P1 may from 100 ms to 500 ms.
For example, the pulse width T1 may be about 200 microseconds
(.mu.s) and the period P1 may about 250 ms.
[0149] In FIG. 16C the signals applied to energize different
regions of the device are different. For example, a first waveform
210 may be applied to a first bipole network of a device, and a
second waveform 220 may be applied to energize a second bipole
network of the device. In this example, the signals are
interleaved. The signal waveform 210 includes several square-wave
pulses 212, 214, and 216 and the signal waveform 220 includes
several square-wave pulses 222, 224, and 226. Each pulse 212, 214,
216, 222, 224, 226 may a have a similar magnitude and envelope. The
waveform 210 may be used to energize the first bipole network
periodically P1 for a predetermined interval T1, where each pulse
212, 214, 216 has an amplitude A1. The second waveform 220 may be
used to energize a second bipole network periodically P2 for a
predetermined interval T2 where each pulse 222, 224, 226 has an
amplitude B1. In some variations, the pulse width T1, T2 is about
100 microseconds (.mu.s) to 500 .mu.s, and the period P1, P2 is
from 100 ms to 500 ms. For example, A1, A2 may be about 0.5
milliamperes (mA) to 5 mA, the pulse width T1, T2 may be about 200
microsecond (.mu.s) and the period P1, P2 may about 250 ms. The
pulses 212, 214, 216 do not substantially overlap the pulses 222,
224, 226. In some variations, T1>T2 and P2 is an integer
multiple of P1.
[0150] FIG. 16D is another example, in which different regions of
the device are energized with pulses having increasing amplitudes.
In this example, an amplitude increasing or ramping pulse waveform
230 may be applied to a first bipole network, and a second
amplitude increasing or ramping pulse waveform 240 may be applied
to a second bipole network. The signal waveform 230 includes
several amplitude increasing or ramping square-wave pulses 232,
234, and 236 and the signal waveform 240 includes several amplitude
increasing or ramping square-wave pulses 242, 244, and 246. In
variations having more than two regions, each region may be
stimulated separately, so that the time period between stimulations
(P1-T1) may be larger than illustrated here. Methods may also
include changing the stimulation applied, or scaling it based on a
response, as described in more detail below.
[0151] FIG. 17A is illustrates a schematic of a subject 310 in
which the device for determining if a nerve is nearby is being
used. In this illustration 300, a tissue localization device 10 is
used as part of a system including sensors 322, 324. In this
system, the device 10 may energize one or more bipole pairs or
bipole networks to depolarize neutral tissue that is near a region
of the device including the bipole pair or network. A sensor 322
may be placed on, near, or within muscle that may be innervated
when neutral tissue is depolarized by a nearby energized bipolar or
optical module. The sensor 322 may be innervately coupled to nerve
tissue via a neural pathway 316 and sensor 324 may be innervately
coupled to nerve tissue via a neural pathway 314. For example, the
device may be used as part of a spinal procedure and the sensors
322 may detect an Electromyography (EMG) evoked potentials
communicated in part by a patient's cauda equina along the pathways
314, 316.
[0152] FIGS. 17B-11D are simplified diagrams of sensors 330, 340,
350 that may be employed according to various embodiments. For
example, a sensor 330 may include a multiple axis accelerometer
employed on or near muscle, particularly muscle innervated by
neurons within the region of tissue being operated on. The
accelerometer may be a low-g triaxial accelerometer. The
accelerometer 330 may detect differential capacitance where
acceleration may cause displacement of the silicon structure of the
accelerometer and change its capacitance. The sensor 340 may
include a strain gauge that also may be applied on or near muscle
innervated by neurons within the region begin operated on. The
strain gauge may a multiple planar strain gauge where the gauge's
resistance or capacitance varies as a function of gauge flex forces
in multiple directions. The sensor 350 may include an EMG probe.
The EMG probe may include a needle to be inserted near or within
muscle innervated by a neuron or neurons within the region being
operated on. For example, a sensor may determine a positive
response when detecting an EMG signal of about 10 to 20 .mu.V on
the EMG probe 350 for about 1 second.
[0153] FIGS. 18A-18B illustrate the outer surface of a device
having an elongate body having two regions 446, 448, wherein each
region includes at least one bipole pair. The bipole pairs in the
different regions may have different geometries. For example the
bipole pair in the second region 444 is spaced further apart
(D2>D1) than the bipole pair in the first region 442. This may
result in the bipole pair in the second region projecting the
bipole field further into the tissue than the bipole pair in the
first region.
[0154] The configuration shown in FIG. 18B is similar, but
illustrates a bipole network 449 in the second region 444 that is a
tripolar electrode, having two anodes (-) separated from the
cathode (+) in this example by different distances D2, D3. A bipole
network may include additional cathodes and electrodes that are
typically electrically coupled (e.g., to the same anodal or
cathodal conductor) so that they can be stimulated substantially
simultaneously.
Methods of Operation
[0155] In general, a method of determining if a nerve is nearby a
device, or a region of a device, includes the steps of exciting a
bipole pair or a bipole network to pass current between the bipole
pair, resulting in a limited broadcast field that can stimulate a
nearby neuron. The broadcast field may be limited by the geometry
of the tight bipole pairs and the bipole networks described herein,
and by the applied energy. It can then be determined if a nerve has
been stimulated in response to the excitation of bipole pair or
network; the magnitude of the response can also be compared for
different bipole networks (or bipole pairs) in different regions of
the device to determine which region is nearest the nerve.
[0156] FIGS. 19A-19C are flow diagrams illustrating methods of
determining if a nerve is near a device as described herein. In the
algorithm 380 shown in FIG. 19A a first bipole network (or bipole
pair) located on a first region or section of a device having two
or more regions is energized 382. The bipole network may be
energized by the application of signal for a predetermined time
interval. The energization of the bipolar module may generate a
current between an anode (-) and cathode (+) (or anodes and
cathodes). The subject is then monitored to determine if a response
is detected 384. If a response is detected, then a nerve may be
nearby. The first bipole network may be energized with a first
signal for a first predetermined time interval. In some variations,
the first bipole network is energized as the device is moved within
the tissue (e.g., as it is advanced) to continuously sense if a
nerve is nearby. For example, FIG. 19B illustrates one method of
sensing as advancing.
[0157] In FIG. 19B the bipole pair in the first region is energized
and a response (or lack of a response) is determined. The bipole
network (or pair) may be energized as described above. For example,
a continuous signal may be applied, a periodic signal may be
applied, or a varying (e.g., ramping) signal may be applied 392. A
response may be detected by muscle twitch, nerve firing, or
otherwise 394. The device can then be moved based on the response
396, or continued to be moved based on the response. Movement may
be continued in the same direction (e.g., if no response is
detected) or in a new direction (if a nerve is detected). Movement
may also be stopped if a nerve is detected. Steps 394 and 396 may b
repeated during motion to guide the device.
[0158] In some variations, multiple regions of the device are
stimulated to determine if a nerve is nearby. For example, FIG. 19C
illustrates one variation in which a second region of the device,
having its own, separated bipole network, is stimulated. In FIG.
19C, the first bipole network (or a bipole pair) in the first
region is energized 532, and the patient is monitored for a
response 534 to the stimulation. The bipole pair in a second region
is then energized 536, and the patient is monitored for a response
538. Additional energizing and monitoring steps (not shown) may
also be included for other regions of the device, if present. The
responses to the different region can be compared 542, and the
device can be moved in response to the presence of a nerve in one
or more of the regions 546. Optionally, it may be determined which
region of the device is closer to the nerve 544. If the nerve is
detected, the tissue may be acted on (e.g., cut, ablated, removed,
etc., or the device may be further oriented by moving it, and these
steps may be repeated. If no nerve is detected, the steps may be
repeated until the device is positioned as desired, and a procedure
may then be performed.
[0159] In some variations, the device may be used to position (or
form a passage for) another device or a region of the device that
acts on the tissue. For example, the device may be used to position
a guide channel or guide wire. In some variations, the method may
include repeatedly energizing only a subset of the bipole networks
(or bipole pairs) until a nerve is detected, and then other bipole
networks on the device may be energized to determine with more
accuracy the relationship (e.g., orientation) of the nerve with
respect to the device.
[0160] As mentioned, the step of monitoring or detecting a response
may be performed manually (e.g., visually), or using a sensor or
sensor. For example, using an accelerometer may be coupled to
muscle. The accelerometer may be a multiple axis accelerometer that
detects the movement of the muscle in any direction, and movement
coordinated with stimulation may be detected. In some variations, a
strain gauge may be used on muscle innervated by a nerve passing
through or originating in the region of tissue being examined. The
strain gauge may be a multiple axis strain gauge that detects the
movement of the muscle in any direction. In some variations, an EMG
probe may be used to measure evoked potentials of the muscle. The
magnitude of any response may also be determined.
Systems
[0161] Any of the devices described herein may be used as part of a
system, which may be referred to as a nerve localization system.
Systems may include components (e.g., hardware, software, or the
like) to execute the methods described herein.
[0162] FIG. 20 is a block diagram of additional components of a
system 580 for determining if a nerve is nearby a device. The
components 580 shown in FIG. 20 may be used with any of the devices
described herein, and may include any computing device, including a
personal data assistant, cellular telephone, laptop computer, or
desktop computer. The system may include a central processing unit
(CPU) 582, a random access memory (RAM) 584, a read only memory
(ROM'') 606, a display 588, a user input device 612, a transceiver
application specific integrated circuit (ASIC) 616, a digital to
analog (D/A) and analog to digital (A/D) convertor 615, a
microphone 608, a speaker 602, and an antenna 604. The CPU 582 may
include an OS module 614 and an application module 613. The RAM 584
may include a queue 598 where the queue 598 may store signal levels
to be applied to one or more bipolar modules 46, 48. The OS module
614 and the application module 613 may be separate elements. The OS
module 614 may execute a computer system or controller OS. The
application module 612 may execute the applications related to the
control of the system.
[0163] The ROM 606 may be coupled to the CPU 582 and may store
program instructions to be executed by the CPU 582, OS module 614,
and application module 613. The RAM 584 is coupled to the CPU 582
and may store temporary program data, overhead information, and the
queues 598. The user input device 512 may comprise an input device
such as a keypad, touch pad screen, track ball or other similar
input device that allows the user to navigate through menus in
order to operate the article 580. The display 588 may be an output
device such as a CRT, LCD, LED or other lighting apparatus that
enables the user to read, view, or hear user detectable
signals.
[0164] The microphone 608 and speaker 602 may be incorporated into
the device. The microphone 608 and speaker 602 may also be
separated from the device. Received data may be transmitted to the
CPU 582 via a serial bus 596 where the data may include signals for
a bipole network. The transceiver ASIC 616 may include an
instruction set necessary to communicate data, screens, or signals.
The ASIC 616 may be coupled to the antenna 604 to communicate
wireless messages, pages, and signal information within the signal.
When a message is received by the transceiver ASIC 616, its
corresponding data may be transferred to the CPU 582 via the serial
bus 596. The data can include wireless protocol, overhead
information, and data to be processed by the device in accordance
with the methods described herein.
[0165] The D/A and A/D convertor 615 may be coupled to one or more
bipole networks to generate a signal to be used to energize them.
The D/A and A/D convertor 615 may also be coupled to one or more
sensors 322, 324 to monitor the sensor 322, 324 state or
condition.
[0166] Any of the components previously described can be
implemented in a number of ways, including embodiments in software.
These may include hardware circuitry, single or multi-processor
circuits, memory circuits, software program modules and objects,
firmware, and combinations thereof, as desired by the architect of
the system 10 and as appropriate for particular implementations of
various embodiments.
Example 1
Neural Localization when Treating Spinal Stenosis
[0167] One area of surgery which could benefit from the development
of less invasive techniques including neural localization is the
treatment of spinal stenosis. Spinal stenosis often occurs when
nerve tissue and/or blood vessels supplying nerve tissue in the
lower (or "lumbar") spine become impinged by one or more structures
pressing against them, causing pain, numbness and/or loss of
function in the lower back and/or lower limb(s). In many cases,
tissues such as ligamentum flavum, hypertrophied facet joint and
bulging intervertebral disc impinge a nerve root as it passes from
the cauda equine (the bundle of nerves that extends from the base
of the spinal cord) through an intervertebral foramen (one of the
side-facing channels between adjacent vertebrae). Here we provide
one example of a device for determining if a nerve is nearby that
may be used as part of method for treating spinal stenosis.
[0168] FIG. 21 is a top view of a vertebra with the cauda equina
shown in cross section and two nerve roots branching from the cauda
equina to exit the central spinal canal and extend through
intervertebral foramina on either side of the vertebra. FIG. 22 is
a side view of the lumbar spine, showing multiple vertebrae, the
intervertebral foramina between adjacent vertebrae, and the 1st-5th
spinal nerves exiting the foramina.
[0169] Surgery may be required to remove impinging tissue and
decompress the impinged nerve tissue of a spinal stenosis. Lumbar
spinal stenosis surgery typically involves first making an incision
in the back and stripping muscles and supporting structures away
from the spine to expose the posterior aspect of the vertebral
column. Thickened ligamentum flavum is then exposed by complete or
partial removal of the bony arch (lamina) covering the back of the
spinal canal (laminectomy or laminotomy). In addition, the surgery
often includes partial or complete facetectomy (removal of all or
part of one or more facet joints), to remove impinging ligamentum
flavum or bone tissue. Spinal stenosis surgery is performed under
general anesthesia, and patients are usually admitted to the
hospital for five to seven days after surgery, with full recovery
from surgery requiring between six weeks and three months. Many
patients need extended therapy at a rehabilitation facility to
regain enough mobility to live independently.
[0170] Removal of vertebral bone, as in laminectomy and
facetectomy, often leaves the affected area of the spine very
unstable, requiring an additional highly invasive fusion procedure
that puts extra demands on the patient's vertebrae and limits the
patient's ability to move. Unfortunately, a surgical spine fusion
results in a loss of ability to move the fused section of the back,
diminishing the patient's range of motion and causing stress on the
discs and facet joints of adjacent vertebral segments. Such stress
on adjacent vertebrae often leads to further dysfunction of the
spine, back pain, lower leg weakness or pain, and/or other
symptoms. Furthermore, using current surgical techniques, gaining
sufficient access to the spine to perform a laminectomy,
facetectomy and spinal fusion requires dissecting through a wide
incision on the back and typically causes extensive muscle damage,
leading to significant post-operative pain and lengthy
rehabilitation. Thus, while laminectomy, facetectomy, and spinal
fusion frequently improve symptoms of neural and neurovascular
impingement in the short term, these procedures are highly
invasive, diminish spinal function, drastically disrupt normal
anatomy, and increase long-term morbidity above levels seen in
untreated patients.
[0171] A number of devices, systems and methods for less invasive
treatment of spinal stenosis have been described, for example, in
U.S. patent application Ser. Nos. 11/250,332, titled "DEVICES AND
METHODS FOR SELECTIVE SURGICAL REMOVAL OF TISSUE," filed Oct. 15,
2005, now U.S. Pat. No. 7,738,968; 11/375,265, titled "METHOD AND
APPARATUS FOR TISSUE MODIFICATION," filed Mar. 13, 2006, now U.S.
Pat. No. 7,887,538; and 11/535,000, titled "TISSUE CUTTING DEVICES
AND METHODS," filed Sep. 25, 2006, Publication No.
US-2008-0033465-A1, now abandoned. all of which applications are
hereby incorporated fully be reference herein.
[0172] Challenges in developing and using less invasive or
minimally invasive devices and techniques for treating neural and
neurovascular impingement include accessing hard-to-reach target
tissue and locating nerve tissue adjacent the target tissue, so
that target tissue can be treated and damage to nerve tissue can be
prevented. These challenges may prove daunting, because the tissue
impinging on neural or neurovascular tissue in the spine is
typically located in small, confined areas, such as intervertebral
foramina, the central spinal canal and the lateral recesses of the
central spinal canal, which typically have very little open space
and are difficult to see without removing significant amounts of
spinal bone. The assignee of the present invention has described a
number of devices, systems and methods for accessing target tissue
and identifying neural tissue. Exemplary embodiments are described,
for example, in U.S. patent application Ser. Nos. 11/251,205,
titled "DEVICES AND METHODS FOR TISSUE ACCESS," filed Oct. 15,
2005, now U.S. Pat. No. 7,918,849; 11/457,416, titled "SPINAL
ACCESS AND NEURAL LOCALIZATION," filed Jul. 13, 2006, now U.S. Pat.
No. 7,578,819; and 11/468,247, titled "TISSUE ACCESS GUIDEWIRE
SYSTEM AND METHOD," filed Aug. 29, 2006, now U.S. Pat. No.
7,857,813, all of which applications are hereby incorporated fully
be reference herein.
[0173] The methods and devices for neural localization described
herein may be used in less invasive spine surgery procedures,
including the treatment of spinal stenosis. For example, the
methods and devices described herein can be used with minimal or no
direct visualization of the target or nerve tissue, such as in a
percutaneous or minimally invasive small-incision procedure.
[0174] FIG. 23 illustrates one device for treatment of spinal
stenosis including a tissue cutting device 1000 including a
guidewire. For further explanation of guidewire systems and methods
for inserting device 1000 and other tissue removal or modification
devices, reference may also be made to U.S. patent application Ser.
Nos. 11/468,247 (now U.S. Pat. No. 7,857,813) and 11/468,252
(Publication No. US-2008-0086034-A1), both titled "TISSUE ACCESS
GUIDEWIRE SYSTEM AND METHOD," and both filed Aug. 29, 2006, the
full disclosures of which are hereby incorporated by reference.
[0175] Cutting device 1000 may be at least partially flexible, and
in some embodiments may be advanced through an intervertebral
foramen IF of a patient's spine to remove ligamentum flavum LF
and/or bone of a vertebra V, such as hypertrophied facet (superior
articular process SAP in FIG. 23), to reduce impingement of such
tissues on a spinal nerve SN and/or nerve root. In one embodiment,
device 1000 cuts tissue by advancing a proximal blade 1012 on an
upper side of device 1000 toward a distal blade 1014. This cutting
device may be used with (or as part of) a system for determining if
a nerve is nearby, and may prevent damage to nerves in the region
which the device operates.
[0176] In various embodiments, device 1000 may be used in an open
surgical procedure, a minimally invasive surgical procedure or a
percutaneous procedure. In any procedure, it is essential for a
surgeon to know that device 1000 is placed in a position to cut
target tissue, such as ligament and bone, and to avoid cutting
nerve tissue. In minimally invasive and percutaneous procedures, it
may be difficult or impossible to directly visualize the treatment
area, thus necessitating some other means for determining where
target tissue and neural tissue are located relative to the tissue
removal device. At least, a surgeon performing a minimally invasive
or percutaneous procedure will want to confirm that the tissue
cutting portion of device 1000 is not directly facing and
contacting nerve tissue. The various nerve localization devices and
systems described herein may help the surgeon verify such
nerve/device location. A neural localization system and method may
be used in conjunction with device 1000 or with any other tissue
removal, tissue modification or other surgical devices.
Furthermore, various embodiments may have applicability outside the
spine, such as for locating nerve tissue in or near other
structures, such as the prostate gland, the genitounrinary tract,
the gastrointestinal tract, the heart, and various joint spaces in
the body such as the knee or shoulder, or the like. Therefore,
although the following description focuses on the use of
embodiments of the invention in the spine, all other suitable uses
for the various embodiments described herein are also
contemplated.
[0177] Referring now to FIG. 24, a diagrammatic representation of
one embodiment of a nerve tissue localization system 1020 is shown.
Neural localization system 1000 may include an electronic control
unit 1024 and a neural stimulation probe 1024, a patient feedback
device 1026, a user input device 1028 and a display 1030, all
coupled with control unit 1022.
[0178] In one embodiment, electronic control unit (ECU) 1020 may
include a computer, microprocessor or any other processor for
controlling inputs and outputs to and from the other components of
system 1020. In one embodiment, for example, ECU 1020 may include a
central processing unit (CPU) and a Digital to Analog (D/A) and
Analog to Digital Converter (A/D). ECU 1022 may include any
microprocessor having sufficient processing power to control the
operation of the D/A A/D converter and the other components of
system 1020. Generally, ECU 1022 may control the operation of the
D/A A/D converter and display device 1030, in some embodiments
based on data received from a user via user input device 1028, and
in other embodiments without input from the user. User input device
1028 may include any input device or combination of devices, such
as but not limited to a keyboard, mouse and/or touch sensitive
screen. Display device 1030 may include any output device or
combination of devices controllable by ECU 1022, such as but not
limited to a computer monitor, printer and/or other computer
controlled display device. In one embodiment, system 1020 generates
electrical signals (or other nerve stimulating energy signals in
alternative embodiments), which are transmitted to electrodes on
probe 1024, and receives signals from patient feedback device 1026
(or multiple feedback devices 1026 in some embodiments). Generally,
ECU 1022 may generate a digital representation of signals to be
transmitted by electrodes, and the D/A A/D converter may convert
the digital signals to analog signals before they are transmitted
to probe 1024. ECU 1022 also receive a return current from probe
1024, convert the current to a digital signal using the D/A A/D
converter, and process the converted current to determine whether
current was successfully delivered to the stimulating portion of
probe 1024. The D/A A/D converter may convert an analog signal
received by patient feedback device(s) 1026 into a digital signal
that may be processed by ECU 1022. ECU 1022 may hold any suitable
software for processing signals from patient feedback devices 1026,
to and from probe 1024 and the like. According to various
embodiments, display device 1030 may display any of a number of
different outputs to a user, such as but not limited to information
describing the signals transmitted to probe 1024, verification that
stimulating energy was successfully delivered to a stimulating
portion of probe 1024, information describing signals sensed by
patient feedback devices 1026, a visual and/or auditory warning
when a nerve has been stimulated, and/or the like. In various
alternative embodiments, system 1020 may include additional
components or a different combination or configuration of
components, without departing from the scope of the present
invention.
[0179] The neural stimulation probe 1024 is an elongate body having
an outer surface including one or more regions with a bipole pair
or bipole network. Furthermore, any suitable number of regions may
be included on a given probe 1024. In various embodiments, for
example, probe 1024 may includes two or more regions, each having a
bipole pair or bipole network (comprising a plurality of bipole
pairs) disposed along the probe in any desired configuration. In
one embodiment, probe 1024 may include four regions, each having at
least one bipole pairs, one pair on each of top, bottom, left and
right sides of a distal portion of the probe that is configured to
address neural tissue.
[0180] In some embodiments, ECU 1022 may measure current returned
through probe 1024 and may process such returned current to verify
that current was, in fact, successfully transmitted to a nerve
stimulation portion of probe 1024. In one embodiment, if ECU 1022
cannot verify that current is being transmitted to the nerve
stimulation portion of probe 1024, ECU 1022 may automatically shut
off system 1020. In an alternative embodiment, if ECU 1022 cannot
verify that current is being transmitted to the nerve stimulation
portion of probe 1024, ECU 1022 may signal the user, via display
device 1030, that probe 1024 is not functioning properly.
Optionally, in some embodiments, system 1020 may include both a
user signal and automatic shut-down.
[0181] Patient feedback device 1026 may include any suitable
sensing device and typically includes multiple devices for
positioning at multiple different locations on a patient's body. In
some embodiments, for example, multiple motion sensors may be
included in system 1020. Such motion sensors may include, but are
not limited to, accelerometers, emitter/detector pairs, lasers,
strain gauges, ultrasound transducers, capacitors, inductors,
resistors, gyroscopes, and/or piezoelectric crystals. In one
embodiment, where nerve tissue stimulation system 1020 is used for
nerve tissue detection in the lumbar spine, feedback device 1026
may include multiple accelerometers each accelerometer attached to
a separate patient coupling member, such as an adhesive pad, for
coupling the accelerometers to a patient. In one such embodiment,
for example, each accelerometer may be placed over a separate
muscle myotome on the patients lower limbs.
[0182] When nerve tissue is stimulated by probe 1024, one or more
patient feedback devices 1026 may sense a response to the
stimulation and deliver a corresponding signal to ECU 1022. ECU
1022 may process such incoming signals and provide information to a
user via display device 1030. For example, in one embodiment,
information may be displayed to a user indicating that one sensor
has sensed motion in a particular myotome. As part of the
processing of signals, ECU 1022 may filter out "noise" or sensed
motion that is not related to stimulation by probe 1024. In some
embodiments, an algorithm may be applied by ECU 1022 to determine
which of multiple sensors are sensing the largest signals, and thus
to pinpoint the nerve (or nerves) stimulated by probe 1024.
[0183] In an alternative embodiment, patient feedback device 1026
may include multiple electromyography (EMG) electrodes. EMG
electrodes receive EMG or evoked muscle action potential (EMAP)
signals generated by muscle electrically coupled to EMG electrodes
and to a depolarized nerve (motor unit). One or more nerves may be
depolarized by one or more electrical signals transmitted by probe.
As with the motion sensor embodiment, ECU 1022 may be programmed to
process incoming information from multiple EMG electrodes and
provide this processed information to a user in a useful format via
display device 1030.
[0184] User input device 1028, in various embodiments, may include
any suitable knob, switch, foot pedal, toggle or the like and may
be directly attached to or separate and coupleable with ECU 1022.
In one embodiment, for example, input device 1028 may include an
on/off switch, a dial for selecting various bipolar electrode pairs
on probe 1024 to stimulate, a knob for selecting an amount of
energy to transmit to probe 1024 and/or the like.
[0185] Referring now to FIG. 25, in one embodiment, a nerve tissue
localization system 1040 may include an ECU 1042, a neural
stimulation probe 1044, multiple patient feedback devices 1026, and
a user input device 48. Probe 1044 may include, in one embodiment,
a curved, flexible nerve stimulating elongate member 1058, which
may slide through a rigid cannula 1056 having a handle 1054.
[0186] The probe 1044 is a device for determining if a nerve is
nearby a region of the device, and includes a plurality of regions
which each include one or more bipole pairs. In some variations the
probe 1044 includes two regions (an upper region and a lower
region), and each region includes a bipole network configured to
form a continuous bipole field along the length of the probe in
either the upper or lower regions. A nerve stimulating member 1058
may include a guidewire lumen for allowing passage of a guidewire
1059, for example after nerve tissue has been detected to verify
that the curved portion of nerve stimulating member 1058 is in a
desired location relative to target tissue TT and nerve tissue NT.
Patient feedback devices 1046 and probe 1044 may be coupled with
ECU 1042 via wires 1050 and 1052 or any other suitable connectors.
ECU 1042 may include user input device 1048, such as a knob with
four settings corresponding to top, bottom, left and right sides of
a nerve tissue stimulation portion of nerve stimulating member
1058. ECU 1042 may also optionally include a display 1047, which
may indicate an amount of muscle movement sensed by an
accelerometer feedback device 1046. In one embodiment, ECU 1042 may
include one or more additional displays, such as red and green
lights 1049 indicating when it is safe or unsafe to perform a
procedure or whether or not probe 1044 is functioning properly. Any
other suitable displays may additionally or alternatively be
provided, such as lamps, graphs, digits and/or audible signals such
as buzzers or alarms.
[0187] In one embodiment, each of patient feedback devices 1046 may
include an accelerometer coupled with an adhesive pad or other
patient coupling device. In one embodiment, a curved portion of
nerve stimulating member 1058 may be configured to pass from an
epidural space of the spine at least partway through an
intervertebral foramen of the spine. In other embodiments, nerve
stimulating member 1058 may be straight, steerable and/or preformed
to a shape other than curved.
[0188] FIGS. 26A and 26B describe a method for localizing nerve
tissue and placing a guidewire in a desired location in a spine
using the device configured to determine if a nerve is nearby.
Before advancing a nerve tissue localization probe into the
patient, and referring again to FIG. 25, multiple patient feedback
devices 1046, such as accelerometers or EMG electrodes, may be
placed on the patient, and ECU 1042 may be turned on. In one
embodiment, a test current may be transmitted to probe 1044, and a
return current from probe 1044 may be received and processed by ECU
1042 to verify that probe 1044 is working properly.
[0189] As shown in FIG. 26A, an epidural needle 1060 (or cannula)
may be passed through the patient's skin, and a distal tip of
needle 1060 may be advanced through the ligamentum flavum LF of the
spine into the epidural space ES. Next, as shown in FIG. 26B, a
probe that is configured to determine if a nerve is nearby the
probe 1062 may be passed through epidural needle 1060, such that a
curved, flexible, distal portion passes into the epidural space ES
and through an intervertebral foramen IF of the spine, between
target tissue (ligamentum flavum LF and/or facet bone) and
non-target neural tissue (cauda equina CE and nerve root NR). As
shown in FIG. 26C, the upper region of the probe having a first
bipole network may be energized to generate a bipole field as
current passes between the anodes and cathodes of the bipole
network in the upper region 1062. In some variations, the bipole
pairs may be monitored to confirm that transmitted energy returned
proximally along the probe, as described previously. As shown in
FIG. 26D, the lower bipole network may then be energized to
generate a bipole field from the curved portion of probe 1062. In
an alternative embodiment, energy may be transmitted only to the
top, only to the bottom, or to the bottom first and then the top
regions. In some embodiments, energy may be further transmitted to
electrodes on left and right regions of probe 1062. Depending on
the use of a given probe 1062 and thus its size constraints and the
medical or surgical application for which it is being used, any
suitable number of electrodes may form the bipole network of a
particular region.
[0190] As energy is transmitted to the bipole network in any region
of the probe 1062, patient response may be monitored manually or
via multiple patient feedback devices (not shown in FIG. 26), such
as, but not limited to, accelerometers or EMG electrodes. In one
method, the same amount of energy may be transmitted to the bipole
network in the different regions of the probe in series, and
amounts of feedback sensed to each transmission may be measured and
compared to help localize a nerve relative to probe 1062. If a
first application of energy does not generate any response in the
patient, a second application of energy at higher level(s) may be
tried and so forth, until a general location of nerve tissue can be
determined. In an alternative embodiment, the method may involve
determining a threshold amount of energy required by bipole network
to stimulate a response in the patient. These threshold amounts of
energy may then be compared to determine a general location of the
nerve relative to the probe. In another alternative embodiment,
some combination of threshold and set-level testing may be
used.
[0191] In one embodiment, as shown in FIG. 26E, nerve probe 1062
may include a guidewire lumen through which a guidewire may be
passed, once it is determined that device 1062 is placed in a
desired position between target and non-target tissue (e.g.,
avoiding a nerve adjacent to the upper region). As shown in FIG.
26F, when epidural needle 1060 and probe 1062 are removed,
guidewire 1064 may be left in place between target tissue (such as
ligamentum flavum LF and/or facet bone) and non-target tissue (such
as cauda equina CE and nerve root NR). Any of a number of different
minimally invasive or percutaneous surgical devices may then be
pulled into the spine behind guidewire 1064 or advanced over
guidewire 1064, such as the embodiment shown in FIG. 23 and others
described by the assignee of the present application in other
applications incorporated by reference herein.
[0192] Referring now to FIGS. 27A-27H, another embodiment of a
method for accessing an intervertebral foramen IF and verifying a
location of a probe relative to tissue (such as ligamentum flavum
LF and nerve/nerve root NR tissue) is demonstrated. In this
embodiment, as shown in FIG. 27A, an access cannula 1070 may be
advanced into the patient over an epidural needle 1072 with
attached syringe. As shown in FIG. 27B, cannula 1070 and needle
1072 may be advanced using a loss of resistance technique, as is
commonly performed to achieve access to the epidural space via an
epidural needle. Using this technique, when the tip of needle 1072
enters the epidural space, the plunger on the syringe depresses
easily, thus passing saline solution through the distal end of
needle 1072 (see solid-tipped arrows). As shown in FIG. 27C, once
epidural access is achieved, needle can be withdrawn from the
patient, leaving cannula in place with its distal end contacting or
near ligamentum flavum LF. Although needle 1072 may be removed, its
passage through ligamentum flavum LF may leave an opening 1073 (or
path, track or the like) through the ligamentum flavum LF.
[0193] As shown in FIG. 27D, a curved, flexible guide 1074 having
an atraumatic distal tip 1075 may be passed through cannula 1070
and through opening 1073 in the ligamentum flavum LF, to extend at
least partway through an intervertebral foramen IF. In this
variation, the guide 1074 is configured as a device for determining
if a nerve is nearby a region of the device. The guide 1074 is an
elongate member that includes at least a first region having a
bipole pair, or more preferably a bipole network thereon.
[0194] In FIG. 27E, a first bipole network on or near an external
surface of guide 1074 may then be energized, and the patient may be
monitored for response. As in FIG. A7F, a second bipole network
disposed along guide 1074 in a different circumferential region
than the region may be energized, and the patient may again be
monitored for response. This process of activation and monitoring
may be repeated for any number of bipole networks or as the device
is manipulated in the tissue, according to various embodiments. For
example, in one embodiment, guide 1074 may include a first region
having a bipole network on its top side (inner curvature), a second
region having a bipole network on the bottom side (outer
curvature), and a third and fourth region each having a bipole
network on the left side and right side, respectively. A
preselected amount of electrical energy (current, voltage, and/or
the like) may be transmitted to a bipole network, and the patient
may be monitored for an amount of response (EMG, muscle twitch, or
the like). The same (or a different) preselected amount of energy
may be transmitted to a second bipole network, the patient may be
monitored for an amount of response, and then optionally the same
amount of energy may be transmitted sequentially to third, fourth
or more bipole networks, while monitoring for amounts of response
to each stimulation. The amounts of response may then be compared,
and from that comparison a determination may be made as to which
region is closest to nerve tissue and/or which region is farthest
from nerve tissue.
[0195] In an alternative method, energy may be transmitted to a
first bipole electrode and the amount may be adjusted to determine
a threshold amount of energy required to elicit a patient response
(EMG, muscle twitch, or the like). Energy may then be transmitted
to a second bipole network, adjusted, and a threshold amount of
energy determined. Again, this may be repeated for any number of
bipole networks (e.g., regions). The threshold amounts of required
energy may then be compared to determine the location of the
regions relative to nerve tissue.
[0196] Referring now to FIG. 27G, once it is verified that guide
1074 is in a desired position relative to nerve tissue and/or
target tissue, a guidewire 1076 may be passed through guide and
thus through the intervertebral foramen IF and out the patient's
skin. Cannula 1070 and guide 1074 may then be withdrawn, leaving
guidewire 1076 in place, passing into the patient, through the
intervertebral foramen, and back out of the patient. Any of a
number of devices may then be pulled behind or passed over
guidewire 1076 to perform a procedure in the spine.
Rotating a Tight Bipole Pair
[0197] Another variation of nerve localizing device including one
or more tight bipole pairs is a device having at least one tight
bipole pair that can be scanned (e.g., rotated) over at least a
portion of the circumference of the device to detect a nearby
nerve.
[0198] In general, a device having a movable tight bipole pair may
include an elongate body that has an outer surface and at least one
bipole pair that can be scanned (moved) with respect to the outer
surface of the device so as to be energized in different regions of
the outer surface of the device to determine if a nerve is nearby.
For example, a device may include an elongate body having an outer
surface that can be divided up into a plurality of circumferential
regions and a scanning that is movable with respect to the outer
surface. At least one tight bipole pair (or a bipole network) is
attached to the scanning surface, allowing the bipole pair or
network to be scanned to different circumferential regions.
[0199] FIGS. 28A and 28B illustrate variations of a device having a
scanning or movable bipole pair (or bipole network). For example,
FIG. 28A includes an elongate body 2801 having an outer surface. In
this variation the elongate body has a circular or oval
cross-section, although other cross-sectional shapes may be used,
including substantially flat. The surface of the outer body
includes a window 2803 region exposing a scanning surface 2807 to
which at least one bipole pair is connected. The scanning surface
may be moved relative to the outer surface (as indicated by the
arrow). In this example, the window extends circumferentially, and
the scanning surface may be scanned radially (e.g., up and down
with respect to the window).
[0200] FIG. 28B illustrates another variation, in which the distal
end of the elongate body 2801' is rotatable with respect to the
more proximal region of the device. The distal end includes one or
more bipole pairs. In FIG. 28 the rotatable distal end includes a
bipole network 2819. The bipole network may be energized as it is
rotated, or it may be rotated into different positions around the
circumference of the device and energized after it has reached each
position.
[0201] The devices illustrated in FIGS. 28A and 28B may include a
controller configured to control the scanning (i.e., rotation) of
the bipole pair. The device may also include a driver for driving
the motion of the bipole pair. For example, the drive may be a
motor, magnet, axel, shaft, cam, gear, etc. The controller may
control the driver, and may control the circumferential position of
the bipole pair (or bipole network). The device may also include an
output for indicting the circumferential region of the bipole
network or pair.
[0202] In operation, the scanning bipole pair can be used to
determine if a nerve is near the device by moving the bipole pair
or network with respect to the rest of the device (e.g., the outer
surfaced of the elongate body). For example, the device may be used
to determine if a nerve is nearby the device by scanning the bipole
pair (or a bipolar network comprising a plurality of bipole pairs)
across a plurality of circumferential regions of the outer surface
of the elongate body, and by energizing the bipole pair(s) when it
is in one of the circumferential regions. As mentioned, the bipole
pair(s) may be energized as they are moved, or they may be
energized once they are in position. The movement may be reciprocal
(e.g., back and forth) or rotation, or the like.
[0203] The examples and illustrations included herein show, by way
of illustration and not of limitation, specific embodiments in
which the subject matter may be practiced. Other embodiments may be
utilized and derived therefrom, such that structural and logical
substitutions and changes may be made without departing from the
scope of this disclosure. Such embodiments of the inventive subject
matter may be referred to herein individually or collectively by
the term "invention" merely for convenience and without intending
to voluntarily limit the scope of this application to any single
invention or inventive concept, if more than one is in fact
disclosed. Thus, although specific embodiments have been
illustrated and described herein, any arrangement calculated to
achieve the same purpose may be substituted for the specific
embodiments shown. This disclosure is intended to cover any and all
adaptations or variations of various embodiments. Combinations of
the above embodiments, and other embodiments not specifically
described herein, will be apparent to those of skill in the art
upon reviewing the above description.
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