Bipolar nerve stimulation/monitoring cuff
An electrode assembly (preferably in the form of a nerve cuff) comprises a base with first and second arms extending from opposite sides of the base, and which, in combination, define an arc. First and second electrically conductive electrodes extend along the inner surface of the first and second arms. Each electrode can comprise a single length of foil can or can comprise multiple discrete foil segments. The foils are electrically isolated from each other. Electrical wires, which are in electrical communication with the each of the foils, extend from the nerve cuff and are adapted to be electrically connected to a signal monitor. When the nerve cuff is applied to a nerve, the foils, in combination, substantially surround the nerve, with the first and second electrodes being on opposite sides of the nerve from each other. Also disclosed is a method of using the nerve cuff to monitor a nerve during a lumbar spinal surgery while the patient is anesthetized and paralyzed.
1 . A method of monitoring a selected nerve during spinal surgery, the selected nerve being the nerve exiting a spine at the adjacent a disc or vertebrae to be operated on, said selected nerve comprising an exiting nerve root extending from a spinal cord between adjacent said vertebrae or disc of said spinal column prior to the nerve root entering muscle; the method comprising:
positioning a first electrode in a surgical incision to be proximate the exiting nerve root of said selected nerve to be in electrical communication with said nerve root proximate the spinal column, said first electrode being positioned (a) to be proximate said disc or vertebrae to be operated on (i.e., the surgical target), (b) such that said first electrode does not interfere with access to the surgical target, and (c) such that said first electrode can be disengaged from said exiting nerve root if said electrode is dislodged during a surgical procedure, said first electrode being in electrical communication with a signal monitor;
positioning a second electrode to be (a) proximate said nerve root or (b) at a scalp, muscle, peripheral nerve, dorsal spine, or abdomen of the patient, said second electrode being in communication with said signal monitor,
periodically generating an electrical pulse at one of said first and second electrodes and transmitting said electrical pulse to said nerve;
receiving responding signals from said nerve at the other of said first electrode and second electrode in response to periodically generated electrical pulses; and
monitoring said responding signals at said signal monitor for changes in said responding signal indicative of irritation or potential damage to said selected nerve.
2 . The method of claim 1 wherein said step of positioning said first electrode comprises positioning said first electrode proximate an exiting lumbar nerve root.
3 . The method of claim 1 wherein the electrical pulse is generated at said second electrode and said responding signal is received at said first electrode proximate the nerve root be monitored.
4 . The method of claim 3 wherein said second electrode is a needle electrode, said method comprising positioning said needle electrode proximate an intervertebral foramen and stimulating the nerve root transforaminally.
5 . The method of claim 4 wherein said needle electrode is positioned to stimulate the cauda equina of the patient.
6 . The method of claim 1 wherein the electrical pulse is generated at said first electrode proximate the spinal nerve root to be monitored and said responding signal is received at said second electrode.
7 . The method of claim 6 wherein said first electrode is positioned proximate an intervertebral foramen and stimulating the nerve transforaminally.
8 . The method of claim 7 wherein first electrode is a needle electrode.
9 . The method of claim 8 wherein the needle electrode stimulates the exiting nerve root transforaminally and adjacent exiting nerve roots.
10 . The method of claim 8 wherein the needle electrode stimulates the exiting nerve root transforaminally and cauda equina.
11 . The method of claim 6 wherein said second electrode is a needle electrode, said method comprising positioning said needle electrode proximate an intervertebral foramen.
12 . The method of claim 1 , wherein the step of positioning the second electrode comprises positioning the second electrode to be proximate a brain of the patient, a dorsal spine of the patient, or a peripheral nerve of the patient; wherein the method of monitoring comprises:
a) stimulating the brain, dorsal spine, or peripheral nerve via the second electrode and receiving the responding signal at the first electrode; or
b) stimulating the exiting nerve root via the first electrode and receiving the responding signal at the second electrode.
13 . The method of claim 12 wherein said second electrode is positioned proximate a peripheral nerve in a muscle of the patient; said method comprising stimulating the exiting nerve root via the first electrode and receiving the responding signal at second electrode proximate muscle.
14 . The method of claim 1 , wherein the second electrode comprises a pair of needle electrodes positioned proximate a dorsal spine of the patient; said needle electrodes being deep subfascial needle electrodes which are electronically linked; the step of positioning said needle electrodes comprising positioning the needle electrodes proximate a dorsal roof of the intervertebral foramen of the spine.
15 . The method of claim 14 wherein the deep subfascial needle electrodes are inserted bilaterally paramidline just lateral to the pars interarticularis at the T12-L1 level to a depth proximate the dorsal roof of the foramen.
16 . The method of claim 1 wherein said step of positioning said first electrode proximate said exiting nerve root comprises positioning an electrode assembly about said exiting nerve root; said electrode assembly comprising said first electrode and being shaped, configured, and adapted to maintain said first electrode in continuous electrical communication with the spinal nerve root throughout the spinal surgery.
17 . The method of claim 16 wherein in the first electrode is contained on an electrode assembly which comprises:
a body having a base and first and second arms extending from opposite sides of said base; said base and said first and second arms being formed from an electrically insulating material; the base and first and second arms defining an inner surface of said body; said arms each comprising a fixed end adjacent said base and a free end remote from said base, said free ends of said arms facing each other such that said arms and said base, in combination, substantially define a circle; said first and second arms and/or said base being flexible such that said cuff is moveable between a relaxed position and an open position, wherein, in said open position, said free ends of said arms define a gap sized to fit over a nerve root; said body having a largest radial width (RW) measured along an axial plane which passes through said arms and an axial width (W) measured in a plane that is generally perpendicular to said radial width;
first and second spaced apart grips extending from said body on opposite sides of said base; said grips being positioned on said body, such that by urging said grasping arms toward each other, said electrode assembly will be moved from its relaxed position to its open position; said grips being sized relative to the body such that the grips do not extend beyond lines tangential to the arms at the largest radial width (RW) of the body;
wherein said first electrode is positioned on an inner surface of said body;
wherein said electrode assembly is sized and shaped to be received in a surgical incision during a spinal surgery and to be removably positioned about a nerve root during said spinal surgery; said electrode assembly being shaped, configured, and adapted to maintain said at least one electrode in continuous electrical communication with the nerve root throughout the spinal surgery;
said step of positioning said electrode assembly about said nerve root comprising opening said cuff sufficiently to enable the gap to pass over said exiting nerve root, positioning said electrode assembly about said exiting nerve root, and allowing said electrode assembly to return to a rest position.
18 . The method of claim 16 wherein said electrode assembly includes said second electrode; said second electrode being circumferentially spaced from said first electrode and being positioned on said electrode assembly, such that said electrode assembly maintains said second electrode in continuous electrical communication with the spinal nerve root throughout the spinal surgery.
19 . The method of claim 18 , wherein the exiting spinal nerve root of the nerve comprises a sensory nerve bundle and a motor nerve bundle, said sensory nerve bundle and motor nerve bundle being separate and distinct from each other;
wherein said step of positioning said first and second electrodes comprises placing said electrode assembly about said nerve root such that one of said first and second electrodes is in electrical communication with said sensory nerve bundle and the other of said first and second electrodes is in electrical communication with said motor nerve bundle.
20 . The method of claim 1 , wherein said monitoring method is carried out while said patient is not paralyzed during the surgical procedure.
21 . The method of claim 1 , wherein said monitoring method is carried out while said patient is substantially anesthetically relaxed or paralyzed during the surgical procedure.
22 . The method of claim 1 , wherein said exiting nerve root is substantially continuously stimulated for monitoring purposes or stimulated intermittently.
23 . The method of claim 1 , wherein said exiting nerve root is substantially continuously recorded for monitoring purposes or recorded intermittently.