Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
1999-06-01
2001-03-27
Jastrzab, Jeffrey R. (Department: 3737)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C607S137000
Reexamination Certificate
active
06208882
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to implantable stimulation devices, e.g., cochlear prosthesis used to electrically stimulate the auditory nerve, and more particularly to an electrode array for use with a cochlear stimulator that is designed to monitor the stapedius reflex of a patient.
In International Application Number PCT/US97/10590, filed internationally on Jun. 19, 1997, there is disclosed a self-adjusting cochlear implant system, and a method for fitting such a system, that relies, in part, on sensing the stapedius reflex of the patient. This PCT application (PCT/US97/10590) is incorporated herein by reference.
The stapedius reflex is used in cochlear implants to determine how much sound energy a patient perceives. This information is very useful in programming the cochlear implant system so that proper signal levels may be maintained. Thus, as is described in the referenced PCT application, an implantable electrode placed over or in the stapedius muscle, in conjunction with the reverse telemetry features of the implantable cochlear stimulator (ICS), which allow sensed data to be telemetered from an ICS to an external unit, provide a very useful tool to enhance the programming of the ICS.
The stapedius reflex operates in a normal ear to dampen movement of the ossicular chain, and in particular the stapes, so that excessive motion of the stapes (which could otherwise be sensed as an extremely-loud, potentially-damaging, sound) is not transmitted through the oval window into the inner ear.
Unfortunately, sensing the stapedius reflex is not an easy task. This is because the stapedius muscle, which is attached to the stapes, is hidden inside a bony channel, and only a very small part of it and its tendon are visible and/or accessible from within the middle ear. Further, because only a very small part of the muscle is accessible, it is difficult to attach an electrode to the stapedius reflex muscle without damaging the integrity of the stapedius reflex muscle.
SUMMARY OF THE INVENTION
The present invention is directed to several different electrode designs that may be used to sense the stapedius reflex of the patient without damaging the stapedius reflex muscle, to implant tools used in positioning the electrode at a desired location, and to an implantable connector that may be used to electrically connect a stapedius reflex electrode to an implantable cochlear stimulator (ICS) or other implantable unit.
A first preferred embodiment of a stapedius reflex electrode made in accordance with the present invention comprises a serrated blade electrode adapted to be inserted through a small slot made in the stapedius muscle. A suitable flexible wire, e.g., a 25 micron diameter platinum/iridium (Pt/Ir) Teflon-coated wire, is mechanically and electrically bonded to a proximal end of the blade electrode. The other end of the wire is attached to a suitable connector that eventually allows the wire to be electrically connected to appropriate monitoring circuitry. Once the blade electrode is inserted in the slot, serrations at a distal tip of the electrode, coupled with an epoxy blob resting snugly against the stapedius muscle on a proximal end of the blade electrode, hold the blade electrode securely in its desired position within the slot. The slot may be made in the stapedius muscle using a conventional needle, such as a 30G needle, or a similar sharp instrument. A special insertion tool may be used to facilitate inserting, positioning and holding of the blade electrode in its desired position within the slot made through the stapedius muscle.
A second preferred embodiment of a stapedius reflex electrode comprises a blade electrode, with or without serrations at its distal tip, that is inserted through an opening made through the bone into the bony channel through which the stapedius muscle and tendon passes. When inserted, such blade electrode lies flat against the stapedius muscle and is positioned so that its distal tip protrudes out from the bony channel pointing towards the stapes. This tip is then bent over against the outside of the bone that defines the bony channel, thereby securing the blade electrode so that it lies flat against the stapedius muscle. Such positioning of the blade electrode advantageously offers a large surface area over which stapedius reflex muscle activity may be electrically sensed.
In addition to the first and second preferred embodiments described above, the present invention also contemplates various other stapedius reflect electrodes. In a first alternative embodiment, for example, a stapedius reflex electrode comprises a biocompatible metal wire, preferably Iridium, shaped into a hook with a small ball at one end. The other end is connected to a light, coiled, insulated lead that provides a connection to the implant (monitoring) circuitry. The hook is preferably insulated, except for the surface of the ball. During implant surgery, the ball is pressed against The stapedius muscle into the bony channel.
A second alternative embodiment of a stapedius reflex electrode includes an electrical contact, made from platinum foil, embedded within a silicone mold. The silicone mold is shaped into a cuff configuration, with an opening slightly smaller than the diameter of the end of The stapedius muscle extending out of the bone. The silicone cuff has an opening allowing easy assembly of the electrode by clipping the cuff over the exposed muscle. Electrical connection of the electrode to the implant circuitry is provided by a flexible coiled, insulated lead.
A third alternative embodiment of a stapedius muscle electrode includes an electrode made from soft, annealed, platinum wire formed into a hook shape. One end is formed into a loop, or ball. The other end is connected to a coiled, insulated lead. The electrode is placed over the visible end of the stapedius muscle and crimped over the muscle to stabilize it and to provide direct contact with the muscle.
A fourth alternative embodiment of a stapedius muscle electrode comprises an electrode made from soft, annealed, platinum wire formed into a U shape. The ends of the electrode are looped, or flamed into a ball. A flexible, coiled, insulated lead is connected preferably in the middle of the U-shaped wire. The electrode is placed over The stapedius muscle and crimped to provide stability and contact.
A fifth alternative embodiment of a stapedius muscle electrode, similar to the first alternative embodiment described above, comprises a ball electrode made by flaming the distal end of a multistrand paltinum/iridium (Pt/Ir) wire. The ball electrode is adapted for implantation in a stable position, squeezed between the stapedius muscle and the bony wall. Advantageously, after a few weeks, the ball electrode partially erodes the bone at the pressure point, making a socket for itself, and thereby securing itself in a stable position. A special implant tool may be used with the ball electrode in order to insert it into its desired position between the stapedius muscle and the bony wall.
A sixth alternative embodiment of a stapedius muscle electrode comprises a harpoon electrode. The harpoon electrode is formed from multistrand Teflon-insulated Pt/Ir wire and reloaded into an insertion tool. The electrode is made at a distal end of the wire by removing about 1.0-1.5 mm of insulation. A preferred delivery tool comprises a delivery needle attached to a handle. The distal tip, with insulation removed, is left protruding from the end of the needle and is bent backwards on the needle. Implantation occurs by drilling a small hole in the bony wall near the stapedius muscle, or by removing part of the bony wall by drilling or chipping away, thereby exposing the stapedius muscle. The tip of the delivery needle is then pushed through the opening into the muscle, forcing the folded-back electrode tip into the muscle tissue. The delivery needle is then removed, which causes the folded-back end of the electrode lead to be securely fixed and embedded within the surrounding stapedius muscle tissue.
In a sec
Balkany Thomas J.
Kuzma Janusz A.
Lenarz Thomas H. R.
Advanced Bionics Corporation
Gold Bryant R.
Jastrzab Jeffrey R.
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