Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1999-08-18
2002-04-16
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C607S056000, C600S379000, C600S393000
Reexamination Certificate
active
06374143
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
“Not Applicable”
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
“Not Applicable”
REFERENCE TO A MICROFICHE APPENDIX
“Not Applicable”
BACKGROUND OF THE INVENTION
This invention relates generally to human hearing, and more specifically to the design and positioning of an electrode array for a cochlear prosthesis.
Human deafness results from numerous factors including trauma, ear infections, congenital factors, ototoxic effects of some antibiotics, and from diseases such as meningitis. Sensorineural damage (damage to the hair cells in the cochlea) is the largest single form of hearing loss. In a healthy ear these hair cells convert acoustic signals in the inner ear to electrical signals that can be interpreted by the brain as sound. It is estimated that over 7% of the U.S. population is affected by sensorineural deafness, and one in a thousand infants is born totally deaf. Extrapolating these percentage figures, it is estimated that there are 30 million people in the world who are profoundly deaf.
Considerable research over the past several decades has been directed towards developing a means to bypass the non-functioning hair cells in the inner ear (or cochlea) by using electrodes to directly stimulate auditory afferent neurons within the cochlea. This so called cochlear implant technology has progressed from early methods of attaching one or more single wire electrodes onto the promontory or the bony shell of the cochlea, to drilling directly into the cochlea, and inserting electrodes into the scalae therein. Electrodes used in modern cochlear prostheses generally use a longitudinal bipolar (or monopolar) electrode configuration where small platinum/iridium balls or circular platinum rings connected internally by thin wires, with the electrodes and wires held together in a smooth elongated silicone carrier, are surgically implanted into the scala tympani (one of the canals within the cochlea), via a hole made in the mastoid bone behind the ear. Entry into the scala tympani is generally via the round window membrane. The electrodes are electrically connected to an electronics package anchored in a cavity made in the mastoid bone. Information is sent to this internal (subcutaneous) electronics package, via RF transmission across the skin barrier, from an external body-mounted electronics package that houses the speech processor, control electronics and power supply.
Such cochlear prostheses are commercially available from a number of companies worldwide, for example, from Cochlear Limited, Sydney, Australia; Advanced Bionics Corporation, Sylmar, Calif., U.S.A.; Med-El Medical Electronics, Innsbruck, Austria; PHILIPS-Antwerp Bionic Systems N.V./S.A., Edegem, Belgium; and MXM Medical Technologies, Vallauris, France.
The surgery time and surgical complexity of implanting these commercial cochlear prostheses is significant, especially for very young and for old persons. The implant procedure usually involves exposure of the mastoid cortex of the implanted ear via elevation of a postauricular skin flap, generally requiring 2.5-4 hours with the patient totally anesthetized, and with the inherent medical risks of total anesthetic. The cost of currently available cochlear prostheses is high, limiting the availability of this technology mostly to the wealthy industrialized countries. A comprehensive introduction to the development of cochlear implants is given in, for example, “Cochlear Prostheses,” edited by G. M. Clark, Y. C. Tong and J. F. Patrick, distributed in the U.S.A. by Churchill Livingstone Inc., New York, N.Y. 1990 (ISBN 0-443-03582-2), and in “The Cochlear Implant,” (ISSN 0030- 6665) by T. J. Balkany, editor of The Otolaryngologic Clinics of North America, Vol. 19, No. May, 2, 1986. Additionally, some of the early cochlear implant work is described in U.S. Pat. Nos. 4,357,497; 4,419,995 and 4,532,930.
In spite of the surgical risks, complexity and device costs, currently available cochlear prostheses do provide a major improvement over the alternative—total silence. However, there are still great differences in hearing percepts amongst implanted patients. Some patients after implantation are able to use the telephone, while others can only perceive environmental sounds. Also, there is the great inconvenience, and social stigma, especially for children, in needing to wear an external head-mounted device, connected to a body-worn (or a recently available ear-mounted) electronics package. A totally implanted cochlear prosthesis does not yet exist.
Researchers have tried for many years to ascertain the reasons for the variable hearing results obtained by cochlear implant patients. The consensus of scientific opinion is that the location of the electrodes in the cochlea, age of implantation, time of implantation since deafness, duration of implant use, knowledge of language prior to implantation, duration and intensity of rehabilitation, and patient ability and desire to learn are key factors in determining speech understanding by the implantee. Other factors include the number of functional peripheral neural processes in the basilar membrane and cochlea spiral lamina and/or surviving spiral ganglion cells in the modiolus, the type of speech coding strategy used, and the extent of trauma from surgery during implantation.
The electrode array design parameters are important. For example, the number of electrodes and the spacing between electrodes, the position of electrodes in the scala tympani (or scala vestibuli) with respect to the stimulatable neural sites, and the orientation of the electric field generated between electrode pairs are all factors affecting patient speech percepts.
In spite of all of the potential factors contributing to hearing results, it is clear that the functionality of a cochlear prosthesis will always be limited by the intrinsic design and positioning of the electrode array within a scala. Interestingly, the simple tapered longitudinal bipolar and monopolar electrode arrays using small platinum/iridium balls or circular rings that are now widely used commercially were developed over a decade ago, and were largely based on the relative ease of fabrication and the practicality of surgical insertability, rather than on critical design parameters necessary to achieve optimum neural stimulation.
The use of the simple longitudinal multi ring electrode design, where the rings are held in place with a silicone carrier, has the advantage of simplicity and does not require rotational orientation within the scala. This design is now commonly used by most commercial manufacturers of cochlear implants. However, the longitudinal electrode configuration not only creates an unwanted bimodal distribution of exited nerve fibers (Frijns, J. H. M. et.al., Hearing Research, 95 (1996), 33-48) but only a small segment of the annulus-shaped electric field generated between electrode ring pairs stimulates nerve fibers, thereby wasting a large amount of electrical energy. Frijns, et. al. also suggest that the efficacy of neural stimulation is enhanced when the electric field lines are parallel to the nerve cells rather than perpendicular as is dictated by the longitudinal configuration. Additionally, electrical cross-talk between adjacent ring electrodes becomes an increasing problem as more electrodes are used to obtain better spatial selectivity along the length of the scala.
The small diameter discrete electrode (ie. platinum/iridium ball) type designs have the distinct problem of rotationally twisting during insertion of the array, resulting in some or all of the electrodes facing away from the stimulatable neural sites. Accordingly, designs have been proposed whereby the array preferentially bends in one plane, while maintaining rigidity in the other plane. For example, Charvin, in U.S. Pat. No. 5,123,422, teaches the use of internal hinges or slits, where such hinges or slits are oriented to give flexibility in only one plane, and can be inserted in the scala tympani without curling, thus orienting the electrode sites
Berrang Peter G.
Bluger Henry V.
Klosowski Henryk
Lupin Alan J.
Epic Biosonics Inc.
Gotlieb, Rackman & Reisman, P.C.
Schaetzle Kennedy
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