Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Ear or nose prosthesis
Reexamination Certificate
1998-05-04
2001-10-23
Isabella, David J. (Department: 2164)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Ear or nose prosthesis
C607S137000
Reexamination Certificate
active
06306168
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to human hearing and more specifically to methods and tools for implanting a device in the canalis cochlearis (or cochlea) to generate auditory percepts in profoundly deaf persons.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates how sound waves are collected by the outer ear
1
in humans to create hearing. Acoustic waves travel down the ear canal
2
, wherein frequencies are enhanced in the 4,000 cycles/second range, and then impinge on the ear drum
3
causing it to vibrate in a complex manner. The ear drum transmits this vibrational energy to the three small bones, the malleus
4
, the incus
5
and the stapes
6
, which transmit and amplify the sound. These are located in the air space behind the ear drum, known as the middle ear
7
. The acoustic energy is further transmitted by the innermost bone, the stapes, which fits like a plunger into a window in the cochlea known as the oval window
8
, which is connected to the inner ear, or cochlea
52
. The vibrational energy from the stapes is thereby converted to pressure waves within the cochlea, which contains two larger and one smaller channels which are arranged in a spiral fashion of approximately two and a quarter turns, as depicted in
FIG. 2
, which, for simplicity, is shown uncoiled.
The external sound is thus transmitted, firstly, into one channel of the cochlea
52
, the scala vestibuli
10
, where it travels to the apex of the channel. At the apex the pressure wave traverses an opening known as the helicotrema
11
into a second spiral channel, the scala tympani
12
, continuing along this channel inside the spiral to the round window
9
. This arrangement of two spiral channels, separated by a thin membrane, activates a sensitive mechanism known as the Organ of Corti
13
illustrated in FIG.
3
. This contains approximately 15,000 hair cells
14
in each ear, in a central channel between the scala vestibuli
10
and the scala tympani
12
, known as the cochlear duct
15
. These are best illustrated in the sketch of the cross-section of the cochlear channels of FIG.
3
. These hair cells respond to the sound originating from the ear canal and act essentially as bionic transducers that change acoustic energy into electrochemical neural responses. The latter are transmitted along the auditory nerve
16
to the brain, where the neural signals are processed in specialized areas of the brain by the auditory nuclei. These have far greater ability to develop in infants—a phenomenon known as brain plasticity. This is also the case in the learning of languages. It is therefore recognized that the ideal age for treatment of deafness is as early as possible, to take advantage of the brain's ability to adapt shortly after birth.
In many cases of deafness, the hair cells or the Organ of Corti are damaged, but the auditory nerves and their cell bodies are present in sufficient numbers to process speech if they are adequately electrically stimulated. This has been clearly described in numerous publications, including the seminal work by Harold F. Schuknecht, M.D, and Mark R. Gacek, M.D., Cochlear Pathology in Presbycusis, Annals of Otology, Rhinology, and Laryngology 1993;102:1-16 Supplement 158. This study suggested that hearing could be mediated electrically. Early attempts were made to stimulate the auditory nerve electrically during neurosurgical procedures or operations in which the auditory nerve was exposed, as in the case of Djoumo and Eyries (Prosthèse auditive par excitation électrique à distance du nerf sensoriel à làide d'un bobinage inclus à demeure, 1957, Presse Médicae35:14-17).
Modern developments to help the deaf include cochlear implant devices which pick up sound, process it, and deliver it in some way to the auditory nerve. Such developments have been well summarized by Clarke et al.,
Cochlear Prostheses
edited by Graeme M. Clark; Yit. Tong & James F. Patrick, Churchill Livingstone, Edinburgh, London, Melbourne and New York, 1990. ISBN 0-443-03582-2.
Numerous inventions have been made regarding the implantation of electrodes to stimulate the auditory nerve. Chouard implanted multiple electrodes in the bony wall of the cochlea and later into the inner ear, as related in Chouard CH, McLeod P. 1976, Implantation of multiple intra-cochlear electrodes for rehabilitation of total deafness, Preliminary Report, Laryngoscope 86. 1743-1746. Similarly, Michelson and House experimented with intracochlear electrodes (William F. House, 1976. Cochlear Implants. Annals of Otology, Rhinology and Laryngology, Supplement 27, Vol. 85, May/June 1976, No. 3, Part 2), as did Hochmair-Desoyer IJ et al. (Four Years of Experience with Cochlear Prostheses, 1981, Medical Progress through Technology, Springer-Verlag, Vol. 8, pp. 107-119). More recent developments are summarized in the Proceedings of the European Symposium held in Hanover in June 1996 (American Journal of Otology, November 1997 Supplement. Lippincott-Raven).
Commercial cochlear implants currently available rely on surgery (see
FIG. 4
a
) which places electronic parts
17
in the bone behind the ear known as the mastoid region
18
by drilling a small aperture
19
from the air cells in the mastoid region into the posterior part of the middle ear between the ear drum and the facial nerve
20
. This nerve shown in cross-section in
FIG. 4
a
, supplies the muscles of the face. Through this cleft electrodes are inserted either through or adjacent to the round window
21
of the cochlea
52
. Using this approach, access is obtained into the scala tympani.
The prior art approach described above is rather lengthy and has other significant limitations. The surgery is generally required to be done under general anesthetic, and the surgeon must navigate around several sharp bends which hinders full insertion of the electrode array into the scala tympani. Also, this approach requires significant drilling of the mastoid bone which creates a degree of bleeding from the bone vessels and marrow and provides a large raw bone surface area open to infection during surgery. Moreover, since the mastoid air cell system does not develop until approximately two years of age, this surgery is not possible for newborns. The bony dissection is extensive and there is a risk of damage to the facial nerve. The small access into the cochlea through the gap between the facial nerve and the tympanic membrane makes insertion of the flexible, delicate electrode array fully into the scala tympani very difficult and imposes a curvature in the line of insertion (see
FIG. 4
a
). The present invention provides an improved method for surgically implanting a cochlear implant which overcomes these limitations of the prior art approach.
In our co-pending application entitled Inner Ear Implant Device filed contemporaneously with this one, the disclosure of which is incorporated herein by reference, a cochlear implant is described which comprises two elongated electrode-bearing prongs allowing insertion of one prong into the scala tympani and the other prong into the scala vestibuli for improved hearing percepts by the patient. It is an object of the present invention to provide a method for surgically implanting a cochlear implant as described in our co-pending application. It can also be adapted for use with conventional electrode arrays.
Surprisingly, the dimensions of the cochlea are remarkably constant from infancy to adulthood. Numerous anatomical studies of the scalae have been made, for example, see Takagi A, Sando I., Computer-aided Three-dimensional Reconstruction: A method of Measuring Temporal Bone Structures Including the Length of the Cochlea, Annals of Otology Rhinology and Laryngology, 1989, 98:515-522. These dimensions are critical in the design of any tools or methods to implant optimum performing stimulation devices into the cochlea of deaf persons. It is a further object of this invention to take advantage of the consistency in the dimensions of the cochlea by providing a template for use in assisting the surgeon in implanting a c
Berrang Peter
Lupin Alan
Epic Biosonics Inc.
Isabella David J.
Paul Smith Intellectual Property Law
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