Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Ear or nose prosthesis
Patent
1994-05-04
1996-11-26
Milano, Michael J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Ear or nose prosthesis
607137, A61F 218
Patent
active
055780849
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to electrode arrays for cochlear implants.
BACKGROUND ART
Electrode arrays for insertion into the cochlea are known in various forms in the prior art. They are generally manufactured in a straight form from a resilient material. When they are inserted into the cochlea, they flexibly curve into the spiral form of the scala tympani. However, the electrode array is resilient and hence tends to "remember" its straight form, and accordingly engages the outer (radially) wall of the scala tympani. For optimum electrical stimulation to occur, it is preferred that the electrodes engage the inner wall, near the modiolus.
One solution which has been proposed is to manufacture the electrode in a spiral shape. This type of arrangement is shown in U.S. Pat. No. 4,284,085 to Hansen et al, and in the device developed by the University of California at San Francisco. However, these devices are difficult to insert in a surgical procedure, and require specialised equipment and skills to approach satisfactory performance. Moreover, they use a curve for the array which is an estimate of average shape, not the actual shape of each patient's cochlea. These devices also require very careful manufacturing techniques to produce a reliable product.
DISCLOSURE OF INVENTION
It is accordingly an objective of the present invention to provide an electrode which combines the manufacturing and insertion advantages of the straight form of electrode, while providing engagement in use with the inner wall of the canal.
The present invention accordingly provides an electrode array which after insertion curves from its original substantially linear form into a curved shape. Preferably, the electrode array is constructed from a first portion which is flexible but stable which contains the electrodes, and a second portion which is formed from material which will expand after insertion so as to curve the overall electrode into a spiral shape. Preferably, this is achieved by utilising a material which expands slowly when in contact with water, so that over a period of hours or days after insertion the electrode slowly curves inwardly so as to engage the inner wall of the canal. Hence, the optimal stimulation arrangement whereby the electrodes engage the inner wall of the canal is likely to be achieved.
BRIEF DESCRIPTION OF DRAWINGS
One embodiment of the invention will now be described with reference to the accompanying figures, in which:
FIG. 1 is a schematic cross-sectional illustration through the plane of the cochlea showing insertion of the electrode;
FIGS. 2 and 3 are crosssectional views along line A--A of alternative constructions of the electrode array;
FIG. 4 is a similar view to FIG. 1 showing the positional change of the electrode array after curving;
FIG. 5 is a lateral section across FIG. 4;
FIG. 6 shows the preferred mechanical properties required of the electrode array according to the present invention;
FIG. 7 is a detailed illustration of one construction of the electrode array according to the present invention;
FIG. 8 is a detailed illustration of another construction of the electrode array according to the present invention; and
FIG. 9 shows one method for electrically connecting the electrodes according to the embodiment of FIG. 8.
DESCRIPTION OF PREFERRED EMBODIMENT
One embodiment of the invention will now be described, however, it is noted that the present invention is of wide scope and that many possible embodiments fall within the general inventive concept.
Referring to FIG. 1, the electrode array 12 is initially preferably formed in a generally straight cylindrical or semi-cylindrical shape. The materials are selected such that this shape will generally be maintained outside of the human body at normal conditions of temperature and humidity. In this form, it is relatively simple to control the insertion of the electrode into the cochlea 30. It will be appreciated that the illustration of the cochlea is purely schematic and is not intended to be anatomically accurate. Immed
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patent: 3752939 (1973-08-01), Bartz
patent: 4284085 (1981-08-01), Hansen et al.
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Guyton, David; "Science", vol. 131, Jul. 1973.
Brown Gordon G.
Kuzma Janusz
Seldon Henry L.
Cochlear Ltd.
Milano Michael J.
University Of Melbourne
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