Cochlear implant electrode array

Abstract

An electrode array (30) which is able to be inserted to a desired depth within the cochlea to provide useful percepts for the recipient which will also preferably not cause damage to the sensitive structures of the cochlea. The electrode array (30) is insertable through an opening in the cochlea and into at least the basal region of the cochlea and comprises an elongate carrier (31) having a proximal end, a distal end, and a plurality of electrodes (32) supported by the carrier at respective spaced locations thereon in a region between the proximal end and the distal end. A stabilising collar (35) extends outwardly from the elongate carrier (31) at or adjacent a proximal end thereof and has an abutment surface adapted to abut a portion of the cochlea surface around the cochleostomy and at least substantially prevent movement of the carrier (31) following completion of insertion of the array (30) into the cochlea.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an implantable cochlear electrode assembly. A method of implanting such a device is also described. BACKGROUND OF THE INVENTION [0002] In modern society, the occurrence of hearing loss is quite common, with approximately 10% of the population suffering from some degree of hearing impairment. This can be attributed to a number of causes, such as prolonged exposure to loud sounds, the result of disease or illness, or congenital problems. [0003] Hearing loss is generally of two types, namely conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicles. In such cases, the hearing loss may often be improved by the use of conventional hearing aids, which amplify the sound so that acoustic information reaches the cochlea and the hair cells. Such hearing aids utilise acoustic mechanical stimula...

AI Technical Summary

Benefits of technology

[0012] The present invention aims to ameliorate the problems associated with the prior art and provide an electrical stimulation device which is able to restore high frequency sound perception whilst allowing natural hearing mechanisms to be restored and maintained for perception of low to medium frequency sounds.

[0075] In a preferred embodiment of the aspects, the implantable component can further comprise an additional electrode assembly that is adapted to be implantable external of the internal passages of the cochlea. This additional extracochlear electrode assembly is typically implanted external of the cochlea in the muscle surrounding the head of the user. The use of this additional assembly allows the stimulation method known as monopolar stimulation to be performed. In monopolar stimulation, the stimulation passes between an intracochlear and an extracochlear electrode, providing for a relatively wide current spread.

Problems solved by technology

Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicles.

Sensorineural hearing loss, however, is due to the absence or destruction of the hair cells in the cochlea which are needed to transduce acoustic signals into auditory nerve impulses.

Individuals suffering from this type of hearing loss are unable to derive any benefit from conventional hearing aid systems, no matter how loud the acoustic stimulus is made, because their mechanisms for transducing sound energy into auditory nerve impulses have been damaged.

Whilst this patent identifies the need to attempt to combine the two stimulation methods it fails to suggest how such a system can be achieved, and the mechanism for performing this task.

Experimental tests have shown that electrode arrays inserted to a depth as described by the above international patent publication will produce unnatural and sharp or high-pitched percepts in a recipient.

Trials of such an array to a depth of 8 mm into the cochlea have indicated that recipients are not able to fuse the electrical stimulus with the auditory stimulus received.

Therefore, the electrode array as described by the above-referenced patent publication will be unable to provide benefit to the recipient because of restriction in depth of insertion which is mandatory to preserve residual hearing.

Further, the electrode array of the above-referenced patent publication will most likely cause damage to the basal membrane due to rotation or twisting of the array about its longitudinal axis.

As the array relies upon flexible flaps for stabilisation and not the fixation of the head of the device, it is highly likely, due to the rounded shoulder of the device, that the array will not be stable within the cochlea, potentially causing damage to the sensitive structures therein.

In addition, placement of such a device through the round window membrane may interfere with the micromechanics of the travelling wave of the inner ear.

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