Endosteal electrode

Abstract

An implantable tissue-stimulating device comprising an elongate electrode carrier member (11) having a plurality of electrodes thereon. The electrodes are preferably disposed in a linear array on the carrier member (11) and are adapted to apply a preselected tissue stimulation to the cochlea. The carrier member (11) is preformed from a resiliently flexible biocompatible silicone and extends from a distal end (12) to a stop member (13). The carrier member (11) is adapted for intracochlear but extraluminar insertion within the cochlea of an implantee. In particular, the carrier member (11) is adapted to be implanted in the crevice (21) between the spiral ligament (22) and the endosteum (23) of the lateral wall of the cochlea (20). This is a quite different location to the normal placement of the cochlear implant electrode array in the scala tympani (24) of the cochlea (20). The placement of the carrier member (11) is designed to avoid any breach of the internal ducts of the cochlea (20), such as the scala tympani (24) and scala vestibuli (25) so that the normal hydrodynamic behaviour of the cochlea (20) is not affected by any intrusive device. By preservng the normal hydrodynamic behaviour of the cochlea (20), use of the carrier member (11) maximises the possibility of also preserving any hearing of the implantee that is offered by the cochlea (20). Use of the device in a system for masking or treating the symptoms of tinnitus is also described.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an auditory prosthesis adapted for intracochlear but extraluminar placement within the cochlea. An application of the device for masking or treating tinnitus is also described. BACKGROUND OF THE INVENTION [0002] Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person may have hearing loss of both types. Of them, conductive hearing loss occurs where the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicdes. Conductive hearing loss may often be helped by use of conventional hearing aids, which amplify sound so that acoustic information does reach the cochlea and the hair cells. [0003] In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. This type of hearing loss is due to the absence of, or destruction of, the hai...

AI Technical Summary

Benefits of technology

[0024] The present invention is firstly directed to an implant that can be inserted in the cochlea but in a position external to the scala tympani. Such an implant provides an alternative option for those persons described above who would benefit from the use of a cochlear implant to improve hearing of relatively high frequencies but who have some residual hearing of relatively low frequencies. The present invention further preferably aims to provide a cochlear implant system that preserves the normal hydrodynamic nature of the cochlea allowing for an electrode array to be positioned to stimulate the desired neurons without causing damage to the important internal ducts of the cochlea.

[0031] The placement of the device is preferably designed to avoid any breach of the internal ducts of the cochlea (eg. scala tympani and scala vestibule) so that the normal hydrodynamic behaviour of the cochlea is not affected by any intrusive device. This is important, as for implantees suffering tinnitus, use of the device does not lead to loss of what otherwise may be good hearing. For implantees with at least some sensorineural hearing loss, use of the device maximises the possibility of also preserving residual hearing offered by the implantee's cochlea. In this case, it is envisaged that use of the device will have particular benefit in those instances where the implantee has substantial residual hearing in the low frequencies but would benefit from supplemental stimulation in a relatively higher frequency range. In this case, the implantee may benefit from use of a hearing aid that amplifies the relatively low frequencies still detectable by the implantee and a cochlear implant for detection of relatively high frequencies.

[0035] The stop member can serve as both a region for grasping the carrier member and also act to prevent insertion of the carrier member within the crevice beyond a predetermined maximum depth.

[0038] The surfaces of the carrier member are preferably smooth to prevent any damage to the cochlea as the array is placed in the cochlea.

[0042] In one embodiment, the lead can extend from the carrier member to the stimulator means or at least the housing thereof. In one embodiment, the lead is continuous with no electrical connectors, at least external the housing of the. stimulator means, required to connect the wires extending from the electrodes to the stimulator means. One advantage of this arrangement is that there is no requirement for the surgeon implanting the device to make the necessary electrical connection between the wires extending from the electrodes and the stimulator means.

[0051] In a still further embodiment, the stimulation regime can comprise a random discontinuous supra-threshold stimulation regime. It is postulated by the present inventors that irregular stimulation may be sufficient to reduce the impact of the tinnitus condition. Irregular stimulation also has the advantage of being relatively power-efficient and hence would result in longer battery life for the device.

Problems solved by technology

In some cases, a person may have hearing loss of both types.

Of them, conductive hearing loss occurs where the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicdes.

In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss.

These people are thus unable to derive suitable benefit from conventional hearing aid systems, no matter how loud the acoustic stimulus is made, because there is damage to or absence of the mechanism for nerve impulses to be generated from sound in the normal manner.

Despite the enormous benefits offered by cochlear implants, one potential disadvantage of placement of the electrode assembly within the scala tympani is that it is necessary to breach the internal ducts of the cochlea, generally the scala tympani.

The breaching of the scala tympani of the cochlea adversely affects the hydrodynamic behaviour of the cochlea and is thought to prevent or at least reduce any chance of preservation of any residual hearing of the implantee.

This can be problematic for those persons who would benefit from use of a cochlear implant to improve hearing of relatively high frequencies but who have some residual hearing of relatively low frequencies.

Therefore the system as described in this application still uses a relatively obtrusive electrode array making it very difficult to preserve any residual hearing the patient may have in such areas.

For others, it can be a quite debilitating condition.

Masking systems known to date are typically worn within the ear canal or positioned nearby so as to ensure provision of a masking sound to the sufferer and as a result these devices stigmatise the wearer and are worn reluctantly.

Such devices utilise electromechanical transducers coupled to the ossicular chain to produce the artificial masking sounds, however, these devices require a very complicated surgery to implant as the electromechanical transducer must mechanically manipulate the ossicular chain.

Also, it has been found that such mechanical coupling is not always guaranteed to be stable as pressure necroses in the area of the middle ear ossicle has been found to occur in a number of cases resulting in bone erosion.

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