Multi-electrode cochlear implant system with distributed electronics

Abstract

An implantable tissue-stimulating device comprising a carrier member having a plurality of electrodes (11) mounted thereon, and at least one signal transmitting wire (13) extending through at least a portion of the carrier member and adapted to transmit signals through the carrier member to and / or from the electrodes (11). The number of wires (13) within the carrier member is less than the number of electrodes (11) mounted thereon.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a tissue-stimulating prosthesis and, in particular, to an implantable tissue-stimulating prosthesis, such as an electrode array for a cochlear implant-type auditory prosthesis. BACKGROUND OF THE INVENTION [0002] Cochlear implants have been developed to assist people who are profoundly deaf or severely hearing impaired, by enabling them to experience hearing sensation representative of the natural hearing sensation. In most of these cases, the individuals have an absence of or destruction of the hair cells in the cochlea which naturally transduce acoustic signals into nerve impulses which are interpreted by the brain as sound. The cochlear implant therefore bypasses the hair cells to directly deliver electrical stimulation to the auditory nerves with this electrical stimulation being representative of the sound. [0003] Cochlear implants have traditionally consisted of two parts, an external speech processor unit and an im...

AI Technical Summary

Benefits of technology

[0025] The data decoder preferably demodulates data and power signals transmitted from the receiver / stimulator circuit, extracts the data and decodes it to obtain the stimulation and telemetry control parameters. Each electrode data decoder preferably determines whether its associated electrode is required to output an electrical stimulation. By devolving this decoding step to circuitry embedded with the respective electrodes, the number of electrical connections between the electrodes and the receiver / stimulator passing through the carrier member can be reduced.

[0041] Despite the above, precise charge balance may not be achievable in practice due to small timing errors or variation in electrode properties. To overcome this problem, the output transmission gates (switches) are preferably closed after the second stimulation phase, thereby connecting all intra-cochlea electrodes to stim 1 and stim 2 simultaneously. These electrodes can be connected to VDD via the output switches of the receiver / stimulator circuit. Depending on the desired shorting scheme, the extra-cochlear electrodes may also be shorted to VDD together with the intra-cochlea electrodes in order to simultaneously discharge any residual charge on all electrodes. The insertion of series capacitors with some, or all, of the four output lines of the receiver / stimulator circuit preferably guarantees the longer term charge balance of the system.

Problems solved by technology

The dimensions and spiral shape of the cochlea also limit the maximum dimensions, particularly the diameter, and the stiffness of any array used as part of a cochlear implant.

In existing designs, this has limited the number of electrically conducting electrodes that can be incorporated into the array, due in the main to limitations imposed on the number of wires that can extend through the array to the electrodes.

However, it has been demonstrated that increasing the number of wires in conjunction with an increased number of electrodes unacceptably increases the dimensions and stiffness of the array.

Merely reducing the diameter of the wires, in order to keep the overall dimensions unchanged, leads to an unacceptable increase in lead resistance.

As a result, this limitation on the number of leads, and hence electrodes, limits the scale and type of electrical stimulations that can be applied to the auditory nerve by the electrode array.

Images