Histological evaluation of a cochlear implant electrode array with the integration of an electrically activated shape memory alloy
23. April 2019 (online)
One of the factors that may improve the quality of the signal transmission between a cochlear implant electrode carrier and the fibers of the auditory nerve is by reducing the distance inbetween. To achieve this, an electrode carrier prototype with an integrated thin wire (Ø100 µm) made of Nitinol, a shape memory alloy, is proposed. The wire acts as an actuator that has been formed to adopt the spiral shape of a cochlea. In order to activate the shape memory effect of the wire, it may be electrically heated.
A cochlear implant electrode carrier prototype was developed by integrating a Ø100 µm Nitinol wire behind the electrode. The first prototypes were developed by modifying a Cochlear Nucleus Hybrid™ L24 (Cochlear Ltd., Sydney, Australia) electrode and replacing the stiffener with the Nitinol wire. To enable electrical heating, copper wires were crimped on both ends of the wire. A proof-of-concept was performed by inserting the developed electrode array prototype into a temporal bone. After successful insertion of the electrode carrier prototype, specimen preparation was performed and histological evaluation was made.
According to the histological evaluation, an angular insertion depth of 360 ° was achieved by the prototype. Furthermore, no indications of thermal damage to the soft tissue structures were revealed. A perimodiolar position of the prototype could be realized.
The histological evaluation from the first temporal bone experiment showed no intracochlear damage and preservation of the basilar membrane. This finding motivates further research on integrating a shape memory alloy to the electrode carrier. Through the shape memory effect of the Nitinol wire, the electrode carrier can be formed to a specified geometry allowing a perimodiolar positioning of the implant.