Electromagnetic implantable middle ear hearing device of the ossicular-stimulating type: principles, designs, and...

This report analyzes the principles, describes designs, and discusses the advantages and disadvantages of different types of implantable middle ear hearing devices. Preliminary acute experiments using an electromagnetic transducer for an implantable hearing device of the ossicular-stimulating type were performed in cats. A miniature samarium cobalt rare earth magnet was cemented on the head of the stapes. An electromagnetic coil powered either by direct wiring or by telemetry was used to stimulate the stapes. The performance of the system was evaluated by electrophysiologic assessment of hearing (brain stem evoked response potentials). The findings showed that the device is functional with good "implant gain" (35 dB average) and consumes reasonably low current (0.6 mA) with telemetry. Further investigation is necessary in order to develop an implantable middle ear hearing device with successful clinical application.