Preoperative assessment of implantable cochlea amplifiers using conventional X-ray and CT scans of the temporal bone

Recently,the transducer and microphone of a cochlea amplifier implant (CAI) for the treatment of sensorineural cochlear hearing loss have been developed further for implantation into the mastoid cavity. At present, the University of Tuebingen implantable cochlea amplifier consists of an implantable microphone and an implantable piezoelectric transducer. It has been implanted into the first patients. Successful future application of this new implant depends on the suitable fit of the CAI within a patient's mastoid cavity. Using conventional X-ray and CT scans, we analyzed 50 cadaver specimens of the temporal bone before total mastoidectomy. After total mastoidectomy,the volume of the mastoid cavity was measured using CT scans and water volume determination. Finally,the CAI was implanted into those temporal bones that were large enough to house it. Our results demonstrate that the degree of pneumatization in the conventional Schuller X-ray is already a good parameter for preoperative evaluation.