Implantable hearing aid in fourteen patients with mixed deafness

An implantable hearing aid (IHA) in which the stapes was directly driven by a ceramic vibrator of bimorph design was applied to fourteen patients with mixed deafness of varying degree due to chronic otitis media. In the partial IHA system, only the output transducer and secondary coil are implanted, the remainder of the components such as microphone, amplifier, battery and primary induction coil remain in the location behind the auricle. The vibrator was activated by an electric signal transmitted electromagnetically through the induction system from the outer unit. All the patients admitted that sound quality provided by the IHA was natural, clear and easy to hear without causing fatigue in long-term use. Speech discrimination test under noise circumstance showed that acoustic perception by the IHA was superior to that by a conventional hearing aid. In four patients, however, the implanted unit was replaced with a new one due to recurrence of cholesteatoma, head trauma, and accidental disruption of wire by manipulating the ear canal. They regained good hearing after re-implantation.