Safety and patient selection of totally implantable hearing aid surgery: Envoy system, Esteem

Patient's low compliance of conventional hearing aids has lead to innovation of totally implantable hearing devices such as Esteem, Envoy system. This study was designed to evaluate safety of device implantation, patient's hearing gain, importance of anatomic landmarks, and to describe suitable criteria for patient selection. Via a non-randomized controlled clinical trial, ten patients with moderate-to-severe sensorineural hearing loss were implanted from 2007 to 2009. Mean follow-up period was 29.4 months. Correlation of pre-operative temporal bone CT scan anatomy with postoperative outcome was evaluated. Except one, all other implanted devices are active and patients' overall average hearing gain are similar to conventional hearing aids (10-22 dB), but patients reported relatively better subjective sound quality compared with their pre-operative conventional hearing aids. One implanted device was explanted in a patient due to facial weakness and low-hearing gain. Revision surgery was done successfully in another patient secondary to excessive bone growth. Totally implantable hearing device surgery seems to be relatively safe and correct patient selection could lead to good outcomes. Lateral location of facial nerve, sclerotic mastoid air cells and narrow facial recess space seems to be related to postoperative complications.