Active Middle Ear Implants in Patients Undergoing Subtotal Petrosectomy

Abstract

The functional outcome of ossiculoplasties in chronic ear and lateral cranium base surgery depends on the presence of a ventilated middle ear space and is guided by the existence or absence of ossicular remnants. In patients with poorly ventilated middle ears, after multiple previous operations, missing stapes suprastructure, or after partial temporal bone resection for tumor removal, restoration of conductive hearing is not possible. The direct placement of a vibrating floating mass transducer (FMT) onto the round window membrane with obliteration of the surgical cavity is a new option. Starting in January 2006, five patients underwent a subtotal petrosectomy to control their chronically discharging ear, to remove residual cholesteatoma, or to revise previous incompletely exenterated cavities. Four patients underwent a simultaneous placement of a Vibrant Soundbridge (VSB) onto the round window membrane; one patient had a staged reconstruction after initial Bone-Anchored Hearing Aid rehabilitation. In all operations, the external ear canal and the eustachian tube were closed, and the cavity was obliterated using abdominal fat. Preoperative and postoperative pure tone audiograms were analyzed in respect to deterioration of inner ear function, aided and unaided (hearing aid, VSB, and Bone-Anchored Hearing Aid) speech audiograms were compared to verify improvements in communication skills, functional gains were calculated at comfortable level settings, and postoperative computed tomographic scans were used to exclude recurrent disease and to confirm the position of the FMT onto the round window membrane. Patient's satisfaction was measured using a standardized questionnaire. All patients were very satisfied daily users of their middle ear implant and had complete eradication of their middle ear pathology. Bone conduction worsened at 2 kHz, with preservation of inner ear function in the other frequencies. Whereas none of the patients had any unaided speech discrimination before the surgery at conversational levels, all patients obtained 95 to 100% correct monosyllabic scores at 70 to 80 dB using the VSB. The functional gain was highest at higher frequencies. Patients with combined hearing loss undergoing subtotal petrosectomy with complete fat obliteration of the middle ear and mastoid area can be safely rehabilitated, placing the FMT of a VSB onto the round window membrane, either at the time of primary surgery, or as a staged secondary procedure.