Multichannel auditory brainstem implant: update on performance in 61 patients

TLDR

Neurofibromatosis type 2 causes deafness after bilateral vestibular schwannoma removal, and cochlear implants are ineffective because the auditory nerve is disrupted, but the first auditory brainstem implant performed in 1979 has shown lasting benefit. This study evaluated the safety and efficacy of a newly developed multichannel auditory brainstem implant in patients with NF2. Patients received an eight‑electrode array placed on the cochlear nucleus surface, activated about six weeks post‑implantation, and were assessed every three months for the first year and annually thereafter with a comprehensive psychophysical and speech‑perception battery. The implant provided useful auditory sensations, improved communication over lipreading alone, enabled detection and recognition of environmental sounds, and in some cases allowed speech understanding, with performance continuing to improve for up to eight years post‑implantation.

Abstract

Neurofibromatosis Type 2 (NF2) has typically resulted in deafness after surgical removal of bilateral vestibular schwannomas (VSs). Cochlear implants are generally ineffective for this kind of deafness because of the loss of continuity in the auditory nerve after tumor removal. The first auditory brainstem implant (ABI) in such a patient was performed in 1979 at the House Ear Institute, and this individual continues to benefit from electrical stimulation of the cochlear nucleus complex. In 1992, an advanced multichannel ABI was developed and a series of patients with NF2 received this implant to study the safety and efficacy of the device.At the time of first- or second-side VS removal, patients received an eight-electrode array applied to the surface of the cochlear nucleus within the confines of the lateral recess of the fourth ventricle. The device was activated approximately 6 weeks after implantation. and patients were tested every 3 months for the 1st year after the initial stimulation, and annually thereafter. The protocol included a comprehensive battery of psychophysical and speech perception tests.The multichannel ABI proved to be effective and safe in providing useful auditory sensations in most patients with NF2. The ABI improved patients' ability to communicate compared with the lipreading-only condition, it allowed the detection and recognition of many environmental sounds, and in some cases it provided significant ability to understand speech by using just the sound from the ABI (with no lipreading cues). Its performance in most patients has continued to improve for up to 8 years after implantation.