New outcomes with auditory brainstem implants in NF2 patients
To determine factors related to high levels of speech recognition in patients with the auditory brainstem implant (ABI). Retrospective case review. International multicenter data from hospitals and tertiary referral facilities. Patients with neurofibromatosis type 2 (NF2) and bilateral vestibular schwannomas. ABIs were placed after the removal of vestibular schwannomas. Demographic and surgical data were collected from 26 patients with ABIs who achieved scores of better than 30% correct identification of sentences presented in quiet listening conditions and without lipreading cues. Scores better than 30% speech recognition of standard sentence test materials (HINT or equivalent) in quiet listening conditions were obtained in 26 of the 84 NF2 patients (31%). ABI speech recognition was correlated with surgical position, length of deafness, the number of distinct pitch electrodes, perceptual levels, and ABI stimulation rate, but not correlated with tumor size, tumor stage, the number of electrodes used, or electrophysiological recordings. This paper presents the consensus opinion from a meeting of surgeons to compare outcomes across ABI surgical centers. The consensus opinion was that brainstem trauma is a primary factor in the variability of outcomes in NF2 patients. The significant co-factors in outcomes implied that ABI surgery should be accomplished with great care to minimize physical and venous trauma to the brainstem. It is clear that high levels of speech recognition, including high levels of open-set speech recognition, are possible with the ABI even in patients with NF2 and large tumors.