Audiometric Outcomes of Auditory Brainstem Implantation during Vestibular Schwannoma Resection: A Single-Institution Case Series

Study Design: Retrospective case series.

Background: Cochlear implantation has proven highly effective for patients with neurofibromatosis type II (NF2) who suffer from sensorineural hearing loss. However, this is often not feasible in NF2 patients due to cochlear nerve compromise. These circumstances make the auditory brainstem implant (ABI) an attractive treatment option for such patients. However, the long-term outcomes and benefits of the device are still being explored.

Methods: In our study, a retrospective review of 11 patients who underwent auditory brainstem implantation at a single-institution tertiary care academic center spanning from November 2017 to August 2022 was assessed. Only patients with a diagnosis of NF2 undergoing resection for concurrent vestibular schwannoma were included. Preoperative hearing and postactivation audiology assessments were reviewed. Audiologic evaluation including pure-tone audiometry (PTA), early speech perception (ESP), and open set word lists were used to assess auditory abilities with the use of the ABI. Open set testing included AzBio sentences, hearing in noise test (HINT), and consonant–nucleus–consonant (CNC) words. Pure-tone behavioral audiometry was used for sound awareness at a variety of different frequencies. Speech testing was performed sequentially from most basic (ESP) to most complex (AzBio) depending on the patient's progress. Auditory, auditory–visual, and visual conditions for ESP and CNC were administered.

Results: In our cohort, 11 patients were included with a median age of 34 years old. All patients underwent a translabyrinthine approach for implant placement with concurrent VS resection. Average tumor size of vestibular schwannoma resection was 2.87 cm. Preoperatively, eight out of the 11 patients had PTAs with no response at 110 dB. Two of the 11 patients had a PTA within mild-moderate hearing loss (25–45 dB) and one patient had a PTA of profound loss (92 dB). Postoperatively, nine of 11 (81%) had improvement in PTA from profound and no response levels to mild-moderate hearing loss in response to auditory stimuli providing access to sound. One patient with a mild PTA remained unchanged. One patient had a worsening of PTA from a moderate level to a severe PTA. In total, seven of 11 patients reported mild side effects upon ABI activation which included dizziness (n = 2), tinnitus (n = 1), and abdominal and lower extremity tingling sensation (n = 3). Of the seven patients with ESP scores, five had a score of > 75%, indicating the auditory ability to detect pattern perception upon auditory stimulation through the ABI alone.

Conclusions: In total, nine of 11 derived benefit from ABI placement. These findings demonstrate that the placement of an ABI during concurrent vestibular schwannoma resection can provide a significant hearing benefit for the NF2 patient.

Publication History

Article published online:
01 February 2023