Novel Statistical Analyses to Assess Hearing Outcomes After ABI Implantation in NF2 Patients: Systematic Review and Individualized Patients Analysis

BACKGROUND: Patients with neurofibromatosis type 2 develop bilateral vestibular schwannomas with progressive hearing loss. Auditory brainstem implants (ABIs) stimulate hearing in the cochlear nuclei and show promise in improving hearing. Here, we assess the impact of ABI on hearing over time by systematically reviewing the literature and re-analyzing available individual patient data. METHODS: A multidatabase search identified 3 studies with individual patient data of longitudinal hearing outcomes after ABI insertion in adults. Data were collected on hearing outcomes of different sound complexities from sound to speech using an ABI +/- lip reading ability plus demographic data. Because of heterogeneity each study was analyzed separately using random effects multilevel mixed linear modeling. RESULTS: Across all 3 studies (n = 111 total) there were significant improvements in hearing over time from ABI placement (P < 0.000 in all). Improvements in comprehension of sounds, words, sentences, and speech occurred over time with ABI use + lip reading but lip reading ability did not improve over time. All categories of hearing complexity had over 50% comprehension after over 1 year of ABI use and some subsets had over 75% or near 100% comprehension. Vowel comprehension was greater than consonant, and word comprehension was greater than sentence comprehension (P < 0.0001 in both). Age and sex did not predict outcomes. CONCLUSIONS: ABIs improve hearing beyond lip reading alone, which represents baseline patient function prior to treatment, and the benefits continue to improve with time. These findings may be used to guide patient counseling regarding ABI insertion, rehabilitation course after insertion, and future studies.