Indications and contraindications of auditory brainstem implants: systematic review and illustrative cases

The number of non-neurofibromatosis type 2 (NF2) indications for auditory brainstem implant (ABI) in the literature is increasing. The objective of this study was to analyze and discuss the indications for ABI. Retrospective chart review and systematic review were conducted at Quaternary referral skull base center and referring centers. Analysis of ABI cases with non-NF2 indications and systematic review presenting non-NF2 ABI cases were performed. Fourteen referred cases with ABI were identified. All cases had unsatisfactory results of ABI and all could have been rehabilitated with a cochlear implant (CI). Of these 14 cases, 9 improved with a cochlear implant, and 2 with a hearing aid, two are still planned for CI, one received bilateral CI, no ABI. In literature, we found 31 articles presenting 144 non-NF2 ABI cases with at least 7 different indications other than NF2. ABI should be restricted to those patients who have no other rehabilitation options. Patency of the cochlea and evidence of an intact cochlear nerve should be examined with imaging and electrophysiologic testing. Sometimes a CI trial should be planned prior to proceeding with ABI. We have shown that in many cases a CI is still possible and CI provided better results than ABI. In vestibular schwannoma in the only hearing ear, cochlear otosclerosis, temporal bone fractures, (presumed) bilateral traumatic cochlear nerve disruption, auto-immune inner ear disease and auditory neuropathy primarily CI are indicated. Traumatic bilateral cochlear nerve disruption is exceptionally unlikely. In cochlear nerve aplasia, testing should be performed prior to meeting indications for ABI. In malformations, ABI is indicated only in severe cochlear hypoplasia or cochlear aplasia.