ABSTRACT
The auditory brainstem implant (ABI) is a device that provides hearing sensation too bilaterally, profoundly deafened patients when a cochlear implant is unsuitable. This is due to damaged or non-functional cochlear nerves or non-implantable cochleas. The main indication is for post-lingually deafened patients with neurofibromatosis type 2, an autosomal dominant genetic condition with an incidence of 1 in 33,000, which leads to bilateral vestibular schwannomas and subsequent destruction of the cochlear nerves. A cochlear implant works so well because the cochlea is tonotopic, meaning that replicating speech patterns is relatively straightforward. An additional problem is that of non-auditory stimulation, where neighbouring cranial nerves are inadvertently stimulated by the implant. Outcomes with the ABI are notoriously variable. Approximately 20–30% of adults will become non-users because so little benefit is gained or they cannot become accustomed to the auditory stimulation.
