Hearing Rehabilitation in Neurofibromatosis Type 2

Bilateral vestibular schwannomas are almost pathognomonic of neurofibromatosis type 2 (NF2). As a result of these tumors, hearing loss is the presenting symptom in 60% of adults and 30% of children with NF2. It is often bilateral. The best means of preserving hearing in patients with NF2 is conservative management. Even so at least 28% of patients have progression of hearing loss following diagnosis. The likelihood of progression of hearing loss is, at least in part, determined by the type of mutation. Treatment of vestibular schwannomas often has a detrimental effect on hearing. Only 41% of patients having stereotactic radiosurgery maintain their hearing at 5 years. Treatment with bevacizumab maintains medium-term hearing in 38% and improves it in 48%. Surgery to remove vestibular schwannomas invariably leads to complete loss of ipsilateral hearing, although in a very limited number of patients hearing preservation surgery may be possible. For those that lose their hearing but have an intact cochlear nerve, for example, conservative management, radiotherapy treatment or cochlear nerve preserving surgery, cochlear implantation has been shown to be an effective option although outcomes are not as good as traditional implant candidates (mean sentence testing scores in quiet: stable untreated tumors 69%; radiotherapy treated tumors 49%; cochlear nerve preserving surgery ∼40%). For those that do not have a functional cochlear nerve, auditory brainstem implantation (ABI) is an option. The non-user rate in this group is 13%. The mean sentence score in users with ABI alone is 12%. ABI therefore acts, in most cases, as an aid to lip reading and rarely provides open set speech discrimination.