Strategy in the Treatment of Bilateral Acoustic Neuromas

Neurofibromatosis 2 (NF2) results in bilateral hearing loss due to tumor growth in the cerebellopontine angle. We present the results of promontory stimulation and transtympanic electrocochleography on 19 ears tested on subjects with deafness due to NF2. Nine ears revealed auditory perception during promontory stimulation indicating cochlear deafness. The other 10 ears (mainly after previous surgery) revealed negative promontory stimulation indicating additional retrocochlear deafness. Cochlear microphonics were absent in all cases. These findings indicate that neurofibromas initially cause cochlear deafness, so that a cochlear implant must be considered in rehabilitating patients with bilateral tumors due to NF2.

Early surgical removal should be performed on the first side attempting preservation of hearing or at least functional preservation of the cochlear nerve. In case of postoperative deafness but functional preservation of the auditory nerve or in case of preoperative deafness and a positive promontory test, a cochlear implant can be used and may provide excellent results. Only in cases where it is impossible to preserve the cochlear nerve or there is a negative promontory test should auditory brainstem implant (ABI) be used on the first side. Surgery on the second side should be performed only if hearing has been preserved on the first side or if there is complete bilateral deafness or life-threatening complications. If the preoperative promontory test was positive, functional preservation of the cochlear nerve should be attempted on the second side too, in order to use a cochlear implant for auditory rehabilitation. Only in cases where it is impossible to preserve the cochlear nerve and there are consecutive negative promontory tests is an ABI indicated.