In rare cases, a person might have acoustic tumours (also called vestibular schwannoma) on both sides (bilateral). This is the hallmark of a disease called Neurofibromatosis Type II (NF2).
The incidence of NF2 is one in 33,000 to 40,000 live births.
Early diagnosis using gadolinium-enhanced MRI and techniques of hearing preservation surgery have improved our ability to prevent total hearing loss while completely removing the tumours. As this is a genetic disease, with a dominant inheritance pattern, family screening and DNA analysis have helped early diagnosis.
Half of the individuals with Neurofibromatosis Type II (NF2) have inherited the disorder from an affected parent, and half seem to have a mutation for the first time in their family.
Each child of an affected parent has a 50% chance of inheriting the disorder.
Unlike those with a unilateral vestibular schwannoma, people with NF2 usually get symptoms in their teens or early adulthood. They frequently also develop multiple brain and spinal cord tumours. NF2 tumours may affect the nerves important for swallowing, speech, eye and facial sensation.
Treatment options offered for NF2 Acoustic tumours include:
observation without surgical intervention,
hearing preservation surgery with total tumour removal,
surgical ‘decompression’ of the tumour without total removal of it,
retrosigmoid surgery, with partial tumour removal,
translabyrinthine total tumour removal which will not preserve any hearing, and
auditory brainstem or cochlear implantation.
For people with larger tumours or no useful hearing, the ABI can restore some auditory function when the tumour is removed. In selected cases, a cochlear implant can be used, with good results.