Neurofibromatosis type 2 is the less common form of neurofibromatosis. This condition is typically characterized by the development of benign tumors called schwannomas that grow along the eighth cranial nerve, which is responsible for hearing and balance.
This usually causes hearing loss, tinnitus and balance problems, particularly when negotiating uneven ground or when walking in the dark. Many people with this condition also experience visual problems.
Another form of neurofibromatosis is the condition schwannomatosis, which has features that commonly overlap with neurofibromatosis type 2. However, in schwannomatosis, the tumors develop anywhere in the body apart from the vetsibular branch of the eighth cranial nerve. Pain is the main symptom, which develops as a schwannoma grows larger and starts to compress nerves.
In type 2 neurofibromatosis, the symptoms depend on where in the body the tumors develop. The tumors usually affect one ear at first but may eventually affect both ears. Less commonly, a person affected by vestibular schwannomas may feel vertigo-like feelings, as if the environment around them is moving. Eventually the tumors can cause facial numbness, weakness in the tongue leading to slurring, and facial pain.
Other features of neurofibromatosis type 2 include non-vestibular schwannomas, cataracts and meningiomas.
Epidemiology and cause
Neurofibromatosis type 2 is less common than type 1 neurofibromatosis and is seen in only 1 in 35,000 live births. In around half of cases, the condition is caused by a mutated gene that is passed on from a parent to their child. In the other half of cases, the mutation develops sporadically in people with no family history of the condition. These patients can also pass the condition onto their offspring.
A diagnosis of neurofibromatosis type 2 is based on the presence of clinical features of the disease, magnetic resonance imaging, hearing tests, vision tests and a genetic test for the NF2 mutation. Prenatal testing can also be performed to check for this mutation and the most commonly used tests include chorionic villus sampling and amniocentesis.