Type 2 Neurofibromatosis (NF-2) is similar in some respect to NF-1 where a mutation in a specific gene (NF-2 gene) on a different chromosome (chromosome 22) causes uncontrolled cell growth. Aside from affecting a different gene than NF-1, it is characterized by specific nervous system tumors including vestibular schwannomas (tumors of the eight cranial nerve involved in balance and hearing), intracranial and spinal meningiomas, and other spinal tumors. It is much less common than NF-1, occurring in roughly 1 in 30,000 individuals.
KEY FEATURES FOR DIAGNOSIS
(one of the following must be present)
- Bilateral 8th nerve tumors on MRI or CT
- Parent or sibling with NF-2 and unilateral 8th nerve tumor or 2 of the following: meningioma, neurofibroma, glioma, schwannoma, or juvenile posterior subscapular lenticular opacity
Most of the signs and symptoms of NF-2 appear during adolescence or later. Most frequently, early signs of hearing loss, balance issues, and ringing in the ears signal the presence of vestibular schwannomas. The tumors appear in both ears in a person’s twenties. Tumors developing in other parts of the nervous system may exhibit different signs and symptoms. NF-2 has a predilection for affecting the central nervous system and cranial nerves, including the facial nerve which can cause facial paralysis. Cataracts can form in one or both eyes and fluid can build up in the brain.
Similar to NF-1, the NF-2 gene mutation causes an error in the formation of a tumor suppressor protein called merlin. The lack of the functional version of the protein leads to uncontrolled growth of tumors arising from the supporting cells of nerves, called Schwann cells.
Similar to NF-1, NF-2 is considered to have an autosomal dominant pattern of inheritance. Once again, half of affected patients inherit a mutated copy of the NF-2 gene. The remaining individuals result from new mutations and have no known family history of the condition.
Two copies of the altered gene are necessary to cause NF-2. One copy may be present at birth, and the other can occur during a person’s lifetime. These secondary mutations are thought to occur in Schwann cells or other nerve cell types.
Genetic testing is sometimes necessary to elucidate the type of neurofibromatosis present. However, the diagnosis is often made on physical exam and testing alone.
What to do if you have been diagnosed with NF-2
If you or a family member are diagnosed with NF-2, the first step is consultation with a neurologist or geneticist with a background in neurofibromatosis. Depending upon the findings and severity, you may need a referral to a neurosurgeon to evaluate the need for surgical removal of vestibular schwannomas or other brain tumors. Once stable in terms of growth of brain masses, you may need to see a plastic surgeon specializing in neurofibromatosis to address peripheral nerve dysfunction and symptoms of pain and/or disfigurement. Dr. Panossian is an expert in the fields of neurofibromatosis and facial paralysis reconstruction, offering cutting-edge options for reanimating the face in the wake of NF-2.