What is Neurofibromatosis 2?
Neurofibromatosis 2 (NF2) is a genetic disorder that causes multiple tumors to grow from the nervous system. These tumors are usually benign (meaning noncancerous). The most common tumors found in NF2 grow from the hearing and balance nerve, and are called vestibular schwannomas or acoustic neuromas. Many patients with NF2 will develop vestibular schwannomas on both the left and the right by the age of 30. NF2 patients also can develop other types of tumors including schwannomas from other nerves in the skull base and spine, meningiomas (tumors from the brain lining), gliomas, or ependymomas. Most patients who are diagnosed with a vestibular schwannoma do not have NF2.
What causes it?
NF2 is caused by genetic mutations in a protein called merlin. This protein is found in the cells that provide insulation for nerves in the brain and spinal cord. NF2 is usually inherited in an "autosomal dominant" fashion, where people with the condition are born with one mutated copy of the gene. In other cases, patients can develop new mutations in the NF2 gene with no prior family history.
Why is it a concern?
The most frequent symptoms NF2 initially causes include hearing loss, ringing in the ears (tinnitus), balance dysfunction, weakness of a single part of the body, or seizures. Patients with NF2 can also develop eye disorders.
How is it diagnosed?
Patients with multiple nervous system tumors are diagnosed with NF2 if they have any of the following:
- Vestibular schwannomas on both the left and right
- A one-sided vestibular schwannoma plus 2 of the following: meningioma, glioma, schwannoma, neurofibroma, cataract in the form of posterior subcapsular lenticular opacities or cortical wedge cataract
- A one-sided vestibular schwannoma plus a first-degree relative with NF2
- A first degree-relative with NF2 plus 2 of the following: meningioma, glioma, schwannoma, neurofibroma, cataract in the form of posterior subcapsular lenticular opacities or cortical wedge cataract
Patients who are suspected of having NF2 can be sent for genetic testing.
How is it treated?
Patients who are suspected of having NF2 are typically evaluated with hearing tests, eye exams, MRIs of the brain and spine, as well as genetics consultation. Specific treatments subsequently depends on the location, size, and symptoms caused by tumor growths.
Vestibular schwannomas in patients with NF2 may be treated initially with observation. The decision to proceed with surgery to remove or debulk the tumor is balanced with preserving hearing, balance, and facial nerve function. Management of tumors in other locations face a similar challenge of balancing surgical risks and preventing disability from tumor growth.
In some cases, radiation is required in patients with NF2, however it has been found to be less effective than in patients without NF2. Therapy using medications, such as bevacizumab, is considered with consultation with medical oncologists.