Neurofibromatosis Type 2
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Neurofibromatosis type 2 (NF2) is a rare genetic condition characterized by tumors in the peripheral and central nervous system. Several options are available to treat these tumors, including observation, surgical removal, peripheral nerve surgery, stereotactic radiosurgery, chemotherapy, and radiation therapy.
NF2 is one of three genetic conditions that make up a group of disorders known as neurofibromatosis. The two other conditions in the group are neurofibromatosis type 1 (NF1) and schwannomatosis. Neurofibromatosis belongs to a broad group of neurological disorders called neurocutaneous syndromes.
Acoustic neuromas, also called vestibular schwannomas, are the most common tumors associated with NF2. They are benign tumors that grow along the auditory nerve, which connects the inner ear to the brain and provides the ability to hear. Nearly all individuals with NF2 develop bilateral acoustic neuromas by age 30.
Other tumors that may occur include meningiomas, gliomas and peripheral nerve tumors—neurofibromas and schwannomas.
Symptoms
Symptoms can vary depending on tumor type, location and size. Common symptoms include ataxia, tinnitus, vertigo and hearing loss. Additional symptoms may include changes in vision and presence of cataracts.
Diagnosis
A neurological examination is often conducted to evaluate symptoms. This exam consists of assessing hearing, sense of smell, eye movements, sensation, motor function, swallowing, balance and coordination. Also, eye and auditory exams may be performed to evaluate eye health and hearing ability.
Imaging studies are required to detect acoustic neuromas, or other tumors, and in turn diagnose NF2. Either computed tomography (CT) scans or magnetic resonance imaging (MRI) scans can be conducted to visualize any tumors; however, the preferred test is MRI. CT and MRI scans can be conducted with or without contrast enhancement.
A tissue biopsy is needed to confirm the type of tumor.
Also, a blood sample may be obtained for genetic testing to identify a possible NF2 mutation.
Risk Factors
A mutation in the NF2 tumor-suppressor gene causes NF2.
About half of individuals acquire the condition by inheriting a non-working NF2 gene from a parent who has NF2. (The other parent contributes a working NF2 gene.) The remaining half of individuals do not have a family history of this disease; instead, a spontaneous mutation in NF2 occurs at conception.
NF2 is passed along in an autosomal dominant pattern, which means that if a parent has NF2, there is a 50 percent chance his or her offspring will have NF2.
The gene NF2 is especially important to various cells in the central nervous system. In individuals with the condition NF2, each of these cells has only one working copy of the gene NF2. Recall that the other copy was inherited in a non-working state, or a mutation at conception rendered it non-working.
One working copy of the NF2 tumor suppressor gene is actually enough to keep a cell healthy. But spontaneous mutations are a usual part of cell life. When the single working copy of NF2 acquires a spontaneous mutation, there is no working copy as “backup”—now the cell has no working copies of the gene. A tumor begins to form.
Symptoms of NF2 typically become evident during adolescence or in the early 20s, but can arise at any age.
Treatments
At Columbia, our neurosurgeons use the latest techniques and most advanced technology to treat acoustic neuromas, and other tumors associated with NF2, to provide the best possible outcomes.
Treatment depends on the size and type of tumor and also whether the tumor is causing symptoms. If the tumor is asymptomatic, close observation using imaging studies may be recommended in lieu of surgical intervention.
For most brain tumors arising with NF2, the standard treatment is brain tumor surgery to resect the tumor. During surgery, a neurosurgeon temporarily removes a portion of the skull to gain access to the tumor, a procedure called a craniotomy. Our neurosurgeons rely on extensive experience to evaluate each tumor during surgery and to determine how much resection is safe. A neurosurgeon excises as much of the brain tumor as possible while maximally preserving the function of nearby healthy tissue.
In surgery to resect acoustic neuromas, removal of tumorous tissue and protecting the patient’s hearing are simultaneous priorities. Small acoustic neuromas may be treated by surgical resection along with stereotactic radiosurgery—a noninvasive technique in which a highly focused beam of radiation is used to destroy the tumor. Chemotherapy is sometimes also used.
For other brain tumors that may arise with NF2, brain tumor surgery, chemotherapy and/or radiation therapy may be used.
The benign peripheral nerve tumors associated with NF2 can be treated by surgical removal. Our experienced neurosurgeons meticulously dissect the tumor away from the fragile nerve, leaving the nerve intact and protecting its function.