Causes and Treatment of Neurofibromatosis Type 2 (NF2)

Neurofibromatosis type 2 (NF2) is a genetic disorder that causes benign (non-cancerous) tumors to grow in the nervous system. It is an autosomal dominant disorder, meaning that you can inherit the gene that causes NF2 from one parent.

NF2 can cause the formation of tumors on the main nerve leading from the inner ear to the brain, causing ringing in the ears and a loss of balance. Tumors that form on the brain or spinal cord can cause headaches, seizures, and other problems.

NF2 can be diagnosed with brain imaging studies and a physical exam. The condition may be routinely monitored if there are no symptoms, but surgery or radiation may be needed if a tumor is growing or symptoms develop.

This article describes the symptoms and causes of neurofibromatosis type 2, including what is involved with the diagnosis and treatment of this uncommon neurological condition.

What Are Symptoms of Neurofibromatosis Type 2?

Neurofibromatosis type 2 causes tumors in different parts of the nervous system but mainly on the vestibulocochlear nerve that carries sensory information from the inner ear to the brain. These tumors, called vestibular schwannomas, typically affect nerves in both ears, causing:

• Hearing loss
• Ringing in the ear (tinnitus)
• Dizziness
• Unsteadiness
• Involuntary eye movement (nystagmus)

NF2 may also cause benign tumors on the brain and spinal cord, known as meningiomas and gliomas, that can lead to:

• Blurred vision
• Double vision
• Headaches
• Loss of smell
• Hearing loss
• Memory problems
• Weakness in the arms or legs
• Seizures

People with NF2 are at an increased risk of cataracts (clouding of the eye's lens). Light-brown skin spots are also characteristic of the disorder.

What Causes Neurofibromatosis 2?

Neurofibromatosis type 2 is a genetic disorder with an autosomal dominant pattern. It involves a mutation of the gene located on chromosome 22, called the NF2 gene.

With an autosomal dominant pattern, only one parent needs to contribute the gene mutation for the child to inherit the disease. In short, if one of your parents has the NF2 gene, you have a 50% chance of getting it, too.

Less commonly, the gene mutation can happen in later life (called a de novo mutation) in someone with no family history of neurofibromatosis type 2.

The NF2 gene encodes the production of a protein called merlin, which can clump together around nerve cells to form benign tumors.

NF2 is a relatively uncommon condition, affecting roughly one of every 40,000 people. The symptoms are typically noticed between the ages of 18 and 22.

The risk of NF2 tumors becoming cancerous is low.

How Is Neurofibromatosis Type 2 Diagnosed?

Central to the diagnosis of neurofibromatosis type 2 is magnetic resonance imaging (MRI). This medical imaging tool is highly sensitive and can readily detect schwannomas, meningiomas, and gliomas. An eye exam would also needed to check for cataracts.

Neurofibromatosis type 2 can be diagnosed if you have any of the following:

• Bilateral vestibular schwannomas (meaning schwannomas in both ears)
• A parent, sibling, or child with NF2 and a single vestibular schwannoma before age 30
• A parent, sibling, or child with NF2 and at least two of the following: a meningioma, glioma, unilateral (one-sided) schwannoma, or cataract
• A single vestibular schwannoma before age 30 with either a meningioma, glioma, schwannoma, or cataract
• Multiple meningiomas and a unilateral vestibular schwannoma before age 30
• Multiple meningiomas with either a glioma, unilateral schwannoma, or cataract
  

Since hearing loss is characteristic of NF2, a hearing test (audiometry) would be performed. Brainstem auditory evoked response (BAER) tests can help determine whether the eighth cranial nerve is functioning properly.

Genetic testing for mutations in the NF2 gene is available for people diagnosed with NF2.

How Is Neurofibromatosis Type 2 Treated?

Scientists have not yet found a way to stop tumor growth in people with neurofibromatosis type 2. Surgery can be used to remove tumors if they are causing pain or affecting your vision or hearing. Radiation treatments can help shrink tumors, particularly those difficult to access with surgery.

If tumors are small and asymptomatic (without symptoms), your healthcare may take a watch-and-wait approach, known as "active surveillance," and only act if the tumor suddenly gets bigger or causes symptoms. In such cases, annual MRIs may be recommended.

Other symptoms such as pain, headaches, or seizures can be managed with medications like nonsteroidal anti-inflammatory drugs (NSAIDs) or anticonvulsants.

Summary

Neurofibromatosis type 2 (NF2) is an uncommon genetic disorder that causes different types of benign tumors in the nervous system. Symptoms include tinnitus, hearing loss, and unsteadiness.

NF2 is an autosomal dominant disorder that you can inherit from one parent. Less commonly, the gene mutation associated with NF2 will develop spontaneously in later life.

The diagnosis of NF2 is based largely on a physical exam and MRI. Treatment may involve active surveillance if tumors are small and asymptomatic; larger tumors may require surgery or radiation.