The features of NF2 are restricted almost entirely to tumors of the nervous system (particularly schwannomas) with few skin or non-nervous system related abnormalities. NF2 is generally noticed during young adulthood, most commonly with hearing loss with the development of vestibular schwannomas or with other symptoms secondary to meningiomas or spinal schwannomas. The average age of symptom onset in patients with NF2 is about 20 years, while the average age of diagnosis is at about age 28.
Symptoms and Treatment
NF2, also known as “central NF” is much less common than NF1. The severity of symptoms varies widely from patient to patient.
Other features which may be seen in patients include:
- Meningiomas - tumors arising from the covering of the brain or spinal cord. They occur in about half of patients with NF2. Treatment is surgical unless the tumor is inaccessible, in which case, radiation therapy may be considered.
- Schwannomas - benign tumors arising from the nerves. This is the most prevalent tumor type in NF2. About 98 percent of patients with NF2 develop tumors on the auditory nerve, called vestibular schwannomas. NF2 is usually not diagnosed until late adolescence or early adulthood when symptoms, often hearing loss, associated with these tumors typically occur. In addition to vestibular schwannomas, tumors can occur along other cranial nerves (particularly the trigeminal nerve), spinal roots and peripheral nerves. Auditory symptoms, like hearing loss or ringing in the ears, are usually the first symptom caused by their growth. They are usually slow growing and cause slow deterioration in hearing. Eventually, balance and other cranial nerve functions may become impaired. Brainstem compression and obstructive hydrocephalus (water on the brain) can occur. The decision to treat is highly individualized and depends on the degree of hearing loss, the size of the tumor, the presence and degree of contralateral symptoms and the presence of signs or symptoms of other cranial nerve or brainstem dysfunction. Treatment is usually surgical, though radiation therapy and radiosurgery are also used. Depending on the type and extent of surgery, hearing loss may be worse post-operatively and may be accompanied by facial or other cranial nerve palsies and headache. Small tumors can often be removed with preservation of hearing. Surgery for larger tumors carries a higher risk of deafness and other cranial nerve dysfunction. For patients who are surgically deafened, one option may include the placement of an auditory brain-stem implant (ABI), which is essentially a cochlear implant with a modified proximal electrode. Schwannomas arising from other cranial nerves are generally surgically removed if necessary. Spinal schwannomas occur in up to 80 percent of patients with NF2, though most are small and asymptomatic. They are slow-growing. Surgical resection is performed in patients with severe or progressive symptoms. Peripheral schwannomas can arise on any peripheral nerve and can cause pain or weakness.
- Tumors of the spinal cord - glial tumors, including ependymomas and astrocytomas, are also more prevalent in patients with NF2. Again, treatment is generally primarily surgical, performed when they become clinically significant.
An initial evaluation of persons with NF2 should include neurologic and ophthalmologic examinations, formal audiologic testing, and a gadolinium enhanced MRI of the brain with thin cuts through internal auditory canals for most patients. A spinal MRI should be considered if there are signs or symptoms suggestive of spinal cord injury. Genetic counseling, including consideration of genetic and/or radiologic screening of at risk relatives should also be provided.
Any new neurologic signs or symptoms need to be evaluated promptly in patients with NF2. For most patients, yearly evaluations should include a thorough clinical/neurologic exam, audiologic testing and brain MRI. Serial spine MRIs need only be performed in patients with known large or symptomatic spinal tumors.