Nerve sheath tumors develop from Schwann cells, which produce the insulating myelin sheath that covers peripheral nerves. Nerve sheath tumors include schwannomas and neurofibromas. They can develop along any nerve of the head and neck. Some arise on nerves before they exit the skull, and as they grow they can compress normal brain structure. Others arise along the length of the nerve outside the skull, usually causing dysfunction of the specific nerve of origin.
Schwannomas and most neurofibromas grow slowly and are almost always benign. Those that become malignant (less than 1 percent) are known as malignant peripheral nerve sheath tumor, malignant schwannoma, or neurofibrosarcoma.
What are the symptoms of nerve sheath tumors?
Symptoms can include dysfunction of any of the nerves that course through the head and neck. Symptoms also can include the presence of an oral or facial mass, which is often accompanied by pain, loss of hearing, muscle weakness, and atrophy.
What causes nerve sheath tumors?
The cause of most nerve sheath tumors is unknown. However, individuals with a hereditary disorder known as neurofibromatosis type 1 (also known as von Recklinghausen disease) and neurofibromatosis type 2 are predisposed to developing benign and malignant lesions of the nerve sheath. A genetic disorder known as schwannomatosis can lead to the development of schwannomas.
Who is affected?
Nerve sheath tumors affect men and women equally. Most patients are diagnosed between the ages of 30 and 50, although children and elderly patients also can be affected.
How is a nerve sheath tumor diagnosed?
If a patient has symptoms that suggest a nerve sheath tumor, the patient’s physician will work with a team of specialists to confirm the diagnosis. A specialist will conduct a neurological examination, followed by CT a scan and/or an MRI. These tests will help determine the size and location of the tumor. The diagnosis can be confirmed by a biopsy.
What treatments are available?
Surgical removal is the standard treatment for benign and malignant nerve sheath tumors. Removal can be difficult, however, if the tumor surrounds important nerves. Specialists are likely to treat malignant tumors with additional therapies, such as radiation or chemotherapy.