Historically, two unique types of neurofibromatosis have been identified: neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). Schwannomatosis is currently considered a third form of neurofibromatosis.
Schwannomatosis is a disease characterized by the development of multiple benign tumors (schwannomas) that originate from cells that cover the nerves in the peripheral nervous system. Known as Schwann cells, these cells surround most of the nerve cells in the body. A tumor that begins from a Schwann cell is called a schwannoma.
Schwannomatosis is a member of the family of diseases known as neurofibromatosis. These diseases are characterized by the development of multiple tumors in the nervous system. Often in neurofibromatosis type 1 (NF1), the types of nerve cell tumors are different and have the risk to become malignant. In neurofibromatosis type 2 (NF2), schwannomas are typically seen in a specific nerve of the inner ear called the vestibular nerve, which carries information about sound and balance from the inner ear to the brain. Unlike the other forms of neurofibromatosis, the diagnosis of schwannomatosis is made when an individual is found to have multiple schwannomas without the involvement of the vestibular nerve.
Schwannomatosis can occur in individuals at any age; however, the majority of people experience their first symptoms in adulthood between the ages of 20 and 40. Many describe that they have problems with pain and discomfort in the area of the tumor. These tumors can develop anywhere in the body but most commonly develop near the base of the skull, spine, arms or legs. About a third of those affected with schwannomatosis have multiple tumors isolated to a single part of their body, such as a single arm or a specific area of their spine. People with schwannomatosis may experience discomfort or pain at the sites of the growths. The discomfort from these tumors may worsen over time, and is often a result of nerve compression. The treatment for schwannomatosis is focused on pain management, often through prescription medication. If this is not successful, surgery can be performed to remove the tumors.
The diagnosis of Schwannomatosis is made based on clinical findings. The main diagnostic criterion is the presence of multiple schwannomas. Schwannomas can be seen by CT (computed tomography) or Magnetic Resonance Imaging (MRI). The most difficult aspect of making this diagnosis is to be able to distinguish between schwannomatosis and neurofibromatosis type 2 (NF2). The only diagnostic difference between these two diseases is that in NF2, there are tumors on the nerve to the inner ear; there are no tumors on this nerve in schwannomatosis. These inner ear tumors may arise later in life. Therefore, a young child cannot be definitively diagnosed with schwannomatosis, as it may turn out that the disease is actually NF2. Patients with schwannomatosis should be monitored by a neurologist, a neurosurgeon, and a geneticist to ensure quality care.
As schwannomatosis is a newly described disease, the population incidence is not clearly known. It is thought that schwannomatosis affects approximately 1 in 40,000 individuals; however, there is debate that many individuals that were classified as having NF2 or other types of nerve tumor disease actually have schwannomatosis. As we learn more about this disease, we may find it occurs with greater frequency than originally thought.
Schwannomatosis is considered to be a genetic disease. In some families, schwannomatosis follows a clear autosomal dominant inheritance pattern, meaning that if a parent is affected, there is a 50 percent chance that any of their children can develop schwannomatosis in their lifetime. Often, with autosomal dominant conditions, you will see the disease in every generation of a family. In most families, schwannomatosis may skip generations due to a genetic phenomenon called reduced penetrance. Penetrance is a term used to define the percentage of people who will actually have symptoms with a particular genetic disorder. If a genetic disease has complete penetrance, symptoms will always be visible. If a disease has low penetrance, the genetic mutation that causes the condition may be inherited, but not everyone who inherits the mutation will show symptoms. Most patients with schwannomatosis have no affected relatives. For these people where the schwannomatosis is a single occurrence within a family, the risk to have an affected child is approximately 15 percent. Recent research has identified a gene which may be responsible for the development of schwannomatosis in many affected individuals. However, no genetic blood test is yet available on a clinical basis to see if an individual has the genetic mutation that causes this condition.
It is important to remember that often information found on the Internet can be incorrect, biased and sometimes very scary. Non-biased, medically sound information on schwannomatosiscan be found at the Children's Tumor Foundation, http://www.ctf.org/camp/
Comprehensive Neurofibromatosis Clinic
NewYork-Presbyterian Komansky Center
for Children's Health
505 East 70th Street
Helmsley Tower, 3rd floor
New York, NY 10021
Phone: (212) 746-3278
Fax: (212) 746-8137