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What

Schwannomatosis is a disease characterized by the development of multiple benign (non-cancerous) tumors that originate from the cells that cover the nerves in the peripheral nervous system (Schwann cells). Schwann cells surround most nerve cells throughout the body, and a tumor that originates from a Schwann cell is called a schwannoma. Schwannomatosis is a member of the family of diseases known as neurofibromatoses. These diseases are characterized by inherited changes in the nervous system resulting in the development of multiple tumors in the nervous system. The tumors of schwannomatosis are unique among the neurofibromatoses because they are always benign (do not spread), while neurofibromas (the tumors of other types of neurofibromatosis) can become malignant.

Who

Schwannomatosis can occur in individuals of all ages, though more than half first show symptoms of the disease between the ages of 20 and 40. The estimated incidence of schwannomatosis is one in two million persons. Males and females are equally affected, and no single race or ethnic group is at an increased risk. Schwannomas are quite common but multiple schwannomas (which is required for the diagnosis of schwannomatosis) are extremely rare.

Signs and Symptoms

The primary symptom of individuals with schwannomatosis is pain in the area of the tumor. These tumors may form anywhere in the body but most commonly grow near the base of the skull, spine, arms, or legs. Approximately one third of patients with schwannomatosis have several tumors all located in one area (i.e. on a single arm or leg or in one particular part of the spine). The pain typically worsens with time as the tumor grows. A mass may be felt at the site of the tumor, but this is not always the case. Only very rarely are neurologic symptoms (memory loss, vision problems, weakness, etc.) seen. The tumors of schwannomatosis grow very slowly and do not spread to other parts of the body. The pain associated with the disease is caused by nerve compression from tumor. It is important to note that an individual with schwannomatosis should not have hearing loss due to a tumor because, as will be explained below, hearing loss is a feature of neurofibromatosis 2 (NF2) rather than schwannomatosis.

Possible Causes

In the vast majority of cases, it seems that schwannomatosis is caused by a mutation in the NF2 gene. This gene is considered a “tumor suppressor gene,” meaning that it normally functions to prevent the development of tumors. When it does not work, however, there is an increased chance that the affected individual will develop some type of tumor (including schwannomas). The NF2 gene is believed to exist on chromosome 22. Interestingly, the mutations found in different tumors taken from the same patient may not necessarily be the same. Most mutations in this gene are thought to be random, but in some cases, the disease can be passed down in families. The mutation exhibits autosomal dominant transmission, meaning that a child only needs to receive a single abnormal copy of the gene from one of his/her parents to be affected. The disease also exhibits incomplete penetrance, meaning that just because an individual has the mutated gene does not mean that he/she will develop the disease. There are other factors that contribute to the development of the disorder.

Diagnosis

Schwannomatosis is diagnosed based on recognition of the clinical features. The main diagnostic criterion is the presence of multiple schwannomas. These tumors can be seen by X-ray, CT (computed tomography), or MRI (magnetic resonance imaging), but MRI seems to provide the best results. The primary hurdle in diagnosis is distinguishing between schwannomatosis and neurofibromatosis 2. The only diagnostic difference between these two diseases is that in NF2 there are tumors in the inner ear, whereas there are none in schwannomatosis. Unfortunately, these inner ear tumors do not always arise until later in life. Therefore, a young child cannot be definitively diagnosed with schwannomatosis, as it may turn out that the disease is actually NF2. Even though we have determined which gene causes many of the symptoms of this disease, no genetic blood test is yet available to see if an individual has the mutation.

Treatment

The treatment for schwannomatosis revolves around symptomatic relief. Treatment usually initially consists of pain medication appropriate for the severity of the pain. If these are not successful, the tumors can usually be removed surgically. Patients with schwannomatosis should be monitored by a pediatric neurologist, a pediatric neurosurgeon, and a geneticist to ensure quality care.

Prognosis

The outlook for an individual with schwannomatosis is very good. Affected children will likely develop several additional tumors over the course of their life and may develop varying amounts of pain as a result. However, with pain medications and surgery (if it is needed), these individuals will live full and healthy lives. Those with schwannomatosis generally experience no loss of function and do not die earlier than those unaffected by the disease.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Children’s Tumor Foundation: Schwannomatosis
This website includes a detailed but easy to understand description of schwannomatosis and schwannomas. It also contains links to other websites, a bulletin board, and a glossary of relevant medical terms. Overall, this is a very valuable resource.

Massachusetts General Hospital Neurofibromatosis Clinic: Schwannomatosis
This website contains a brief description of schwannomatosis, but its real value is in the links to research on neurofibromatosis, support groups, and clinical centers focusing on schwannomatosis and other types of neurofibromatosis.

Neurofibromatosis support
Useful information for related disorders.

March of Dimes
Nicely constructed website with lots of useful general information.

Acoustic Neuroma Association
Support website for patients.

National Institute of Neurological Disorders and Stroke
Up to date information on the latest in research and advances in the neurological disorders.

Google Search for Schwannomatosis

References and Sources

MacCollin M, et al. (2005) Diagnostic criteria for schwannomatosis, Neurology, 64, p. 1838-45. srs.sanger.ac.uk/srsbin/cgi-bin/wgetz?%5Bomim-ID:162091%5D+-e www.emedicine.com/radio/topic7.htm