Schwannomatosis is a rare form of neurofibromatosis that has only recently been identified. The genetic disorder affects less than 1 in 40,000 people, and causes the development of benign tumours — called schwannomas — usually on spinal and peripheral nerves. These tumours develop when Schwann cells, which form the insulating cover around nerve fibers, grow abnormally. Tumour development appears to be primarily related to a change, or mutation, in certain genes that help regulate cell growth in the nervous system. These mutations prevent the genes from making the normal proteins that control cell proliferation, allowing cells to multiply excessively and form tumours. These tumours may cause pain that may be hard to manage. Schwannomatosis is usually diagnosed in adulthood.
Schwannomatosis can be difficult to diagnose because symptoms vary widely among affected individuals, and many of the symptoms are shared by other disorders. For these reasons, it’s important to know that an accurate diagnosis of schwannomatosis can only be made by a physician with expertise in the diagnosis and treatment of neurofibromatosis. Criteria for a clinical diagnosis includes any ONE of the following:
- Two or more non-intradermal schwannomas, one with a pathological confirmation, including no bilateral vestibular schwannoma by high-quality MRI (a detailed study of internal auditory canal with slices no more than 3mm thick). We recognize that some segmental NF2 patients will be included in this diagnosis at a young age and that some schwannomatosis patients have been reported to have unilateral vestibular schwannomas or multiple meningiomas.
- OR - One pathologically confirmed schwannoma or intracranial meningioma, AND an affected first-degree relative (such as a parent or a sibling).
- OR - It will be considered as a possible diagnosis if there are two or more non-intradermal tumours but none has been pathologically proven to be a schwannoma; the occurrence of chronic pain in association with the tumour(s) increase the likelihood of schwannomatosis.
Genetic mutations associated with schwannomatosis can be detected with genetic testing, using DNA extracted from blood or tumour samples. Genetic testing might be appropriate for people who want to confirm a diagnosis or a suspected case of schwannomatosis, or those at risk of developing the disorder who are interested in early detection. However, it’s important to understand that current genetic testing doesn’t reveal a mutation in all affected individuals, and there may be additional genes responsible for the disorder in some people yet to be discovered. For guidance and information about the suitability of genetic testing, it’s important to consult a physician who specializes in the treatment of schwannomatosis or a genetic counselor, who has specialized training in medical genetics and counseling.
Signs of schwannomatosis usually occur between the ages of 30 and 60, though they can occur at any age.
The most common is chronic pain, which can occur anywhere in the body. It is believed to be caused, at least in part, by schwannomas pressing on nerves. In some cases, the pain that people experience is disproportionate to the size of the tumours that are present. Also, the intensity and frequency of pain varies significantly among individuals who are affected. While most people with schwannomatosis experience some degree of pain that requires medical management, a small number of people have only mild pain. Although some people may also experience neurological symptoms, many people with schwannomatosis experience pain as the only symptom for several years before the source of the pain is identified. For this reason, the condition is often difficult to diagnose.
Other signs of schwannomatosis may include:
- Numbness or tingling
- Weakness, including facial weakness
- Bowel dysfunction or difficulty urinating
- Vision changes
There is currently no cure for schwannomatosis, and no medication that has been shown to be effective in treating schwannomas. Management of the condition is based on the specific symptoms a person develops. Surgical intervention to remove schwannomas can occur, depending on a person’s particular case of schwannomatosis. Anytime surgery is considered for a person with schwannomatosis, it’s important that a surgeon experienced in schwannomatosis care be involved to ensure the best possible outcome. In patients for whom surgical removal of tumours isn’t possible, pain management is usually an integral part of care. Patients are best served in an NF clinic where multidisciplinary specialists experienced in schwannomatosis can administer pain management protocols that have been shown to be effective for people with this condition.
The main clinical manifestation of schwannomatosis is the development of schwannomas, distinctive tumours that grow on peripheral nerves. These often slow-growing tumours remain on the outside of the nerve, but they can push the nerve aside or press it against a bony structure or other tissue, causing pain and complications.
Unlike neurofibromas found in people with NF1, schwannomas are typically located deeper inside the body. Some people with schwannomatosis develop tumours throughout their body, while others may have only one or two tumours throughout their lifetime.
Schwannomas are the same type of tumours that develop in people with NF2, although schwannomatosis lacks many of the clinical features common in people with NF2. The most important distinction is that people with schwannomatosis typically don't develop tumours on the vestibular nerve that cause hearing loss in individuals with NF2 (although rare cases have been reported). Also, other types of tumours that can occur in people with NF2 (including meningiomas, ependymomas, and astrocytomas) don’t occur in those with schwannomatosis, with rare exceptions. Features of NF1, such as learning problems and café au lait spots, are also not present in people with schwannomatosis.
Because of the small number of people that have been diagnosed with schwannomatosis, and because of the little amount of information that doctors have about what causes this condition and how to treat it, the International Schwannomatosis Database (ISD) project is proposing to bring together people with this diagnosis and people studying and managing this condition around the world. ISD is collecting limited information on all schwannomatosis patients, their symptoms, and their management and medication. The aim is that the information collected will help improve how patients are cared for, with the goal of understanding more about the symptoms of schwannomatosis and making treatment as effective as possible.
Learn more about the schwannomatosis here.