Schwannomatosis: causes, symptoms and diagnosis

Schwannomatosis belongs to a family of conditions in which schwannomas appear repeatedly. Nerve Tumours UK explains that these are benign tumours arising from the cells that cover and protect nerves, and that anyone can develop a single schwannoma. When several appear, the likely explanations are schwannomatosis or neurofibromatosis type 2 (now often called NF2-related schwannomatosis).

Cancer Research UK calls the non-NF2 form a rare condition in which non-cancerous schwannomas form on the nerve sheath, in particular on the spinal nerves and nerves around the body. Because the nomenclature has changed, you may see the terms NF2-related schwannomatosis and non-NF2-related schwannomatosis used to separate the two.

The two conditions share a tumour type but not the full picture. Nerve Tumours UK says that in schwannomatosis, schwannomas occur infrequently on the hearing and balance nerve and are only found on one side, whereas bilateral vestibular schwannomas are the hallmark of NF2. A single meningioma can occur in schwannomatosis but may be multiple in NF2, and ependymomas and eye problems do not occur in schwannomatosis but are found in NF2.

The NHS describes NF2 as a rare genetic condition in which non-cancerous tumours grow on nerves in the brain, inner ear and spinal cord, typically beginning in the late teens or twenties and often leading to hearing loss. The genetic difference matters because it shapes surveillance, family planning advice and expected outlook.

Pain is usually the dominant problem. Cancer Research UK says the main symptom is pain, and you might also have a lump that may be painful, numbness, weakness and pins and needles. Symptoms usually start in early adulthood but can develop in younger people. Because the tumours sit on different nerves, the pattern varies a great deal from person to person.

• Pain in a limb, the trunk or along the spine, sometimes constant and sometimes in bursts.

• A lump under the skin that may be tender.

• Numbness, tingling or weakness in the area served by the affected nerve.

• Some people have symptoms but no detectable genetic change.

Nerve Tumours UK explains that the genetics are more complicated than in NF1 or NF2. Two genes have been identified: SMARCB1 (also called INI1), found in 2007, and LZTR1, found in 2013. It says mutations are found in 60 to 70 per cent of people from affected families, but only about 20 to 25 per cent of people who are the only person in the family, and that doctors expect other genes to be found.

Most people with schwannomatosis are the only person in their family affected. Where two or more relatives have it, inheritance is dominant, but not everyone carrying the gene develops tumours. Nerve Tumours UK also describes a mosaic presentation in about 30 per cent of patients, where tumours are confined to one area, such as one arm or leg.

Nerve Tumours UK says the diagnosis is considered only after the more likely possibility of NF2 has been excluded. People with suspicious symptoms are usually referred to a specialist neurofibromatosis centre or a regional genetics service, where doctors check the skin and eyes, arrange head and spine MRI scans and offer genetic testing, which may need to be done on both removed tumour tissue and blood.

For someone with at least two schwannomas outside the skin layers, an MRI is used to confirm or exclude NF2. If there are no vestibular schwannomas and no other evidence of NF2, schwannomatosis is considered. The charity says there is no confirmatory blood test at present, and that there can be a period when the diagnosis is unclear, sometimes resolved only by annual MRI scans. Cancer Research UK adds that children with a single schwannoma may also be tested.

There is no cure, and care focuses on controlling symptoms. Cancer Research UK says controlling pain is very important in this condition, and that removing a schwannoma by surgery can also help relieve pain. For NF2-related schwannomatosis the list adds regular check-ups with MRI, hearing and eye tests, surgery and targeted radiotherapy.

Because pain can be difficult, a specialist in pain control is often part of the team. Decisions about operating are individual: the potential benefit for a painful tumour is weighed against the risk of nerve damage, which depends on the nerve involved.

Cancer Research UK says coping with a diagnosis of a rare condition can be especially difficult, and that knowing more about the condition can make decisions easier. Nerve Tumours UK is the national charity that supports people with nerve tumour conditions, and the NHS directs people with NF2 to it as well. The NHS also notes that information about NF2 is passed to a national rare disease registration service, from which people may opt out.