Every nerve in your body is protected by a layer of tissue called a sheath. A schwannoma is a tumor that grows in the sheaths of nerves in your peripheral nervous system, or the parts of your nervous system that aren’t in your brain or spinal cord. You may hear schwannomas referred to as neurilemomas, neuromas, or neurolemomas.
Most people with schwannomas only have one, but it’s possible to have more. Multiple schwannomas are usually a result of schwannomatosis.
This is the least common type of a rare condition called neurofibromatosis, a genetic disorder that causes tumors in the nervous system. Another form, called neurofibromatosis type 2 (NF2), can also cause schwannomas.
Schwannomas usually don’t produce symptoms until they become large enough to put pressure on the nerves around them. You may feel occasional pain in the area that’s controlled by the affected nerve. Some other common systems include:
- a visible lump under the skin
- sharp, aching, or burning pain
- a pins-and-needles sensation
- muscle weakness
- nighttime pain in back or neck
Depending on where the schwannoma is, you may feel these symptoms in your face, arms, legs, or torso. Your symptoms may change as the tumor gets bigger.
Many schwannomas occur on the nerve that connect your inner ear and brain. This is known as a vestibular schwannoma, or acoustic neuroma. In addition to the symptoms above, an acoustic neuroma can also cause:
- hearing problems in one or both ears
- ringing in one or both ears
- loss of coordination and balance
Aside from NF2 and schwannomatosis, researchers don’t know what causes schwannomas. People with a family history of spinal cancer are more likely to have a spinal schwannoma, which suggests they could be genetic. Exposure to radiation is another possible cause.
Diagnosing schwannomas is hard because their symptoms are similar to those of many conditions. They also grow very slowly, so any symptoms they do produce are usually very subtle if they’re even noticeable.
If you do have symptoms, your doctor will perform an X-ray, ultrasound, CT scan, or MRI scan to pinpoint the affected area. They may also give you a hearing and balance test if they think you may have an acoustic neuroma.
Malignant schwannomas do exist, but they’re very rare. They usually appear in the legs, lower back, and upper arms. They also sometimes occur in the nerves between your legs. When this happens, you might feel pain or discomfort in your bowels or bladder.
Depending on their location and size, schwannomas can also cause permanent nerve damage. For example, acoustic neuromas can sometimes cause permanent hearing loss.
Most problems caused by schwannomas are the result of the tumor becoming large and putting pressure on nearby nerves.
Schwannomas are usually removed with surgery. They can often be scraped off without damaging the nerve. Your recovery time and any remaining symptoms can vary widely based on the size and location of the schwannoma.
If the schwannoma is small and not causing any problems, your doctor may decide to simply monitor the tumor for signs of growth or change. This usually involves regular MRI scans.
If your schwannoma is cancerous or you have other conditions that make surgery dangerous, your doctor may recommend stereotactic body therapy. This is also referred to as stereotactic radiosurgery when it’s used to treat tumors in the brain or spine.
Both treatments send a strong dose of radiation directly to the tumor to shrink it over the course of one to five treatments. It has fewer side effects than traditional radiation, which involves smaller doses of radiation over a longer period of time.
Cancerous schwannomas can also be treated with chemotherapy and immunotherapy medications.
The outlook for people with schwannomas depends largely on the schwannoma’s size, location, and whether or not it’s cancerous. Keep in mind that most schwannomas are harmless and may never produce any symptoms.
Make sure to tell your doctor about any symptoms you do have, as well as any changes in them.