ConditionBrain & nerves
Schwannoma
A schwannoma is a slow-growing, almost always benign tumor that arises from Schwann cells, which form the insulating sheath around nerves. It can grow on any nerve, most often the hearing and balance nerve (acoustic neuroma or vestibular schwannoma), spinal nerve roots, or nerves in the arms and legs. Symptoms depend on location and include hearing loss, a lump, tingling, numbness or pain. Many small schwannomas are monitored. Others are removed surgically or treated with focused radiation.
Also called: Neurilemmoma, neurinoma, nerve sheath tumor, acoustic neuroma (vestibular schwannoma)
At a glance
- What it is
- A benign tumor of the nerve sheath. Malignant change is very rare.
- Common sites
- Vestibular nerve (acoustic neuroma), spinal nerve roots, limb nerves, head and neck.
- Symptoms
- Depend on location: one-sided hearing loss and tinnitus, a painless lump, tingling or pain along a nerve, back pain.
- Associated conditions
- NF2-related schwannomatosis and other schwannomatosis syndromes.
- Diagnosis
- MRI with contrast. Hearing tests for vestibular schwannoma.
- Treatment
- Observation, surgery, or stereotactic radiosurgery.
When to get help
Call 911 or go to the ER
- New weakness in both legs, numbness in the groin or buttocks, or loss of bladder or bowel control
- Severe headache with vomiting, drowsiness or unsteadiness in someone with a known brain tumor
See a doctor within a day or two
- Sudden hearing loss in one ear (see a doctor within days, as steroids may help)
- Progressive weakness, numbness or loss of hand dexterity
- A known schwannoma that is rapidly growing or becoming very painful
Book a routine appointment
- Hearing loss or ringing in one ear only
- A painless lump along a nerve, especially one that causes tingling when tapped
- Persistent unexplained back pain with radiating nerve pain
Where schwannomas occur
| Location | Typical symptoms |
|---|---|
| Vestibular nerve (acoustic neuroma) | One-sided hearing loss, tinnitus, unsteadiness, later facial numbness |
| Spinal nerve roots | Back or neck pain, radiating nerve pain, numbness, weakness |
| Peripheral nerves of the arms and legs | A slow-growing lump, tingling when pressed, sometimes pain |
| Head and neck (other cranial nerves, sympathetic chain) | A neck lump, facial numbness, hoarseness |
| Other (abdomen, chest) | Usually found incidentally on scans |
See acoustic neuroma and spinal tumor for more on those sites.
Causes and risk factors
Most schwannomas occur on their own (sporadic), often from a change in the NF2 gene within the tumor. Inherited conditions raise the risk of multiple schwannomas:
- NF2-related schwannomatosis (formerly neurofibromatosis type 2): schwannomas on both hearing nerves are the hallmark. See neurofibromatosis
- SMARCB1- and LZTR1-related schwannomatosis: multiple schwannomas, often painful, usually sparing the hearing nerves
Previous radiation exposure is another risk factor.
Symptoms
Vestibular schwannoma
- gradual hearing loss in one ear, sometimes sudden
- tinnitus in one ear
- unsteadiness and dizziness
- facial numbness or, rarely, weakness with larger tumors
- headaches and balance problems if very large
Spinal and peripheral schwannomas
- pain along the nerve, often worse at night
- tingling or electric sensations when the lump is tapped (Tinel's sign)
- numbness or weakness in the area supplied
- a firm, movable lump under the skin
Diagnosis
- MRI with contrast: the key test, showing a well-defined tumor along a nerve
- audiology and hearing tests for suspected vestibular schwannoma. Any one-sided hearing loss should prompt MRI
- nerve conduction studies for limb nerves
- biopsy is rarely needed but may be done if imaging is atypical or malignancy is suspected
- genetic testing for people with multiple schwannomas, young age at diagnosis or schwannomas on both sides
Treatment
Observation ("wait and scan")
Small, slow-growing tumors with few symptoms, especially vestibular schwannomas in older adults, are often monitored with MRI every 6 to 12 months initially, then less often.
Surgery
Microsurgical removal is used for growing or symptomatic tumors. Peripheral schwannomas can usually be removed while preserving the nerve, because they grow beside the nerve fibers rather than through them. Surgery for vestibular schwannomas aims to preserve facial nerve function and, where possible, hearing.
Stereotactic radiosurgery
Gamma Knife or similar focused radiation stops tumor growth in most small to medium vestibular and some spinal schwannomas, without open surgery.
Medicines
For NF2-related schwannomatosis, bevacizumab can shrink vestibular schwannomas and improve hearing in some patients.
Outlook
Most schwannomas are benign and slow-growing, and many people live normally with monitoring or after treatment. Outcomes depend on size and location. Hearing loss from vestibular schwannomas is often permanent, even after treatment. Recurrence after complete removal is uncommon. Malignant transformation is extremely rare; malignant peripheral nerve sheath tumors more often arise from neurofibromas.
Frequently asked questions
Is a schwannoma cancer?
Almost never. Schwannomas are benign tumors that grow slowly and do not spread. Malignant change is extremely rare. However, they can cause symptoms by pressing on nerves or nearby structures.
What are the symptoms of a schwannoma?
Symptoms depend on location. Vestibular schwannomas cause hearing loss, ringing and unsteadiness on one side. Spinal schwannomas cause back pain and nerve symptoms. Peripheral schwannomas cause a lump with tingling or pain along the nerve.
Does a schwannoma need to be removed?
Not always. Small tumors without significant symptoms are often monitored with MRI. Removal or radiosurgery is recommended for tumors that grow, cause symptoms or press on important structures.
Can a schwannoma come back after surgery?
After complete removal, recurrence is uncommon. If part of the tumor is left to protect nerve function, it may regrow slowly and need monitoring or radiosurgery.
What causes schwannomas?
Most occur sporadically, often due to a change in the NF2 gene within the tumor cells. People with inherited conditions such as NF2-related schwannomatosis develop multiple schwannomas. Previous radiation exposure also increases risk.
Sources
This guide was written from current patient and clinical guidance, including:
- National Institute on Deafness and Other Communication Disorders: Vestibular Schwannoma (Acoustic Neuroma) and Neurofibromatosis
- American Association of Neurological Surgeons: Acoustic Neuroma
- National Cancer Institute: Schwannoma (NCI-CONNECT)
- MedlinePlus: Acoustic neuroma
- Children's Tumor Foundation: NF2-related schwannomatosis