Schwannoma
A usually benign tumor of the nerve covering
Quick Facts
- Type: Nerve sheath tumor (usually benign)
- Grows from: Schwann cells around nerves
- Common sites: Limbs, head and neck, hearing nerve
- Main symptoms: Lump, pain, numbness, or weakness
Overview
A schwannoma is a tumor that grows from Schwann cells, the cells that form the insulating sheath around nerves. Most schwannomas are benign (non-cancerous) and grow slowly. Because they arise on a nerve, they can cause symptoms by pressing on or stretching the nerve fibers, even when the tumor itself is not dangerous.
Schwannomas can develop on almost any nerve in the body, including nerves in the arms and legs, the head and neck, the spine, and the hearing and balance nerve, where the tumor is known as an acoustic neuroma. Most occur on their own, but multiple schwannomas can be a sign of an inherited condition such as schwannomatosis or neurofibromatosis type 2.
Symptoms
Many small schwannomas cause no symptoms and are found by chance. When symptoms occur, they depend on which nerve is affected.
- A slowly growing, painless or tender lump
- Pain, tingling, or an electric-shock sensation when the lump is pressed
- Numbness or weakness in the area the nerve supplies
- On the hearing nerve: hearing loss, ringing in the ear, or balance problems
- Depending on location: facial weakness, swallowing trouble, or other nerve-specific symptoms
Schwannomas rarely become cancerous, but a lump that grows rapidly, becomes very painful, or causes fast-worsening weakness should be evaluated promptly.
Causes
Schwannomas form when Schwann cells multiply abnormally to create a tumor. The trigger is often unknown.
- Sporadic schwannomas: Most occur as a single tumor with no clear cause.
- Schwannomatosis: A rare inherited condition that causes multiple schwannomas, often with pain as a main feature.
- Neurofibromatosis type 2 (NF2): A genetic condition that typically causes schwannomas on both hearing nerves.
Schwannomas are not contagious, and single tumors are usually not inherited.
Risk Factors
- Neurofibromatosis type 2 or schwannomatosis
- A family history of these inherited tumor conditions
- Previous radiation exposure to the affected area (an uncommon factor)
Most people with a schwannoma have no identifiable risk factor.
Diagnosis
Diagnosis involves examination and imaging.
- Physical and neurological exam: Checking the lump and the function of the nerve it affects.
- MRI scan: The main imaging test, showing the tumor's size, location, and relationship to the nerve.
- Ultrasound or CT: Sometimes used depending on location.
- Biopsy: A tissue sample may be taken to confirm the diagnosis and rule out a malignant tumor when the picture is unclear.
Treatment
Treatment depends on the tumor's size, location, symptoms, and whether it is growing.
- Observation: Small, symptom-free schwannomas may simply be monitored with periodic scans.
- Surgery: The main treatment when a schwannoma causes symptoms or is enlarging; surgeons aim to remove the tumor while preserving the underlying nerve.
- Stereotactic radiosurgery: Focused radiation can be used for certain tumors, such as some acoustic neuromas, especially when surgery is risky.
- Symptom management: Pain control and physical therapy, particularly in schwannomatosis where pain is prominent.
Most benign schwannomas can be successfully removed, though there is a small risk of nerve injury depending on the location.
Prevention
Schwannomas cannot generally be prevented because they arise from changes in cell growth. For inherited conditions, the focus is on monitoring and early treatment:
- Regular follow-up and imaging for people with neurofibromatosis type 2 or schwannomatosis
- Genetic counseling for affected families
- Prompt evaluation of any new lump or nerve symptom
When to See a Doctor
See a doctor if you notice a new lump, especially one that is tender or sends an electric-shock sensation when pressed, or if you have unexplained numbness, weakness, hearing loss, or ringing in one ear. Seek prompt evaluation for:
- A lump that grows quickly or becomes increasingly painful
- Rapidly worsening weakness or numbness
- New facial weakness, balance problems, or swallowing difficulty
Frequently Asked Questions
Is a schwannoma cancerous?
Most schwannomas are benign and grow slowly, so they are not cancer. A malignant nerve sheath tumor is much rarer; a lump that grows rapidly or becomes very painful should be checked promptly.
What symptoms does a schwannoma cause?
Many cause no symptoms. When they do, a schwannoma may appear as a lump and cause pain, tingling, numbness, or weakness in the area its nerve supplies. On the hearing nerve it can cause hearing loss, ringing, or balance problems.
Do schwannomas need to be removed?
Not always. Small, symptom-free tumors can be monitored with periodic scans. Surgery is recommended when a schwannoma causes symptoms or is growing, and surgeons try to preserve the affected nerve.
Can schwannomas run in families?
Single schwannomas are usually not inherited. Multiple schwannomas can be part of inherited conditions such as schwannomatosis or neurofibromatosis type 2, which warrant genetic counseling and monitoring.
Will surgery damage the nerve?
Surgeons aim to remove the tumor while sparing the nerve, and many people keep normal function. There is a small risk of nerve injury that depends on the tumor's size and location, which your surgeon will discuss.
References
- National Cancer Institute (NCI). Schwannoma.
- Mayo Clinic. Schwannoma.
- MedlinePlus, U.S. National Library of Medicine. Schwannoma.
- National Institute of Neurological Disorders and Stroke (NINDS). Neurofibromatosis.