What is a schwannoma?
A schwannoma is a tumor that develops from the Schwann cells in the peripheral nervous system or cranial nerves. Schwann cells assist conduction of nerve impulses. This type of tumor is usually benign. Schwannomas are sometimes called neurilemomas, neurolemomas, or neuromas. If a schwannoma is malignant (cancer), it may be referred to as a soft tissue sarcoma.
Where are schwannomas typically found?
Schwannomas can be found in the sheath that covers the nerves. They are found in the peripheral nervous system, cranial nerves or the root of a nerve and not in the brain or spinal cord.
A common area for schwannomas is the nerve connecting the brain to the inner ear. This type is called a vestibular schwannoma or an acoustic neuroma.
Cancerous schwannomas most frequently affect the sciatic nerve of the leg, the brachial plexus nerves in the arm, and the group of nerves in the lower back called the sacral plexus.
Symptoms and Causes
What are the symptoms of schwannomas?
Symptoms usually appear when they have grown to the point where they are putting pressure on the nerves near them. Symptoms will vary and are tied to the location of the tumor. Symptoms can include:
- A visible lump
- Muscle weakness
- Pins-and-needles feeling
- Night-time back or neck pain
- Pains that are aching, burning or sharp
Schwannomas near the ear can affect hearing, balance, or cause ringing sensations (tinnitus).
Tumors by the facial nerve can affect swallowing, eye movement, and taste sensations or cause facial paralysis.
In some cases, schwannomas cause no symptoms.
What are the causes of schwannomas?
The cause of schwannomas is not known in most cases. Most often they occur spontaneously. Genetic disorders such as Carney complex, neurofibromatosis 2 (NF2) and schwannomatosis can cause schwannomas.
Who is at risk for developing schwannomas?
Schwannomas can occur at any age. However, diagnoses peak between the ages of 20-50 years. There is no difference between the sexes in terms of incidence of schwannomas. However, women are slightly more likely to develop a schwannoma due to NF2.
There is no difference in the incidence based on ethnic or racial backgrounds. A parent with a genetic disorder causing schwannomas can pass the disorder on to their children.
Diagnosis and Tests
How are schwannomas diagnosed?
Diagnosing schwannomas can be difficult, as they grow slowly. Symptoms are often mild and they are similar to other conditions.
What tests are used in diagnosing schwannomas?
Tests used to diagnose schwannomas include:
Other tests may be done depending on the location, such as balance and hearing tests for schwannomas affecting the inner ear. A biopsy may be completed in order to make a definitive diagnosis.
Management and Treatment
How are schwannomas managed and treated?
Surgery is usually performed to remove schwannomas in the peripheral nervous system, although radiosurgery is commonly used for schwannomas in the head. Since they are found in the sheath surrounding the nerve, the procedure often can be completed without any damage to the nerve except for vestibular schwannomas where hearing is frequently lost after surgery. Smaller benign schwannomas may just be monitored. Other treatments, such as radiation, may be used in some cases. Malignant schwannomas may be treated with immunotherapy and chemotherapy medications as well. If a schwannoma develops on a smaller nerve, it may not be possible to separate the tumor from the nerve. If a schwannoma is not completely removed, a slow-growing recurrence may be noted.
Outlook / Prognosis
What is the prognosis for someone with a schwannoma?
The prognosis may vary depending on the type and location of the schwannoma, as well as whether or not the tumor is cancerous. If muscle weakness occurs in an area affected by a schwannoma, the affected muscle might not regain full strength after the tumor is removed. Hearing loss due to a vestibular schwannoma or its treatment is usually permanent. Large schwannomas have a low recurrence rate. Long-term monitoring and follow-up care may be required.