What You Need to Know
- A schwannoma, which is a type of peripheral nerve sheath tumor, is sometimes called a neurinoma or neurilemoma. It is composed of Schwann cells, which create the lining around nerves and produce myelin.
- A person can have one schwannoma or many. Schwannomatosis is a genetic condition characterized by multiple schwannomas.
- Some schwannomas do not cause symptoms. Others cause pain, numbness, weakness or tingling.
- Schwannomas can become malignant (cancerous)
- Treatment for schwannomas includes observation and monitoring, and surgery for tumors that restrict movement, cause pain or other symptoms, or become cancerous.
What is a schwannoma?
A schwannoma (also known as a neurinoma or neurilemoma) is a type of nerve sheath tumor that is formed by Schwann cells. These cells form the insulating layer around the peripheral nerves.
Schwannomas can grow on peripheral nerves or nerve roots. Peripheral nerves convey electrical signals from the brain and spinal cord to the muscles and organs throughout the body. The nerve root is where the peripheral nerve joins the spinal cord.
Schwannomas can appear in nerves that enable sensation and motion in the arms, legs, face, and even the eyes or skin. When schwannomas grow, they can place pressure on these nerves, causing symptoms.
Schwannoma Versus Neurofibroma
Although both are nerve sheath tumors, there are some differences between a schwannoma and a neurofibroma.
Using a microscope, a doctor can see that the tissues of schwannomas and neurofibromas are different. A schwannoma is made up solely of Schwann cells, while neurofibromas may include other kinds of cells, such as mast cells and the axons of nerves, mingled together with collagen bundles and other material.
What causes schwannomas?
Solitary schwannomas are the most common kind, and most appear spontaneously, for unknown reasons.
However, certain genetic mutations can cause conditions such as schwannomatosis, neurofibromatosis type 2 and Carney complex, all of which are associated with multiple schwannomas. A person can inherit a tendency to form schwannomas from a parent, and can pass the genetic condition to his or her children.
Schwannoma Symptoms and Types
Schwannomas can cause different symptoms based on where they are located.
- One common type of schwannoma is a vestibular schwannoma that grows on the nerves connecting the brain and the inner ear. These schwannomas are usually benign and are almost always present in people with neurofibromatosis type 2. They can cause difficulties with hearing and balance.
- Schwannomas that grow on a nerve in an arm or leg can cause pain, weakness, tingling, “pins and needles” sensations, and carpal tunnel syndrome or tarsal tunnel syndrome.
- Schwannomas can also affect nerves in the face and neck, resulting in facial muscle pain or paralysis, problems swallowing or moving an eye, and loss of the sense of taste. As they grow, schwannomas can become visually apparent and cause cosmetic concerns.
- When a schwannoma grows on a nerve root (where the nerve exists the spinal cord), it can cause symptoms similar to those associated with spinal problems such as a herniated disk. Large nerve root schwannomas in the neck or spine can cause tingling, numbness and weakness along the length of the attached nerves, as well as severe pain, impaired nerve function (including bowel or bladder dysfunction) and even paralysis.
Schwannomas and Cancer
Most schwannomas are benign (noncancerous.) However, in about 5% of cases, a schwannoma can become malignant and become a cancerous soft tissue sarcoma or malignant nerve sheath tumor. Some of these tumors can be aggressive and call for a prompt, comprehensive treatment plan that could include surgery, chemotherapy, radiation therapy or a combination of these approaches.
Schwannomas can cause problems similar to those caused by other, more common conditions, and diagnosing a schwannoma without tests can be challenging.
Based on your description of your symptoms and an examination, your doctor may recommend imaging scans such as a magnetic resonance imaging (MRI) study, computerized tomography (CT), an ultrasound (sonogram) or an X-ray. Sometimes, a doctor will discover a schwannoma when testing a patient for another suspected problem.
If a tumor appears on one of the scans, the doctor may want to collect a biopsy — a sample of the tumor tissue for a pathologist to examine under a microscope.
Your doctor may recommend regular follow-up and observation for schwannomas that are not causing symptoms.
When schwannomas grow large enough to compress nerves or nearby structures or cause disfigurement, surgery can usually remove the tumor with little chance of it returning. Because schwannomas are relatively compact, removing the entire tumor may be possible using conventional surgery. The surgeon opens up the nerve, and using precise microsurgical techniques, separates the schwannoma from the normal nerve tissue and removes it.
Consulting an experienced nerve tumor surgeon is important, since some schwannoma surgical procedures will require nerve repair if the tumor cannot be removed without harming the nerve.
For procedures on schwannomas of the peripheral nerves, nerve function may improve soon after successful surgery, but if the schwannoma affected muscles, they may not heal for several months or for years. In some cases, muscle weakness or dysfunction is permanent.
After surgery for vestibular schwannoma, headaches, hearing and balance problems and facial weakness may persist for several weeks or even months before improving.