A neurilemmoma is a benign tumor that typically grows on the myelin sheath around nerves in the head and neck, or in the nerves associated with flexing in the arms and legs. A tumor is a lesion caused by the abnormal growth of cells, and a benign tumor is a tumor that is unlikely to progress or become cancerous, as opposed to a malignant tumor. The neurilemmoma is thought to stem from Schwann cells, the cells that line the axons of neurons in the peripheral nervous system and help conduct nerve impulses. The peripheral nervous system includes all nerves outside the brain and spinal cord.
Neurilemmoma patients often don’t notice any symptoms for an average of five years. Once they do begin noticing symptoms, it is usually because the tumor has gotten big enough to see or feel, or large enough to begin compressing the nerve. If the tumor is palpable, it will often be sensitive to the touch. The neurilemmoma may also start causing pain due to nerve compression syndrome, also called compression neuropathy, or more commonly, a pinched nerve. Symptoms of this might include muscle weakness, numbness, pain, or a tingling sensation.
Neurilemmomas are particularly associated with thoracic outlet syndrome, where the nerves between the top rib and the collarbone get compressed. This can cause head and neck pain and numbness in the fingers. Similarly, a tumor along the sciatic nerve can lead to lower back pain, very close symptomatically to a slipped disc. A neurilemmoma can also be the underlying cause of carpal tunnel syndrome or tarsal tunnel syndrome.
While it is considered the most common neurogenic tumor, the exact amount of people with neurilemmomas is unknown. The cause of these tumors is also unknown, though it has been associated with neurofibromatosis type 1 (NF-1), formerly known as von Recklinghausen disease. NF-1 is an inherited disorder caused by a malfunctioning in the gene responsible for cell division. It tends to crop up in people from age 20 to 50 and there does not seem to be any difference in susceptibility based on gender or race.
A neurilemmoma can either take the form of a Schwannoma or a neurofibroma. They are both tumors of the peripheral nervous system and can occur anywhere in the body, but they have slight differences. A Schwannoma occurs only in the lining of the neurons, whereas the neurofibroma has a deeper connection to the nerve, making it a bit more difficult to surgically remove.
A doctor will usually order some scans, such as a computed tomography (CT) scan or magnetic resonance imaging (MRI) to find the tumor and then biopsy the tumor to make sure it’s not malignant. A neurlimmoma does not become cancerous except in extremely rare cases and does not need surgery unless the tumor is causing pain or discomfort. If surgery is needed, the tumor can usually be removed without causing too much damage to the nerve.