Schwannoma

Schwannomas may grow slowly and may be present for months or years without causing symptoms.^[2] Therefore, some people may never experience any symptoms.^[1] Others may experience radiating pain, muscle weakness, tingling, a "pins and needles" sensation, or numbness, but symptoms vary depending on the peripheral nerve which is affected.^[1] The following are examples of symptoms that may occur due to a schwannoma in a specific nerve or area of the body:

• Vestibular nerve (the nerve connecting the ear and brain) - hearing loss, dizziness, balance problems, and/or ringing or buzzing in the ear.^[6]
• Facial nerve - facial paralysis, swallowing problems, difficulty moving the eye, facial pain, and/or loss of sense of taste.^[3]
• Spinal nerve root - symptoms similar to a herniated disk such as radiating arm or leg pain, numbness, tingling, and muscle weakness.^[2][7]
• Arm or leg nerve - localized pain, "pins and needles" sensation, carpal tunnel syndrome (if on a wrist nerve), and tarsal tunnel syndrome (if on an ankle nerve).^[2]

In most cases, it is not known why a schwannoma develops. In some cases, a schwannoma develops in association with an underlying genetic disorder such as neurofibromatosis 2 (NF2), schwannomatosis, or Carney complex. These disorders may cause multiple tumors to develop.^[1][2][6] When a schwannoma is a feature of a genetic disorder, it is caused by a genetic mutation that causes an increased risk for tumor growth.^[4][8]

Schwannomas develop from the Schwann cells which normally form a protective lining around most of the nerves of the peripheral nervous system and also the nerve root. The peripheral nervous system carries signals from the brain and spinal cord (central nervous system) to the muscles and tissues of the body. The nerve root is the first part of nerve leaving the spinal cord and then becomes a peripheral nerve. Schwann cells provide support by wrapping around nerves and nerve roots but also produce the fatty insulation called myelin that surrounds nerves and helps nerve signals travel fast. When a schwannoma grows large enough, it may begin compressing or putting a squeezing pressure on the nerve. It also damages the myelin in that area of the nerve. Together the compression of the nerve and myelin damage cause the symptoms related to schwannomas.^[2][6]  

Most schwannomas are not inherited. The vast majority occur by chance and as a single tumor.^[9]

In some cases, a person develops a schwannoma (or multiple schwannomas) due to having an underlying genetic disorder such as neurofibromatosis 2 (NF2), schwannomatosis, or Carney complex.^[1][2][4] These disorders are inherited in an autosomal dominant manner.^[8][4] This means that having a change (mutation) in only one copy of the responsible gene in each cell is enough to cause features of the condition.

In some cases, a person with an autosomal dominant disorder inherits the mutation from a parent with the disorder. In other cases, the mutation occurs for the first time in a person with no family history of the condition. This is called a de novo mutation.

When a person with a mutation that causes an autosomal dominant disorder has children, each of his/her children has a 50% (1 in 2) chance to inherit that mutation.

A schwannoma may be difficult to diagnosis at first because, depending on its location, the symptoms it causes may be similar to the symptoms caused by other health problems. The following tests may be used to rule out other causes of the symptoms and confirm the diagnosis:^[1][2][10]

• X-ray
• Ultrasound
• CT scan
• Magnetic resonance imaging (MRI) - MRI can help determine if a tumor is on the outside of a nerve or part of a nerve and if it involves other nearby structures
• Biopsy of the tumor to confirm the diagnosis - a biopsy involves removing a small sample of the schwannoma to be examined under the microscope

In some cases, a schwannoma is discovered incidentally (by chance) when a person has imaging studies for another reason.^[1]

Treatment for a schwannoma may depend on the location of the tumor, severity of symptoms, and whether the tumor is benign or malignant (cancerous).^[6] A benign schwannoma causing symptoms or affecting a person's appearance is typically treated with surgery to remove as much as the tumor as possible, while keeping the affected nerve intact. It is often possible to remove the entire tumor. Surgery usually quickly relieves the related symptoms, although if muscle weakness was present before surgery, the muscle may not return to full strength.^[2][6][10]

Treatment for a malignant schwannoma may involve both surgery and radiation therapy.^[2][6][10]