Schwannoma (Including Acoustic Neuroma)

Schwannomas develop from Schwann cells, which surround and insulate cranial nerves and other nerves. They make up about eight percent of all central nervous system (CNS) tumors. They’re almost always benign (noncancerous) tumors. They can arise from any cranial nerve. When they form on the cranial nerve responsible for hearing and balance near the cerebellum, they’re called vestibular Schwannomas or acoustic neuromas. They can also start on spinal nerves after the point where they have left the spinal cord. When this happens, they can press on the spinal cord, causing weakness, sensory loss and bowel and bladder problems.  

Types & Stages 

Types of Schwannomas include:

• Vestibular Schwannoma (acoustic neuromas). These are the most common types of Schwannomas arising from the nerve that connects the inner ear to the brain. They account for about 6 to 8 percent of all primary brain tumors. These Schwannomas are usually benign and are almost always present in people with neurofibromatosis type 2. They can cause difficulties with hearing and balance.  
   
• Spinal Schwannomas. These are less common than vestibular Schwannomas. They can occur within the spinal canal and may cause symptoms related to compression of spinal nerves. The incidence rate of spinal Schwannomas is not well documented. Still, it’s considered to be lower than that of vestibular Schwannomas.
   
• Schwannomatosis. This is a rare disorder characterized by developing multiple Schwannomas throughout the nervous system, excluding the vestibular nerve. The incidence of Schwannomatosis is estimated to be about 1 in 40,000 individuals.  
   
• Neurofibromatosis Type 2 (NF2). This is a genetic disorder that makes it more likely that people will develop multiple tumors in their nervous system, including Schwannomas, particularly on the cranial and spinal nerves. The incidence of NF2 is approximately 1 in 25,000 to 1 in 40,000 births.

Signs & Symptoms 

A visible or palpable lump can develop at the site of the Schwannoma, especially if it’s growing near the skin. Other symptoms include:

• Intermittent or consistent pain in the area where the tumor is located (although not all Schwannomas cause pain)
• Numbness and tingling sensations in the area of the affected nerve
• Loss of sensation in the area of the affected nerve
• Muscle weakness or changes in reflexes
• Dizziness or balance problems
• Hearing loss or ringing in ears

Schwannomas often grow slowly and may not cause symptoms for years. Because their symptoms can be similar to many other conditions, imaging tests and evaluation by a medical professional are needed to make an accurate diagnosis.

Diagnosis 

Tests and procedures to diagnose a Schwannoma may include:  

• Imaging tests. These may include:  
   
  • Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body.  
     
  • Computerized tomography scan (CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body.  
     
  • Electromyogram (EMG). For this test, your doctor places small needles in your muscles so an electromyography instrument can record the electrical activity in your muscle as you try to move it.
     
• Nerve conduction study. You're likely to have this test along with your EMG. It measures how quickly your nerves carry electrical signals to your muscles.
   
• Biopsy. If imaging tests identify a nerve tumor, your doctor may remove and analyze a small sample of cells (biopsy) from your tumor. Depending on the tumor's size and location, you may need local or general anesthesia during the biopsy.
   
• Nerve biopsy. If you have a condition such as progressive peripheral neuropathy or enlarged nerves that mimic nerve tumors, your doctor may take a nerve biopsy, which is the removal of a small piece of a nerve for examination.

Treatment 

Schwannoma treatment depends on where the abnormal growth is located and whether it’s causing pain or growing quickly. Treatment options include:

• Monitoring. Your doctor may suggest observing your condition over time. Observation may include regular checkups and a CT or MRI scan every few months to see if your tumor is growing.
   
• Surgery. 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. An experienced peripheral nerve surgeon opens up the nerve, and using precise microsurgical techniques, separates the Schwannoma from the normal nerve tissue and removes it.
   
• Radiation therapy. Radiation therapy is used to help control the tumor growth and improve your symptoms. It may be used in combination with surgery.
   
• Stereotactic radiosurgery. If the tumor is near vital nerves or blood vessels, a technique called stereotactic body radiation therapy may be used to limit damage to healthy tissue. With this technique, your doctor delivers radiation precisely to a tumor without making an incision.

Causes & Risk Factors  

Risk factors for Schwannomas include:

• Age. Schwannomas most commonly affect people between the ages of 50 and 60. They rarely occur in children.
   
• Gender. They are slightly more common in women than in men.
   
• A history of radiation treatment. A person who was exposed to radiation is at higher risk of developing these peripheral nerve tumors years later.
   
• Genetic history. They are more common in people with the genetic disorders neurofibromatosis (types 1 and 2) and Schwannomatosis. Schwannomas rarely run in families, but these same genetic disorders in a family may increase a family member’s risk of Schwannoma.

Screening 

There is no routine screening for Schwannoma.