What Is It?
An acoustic neuroma is a type of benign (noncancerous) brain tumor that grows in the middle ear. It is one of the most common types of benign brain tumors, and is a major cause of hearing loss.
The auditory nerve (also called the eighth cranial nerve) connects the inner ear to the brain. It is responsible for sending information about hearing and balance to the brain. The nerve normally is wrapped in layers of specialized cells called Schwann cells. An acoustic neuroma develops when the Schwann cells that surround the auditory nerve grow at an abnormal rate. This problem sometimes is called an acoustic or vestibular schwannoma. If an acoustic neuroma is not diagnosed or treated, it can grow through the skull bones that make up the middle ear and press on important structures in the brain.
The main symptoms of an acoustic neuroma — dizziness, hearing loss and ringing in the ears (tinnitus) — are caused by the tumor pressing on the auditory nerve. If the tumor grows large enough, it also may press on other nearby nerves and cause weakness, pain or tingling in the face. Although acoustic neuromas are not cancerous, they can become life threatening if they grow so large that they press on parts of the brain that control vital body functions.
No one knows what causes these tumors to develop. In most cases, the tumor grows only on one side of the head, and is diagnosed between the ages of 30 and 50. Acoustic neuromas in children are very rare. People with a hereditary disease called neurofibromatosis have a higher risk of developing acoustic neuromas, and can develop tumors in both ears. About 10 percent of all acoustic neuromas occur in people with neurofibromatosis. Some studies also have linked acoustic neuromas to long-term exposure to loud noises.
Acoustic neuromas generally grow slowly, so the symptoms develop gradually and are easy to miss or misinterpret. The earliest and most common symptoms of an acoustic neuroma are:
- Loss of hearing in one ear (this usually is gradual, but can occur suddenly in some cases)
- Tinnitus, a ringing, buzzing or noisy sound in the ear that may distort normal hearing
Less common symptoms include:
- Loss of balance or clumsiness
- Facial weakness, pain, numbness or tingling
- A feeling of something clogging the ear
- Mental confusion
Because the symptoms of acoustic neuroma are often subtle and slow to develop, they can be missed easily in their early stages. Gradual hearing loss, especially if it occurs only in one ear, always should be checked by a physician.
If your doctor suspects an acoustic neuroma, he or she will perform a thorough examination to look for other conditions that can cause similar symptoms. This usually will include:
- Looking in your ears with a lighted magnifying lens
- Using tuning forks to test your hearing
- Examining your nose, throat and neck
- Testing the nerves in your face
- Checking your balance
Your doctor also may recommend a formal hearing test (audiogram) to determine the type and amount of the hearing loss.
If an examination and hearing test indicate a possible acoustic neuroma, your doctor may order additional tests to confirm the diagnosis. Most commonly, he or she will recommend a magnetic resonance imaging (MRI) scan. MRI uses magnetic waves to create pictures of structures inside the body. These pictures can show whether an acoustic neuroma is present, how big the tumor is, and where it is located.
As an alternative, your doctor may recommend an auditory brain-stem response test, sometimes called evoked potentials or evoked responses. In this test, electrodes are placed on the scalp to measure the brain’s electrical responses to various noises. This test will be abnormal if a tumor is growing along the nerve that carries signals from the ear to the brain.
Most acoustic neuromas grow slowly, taking years before they become large enough to cause symptoms. Since these tumors rarely shrink on their own, they must be treated or observed carefully.
Avoiding loud noises is very important to protect your hearing, and may actually reduce your risk of developing this rare condition. However, most acoustic neuromas cannot be prevented.
Most acoustic neuromas are treated with surgery. The goals of surgery are to remove the tumor completely, but also to preserve hearing and to avoid damage to surrounding brain structures. Occasionally, some of the tumor must be left behind, or hearing must be sacrificed. Choosing a surgeon with experience in treating this condition may improve your chances of good results. Occasionally, the operation will involve more than one surgeon, such as a neurosurgeon (brain surgeon) and an otologist (ear specialist).
Radiation therapy may be a good alternative for people who do not want surgery or for whom surgery may pose too many risks. New technology allows radiation to be focused in one small area, producing minimal damage to surrounding structures. This type of radiation will not remove an acoustic neuroma completely, but may shrink the tumor and prevent further growth or the need for future surgery.
For some patients who have small, slow-growing tumors, it may be reasonable to delay treatment and monitor the growth of the tumor. This is particularly true for the elderly or those in poor health. However, delaying treatment may lead to permanent hearing loss.
All patients who have been diagnosed with an acoustic neuroma require close follow-up, no matter which option is chosen. Patients and their physicians need to pay close attention to symptoms such as hearing loss or worsening balance. Your doctor may recommend periodic hearing tests or MRI scans to look for evidence that your tumor is growing or that it has returned after treatment.
When To Call A Professional
See your physician if you develop new hearing loss, particularly if the hearing loss is only on one side or is accompanied by ringing in the ears.
Acoustic neuromas are not cancerous (malignant) and do not spread to other parts of the body. Once they are treated, is it very unusual for them to grow back.
However, some untreated neuromas can grow very aggressively and cause severe and permanent damage to nerves, ear and brain tissue. Hearing loss and balance problems caused by a tumor may be permanent, despite treatment with surgery or radiation.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.