An acoustic neuroma is a slow-growing tumour of the nerve that connects the ear to the brain. This nerve is called the vestibular cochlear nerve. It is behind the ear right under the brain.
An acoustic neuroma is not cancerous (benign), which means it does not spread to other parts of the body. However, it can damage several important nerves as it grows.
Causes, incidence, and risk factors
Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are relatively uncommon.
Symptoms
The symptoms vary based on the size and location of the tumour. Because the tumour grows so slowly, symptoms usually start after the age of 30.
Common symptoms include:
- Abnormal sensation of movement (vertigo)
- Hearing loss in the affected ear that makes it hard to hear
- conversations
- Ringing (tinnitus) in the affected ear
Less common symptoms include:
- Difficulty understanding speech
- Dizziness
- Headache
- Upon waking up in the morning
- Wakes you from sleep
- Worse when lying down
- Worse when standing up
- Worse when coughing, sneezing, straining, or lifting (Valsalva maneuver)
- With nausea or vomiting
- Loss of balance
- Numbness in the face or one ear
- Pain in the face or one ear
- Sleepiness
- Vision problems
- Weakness of the face
Signs and tests
The health care provider may diagnose an acoustic neuroma based on your medical history, an examination of your nervous system, or tests.
Often, the physical exam is normal at the time the tumour is diagnosed. Occasionally, the following signs may be present:
- Drooling
- Facial drooping on one side
- Unsteady walk
- Dilated pupil on one side only (See: Eyes, pupils different size)
The most useful test to identify an acoustic neuroma is an MRI of the head. Other useful tests to diagnose the tumour and tell it apart from other causes of dizziness or vertigo include:
- Head CT
- Hearing test (audiology)
- Test of equilibrium and balance (electronystagmography)
- Test of hearing and brainstem function (brainstem auditory evoked response)
- Test for vertigo (caloric stimulation)
Treatment
Treatment depends on the size and location of the tumour, your age, and overall health. You and your health care provider must decide whether to watch the tumour (observation), use radiation to stop it from growing, or try to remove it.
Many acoustic neuromas are small and grow very slowly. Small tumours with few or no symptoms may be followed, particularly in older patients. Regular MRI scans will be done.
If they are not treated, some acoustic neuromas can damage the nerves involved in hearing and balance, as well as the nerves responsibility for movement and feeling in the face. Very large tumours can lead to a build up of fluid (hydrocephalus) in the brain, which can be life-threatening.
Removing an acoustic neuroma is more commonly done for:
- Large tumours
- Tumours that are causing symptoms
- Tumours that are growing quickly
- Tumours that are growing near a nerve or part of the brain that is more likely to cause problems
Surgery is done to remove the tumour and prevent other nerve damage. Any remaining hearing is often lost with surgery.
Stereotactic radiosurgery focuses high-powered x-rays on a small area. It is considered to be a form of radiation therapy, not a surgical procedure. It may be used:
- To slow down or stop the growth of tumours that are hard to remove with surgery
- To treat patients who are unable to have surgery, such as the elderly or people who are very sick. Removing an acoustic neuroma can damage nerves, causing loss of hearing or weakness in the face muscles. This damage is more likely to occur when the tumour is next to or around the nerves.
Expectations
An acoustic neuroma is not cancer. The tumour does not spread (metastasize) to other parts of the body. However, it may continue to grow and press on important structures in the skull.
People with small, slow-growing tumours may not need treatment. Once hearing loss occurs, it does not return after surgery.
Complications
Brain surgery can completely remove the tumour in most cases.
Most people with small tumours will have no permanent paralysis of the face after surgery. However, about two-thirds of patients with large tumours will have some permanent facial weakness after surgery.
Approximately one-half of patients with small tumours will still be able to hear well in the affected ear after surgery.
There may be a delayed radiation effects after radiosurgery, including nerve damage, loss of hearing, and paralysis of the face.
