Overview
Acoustic neuroma (vestibular schwannoma)
Acoustic neuroma (vestibular schwannoma)
An acoustic neuroma, also known as a vestibular schwannoma, is a noncancerous tumor. It develops on the balance nerve, known as the vestibular nerve, and on the auditory nerve, known as the cochlear nerve. These nerves lead from the inner ear to the brain, as shown in the top image. The pressure on the nerve from the tumor may cause hearing loss and imbalance. In some cases, the tumor may grow and affect the cerebellum or other brain tissues, as shown in the magnetic resonance imaging (MRI) scan and illustrations above.
An acoustic neuroma is a noncancerous tumor that develops on the main nerve leading from the inner ear to the brain. This nerve is called the vestibular nerve. Branches of the nerve directly affect balance and hearing. Pressure from an acoustic neuroma can cause hearing loss, ringing in the ear and trouble with balance. Another name for an acoustic neuroma is vestibular schwannoma.
An acoustic neuroma develops from the Schwann cells covering the vestibular nerve. A Schwann cell helps protect and support other nerve cells in the body. An acoustic neuroma is usually slow growing. Rarely, it may become large enough to press against the brain and affect vital functions.
Treatments for an acoustic neuroma include monitoring, radiation and surgical removal.
Symptoms
Symptoms of an acoustic neuroma often are easy to miss and may take years to develop. Symptoms may occur because of the tumor's effects on the hearing and balance nerves. The tumor also can put pressure on the facial nerve that directs facial muscles and the trigeminal nerve that affects feeling in the face. Blood vessels or other brain structures also can be affected by an acoustic neuroma.
As the tumor grows, it may be more likely to cause more noticeable or worse symptoms.
Common signs and symptoms of an acoustic neuroma include:
- Hearing loss, usually gradually over months to years. In rare cases, hearing loss can be sudden. Hearing loss usually occurs on one side or is worse on one side.
- Ringing in the affected ear, known as tinnitus.
- Loss of balance or not feeling steady.
- Dizziness.
- Facial numbness and, very rarely, weakness or loss of muscle movement.
Rarely, an acoustic neuroma may grow large enough to compress the brainstem and become life-threatening.
When to see your doctor
See a healthcare professional if you notice hearing loss in one ear, ringing in your ear or trouble with balance.
Early diagnosis of an acoustic neuroma may help keep the tumor from growing large enough to cause complications such as total hearing loss.
Causes
The cause of acoustic neuromas can sometimes be linked to a change to a gene on chromosome 22. Typically, this gene produces a tumor suppressor protein that helps regulate the growth of Schwann cells covering the nerves. Experts don't know what causes this change to the gene. Often there is no known cause. In some people, the gene change is related to a rare condition called NF2-related schwannomatosis, also known as NF2. The condition was previously known as neurofibromatosis type 2. People with NF2 usually have growth of tumors on the hearing and balance nerves on both sides of the head. These tumors are known as bilateral vestibular schwannomas.
Risk factors
NF2-related schwannomatosis
Autosomal dominant inheritance pattern
Autosomal dominant inheritance pattern
In an autosomal dominant inheritance pattern, the changed gene is a dominant gene. It's located on one of the nonsex chromosomes, called autosomes. Only one changed gene is needed for someone to be affected by this type of condition. A person with an autosomal dominant condition — in this example, the father — has a 50% chance of having an affected child with one changed gene and a 50% chance of having an unaffected child.
The only confirmed risk factor for acoustic neuromas is having a parent with the rare genetic condition NF2-related schwannomatosis, also known as NF2. However, only a small number of people with acoustic neuromas have NF2.
A hallmark characteristic of NF2 is noncancerous tumors on the balance nerves on both sides of the head. Tumors also may develop on other nerves.
NF2 is known as an autosomal dominant condition. This means that the gene related to the condition can be passed to a child by just one parent. Each child of an affected parent has a 50-50 chance of inheriting it.
Complications
An acoustic neuroma may cause permanent complications, including:
- Hearing loss.
- Facial numbness and weakness.
- Trouble with balance.
- Ringing in the ear.
Large tumors may press on the brainstem, occasionally preventing the flow of cerebrospinal fluid between the brain and spinal cord. Fluid can build up in your head, a condition known as hydrocephalus. This increases the pressure inside the skull.