Acoustic neuroma

Overview

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 problems with balance. Another name for an acoustic neuroma is vestibular schwannoma.

An acoustic neuroma develops from the Schwann cells covering the vestibular nerve. An acoustic neuroma is usually slow-growing. Rarely, it may grow quickly and 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 are often 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 nearby nerves controlling facial muscles, known as the facial nerve, and sensation, known as the trigeminal nerve. Blood vessels or 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 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 health care professional if you notice hearing loss in one ear, ringing in your ear or balance problems.

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 problem with a gene on chromosome 22. Typically, this gene produces a tumor suppressor protein that helps control the growth of Schwann cells covering the nerves.

Experts don't know what causes this problem with the gene. Often there is no known cause for an acoustic neuroma. This gene change is inherited in people with a rare disorder called neurofibromatosis type 2. People with neurofibromatosis type 2 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

Neurofibromatosis type 2

The only confirmed risk factor for acoustic neuromas is having a parent with the rare genetic disorder neurofibromatosis type 2. However, neurofibromatosis type 2 only accounts for about 5% of acoustic neuroma cases.

A hallmark characteristic of neurofibromatosis type 2 is noncancerous tumors on the balance nerves on both sides of the head. Tumors also may develop on other nerves.

Neurofibromatosis type 2 is known as an autosomal dominant disorder. This means that the gene related to the disorder 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.
Balance problems.
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.

Diagnosis

An acoustic neuroma is often hard to diagnose in the early stages because symptoms may be easy to miss and develop slowly over time. Common symptoms such as hearing loss also are associated with many other middle and inner ear problems.

After asking questions about your symptoms, a member of your health care team conducts an ear exam. You may need the following tests:

Hearing test, known as audiometry. This test is conducted by a hearing specialist called an audiologist. During the test, sounds are directed to one ear at a time. The audiologist presents a range of sounds of various tones. You indicate each time you hear the sound. Each tone is repeated at faint levels to find out when you can barely hear.

The audiologist also may present various words to test your hearing.
Imaging. Magnetic resonance imaging (MRI) with contrast dye is usually used to diagnose an acoustic neuroma. This imaging test can detect tumors as small as 1 to 2 millimeters in diameter. If MRI is not available or you can't have an MRI scan, computerized tomography (CT) may be used. However, CT scans may miss small tumors.

Treatment

Your acoustic neuroma treatment may vary, depending on:

The size and growth rate of the acoustic neuroma.
Your overall health.
Your symptoms.

There are three treatment approaches for acoustic neuroma: monitoring, surgery or radiation therapy.

Monitoring

You and your health care team may decide to monitor an acoustic neuroma if it's small and isn't growing or if it's growing slowly. This may be an option if the acoustic neuroma causes few or no symptoms. Monitoring also may be recommended if you're an older adult or if you're not a good candidate for more-aggressive treatment.

While being monitored, you'll need regular imaging and hearing tests, usually every 6 to 12 months. These tests can determine whether the tumor is growing and how quickly. If the scans show the tumor is growing or if the tumor causes worse symptoms or other problems, you may need to have surgery or radiation.

Surgery

You may need surgery to remove an acoustic neuroma, especially if the tumor is:

Continuing to grow.
Very large.
Causing symptoms.

Your surgeon may use one of several techniques for removing an acoustic neuroma. The surgery technique depends on the size of the tumor, your hearing status and other factors.

The goal of surgery is to remove the tumor and preserve the facial nerve to prevent paralysis of muscles in your face. Removing the entire tumor may not always be possible. For example, if the tumor is too close to important parts of the brain or the facial nerve, only part of the tumor may be removed.

Surgery for an acoustic neuroma is performed under general anesthesia. Surgery involves removing the tumor through the inner ear or through a window in your skull.

Sometimes removing the tumor may worsen symptoms if the hearing, balance, or facial nerves are irritated or damaged during the operation. Hearing may be lost on the side where the surgery is performed. Balance is usually affected temporarily.

Complications may include:

Leaking of the fluid that surrounds your brain and spinal cord, known as cerebrospinal fluid. Leaking may happen through the wound.
Hearing loss.
Facial weakness or numbness.
Ringing in the ear.
Balance problems.
Persistent headache.
Rarely, infection of the cerebrospinal fluid, known as meningitis.
Very rarely, stroke or brain bleeding.

Radiation therapy

There are several types of radiation therapy used to treat an acoustic neuroma:

Stereotactic radiosurgery. A type of radiation therapy known as stereotactic radiosurgery can treat an acoustic neuroma. It's often used if the tumor is small — less than 2.5 centimeters in diameter. Radiation therapy also may be used if you are an older adult or you cannot tolerate surgery for health reasons.

Stereotactic radiosurgery, such as Gamma Knife and CyberKnife, uses many tiny gamma rays to deliver a precisely targeted dose of radiation to a tumor. This technique offers treatment without damaging the surrounding tissue or making an incision.

The goal of stereotactic radiosurgery is to stop the growth of a tumor, preserve the facial nerve's function and possibly preserve hearing.

It may take weeks, months or years before you notice the effects of radiosurgery. Your health care team monitors your progress with follow-up imaging studies and hearing tests.

Risks of radiosurgery include:
- Hearing loss.
- Ringing in the ear.
- Facial weakness or numbness.
- Balance problems.
- Continued tumor growth.
Fractionated stereotactic radiotherapy. Fractionated stereotactic radiotherapy (SRT) delivers a small dose of radiation to the tumor over several sessions. SRT is done to slow the growth of the tumor without damaging surrounding brain tissue.
Proton beam therapy. This type of radiation therapy uses high-energy beams of positively charged particles called protons. The proton beams are delivered to the affected area in targeted doses to treat tumors. This type of therapy lowers radiation exposure to the surrounding area.

Supportive therapy

In addition to treatment to remove or stop the growth of the tumor, supportive therapies can help. Supportive therapies address symptoms or complications of an acoustic neuroma and its treatment, such as dizziness or balance problems.

Cochlear implants or other treatments can be used for hearing loss.

Coping and support

Dealing with the possibility of hearing loss and facial paralysis can be quite stressful. Deciding which treatment would be best for you also can be challenging. These suggestions may help:

Educate yourself about acoustic neuromas. The more you know, the better prepared you can be to make good choices about treatment. Besides talking to your health care team and your audiologist, you may want to talk to a counselor or social worker. Or you may find it helpful to talk to other people who've had an acoustic neuroma. It may help to learn more about their experiences during and after treatment.
Maintain a strong support system. Family and friends can help you as you go through this challenging time. Sometimes, though, you may find the concern and understanding of other people with an acoustic neuroma especially comforting.

Your health care team or a social worker may be able to put you in touch with a support group. Or you may find an in-person or online support group through the Acoustic Neuroma Association.

Preparing for an appointment

You first may see a health care professional. This person may refer you to a doctor trained in ear, nose and throat conditions. Or you may be referred to a doctor trained in brain and nervous system surgery, known as a neurosurgeon.

Because there's often a lot to talk about during your appointment, it's a good idea to be well prepared. Here's some information to help you get ready and get an idea of what to expect.

What you can do

Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
Make a list of all medicines, vitamins or supplements that you're taking.
Ask a family member or friend to join you, if possible. Sometimes it can be hard to remember all the information provided to you during an appointment. Someone who comes with you may remember something that you missed or forgot.
Write down questions to ask your health care team.

Preparing a list of questions will help you make the most of your time. For an acoustic neuroma, some basic questions to ask include:

What is likely causing my symptoms?
Are there any other possible causes for my symptoms?
What kinds of tests do I need?
What treatment options are available?
Which one do you recommend for me?
What is the likelihood of side effects from each treatment option?
What happens if I do nothing?
Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

In addition to the questions that you've prepared, don't hesitate to ask any that come up during your appointment.

What to expect from your doctor

You'll be asked a number of questions. Being ready to answer them can give you more time to go over any points that you need to clarify. You may be asked:

When did you first begin experiencing symptoms?
Have your symptoms been continuous or occasional?
How bad are your symptoms?
Do you have any family members with an acoustic neuroma?
At its current level, can you hear using the affected ear? For example, can you use that ear on the phone? Does that ear help you tell where sound is coming from?
Do you have regular headaches currently or have you had them in the past?