Acoustic neuroma

Definition

Acoustic neuroma is a noncancerous (benign) and usually slow-growing tumor that develops on the main nerve leading from your inner ear to your brain. Because branches of this nerve directly influence your balance and hearing, pressure from an acoustic neuroma can cause hearing loss, ringing in your ear and unsteadiness.

Also known as vestibular schwannoma, acoustic neuroma is an uncommon cause of hearing loss. Acoustic neuroma typically grows slowly or not at all, but in a few cases it may grow rapidly and become large enough to press against the brain and interfere with vital functions.

Treatment options for acoustic neuroma include regular monitoring, radiation and surgical removal.

Acoustic neuroma

Acoustic neuroma

An acoustic neuroma is a benign tumor that develops on the balance and hearing nerves leading from your inner ear to your brain. These nerves are twined together to form the vestibulocochlear nerve (...

Symptoms

The signs and symptoms of acoustic neuroma develop from the tumor pressing on the adjacent nerves, or nearby blood vessels or brain structures.

As the tumor grows, it may be more likely to cause signs and symptoms, although tumor size doesn't always determine effects. It's possible for a small tumor to cause significant signs and symptoms.

Signs and symptoms may include:

• Hearing loss, usually gradual — although in some cases sudden — and occurring on only one side or more pronounced on one side
• Ringing (tinnitus) in the affected ear
• Unsteadiness, loss of balance
• Dizziness (vertigo)
• Facial numbness and weakness

In rare cases, an acoustic neuroma may grow large enough to compress the brainstem and be life-threatening.

When to see your doctor
See your doctor if you notice any hearing loss, ringing in your ear, or trouble with your balance. Early diagnosis of an acoustic neuroma may help keep the tumor from growing large enough to cause serious consequences, such as total hearing loss or a life-threatening buildup of fluid within your skull.

Causes

The cause of acoustic neuromas — tumors on the main nerve leading from your inner ear to your brain (vestibulocochlear nerve) — appears to be a malfunctioning gene on chromosome 22. Normally, this gene produces a protein that helps control the growth of Schwann cells covering the nerves. What makes this gene malfunction isn't clear. Scientists do know the faulty gene is inherited in about half the cases of neurofibromatosis 2, a rare disorder that typically involves the growth of tumors on the vestibulocochlear nerve on each side of the head (bilateral neuromas).

Acoustic neuroma

Acoustic neuroma

An acoustic neuroma is a benign tumor that develops on the balance and hearing nerves leading from your inner ear to your brain. These nerves are twined together to form the vestibulocochlear nerve (...

Risk factors

Genetic risk of neurofibromatosis 2
The only known risk factor for acoustic neuroma is having a parent with the rare genetic disorder neurofibromatosis 2, but this accounts for only a minority of cases. A hallmark characteristic of neurofibromatosis 2 is the development of benign tumors on the acoustic nerves on both sides of your head, as well as on other nerves.

Neurofibromatosis 2 is known as an autosomal dominant disorder, meaning the mutation occurs on a nonsex chromosome (autosome) and can be passed on by just one parent (dominant gene). Each child of an affected parent has a 50-50 chance of inheriting it.

Other possible but unconfirmed risk factors for acoustic neuroma include:

• Exposure to loud noise
• Childhood exposure to low-dose radiation of the head and neck
• History of parathyroid adenoma, a benign tumor of the parathyroid glands in the neck
• Heavy use of cellular telephones

Autosomal dominant inheritance pattern

Autosomal dominant inheritance pattern

In an autosomal dominant disorder, the mutated gene is a dominant gene located on one of the nonsex chromosomes (autosomes). You only need one mutated gene to be affected by this type of ...

Complications

An acoustic neuroma may cause a variety of complications, including:

• Permanent hearing loss
• Facial numbness and weakness
• Difficulties with balance and clumsy gait

Large tumors may press on your brainstem, preventing the normal flow of fluid between your brain and spinal cord (cerebrospinal fluid). In this case, fluid can build up in your head (hydrocephalus), increasing the pressure inside your skull.

Preparing for your appointment

You're likely to start by seeing your family doctor or a general practitioner. Your doctor may then refer you to an ear, nose and throat specialist (otolaryngologist), a neurologist, a neurosurgeon or an otolaryngologist that specializes in neurological surgeries (neurotologist).

Because there's often a lot of ground to cover during your appointment, it's a good idea to be well prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

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.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, as well as any vitamins or supplements, that you're taking.
• Ask a family member or friend to join you, if possible. Sometimes it can be difficult to soak up all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. For acoustic neuroma, some basic questions to ask your doctor 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 to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous, or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do you have any risk factors for acoustic neuroma?

Tests and diagnosis

Because signs and symptoms of acoustic neuroma are likely to develop gradually and because hearing loss, tinnitus and problems with balance can be indicators of other middle and inner ear problems, it may be difficult for your doctor to detect the tumor in its early stages. Acoustic neuromas often are found during screening for other conditions.

After asking questions about your symptoms, your doctor will conduct an ear exam and may request the following tests:

• Hearing test (audiometry). During this test conducted by a hearing specialist (audiologist), you wear earphones and hear sounds directed to one ear at a time. The audiologist presents a range of sounds of various tones and asks you to indicate each time you hear the sound. Each tone is repeated at faint levels to find out when you can barely hear. The audiologist will also present various words to determine your hearing ability.
• Brainstem auditory evoked response (BAER). This test checks hearing and neurological functions. Electrodes on your scalp and earlobes capture your brain's responses to clicking noises you hear through earphones and record the responses on a graph.
• Electronystagmography (ENG). This test evaluates balance (vestibular) function by detecting abnormal rhythmic eye movement (nystagmus) often present with inner ear conditions. The test measures your involuntary eye movements while stressing your balance in various ways.
• Scans. Magnetic resonance imaging (MRI) or computerized tomography (CT) scans of your head can provide images that confirm the presence of an acoustic neuroma.

Treatments and drugs

There are three options for managing an acoustic neuroma: periodic monitoring, radiation and surgical removal.

Monitoring
If you have a small acoustic neuroma that isn't growing or is growing slowly and causes few or no signs or symptoms, you and your doctor may decide to monitor it, especially if you're an older adult or otherwise not a good candidate for treatment.

Your doctor may recommend that you have regular imaging and hearing tests, usually every six to 12 months, to determine whether the tumor is growing and how quickly. If the scans show the tumor is growing or if the tumor causes progressive hearing loss or other difficulties, you may need to undergo treatment.

Stereotactic radiosurgery
Stereotactic radiosurgery, such as gamma-knife radiosurgery, enables doctors to deliver radiation precisely to a tumor without making an incision. The doctor attaches a lightweight headframe to your numbed scalp. Using imaging scans, your doctor pinpoints the tumor and then plots where to apply the radiation beams.

The purpose of radiosurgery is to stop the growth of a tumor. It's generally an option if you have a small tumor or if you're not a candidate for surgery. It may also be used for residual tumors — portions of a tumor that traditional brain surgery can't remove without damaging brain tissue.

It may take weeks, months or years before the effects of radiosurgery become evident. Your doctor will monitor your progress with follow-up imaging studies and hearing tests. Risks of radiosurgery include hearing loss, facial weakness and balance problems.

Surgical removal
There are several techniques for removing an acoustic neuroma, but in general the goal of surgery is to remove the tumor, preserve the facial nerve to prevent facial paralysis and preserve hearing as much as possible. Performed during general anesthesia, surgery for an acoustic neuroma involves removing the tumor through the inner ear or through an incision in your skull. You may need to stay in the hospital from four to six days after the surgery, and recovery may take six weeks or more.

Surgery can create complications, including worsening of symptoms, if certain nerve or cranial structures are affected during the operation. These risks are often based on the size of the tumor and the surgical approach used:

• Leakage of cerebrospinal fluid through the wound
• Hearing loss
• Facial weakness
• Ringing in the ear
• Balance problems
• Persistent headache

Coping and support

Dealing with the possibility of hearing loss and facial paralysis and deciding which treatment would be best for you can be quite stressful. Here are some suggestions you may find helpful:

• Educate yourself about acoustic neuroma. The more you know, the better prepared you'll be to make good choices about treatment. Besides talking to your doctor and your audiologist, you may want to talk to a counselor or medical social worker. Or you may find it helpful to talk to other people who've had an acoustic neuroma and learn more about their experiences during treatment and beyond.
• Maintain a strong support system. Family and friends can help you tremendously as you go through this difficult time. Sometimes, though, you may find the concern and understanding of other people with acoustic neuroma especially comforting. Your doctor or a medical social worker may be able to put you in touch with a support group. Or you may find a real or virtual support group through the Acoustic Neuroma Association.