Acoustic neuroma (vestibular schwannoma)

Overview

An acoustic neuroma, now called vestibular schwannoma, is a tumor that develops on the main nerve leading from the inner ear to the brain. These tumors are considered benign, meaning they are not cancerous and they do not spread to other parts of the body. The affected nerve is called the vestibulocochlear nerve. There is one on each side of the head. The vestibulocochlear nerve directly affects balance and hearing. Growth from an acoustic neuroma can cause hearing loss, ringing in the ear and balance problems.

Acoustic neuroma can affect both ears but usually affects just one. Acoustic neuroma may cause numbness or weakness in the muscles on the affected side of the face.

Acoustic neuromas are a type of peripheral nerve tumors. They form from Schwann cells, which help protect and support nerve cells in the body, including the vestibular nerve. The vestibular nerve is part of the peripheral nervous system. Although acoustic neuromas grow inside the skull, close to the brainstem, they do not arise from brain tissue and are not classified as central nervous system tumors. Acoustic neuromas may sometimes be referred to as a type of benign brain tumor because of their location, but technically they are not brain tumors.

Acoustic neuromas usually are slow growing. Rarely, they may become large enough to press against the brain and affect vital functions.

Acoustic neuroma is a rare type of benign tumor. Each year, fewer than 1 in 20,000 people are diagnosed. The risk of developing acoustic neuroma increases with age. About 1 in 5,000 people over age 70 are diagnosed each year.

Treatments for acoustic neuroma include monitoring, radiation and surgical removal.

Symptoms

Symptoms of an acoustic neuroma, now called vestibular schwannoma, often are easy to miss and may take years to develop, as these tumors grow very slowly. Acoustic neuromas usually grow at a rate of about 1 millimeter a year. That is about the thickness of a credit card. Some may grow a little faster. But it's possible for some to stay the same size for years.

Acoustic neuroma symptoms may happen because of the pressure on the vestibular-cochlear nerve from the tumor. The tumor also can put pressure on the facial nerve that directs facial muscles and the trigeminal nerve that affects feeling in the face. This can lead to numbness in the face or difficulty moving the face. Acoustic neuroma generally doesn't cause neck pain. Blood vessels or other brain structures also can be affected by an acoustic neuroma.

As the tumor grows, symptoms may become more noticeable or may worsen.

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.

Hearing loss and acoustic neuroma

Hearing loss related to acoustic neuroma is considered sensorineural hearing loss. This means that the hearing loss is caused by damage to the inner ear or the nerves responsible for hearing, rather than some sort of buildup or blockage that affects hearing.

There can be a particular pattern to hearing loss caused by acoustic neuroma. Most people with an acoustic neuroma lose hearing in just one ear. About 9 out of 10 people with acoustic neuroma experience this.

Hearing loss that's related to acoustic neuroma often starts with trouble hearing higher pitched sounds. Difficulty hearing usually gets worse over time. For some people, hearing fades slowly over time. For others, it may decline more suddenly. Sudden hearing loss is rare. Sometimes hearing can partly come back. But typically hearing loss continues to decline, even if the tumor itself is not growing.

People with hearing loss from acoustic neuroma may find that they:

• Rely more on one ear to listen.
• Ask people to speak into their "better" ear in conversations.
• Find it hard to tell where voices are coming from.
• Struggle to follow conversations in crowded rooms.
• Feel that voices sound unclear or muffled even when the volume seems loud enough.
• Have ringing in the ears, called tinnitus.

Typically, acoustic neuroma tumors don't cause symptoms often seen with other brain tumors, such as headaches, memory loss, neck pain or thinking difficulties. These symptoms are rare and generally occur only if the tumor becomes large enough to press on nearby brain structures.

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

Experts don't really understand what causes acoustic neuroma, now called vestibular schwannoma. In most people with an acoustic neuroma, there is no clear cause.

In some people, the tumor is linked to a change in a gene on chromosome 22. This gene makes a protein that helps control the growth of Schwann cells, which cover and protect nerves. When the gene doesn't work properly, these cells can grow out of control and form a tumor.

The gene change may be related to a rare condition called NF2-related schwannomatosis, also known as NF2. The condition used to be known as neurofibromatosis type 2. People with this condition usually have tumors on the hearing and balance nerves on both sides of the head. These tumors are known as bilateral vestibular schwannomas.

Risk factors

Acoustic neuroma, now called vestibular schwannoma, has one confirmed risk factor.

NF2-related schwannomatosis and acoustic neuroma risk

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 feature of NF2 is the growth of acoustic neuromas on the vestibulocochlear nerve on both sides of the head. People with NF2 also may develop tumors on other nerves.

NF2 is known as an autosomal dominant condition. This means that the gene related to the condition can pass to a child from just one parent. Each child of an affected parent has a 50-50 chance of inheriting the gene.

Noise exposure and acoustic neuroma risk

Research shows that being around loud noise for many years may affect more than your hearing. It also may be linked to a slightly higher chance of developing an acoustic neuroma. The overall risk is still low. But these findings suggest that long-term noise exposure might influence your health in more ways than just causing hearing loss.

Complications

If an acoustic neuroma, now called vestibular schwannoma, grows larger or is left untreated, it can lead to complications. The most common complications involve hearing loss and balance issues. But larger tumors also may affect nearby nerves and brain structures, causing more serious health issues.

Common in many acoustic neuromas

• Hearing loss in one ear that is usually permanent.
• Ringing in the ear, also called tinnitus.
• Balance trouble or unsteadiness, sometimes with brief periods of vertigo.

More likely with large or untreated acoustic neuromas

• Facial numbness when the trigeminal nerve is affected, and facial weakness when the facial nerve is involved.
• Headaches or pressure caused by crowding of the brainstem.
• Worsening balance and walking difficulties, also called ataxia.
• Hydrocephalus, a buildup of fluid in the skull that can occur when a large acoustic neuroma blocks the flow of cerebrospinal fluid between the brain and spinal cord. Hydrocephalus raises pressure inside the head and can lead to upset stomach, vomiting, sleepiness or vision changes.
• Swallowing or voice changes, which may occur rarely if very large tumors affect lower cranial nerves.

Special situations

• In NF2, tumors can occur on both sides of the head, leading to hearing loss in both ears.

Diagnosis

An acoustic neuroma, now called vestibular schwannoma, may be difficult to diagnose in the early stages since the symptoms develop gradually and can be overlooked. Common symptoms such as hearing loss also are associated with many other middle and inner ear issues.

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

• Hearing test. Known as an audiogram or audiometry, this test is conducted by a hearing specialist called an audiologist. During the test, sounds of various tones are directed to one ear at a time. You indicate each time you hear the sound. Each tone is repeated at fainter levels to find out when you can barely hear. The audiologist also may use words to test your hearing. A hearing test by itself can't confirm an acoustic neuroma. But it is often one of the first steps healthcare teams use to investigate hearing loss or ringing in the ears. If the test shows certain patterns, an MRI may be ordered to look for an acoustic neuroma.
• Imaging. MRI with contrast 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, a CT scan may be done. However, CT scans may miss small tumors.

Because other conditions, such as Meniere's disease, can cause similar symptoms, testing is especially important. A hearing test helps identify patterns of hearing loss, while imaging like MRI or CT can detect whether a tumor is present. Together, these evaluations help doctors to accurately distinguish between the two conditions.

Treatment

Treatment for an acoustic neuroma, now called vestibular schwannoma, usually cannot bring back hearing that has already been lost. But if the tumor is found early, surgery or radiation may sometimes help keep the hearing you have. If much of your hearing is already gone, your care team may talk with you about ways to manage the loss. These options may include hearing aids and cochlear implants. In rare cases, a special device called an auditory brainstem implant, which sends sound signals directly to the brain, may help.

Your acoustic neuroma treatment may vary, depending on:

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

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

Monitoring

You and your healthcare team may decide to monitor an acoustic neuroma if it is small and not growing or if it is growing slowly. Also called watchful waiting, 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 such as surgery.

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, you may need to have surgery or radiation.

Surgery

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

• Continues to grow.
• Is very large.
• Causes symptoms.

Surgeons can use different techniques to remove an acoustic neuroma. Usually, acoustic neuroma surgery involves a craniotomy. This is a surgery that removes part of the skull. Several different types of craniotomy approaches may be used to remove an acoustic neuroma. The approach depends on the tumor's size, your hearing and other individual factors.

Surgeons use three main approaches for acoustic neuroma craniotomy surgery:

• Retrosigmoidal. Also called suboccipital, this is the most common approach, made through an opening behind the ear. It can be used for tumors of many sizes and sometimes allows hearing preservation.
• Translabyrinthine. This is done through the inner ear bone. This approach sacrifices hearing but gives the surgeon a wide view to safely remove larger tumors and protect the facial nerve. This may be recommended when significant hearing is already lost.
• Middle fossa. This is done through a small opening above the ear. It's often chosen for small tumors when hearing preservation is the main goal.

The main goals of surgery are to remove as much of the tumor as possible and to preserve the facial nerve, which controls the muscles in the face. In some cases, complete removal is not possible. If the tumor is very close to the brainstem or facial nerve, the surgeon may leave a small portion behind to avoid serious complications.

Before surgery, you may have a brain MRI. MRI is the preferred imaging test because it shows the exact size and location of the tumor and its relationship to nearby nerves and brain structures. This information helps your surgeon plan the safest and most effective approach.

Surgery is done under general anesthesia. The tumor is removed either through the inner ear or through an opening in the skull, depending on the chosen surgical approach.

As with any surgery, there are some risks. Hearing loss on the side of the tumor is possible. Balance issues are common right after the procedure, but these usually improve with time. In some cases, the hearing, balance or facial nerves may be irritated or damaged during surgery, which can lead to lasting changes.

Complications of surgery may include:

• Cerebrospinal fluid CSF) leak. Leaking may happen through the area where the surgery was performed.
• Hearing loss.
• Facial weakness or numbness.
• Ringing in the ear, also called tinnitus.
• Trouble with balance.
• Persistent headache.
• Rarely, infection of the cerebrospinal fluid, known as meningitis.
• Very rarely, stroke or brain bleeding.

Recovery after acoustic neuroma surgery varies depending on the tumor's size and the surgical approach. Hospital stays are usually 3 to 7 days. You may need several weeks at home to rest. Balance troubles often get better within weeks to months as the brain adapts. Fatigue can last for several months. Full recovery may take weeks to months, though some nerve-related changes, such as hearing loss, are permanent.

Radiation therapy

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

• Stereotactic radiosurgery is a form of highly focused radiation therapy often used to treat small acoustic neuromas, usually less than 2.5 centimeters in size. That's about the size of a peanut. It also may be recommended if you are an older adult or if health conditions make surgery too risky.
• Fractionated stereotactic radiotherapy, also called SRT, is another type of radiation treatment for acoustic neuroma. It gives small doses of radiation over several sessions to slow the tumor's growth. This helps protect nearby healthy brain tissue.
• Proton beam therapy is another kind of radiation treatment for acoustic neuroma. It uses tiny particles called protons to target the tumor. This method lowers the amount of radiation that reaches healthy areas of the brain.

How is Gamma Knife surgery used to treat acoustic neuroma?

Gamma Knife is one of the most common forms of stereotactic radiosurgery. It uses many small beams of gamma rays to deliver a precise dose of radiation directly to the tumor. Other systems, such as CyberKnife and linear accelerator based radiosurgery, work in a similar way by shaping multiple beams of radiation so they meet at the tumor. This allows treatment without an incision and helps protect the surrounding brain and nerves.

The goal of radiosurgery is to stop the tumor from growing, preserve facial nerve function, and in some cases, preserve hearing. The effects happen slowly, so it may take weeks, months or even years before changes are seen. Your healthcare team monitors your progress with follow-up MRI scans and hearing tests.

Risks and side effects of radiosurgery may include:

• Changes in hearing, including hearing loss.
• Ringing in the ear, also called tinnitus.
• Weakness or numbness in the face.
• Poor balance.
• The possibility that the tumor continues to grow and needs additional treatment.

Outcomes after surgery or radiosurgery for acoustic neuroma

Research looking at many studies shows that both surgery and radiosurgery are effective treatments for acoustic neuroma. Here's what people should know:

• Tumor control. Both surgery and radiosurgery are effective at controlling tumor growth. For smaller tumors, the results are similar. For larger tumors, surgery offers better long-term control.
• Hearing. Hearing loss is common after either treatment. Radiosurgery tends to preserve hearing in more people than surgery does, especially when the tumor is small.
• Facial nerve function. Right after surgery, some people may experience facial weakness, though most recover over time. Radiosurgery is more likely to preserve facial nerve function overall.
• Other symptoms. Surgery is more likely to improve symptoms such as tinnitus, vertigo, imbalance and facial numbness. Radiosurgery is less likely to improve these symptoms but generally causes fewer new nerve problems.

Can acoustic neuroma grow back after treatment?

Yes, acoustic neuroma sometimes can return after treatment. The risk depends on how it was treated.

• After surgery. If the tumor is removed completely, regrowth is rare, usually less than 5%. But when part of the tumor is left behind to protect nearby nerves or the brainstem, the chance of regrowth is between 10% and 20%.
• After radiosurgery. Treatments such as Gamma Knife and CyberKnife are designed to stop the tumor from growing, not to remove it. Most tumors remain stable or shrink, but in about 5% to 10% of cases, the tumor may continue to grow or regrow later.

Follow-up after acoustic neuroma treatment

Regular MRI scans are recommended after either surgery or radiosurgery. These scans help check whether the tumor is stable or if additional treatment is needed.

Can acoustic neuroma shrink on its own?

Most acoustic neuromas grow slowly. Some stop growing for years. Rarely, studies have shown that an acoustic neuroma may shrink slightly without treatment. But this is not common, and it's not possible to predict which tumors might do this. For this reason, regular MRI scans are important if you and your care team choose monitoring, also called observation or watchful waiting, for acoustic neuroma.

What are the risks of untreated acoustic neuroma?

If left untreated, an acoustic neuroma can continue to grow and cause permanent complications. These include hearing loss (usually in one ear), ringing in the ear and problems with balance. Larger tumors may press on nearby nerves, leading to facial numbness or weakness. In rare cases, very large tumors can block the flow of cerebrospinal fluid and cause hydrocephalus, a dangerous buildup of fluid and pressure in the brain.

Supportive therapy

In addition to treatment to remove or stop the growth of the tumor, supportive therapies can help reduce your symptoms. The therapies help with dizziness, trouble with balance or other complications. For hearing loss, you can use cochlear implants or other treatments.

Lifestyle and home remedies

No natural remedies, vitamins or lifestyle changes can shrink or cure an acoustic neuroma, now called vestibular schwannoma. Because this tumor grows from Schwann cells on the nerve responsible for hearing and balance, it requires medical monitoring and sometimes treatment such as surgery or radiosurgery. Healthy habits such as reducing noise exposure, managing stress, eating well and staying active can support overall wellness, but they do not stop tumor growth.

Coping and support

Dealing with the possibility of hearing loss and facial paralysis can be quite stressful. Deciding which treatment approach is right 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 choices about treatment. Besides talking to your healthcare 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. You also might find the concern and understanding of other people with an acoustic neuroma especially comforting. A member of your healthcare team or a social worker may be able to put you in touch with a support group. Or you can find an in-person or online support group through the Acoustic Neuroma Association.

Preparing for an appointment

You first may see a healthcare 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. Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as fasting before having a specific test. Make a list of:

• 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 healthcare 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 some 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 your symptoms begin?
• Have your symptoms been constant or off and on?
• How bad are your symptoms?
• Do you have any family members with an acoustic neuroma?
• Can you hear with 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?