Acoustic Neuroma

An acoustic neuroma is a noncancerous tumor that develops on the nerve connecting your inner ear to your brain, causing symptoms like hearing loss, ringing in the ears, and balance problems that often develop gradually over years.

Table of contents

• What Is Acoustic Neuroma?
• Other Names for This Condition
• Signs and Symptoms
• What Causes Acoustic Neuroma?
• How Common Is This Condition?
• How Doctors Diagnose Acoustic Neuroma
• Treatment Options
• Possible Complications
• What to Expect

vestibular schwannoma, acoustic neurinoma, vestibular neuroma, acoustic neurofibroma

What Is Acoustic Neuroma?

An acoustic neuroma is a noncancerous tumor that grows on the main nerve leading from your inner ear to your brain. This nerve is called the vestibular nerve, which is part of your 8th cranial nerve (also called the vestibulocochlear nerve). This nerve has branches that directly affect your ability to hear and maintain your balance.^[1][2]

The tumor develops from Schwann cells, which are special cells that help protect and support other nerve cells in your body. These cells normally cover and insulate the vestibular nerve. When they multiply abnormally, they form the tumor.^[1]

Acoustic neuromas are usually slow growing. As the tumor grows, it puts pressure on the hearing and balance nerves, which causes various symptoms. In most cases, these tumors remain small and manageable. However, rarely, a tumor may become large enough to press against your brain and affect vital functions.^[1]

These tumors are commonly located in an area called the cerebellopontine angle, which is a space near your cochlear and vestibular nerves. The tumor can occur either inside the skull (intracranially) or outside the main brain tissue (extra-axially).^[3]

Other Names for This Condition

Acoustic neuroma is known by several other medical names. The most common alternative name is vestibular schwannoma, which describes where the tumor originates. Healthcare providers may also call it acoustic neurinoma, vestibular neuroma, or acoustic neurofibroma. All these terms refer to the same condition.^[3][4]

Signs and Symptoms

Symptoms of an acoustic neuroma often develop slowly and can be easy to miss in the early stages. It may take years before symptoms become noticeable. The type and severity of symptoms depend on the tumor’s size and location.^[1][4]

The most common early symptom is hearing loss that usually affects only one ear. This hearing loss typically develops gradually over time. Along with hearing loss, early signs often include ringing in your ears (a condition called tinnitus), balance issues, and the sensation that you’re moving or spinning when you’re not (called vertigo).^[2][4]

Because vestibular schwannomas grow very slowly, additional symptoms may develop as the tumor becomes larger. These later symptoms can include facial paralysis or numbness on one side of your face, persistent headaches, nausea and vomiting, changes in your sense of taste, difficulty swallowing, and blurred vision or double vision.^[2]

Some people may also experience problems with limb coordination on one side of the body (called ataxia) or voice changes. These symptoms occur when a large tumor begins to affect nearby structures in the brain.^[4]

What Causes Acoustic Neuroma?

Acoustic neuromas form when Schwann cells multiply abnormally. Normally, these cells support and protect the balance and hearing nerves in your peripheral nervous system (the network of nerves outside your brain and spinal cord). Researchers are not completely sure why these cells begin to multiply and form tumors.^[2]

Most acoustic neuromas occur sporadically, meaning they happen without any obvious cause and affect only one side. However, some cases are linked to a genetic condition called neurofibromatosis type 2 (NF2). This condition is caused by a defect on chromosome 22 at a location called 22q12.2, where the neurofibromin 2 gene is located. This gene is responsible for producing a protein called merlin. Studies have indicated that there may be a predisposing mutation for developing acoustic neuroma.^[3][4]

People with neurofibromatosis type 2 may develop a type of vestibular schwannoma called bilateral acoustic neuroma, which affects the hearing nerves on both sides of the brain. This hereditary form accounts for less than 5% of all acoustic neuromas.^[2][3]

Radiation exposure may increase the likelihood of developing this condition. While there have been concerns about mobile phone radiation, several studies have failed to establish a direct causal relationship between mobile phone radiation and the development of vestibular schwannomas.^[3]

Acoustic neuromas typically affect adults and are usually diagnosed between the fourth and sixth decades of life (roughly ages 40 to 60). However, individuals with neurofibromatosis type 2 tend to present earlier, with the peak incidence occurring in the third decade of life (ages 20 to 30). Although rare, acoustic schwannomas can occur in children.^[3][4]

There is a slight female preponderance, meaning women are affected slightly more often than men. Symptoms can worsen during pregnancy.^[3]

How Common Is This Condition?

Acoustic neuromas are not common tumors. Each year, about 1 in 100,000 people develop an acoustic neuroma. Schwannomas, the broader category that includes acoustic neuromas, account for approximately 8% of all clinically manifested tumors inside the skull.^[2][3]

How Doctors Diagnose Acoustic Neuroma

Diagnosing an acoustic neuroma can be difficult in the early stages because the symptoms may be easy to miss and can be caused by other conditions. Common symptoms like hearing loss are also associated with many other middle and inner ear issues.^[1][4]

If you have persistent or troublesome symptoms, your doctor will start by asking questions about your symptoms and conducting a physical exam, including a thorough ear exam. From there, several tests may be recommended.^[2][5]

A hearing test, known as audiometry, is conducted by a hearing specialist called an audiologist. During this test, sounds of various tones are directed to one ear at a time. You indicate each time you hear the sound, and each tone is repeated at fainter levels to find out when you can barely hear. The audiologist may also use words to test your hearing. Other hearing tests may include an auditory brainstem response test.^[2][5]

Balance tests and a procedure called electronystagmography may also be performed to assess how the tumor is affecting your balance.^[2]

Imaging tests are essential for confirming the diagnosis. 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 cannot have an MRI scan, a CT scan (computed tomography scan) may be done. However, CT scans may miss small tumors.^[2][5]

Treatment Options

Treatment for acoustic neuroma varies depending on several factors, including the size and position of the tumor, how fast it’s growing, the tumor’s location, how it affects your hearing and balance, your age, and your general health.^[2][4][5]

One option is observation or monitoring. If the tumor is small, not growing, and you have no symptoms or only mild symptoms, your healthcare provider may recommend regular MRI scans to look for changes. Treatment is generally only recommended if scans show the tumor is getting bigger. This approach recognizes that many acoustic neuromas grow very slowly or not at all.^[2][4]

Surgery is another treatment option. A surgeon uses small tools to remove all or some of the tumor through a cut in the skull. This procedure is called microsurgery and may be carried out under general anesthetic if the tumor is large or getting bigger. Surgery is the only treatment that can fully get rid of an acoustic neuroma. There are different surgical approaches, and your surgeon will choose the method that’s safest and most effective based on the tumor’s size and location.^[2][4][5]

Stereotactic radiosurgery is a treatment that uses focused beams of radiation to treat the tumor and protect healthy tissue nearby. This treatment may be used for small tumors or for any pieces of a larger tumor that remain after surgery. The goal is to stop the tumor from getting any bigger.^[2][4]

In rare cases, doctors may use chemotherapy. A drug called bevacizumab (sold under brand names such as Alymsys, Avastin, MVASI, or Zirabev) may shrink tumors. For children, it may help them keep their hearing longer. It can also treat radiation side effects called necrosis.^[2]

Vestibular rehabilitation therapy is a type of physical therapy that helps improve balance if surgery affects the nerves that control it. This therapy can be an important part of recovery.^[2]

All treatment options carry some risks. For example, surgery and radiosurgery can sometimes cause facial numbness or an inability to move part of your face (paralysis). It’s important to speak with your specialist about the best option for you and what the benefits and risks are.^[4]

Possible Complications

While rare, an acoustic neuroma may grow large enough to be life-threatening. This happens when it presses on the part of your brain that manages the flow of spinal fluid, potentially causing a life-threatening build-up of fluid in the brain (called hydrocephalus). However, it’s rare for tumors to reach this stage, as many grow very slowly or not at all, and those that grow more quickly can be treated before they become too big.^[2][4]

Even with treatment, symptoms such as hearing loss and tinnitus can persist and affect your ability to work, communicate, and drive. These problems may need additional treatment to help manage them.^[4]

What to Expect

The outlook for people with acoustic neuroma varies depending on the tumor’s size, growth rate, and the treatment chosen. Large acoustic neuromas can be serious, but with modern treatment approaches, many people have good outcomes.^[4]

An acoustic neuroma can occasionally return after treatment. This is thought to happen to around 1 in every 20 people who have had surgical removal. Because of this possibility, you will probably continue having regular MRI scans after any treatment to check if the tumor is growing again or coming back.^[4]

Even after successful treatment, some challenges may remain. Hearing loss and tinnitus may continue, and some people may experience ongoing balance issues. Working with your healthcare team to address these long-term effects is an important part of living with acoustic neuroma.^[4]