Summary
An acoustic neuroma is a slow-growing, non-cancerous (also known as benign) tumor that grows on the nerve connecting the ear to the brain. This nerve, responsible for hearing and balance, can be found behind the ear and directly under the brain.

Find A Specialist
Cedars-Sinai is one of the nation’s leading centers for innovative and aggressive treatment of brain and cranial base tumors, including acoustic neuromas. With state-of-the-art technology and facilities, Cedars-Sinai conducts ongoing scientific research at the Maxine Dunitz Neurological Institute that is translated into practical and effective clinical trials at the Johnnie L. Cochran, Jr., Brain Tumor Center.  Our physicians are committed to putting the patient first. Patients are not numbers, they are people – wives, husbands, mothers, fathers and siblings – and are treated as such with one-on-one consultations and extensive conversations with dedicated specialists. We leave no question unanswered, no emotion unaddressed, no scenario unimagined.  

Causes
While a definitive cause is unknown, acoustic neuromas are relatively uncommon tumors believed to be caused by a defect in a gene that prevents tumors from forming. Researchers are also investigating potential links to excessive exposure to loud noise as well as radiation.

More concretely, acoustic neuromas are linked to the genetic disorder NF2, or Neurofibromatosis type 2. People with NF2 are more likely to develop tumors (neuromas) on the nerves in their brain and spinal cord.

Diagnosing an Acoustic Neuroma
There are three main methods used to diagnose an acoustic neuroma:

1. Hearing Exam: One of the first steps in diagnosis of an acoustic neuroma is to schedule a hearing exam with a hearing specialist (also known as an otologist). Depending on exam results and recommendations from the specialist, further tests might be necessary.

2. MRI: Since Acoustic Neuromas grow so slowly, they are often discovered during a brain scan/MRI intended to diagnose another condition. An MRI (magnetic resonance imaging) test is a non-invasive scan that reveals detailed images of the brain and its surrounding nerves and tissue.

3. CT Scan: While a surefire diagnosis comes from an MRI scan, a CT scan (computed tomography) can also help identify the exact location and size of the tumor. A CT scan uses X-rays to make detailed images of structures inside the body.

Treatment & Risks
While survival rates are very high, early detection of acoustic neuromas offers the best chance for successful treatment. Each patient and tumor is unique and requires a team of specialists that work together to develop a customized treatment plan.  Depending on the location and size of the tumor, your personalized team may include one or more of the following specialists:

• Neurosurgeon: A physician trained in surgery on the nervous system, especially the spine and the brain.
• Neurotologist (also known as an otoneurologist): A specialist in cranial base and ear surgery.
• Radiation oncologist: A physician who specializes in the treatment of cancer patients, using radiation therapy as the main method of treatment.

Although treatment options and techniques have improved, hearing loss and balance disorders continue to be a main consequence of the tumors themselves and the methods used to control and/or remove them. As a result, treatment of an acoustic neuroma is often done in stages to reduce the amount of risk to the patient. Treatment options include observation, Gamma Knife® radiosurgery and surgery. The goals of each individual and combination of treatment methods are to remove the tumor, prevent it from causing further damage and preserve as much hearing and facial nerve function as possible.

1. Observation: Since acoustic neuromas grow very slowly and surgical removal of the tumors poses many risks, often the best treatment is no treatment at all. If the tumor is found when it is very small and causing few, if any, symptoms, or if it is found in an elderly person, physicians may choose to simply monitor the tumor over time.

2. Gamma Knife® Radiosurgery: The Gamma Knife® radiosurgery has emerged as the preferred first choice for many acoustic neuroma cases. While the procedure is technically called “radiosurgery,” it does not remove tumors the same way as conventional, invasive surgery. Technically, it is not a surgery; there is no incision, minimal healing time and no hospital stay is required.

Gamma Knife® radiosurgery is extremely precise because the patient’s head is stabilized during the radiation procedure. The tumor is targeted by 201 tiny, precise beams of radiation that result in a high dose at the site of the tumor but only minimal exposure at any other single point. Radiosurgery can be used alone, especially in the treatment of smaller tumors, or as a follow-up to invasive surgery, treating tumor cells that could not be removed.

Radiosurgery has been found to provide long-term tumor control in 93 percent of cases and according to the Acoustic Neuroma Association, radiosurgery has a 50 to 70 percent chance of preserving useful hearing with minimal risk or permanent facial weakness.

3. Surgery: Acoustic neuroma surgeries can be extensive procedures that require a close teamwork of a neurosurgeon, neurotologist and potentially other surgical specialists. While surgical outcomes have improved with advances in microsurgical tools and imaging technologies, talk to your doctor about whether surgical removal of an acoustic neuroma is an option.  Surgical removal of an acoustic neuroma may not be a preferred choice as the surgery can be difficult, for three reasons:

• Access: Acoustic neuromas exist in tight spaces that are filled with very important blood vessels and nerves. The nerves are covered by an area of dense bone that is difficult to penetrate.
• Location: Acoustic neuromas grow near the brainstem, home to twelve cranial nerves, each responsible for crucial motor and sensory functions, e.g. balance and movement, sight, smell, swallowing, breathing, feeling, etc. Acoustic neuromas occur inside a narrow, bony tunnel called the internal auditory canal. This tiny area is shared by the seventh and eighth cranial nerves, which control facial movement/expression, hearing and balance. Damage to the seventh and eighth cranial nerves may result in permanent loss of hearing and facial paralysis.
• Size: Very large tumors may put pressure on the brainstem and cranial nerves, interrupting the flow of cerebrospinal fluid and threatening crucial body functions. If the resulting build-up of pressure inside the head is not released, it may be life-threatening.

Symptoms
Acoustic neuromas grow very slowly, often going undetected for years. As a result, symptoms typically start between ages 30 and 60, when the tumor becomes large enough to start putting pressure on the nerve connecting the ear to the brain.

Most common symptoms include:
• One-sided hearing loss
• Ringing in the ear (also known as tinnitus)
• Dizziness
• Loss of balance while walking and standing up

Less common symptoms include:
• Weakness of the face
• Numbness of the face
• Sleepiness
• Headache
• Nausea/vomiting