Diseases & Conditions

Acoustic neuroma

Although it's frightening to learn that you have a tumor growing inside your head, it may be somewhat comforting to know that an acoustic neuroma is noncancerous (benign) and usually slow growing. These tumors develop adjacent to your brain on a portion of the eighth cranial nerve, which runs from your brain to your inner ear. Also known as vestibular schwannoma, acoustic neuroma is one of the most common types of brain tumors.

Symptoms of acoustic neuroma, including hearing loss, develop from the tumor pressing on the nerve. But, acoustic neuromas don't invade brain tissue like cancer does.

For some people, an acoustic neuroma remains so small it never causes problems. Treatment options include regular monitoring, radiation and surgical removal.

The signs and symptoms of acoustic neuroma develop from a tumor pressing on cranial nerves.

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. In many cases, however, a small tumor of less than about six-tenths of an inch — about 1.5 centimeters (cm) — may cause no signs or symptoms. Some tumors grow as large as about 2.5 inches (more than 6 cm).

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
• Dizziness (vertigo)
• Loss of balance
• Facial numbness and weakness

The tumor also may press on the brainstem. 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 hearing loss, particularly in one ear, or develop ringing in your ear, dizziness or have trouble with 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.

Your eighth cranial (vestibulocochlear) nerve has three branches, which transmit information from your inner ear to your brain. The cochlear branch carries sound. The superior vestibular branch and the inferior vestibular branch carry information regarding balance. Most acoustic neuromas develop on a vestibular branch.

The cause of acoustic neuromas is unknown. However, the tumors, in rare cases, are an indication of neurofibromatosis 2, a genetic disorder that involves the growth of tumors on the vestibulocochlear nerve. Tumors associated with neurofibromatosis often affect the nerve on both sides (bilateral).

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.

There are three options for managing an acoustic neuroma: observation to determine whether it's growing and how fast, 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 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. This procedure often is performed under local anesthesia.

The purpose of radiosurgery is to stop the growth of a tumor. 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.

Surgical removal
The goal of surgery is to remove the tumor and preserve the facial nerve to prevent facial paralysis and preserve hearing. Performed under general anesthesia, this type of surgery involves removing the tumor 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.