Acoustic Neuroma

Vestibular Schwannomas - commonly called by the misnomer, acoustic neuroma - are benign growths arising from the balance nerve. Because they are benign, the do not metastasize, or spread to other parts of the body. They are uncommon, and occur in approximately 10 people per million per year in the United States. They tend to be found in patients older than 40 years.

The vast majority (95%) of these tumors are sporadic, meaning they are not passed on through genes. Sporadic tumors occur in only one ear, and there are no known risk factors. Rarely these tumors are associated with a genetic disease called Neurofibromatosis Type II. Patients with Neurofibromatosis develop tumors at a younger age, usually have tumors on both sides and also have other manifestations, including benign tumors of the brain and dura (the covering of the brain).

Symptoms

Vestibular Schwannomas are generally slow growing (less than 3 millimeters per year) and may not grow at all if followed over time. However, tumor growth is not predictable, and some tumors grow more rapidly. When tumors are small they may give no symptoms or very subtle symptoms, such as a slight hearing loss or a noise in the ear (tinnitus). When tumors grow, they begin to cause injury to the hearing nerve and balance nerve, by compressing them. Patients may experience severe hearing loss (either suddenly or progressively over a period of years) or balance problems. Large tumors may compress the brainstem and result in headaches and other symptoms of increased intracranial pressure. Symptoms don't correlate well with size. Some patients with very small tumors may have obvious symptoms and likewise, some patients with large tumors may have no symptoms at all.

Diagnosis

The diagnosis of Vestibular Schwannoma is made by history, hearing tests, and MRI scan. Gadolinium is a special contrast agent used during the MRI to allow visualization of the tumors. With good technique, MRI will show tumors as small as 2-4 millimeters.

MRI showing 2mm Vestibular Schwannoma in right internal auditory canal. MRI showing bilateral Vestibular Schwannomas
MRI showing 2mm vestibular schwannoma in right internal auditory canal. MRI showing bilateral vestibular schwannomas.

How is vestibular schwannoma treated?

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The goal of treatment for benign tumors is to eradicate the tumor while preserving form and function. This holds true for Vestibular Schwannomas as well. There are three treatment options for patients with a Vestibular Schwannoma, observation, radiotherapy, and surgery. Which option is best for each individual must be carefully determined based on the size of the tumor, the location of the tumor, the symptoms, the patient's age and general health, and the patient's goals and concerns. This decision is made by the patient after discussing all the options, each with unique risks and benefits.