An acoustic neuroma, also known as a vestibular schwannoma, is a slow-growing, benign (non-cancerous) tumor. It arises from the eighth cranial nerve, which is associated with transmitting hearing and balance information to the brain from the inner ear. As it grows, it presses on adjacent nerves.

Acoustic tumors do not invade the brain, but large tumors displace brain tissue, pushing the brain as they grow. Vital functions to sustain life can be threatened when large tumors cause severe pressure on the brainstem and the cerebellum, important parts of the brain. Tumors are typically described as small (less than 1.5 cm), medium (1.5 cm to 2.5 cm) or large (more than 2.5 cm).

More women than men are affected, and most acoustic neuromas are diagnosed in individuals between the ages of 30 and 60. The cause of acoustic neuromas is unknown. In a very small percentage of individuals, there is a hereditary factor to tumor development, known as neurofibromatosis.

Signs and Symptoms

The first and most common symptom is hearing loss on the side where the tumor is located. This can often be accompanied by ear noise or tinnitus and sometimes by a feeling of fullness in the ear. Additional symptoms can include headache, dizziness, ear pain, balance problems, unsteadiness and changes in facial sensation with numbness, tingling, and tics.

Because gradual hearing loss is often associated with aging, early symptoms are often overlooked and diagnosis delayed. If a routine auditory test reveals a loss of hearing and speech identification in one ear, further testing to evaluate for an acoustic neuroma may be indicated.

Diagnostic testing can include:

• An audiogram or hearing test to assess acuity and level of speech discrimination.
• A brainstem auditory evoked response (BAER), a painless test used to assess the electrical impulse along the acoustic nerve from the ear through the brainstem pathways. This can be useful to assess the potential of hearing preservation if one is considering surgery.
• A magnetic resonance imaging scan (MRI), which, with almost 100 percent accuracy, is the most effective tool in identifying an acoustic neuroma.
• A Cat Scan (CT), which is done to identify the bony structures.