An acoustic neuroma is a noncancerous, slow-growing tumor that develops on the principle nerve leading from the inner ear into the brain, according to Mayo Clinic. Pressure from an acoustic neuroma may cause hearing loss, ringing in the ear and unsteadiness, since this nerve directly influences balance and hearing.
An acoustic neuroma is also called a vestibular schwannoma, states Mayo Clinic. Acoustic neuromas normally grow slowly or not at all. In rare cases, the benign tumor may grow quickly to become large enough to affect the brain's essential functions. Treatments include monitoring, radiation therapy and surgical removal.
The most common, and normally first, symptom of an acoustic neuroma is hearing loss, notes the Acoustic Neuroma Association. The cause of this type of tumor is unknown, although genetics may represent a risk factor for the disease. Most acoustic neuromas are diagnosed in people between the ages of 30 and 60.
The growth usually starts within the internal auditory canal at the tip surrounding the eighth cranial nerve, according to the ANA. The eighth cranial nerve goes from the brain to the inner ear, and two separate parts transmit sound and balance information to the brain. If the benign tumor grows, it normally expands 1.5 millimeters per year from its origination point. Large tumors may press against a nerve responsible for facial sensation. The tumor may put pressure on the brain stem but not actually grow into brain tissue.