An acoustic neuroma (AN), also known as vestibular schwannoma, is a benign brain tumour, which develops on the eighth cranial nerve, which is the main nerve leading from the inner ear to the brain.
Acoustic neuromas typically grow very slowly over an extended period. They do not invade the brain, but as the tumour grows, it can push on the brain. Larger tumours can press on the facial nerves, leading to facial paralysis, or they can press on the brain stem or cerebellum, which can cause further complications.
The first symptom to appear is usually some hearing loss, tinnitus or balance issues. An MRI, auditory test or CT (CAT scan) will typically confirm a diagnosis.
1-2% of the population are estimated to have this tumour, although because it is slow growing in many cases, perhaps 1% of the population is believed to be undiagnosed with this condition.
Approximately 95% occur on only one side of the head (unilaterally). Fortunately, they do not spread to other parts of the brain or body. A bilateral acoustic neuroma, which is on both sides, is commonly referred to as neurofibromatosis, or NF2.
Causes of acoustic neuromas are unknown although current belief is that acoustic neuromas arise due to a spontaneous mutation (alteration in genetic material) on chromosome 22, which produces an overproduction of the Schwann cells.