Acoustic Neuroma

The term "acoustic neuroma" is actually a misnomer since the tumor never arises from the acoustic division of the vestibulocochlear nerve (cranial nerve VIII) and the tumor is not a neuroma but a schwannoma.

Acoustic neuroma (or Vestibular Schwannoma) is a benign primary intracranial tumor, or brain tumor, of the myelin forming cells called "Schwann cells" (Schwannoma) of the 8th cranial nerve -also known as the acoustic nerve, (or more properly the vestibulocochlear nerve).

The vast majority (95%) of these tumors are sporadic, meaning they are not passed on through genes. Sporatic 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).

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.

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.