Acoustic Neuroma

( Vestibular Schwannoma ) Acoustic neuroma is a benign tumor that grows in the internal auditory canal and affects the hearing, facial, and balance nerves.

Etiology for Acoustic Neuroma

What causes a schwann cell to become a tumor? 

The answer to why these tumors form remains unclear. There appear to be two regions within the genetic makeup of a schwann cell termed tumor suppressor genes. The function of these genes is to prevent the formation of tumors. Only one properly functioning gene is needed to prevent a tumor from occurring. In very simple terms, a change or a mutation has to occur in the same schwann cell twice, thereby affecting both tumor suppressor genes, before a tumor can form. 

Acoustic neuromas arise from these mutations acquired after birth. As such, they are almost always unilateral and cannot be transmitted from one generation to the next. The chance of having a tumor develop in the opposite ear is almost unheard of.

In Type 2 neurofibromatosis, the situation is quite different. We believe these patients are born with a defective tumor suppressor gene. This disorder can be transmitted from generation to generation. These patients need only one mutation in any schwann cell during their lifetime to cause development of a tumor. At the time of detection, these patients are usually found to have bilateral acoustic neuromas. A better term for this condition is vestibular neurofibroma.  In addition, these patients can have schwannoma and neurofibroma of other cranial nerves.