Vestibular schwannoma

Why do medical professionals prefer the expression vestibular schwannoma (sometimes written vestibula schwannoma) to the more common term acoustic neuroma?

Vestibular schwannomas are intracranial tumors that arise from the Schwann cells which form the sheath of either the vestibular (balance) or cochlear (hearing) nerve. They are in fact more commonly found on the vestibular nerve and hence are logically called vestibular schwannoma. However the balance and hearing nerves are close to each other in the internal auditory canal (IAC), a short bony channel that links the inner ear to the cranial cavity which surrounds the brain.

Since vestibular schwannomas typically start to grow in the IAC, they tend to compress the hearing nerve. The first symptom noticed by patients is almost always hearing loss on the affected side, and/or tinnitus - a constant ringing in the ear. Hence the more common name: acoustic neuroma.

As vestibular schwannomas grow they usually fill the IAC and then start to protrude into the brain cavity, called the CPA at that point. A sketch shows typical vestibular schwannoma growth and the way it is classified into stages.

The facial nerve which controls movement of the face muscles also passes through the IAC and can be stretched and compressed as the vestibular schwannoma grows. It can also be damaged during surgery to remove the vestibular schwannoma. Partial or complete unilateral facial paralysis is thus frequently associated with vestibular schwannoma, especially when it grows to be fairly large and has to be removed by surgery.

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