Acoustic Neuromas / Vestibular Schwannomas

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An acoustic neuroma (right) forms on the vestibular portion of the acoustic nerve, but since the location is so close to the cochlear nerve it can also affect hearing.

A schwannoma, also known as a Schwann cell tumor, is a benign tumor that develops in the protective sheathing surrounding the nerve cells, called myelin. Schwann cells are the building blocks of that myelin, so schwannomas can develop anywhere Schwann cells are present.  When a schwannoma develops in the Schwann cells of the eighth cranial nerve — also called the vestibulocochlear or acoustic nerve because it connects the ear to the brain — it is called a vestibular schwannoma, more commonly called an acoustic neuroma.

The acoustic nerve branches into the vestibular nerve, which controls balance, and the cochlear nerve, which controls hearing.  Acoustic neuromas develop on the vestibular portion of the acoustic nerve, but since they are so close to the cochlear nerve they can also affect hearing. Acoustic neuromas are not usually life-threatening, but they need to be treated since they can cause hearing loss and facial paralysis. They are slow growing, but if left untreated they may grow so large that they cause pressure on nearby brain structures — which in turn may cause a life-threatening condition.

Like almost all schwannomas, acoustic neuromas are benign (not cancerous). But even a benign tumor needs to be evaluated. Not all acoustic neuromas need to be removed — in some cases a surgeon may recommend ongoing monitoring before surgery.

More about the Acoustic Neuroma Program

What Causes Schwannomas?
The cause of schwannomas is not usually clear, since in most cases there is no family history of the condition and the tumor seems to develop spontaneously. Some studies have suggested a link between acoustic neuromas and long-term exposure to loud noise, or a history of exposure to radiation — but these links have not been conclusively established. Some people develop acoustic neuromas as a result of a genetic condition called NF2 (neurofibromatosis type 2), which typically causes tumors on both sides of the head and can lead to complete hearing loss. Acoustic neuromas can develop at any age, but they are most commonly diagnosed in those between 30 and 60 years of age.

Vestibular schwannomas are complicated tumors that should be treated at major medical centers where neurosurgeons have advanced training in treating them. At the Weill Cornell Brain and Spine Center, vestibular schwannomas are treated by an interdisciplinary team in our Skull Base Surgery Program.

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Reviewed by: Jared Knopman, M.D.
Last reviewed/last updated: January 2015
Illustration by Thom Graves, CMI