A schwannoma, also known as a nerve sheath tumor, is a benign tumor that develops in the protective covering surrounding the nerve cells, called myelin. Schwann cells are the building blocks of that covering, so schwannomas can develop anywhere Schwann cells are present: in the cranial nerves in the brain, or the peripheral nerves in the body. 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 referred to as an acoustic neuroma.
The vestibulocochlear nerve branches into the vestibular nerve, which controls balance, and the cochlear nerve, which controls hearing. Acoustic neuromas typically develop on the vestibular portion of the nerve, but since they are so close to the cochlear nerve they can also affect hearing. Acoustic neuromas are not usually a life-threatening emergency, as they are typically slow growing. However, if left untreated, as they grow they can cause hearing loss, facial paralysis, and even arm and leg weakness as they start to compress the critical brain structures nearby.
Like almost all schwannomas, acoustic schwannomas are usually benign (not cancerous). Due to the potential to cause damage to surrounding structures, these tumors still need to be evaluated by an expert. Not all acoustic neuromas need to be removed — in some cases a surgeon may recommend ongoing monitoring before treatment. Stereotactic radiosurgery, which precisely delivers focused, high-dose radiation to the tumor while protecting the surrounding brain, is an alternative to surgery for carefully selected small- to medium-sized vestibular schwannomas. Your surgeon will talk to you about whether you are a candidate for this type of treatment. (More about surgical and stereotactic radiosurgery treatments for acoustic neuromas.) There are currently no known medications that treat vestibular schwannomas.
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 Weill Cornell Neurological Surgery, vestibular schwannomas are treated by a multidisciplinary team in our Skull Base Surgery Program.
Reviewed by: Philip E. Stieg, PhD, M.D.
Last reviewed/last updated: October 2023
Illustration by Thom Graves, CMI
