Author: Andrew A. McCall, MD, University of Pittsburgh Medical Center
Acoustic neuroma, otherwise known as vestibular schwannoma, is a benign intracranial tumor that develops in the space between the brainstem and inner ear (the cerebellopontine angle). Although the tumor is commonly referred to as acoustic neuroma, this term is a misnomer because these tumors usually arise from the vestibular (balance) nerve rather than the acoustic (hearing) nerve. Most often these tumors develop spontaneously, however in a small percentage of cases they develop as a result of an underlying genetic disorder (Neurofibromatosis type 2) where the tumors are present on both sides.
Symptoms of acoustic neuroma include unilateral or asymmetric sensorineural hearing loss (hearing loss originating from the inner ear and/or hearing nerve), tinnitus (ringing or buzzing in the ear), and imbalance or dizziness. Less common symptoms include facial numbness and rarely facial weakness or paralysis.
What to Expect at Your Otolaryngologist Office Visit:
A complete history and physical examination of the head and neck will usually be obtained for patients who present with symptoms suggestive of an acoustic neuroma. An audiogram will often be obtained for hearing related complaints. Vestibular testing may be performed for balance related symptomatology. If an acoustic neuroma is suspected, a MRI scan will typically be obtained to evaluate for the presence of a tumor. Many other disease processes (e.g. Meniere’s disease, sudden sensorineural hearing loss, labyrinthitis, etc.) can mimic the symptoms of acoustic neuroma, but do not share the MRI findings of a tumor. Once the diagnosis of acoustic neuroma is established, consultation is typically sought with a specialized otolaryngologist known as an otologist/neurotologist.
While each patient and situation is unique, three main treatment options should be considered: observation, surgical resection, and radiosurgery.
Observation of acoustic neuroma entails evaluating the tumor for growth with serial MRI scanning. Acoustic neuroma, on average, tends to be very slow growing – on the order of one or two millimeters per year. However, some tumors are dormant and do not grow and, occasionally, some tumors grow at a more rapid pace. If a tumor should grow during observation, more active intervention with surgery or radiosurgery would likely be recommended.
There are three surgical approaches used to remove acoustic neuroma: translabyrinthine, retrosigmoid, and middle fossa. The decision upon which surgical approach is best for a particular patient and tumor is highly individualized and should be discussed in detail with the treating physician. Surgery for these tumors is often performed as a team approach incorporating the skills of an neurotologist and a neurosurgeon because these tumors reside at the junction between the inner ear and brainstem.
Radiosurgery is used to arrest growth of acoustic neuroma. Radiosurgery involves steering beams of radiation from multiple angles to concentrate the radiation on the tumor and spare adjacent structures, such as the inner ear or brainstem. One of several different machines may be recommended for delivery of the radiation treatment (e.g. Gamma Knife and Cyber Knife).