An acoustic neuroma (also known as a vestibular schwannoma) is a benign tumor that originates on the eighth cranial nerve, which connects the inner ear with the brain. This nerve, called the vestibulocochlear nerve, is involved in transmitting sound and sending balance information from the inner ear to the brain.
Acoustic neuromas are typically slow growing over a period of years. Although these tumors do not invade the brain, they commonly cause hearing loss and can result in neurological deficits. Acoustic neuromas can also be life threatening if they become large enough to compress the brain stem or cerebellum.
Types of Acoustic Neuromas
There are two types of acoustic neuromas: a sporadic type and a type associated with a syndrome called neurofibromatosis type II (NF2). NF2 is a genetic, inherited disorder characterized by the growth of noncancerous tumors in the nervous system.
Sporadic acoustic neuromas are the most common type. Each year approximately 2,500-3,000 individuals in the United States are diagnosed with this tumor, which typically affects only one ear. NF2, the genetic variant, is a rare cause of these tumors accounting for only 5 percent of acoustic neuromas. These patients are often diagnosed with tumors affecting both ears by the age of 30.
Diagnosis
Acoustic neuromas are diagnosed with a detailed MRI and CT scan of the head if the patient presents with a decrease in hearing, tinnitus (ringing in the ear), dizziness or other common symptoms.
When an acoustic neuroma is caught early, the likelihood that an experienced surgeon can remove it while preserving the delicate facial nerve is quite good (greater than 90 percent). Preservation of hearing is more difficult but may also be possible in select centers with very experienced treatment teams. Advances in hearing preservation with surgical intervention is a particular focus of clinical research at the University of Michigan.
Symptoms
The most common symptoms of acoustic neuroma are hearing loss and tinnitus. Other symptoms, which can be mild or severe, may include:
- Dizziness or vertigo (dysequilibrium)
- Facial numbness, tingling, weakness or paralysis
- Clumsiness or unsteadiness
- Changes in taste
- Difficulty swallowing and hoarseness
- Confusion
- Headache and/or ear pain
Treatment
At Michigan Medicine, each patient is thoroughly evaluated, with a complete history, a physical examination, MRI or CT imaging and hearing and balance tests. We take into consideration health issues, the size and location of the tumor and its symptoms, and then discuss all treatment options with the patient.
Treatment options include:
Observation: This method is typically an option for small tumors or tumors with no accompanying symptoms as well as for patients who are elderly or too ill for surgery.
Stereotactic radiosurgery: In select cases, this radiation treatment can control tumors using precisely targeted X-ray beams. This type of advanced technique makes it possible to send radiation to the tumor while limiting exposure/damage to surrounding tissue.
Microsurgery, which includes three potential approaches:
- Middle Fossa approach: A hearing preservation approach used for patients with good hearing and smaller tumors that are primarily located within the internal auditory canal. This procedure is used in situations where hearing preservation is possible.
- Retrosigmoid approach: Used for small- to moderate-sized acoustic neuromas that are growing beyond the internal auditory canal and near the brainstem. This procedure is also used for patients where hearing preservation is possible, although the chance for hearing preservation decreases with larger tumors.
- Translabyrinthine approach: Used for any size tumor that has caused significant hearing loss, or where hearing preservation is not possible due to tumor size. This procedure results in complete hearing loss on the tumor side, but offers the best chance for facial nerve preservation in such patients.
Why Choose Michigan
At Michigan Medicine, our Neurosurgery and Otology departments have collaborated for more than 20 years, with outstanding outcomes for the treatment of acoustic neuromas. Our multidisciplinary evaluation includes a complete history, a physical examination, MR and CT imaging and hearing and balance tests.
Publications over the last two decades from the University of Michigan report high rates of success with preservation of hearing when the middle fossa approach was used to remove small to moderate size tumors. Of the people in the study who had useful hearing before the surgery, over three-quarters retained a level of useful hearing after their tumors were removed. The results published in this study represent the highest hearing preservation rates published to date.
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