An acoustic neuroma is a benign (noncancerous) tumor on the eighth cranial nerve, the vestibulocochlear nerve. This nerve leads from the brainstem to the ear and is involved in hearing and maintaining balance. The more precise term for this tumor is “vestibular schwannoma,” because the tumor involves the vestibular portion of the nerve, not the acoustic (cochlear) portion, and it arises from Schwann cells rather than from neurons.
Acoustic neuromas are usually solitary tumors that grow slowly over a period of years, expanding in size at their site of origin. The earliest symptoms of an acoustic neuroma include gradual hearing loss and ringing in the affected ear. Balance problems often arise as the tumor grows. Larger tumors that compress the adjacent brainstem may affect other local cranial nerves, leading to facial weakness, numbness and tingling, and impaired sensation in the face and mouth on the involved side. For acoustic neuromas that require surgery, UPMC offers a variety of surgical techniques, depending upon the exact location of the tumor.
Symptoms of an acoustic neuroma may include:
- gradual hearing loss and tinnitus (ringing) in the affected ear
- balance problems
MRI or CT scans are used to confirm the presence of an acoustic neuroma. Other tests may include:
- Audiogram to evaluate hearing in both ears.
- Auditory Brainstem Response test (ABR, BAER, or BSER) to measure the rate of electric impulses traveling from the inner ear to the brainstem. A slowed or absent impulse may indicate the presence of an acoustic neuroma.
- Electronystagmography to test balance.
Treatment depends on the age and general health of the patient as well as the tumor's size, location, and rate of growth. If the tumor is very small and if there are no serious symptoms, the physician may decide simply to monitor its growth. This conservative route is common among people over age 70.
As the tumor grows, or if hearing becomes impaired, removal of all or part of the tumor may be necessary. The surgical approach depends on the size and location of the tumor, and includes the retrosigmoid, translabyrinth and middle fossa approach. All of these surgical approaches are available at UPMC. In all cases, neurophysiological monitoring of cranial nerves, especially the seventh cranial nerve (the facial nerve), is always performed.
At UPMC, we take a 360° Approach to treatment when evaluating each patient—looking at their conditions from every direction—to find the path that is least disruptive to the patient's brain, critical nerves, and ability to return to normal functioning. Our neurosurgical team may recommend a combination of surgical and non-surgical approaches to maximize the benefits of surgery while minimizing risks.
Radiation may be used as the first treatment option, particularly in cases where the tumor is not causing mass effect or as an adjuvant treatment after surgery for large acoustic neuromas from which there is a small residual lesion. Radiation is utilized to prevent further growth of the tumor and is usually indicated when tumors are small. This method may preserve hearing. Two types of radiation are commonly used: Gamma Knife radiosurgery and fractionated stereotactic radiotherapy. Radiosurgery or radiotherapy can also be used as supplementary treatment for patients who had surgery with partial resection of the tumor.