Gamma Knife stereotactic radiosurgery effective for patients with large acoustic neuromas: Study

A new Mayo Clinic study has found that Gamma Knife™ stereotactic radiosurgery is a successful treatment for the majority of patients who have large acoustic neuromas (also known as vestibular schwannoma or neurolemmoma). Gamma Knife surgery already is an accepted treatment for small to medium-sized acoustic neuromas. This study was presented at the American Association of Neurological Surgeons Annual Meeting in Philadelphia this week.

“Instead, we use gamma radiation to destroy diseased tissue while preserving the surrounding healthy tissue. It is typically a short procedure and most patients can be discharged from the hospital the same day.”

An acoustic neuroma is a noncancerous tissue growth that arises on a cranial nerve leading from the brain to the inner ear. This nerve is associated with transmitting sound and sending balance information to the brain from the inner ear. Symptoms of acoustic neuromas may include hearing loss, dizziness and ringing in the ears. Treatment options include observation, surgical removal and stereotactic radiosurgery. Each year, Mayo Clinic neurologists and neurosurgeons care for more than 2,200 patients with brain and nervous system tumors, including many with acoustic neuromas.

"Gamma Knife stereotactic radiosurgery allows us to perform neurosurgery without an incision," says Michael Link, M.D., a Mayo Clinic neurosurgeon and study author. "Instead, we use gamma radiation to destroy diseased tissue while preserving the surrounding healthy tissue. It is typically a short procedure and most patients can be discharged from the hospital the same day."

Dr. Link and a team of Mayo Clinic researchers collected data from 34 patients who had Gamma Knife stereotactic radiosurgery for a large acoustic neuroma between 1997 and 2006. These individuals' acoustic neuromas represented tumor volumes that were considered large (one standard deviation above the mean). At three years, 89.4 percent of these patients had not experienced tumor progression, 91.6 percent were free of new facial neuropathy and 52.8 percent had preserved functional hearing. At five years, the rates decreased to 82.9 percent with no tumor recurrence or progression, 86.4 percent free of new facial neuropathy and 34.5 percent with preserved functional hearing. At the most recent follow-up, 85 percent of the tumors were smaller than at the time of stereotactic radiosurgery.

"This data shows us that Gamma Knife stereotactic radiosurgery is a very well-tolerated, successful treatment for the majority of patients with large acoustic neuromas," says Dr. Link. "However, it should be noted that with large acoustic neuromas, the rates of cranial nerve disability and tumor progression are higher, compared to patients with smaller tumors. Therefore, careful consideration of all the available treatment options needs to be entertained before making a treatment decision."