Acoustic Neuroma

Acoustic neuromas are benign tumors which arise from the nerve responsible for hearing, the eighth cranial nerve. As these tumors grow, they can cause hearing loss, headaches, difficulty with balance and ringing in the ear (tinnitus). Although rates of growth vary, most tumors enlarge within one to two years without treatment. Magnetic resonance imaging (MRI) has greatly improved the ease and accuracy of detection of these tumors, leading to improved early diagnosis in recent years.

The alternatives for treatment acoustic neuromas include surgical removal and radiosurgery. A key factor in achieving a successful outcome is early diagnosis, as smaller tumor size is associated with better results with both conventional surgery and radiosurgery.

Although complete surgical removal can cure acoustic neuromas, there are risks from surgery as well. Overall, approximately 80% of patients have their tumors completely removed at surgery; if removal is incomplete, tumor recurrence may occur. Problems related to surgical removal of these tumors include injury to the facial nerve (occurring in approximately 20% of cases), as well as infections and cerebrospinal fluid (CSF) leaks (occurring in approximately 17% of cases). The risk of operative death is less than 1%. In cases where preservation of useful hearing is attempted, this can be achieved less the one-quarter of the time.

Radiosurgery with the Gamma Knife results in long-term tumor control in approximately 95% of cases, as measured by prevention of further tumor growth or reduction in tumor size. Injuries to the facial nerve as well as other cranial nerves occurs in less than 1% of cases using current radiosurgical techniques, with no risk of operative death, infection or CSF leak. Rates of hearing preservation are variable depending on the extent of hearing problems prior to treatment, but useful hearing can be preserved in up to 70% of cases without significant pretreatment hearing deficits.

In cases of tumor recurrence after conventional surgery, radiosurgery may result in long-term tumor control.

References

Pollock B et al: Outcome Analysis of Acoustic Neuroma Management: A Comparison of Microsurgery and Stereotactic Radiosurgery. Neurosurgery 36:215-224, 1995

Lundsford LD, et al: Gamma Knife Radiosurgery for Acoustic Neuromas, in Gamma Knife Brain Surgery. Prog Neurol Surg. Basel, Karger, 1998, vol 14, pp 89-103

Prasad D et al: Gamma surgery for vestibular schwannoma. J. Neurosurg. 92:745-759, 2000

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