Treatment of acoustic neuroma: stereotactic radiosurgery vs. microsurgery.

PURPOSE: Two major treatment options are available for patients with acoustic neuroma, microsurgery and radiosurgery. Our objective was to compare these two treatment modalities with respect to tumor growth control, hearing preservation, development of cranial neuropathies, complications, functional outcome, and patient satisfaction.

METHODS AND MATERIALS: To compare radiosurgery with microsurgery, we analyzed 96 patients with unilateral acoustic neuromas treated with Leksell Gamma Knife or microsurgery at Memorial Hermann Hospital, Houston, Texas, between 1993 and 2000. Radiosurgery technique involved multiple isocenter (1-30 single fraction fixed-frame magnetic resonance imaging) image-based treatment with a mean dose prescription of 14.5 Gy. Microsurgery included translabyrinthine, suboccipital, and middle fossa approaches with intraoperative neurophysiologic monitoring. Preoperative patient characteristics were similar except for tumor size and age. Patients undergoing microsurgery were younger with larger tumors compared to the radiosurgical group. The tumors were divided into small <2.0 cm, medium 2.0-3.9 cm, or large >4.0 cm. Median follow-up of the radiosurgical group was longer than the microsurgical group, 48 months (3-84 months) vs. 24 months (3-72 months).

RESULTS: There was no statistical significance in tumor growth control between the two groups, 100% in the microsurgery group vs. 91% in the radiosurgery group (p > 0.05). Radiosurgery was more effective than microsurgery in measurable hearing preservation, 57.5% vs. 14.4% (p = 0.01). There was no difference in serviceable hearing preservation between the two groups. Microsurgery was associated with a greater rate of facial and trigeminal neuropathy in the immediate postoperative period and at long-term follow-up. The rate of development of facial neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (35% vs. 0%, p < 0.01 in the immediate postsurgical period and 35.3% vs. 6.1%, p = 0.008, at long-term follow-up). Similarly, the rate of trigeminal neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (17% vs. 0% in the immediate postoperative period, p < 001, and 22% vs. 12.2%, p = 0.009, at long-term follow-up). There was no significant difference in exacerbation of preoperative tinnitus, imbalance, dysarthria, dysphagia, and headache. Patients treated with microsurgery had a longer hospital stay (2-16 days vs. 1-2 days, p < 0.01) and more perioperative complications (47.8% vs. 4.6%, p < 0.01) than did patients treated with radiosurgery. There was no correlation between the microsurgical approach used and postoperative symptoms. There was no difference in the postoperative functioning level, employment, and overall patient satisfaction. There was no correlation between the radiation dose, tumor size, number of isocenters used, and postoperative symptoms in the radiosurgical group.

CONCLUSION: Radiosurgical treatment for acoustic neuroma is an alternative to microsurgery. It is associated with a lower rate of immediate and long-term development of facial and trigeminal neuropathy, postoperative complications, and hospital stay. Radiosurgery yields better measurable hearing preservation than microsurgery and equivalent serviceable hearing preservation rate and tumor growth control.