Cranial nerve preservation after stereotactic radiosurgery for small acoustic tumors.

OBJECTIVE: To assess those factors associated with and predictive of cranial nerve preservation after stereotactic radiosurgery in patients with small acoustic tumors identified by magnetic resonance imaging. DESIGN: We performed a retrospective analysis of our experience with 31 patients with preserved hearing and acoustic tumors measuring 10 mm or smaller (pons-to-petrous dimension). All patients underwent clinical and audiologic evaluations varying from 6 to 48 months (mean, 20 months) after stereotactic radiosurgery performed with use of the 201 source cobalt 60 gamma unit. RESULTS: Stabilization or reduction in tumor volume was achieved in 29 of 31 patients. One patient required delayed microsurgical resection. Useful hearing (pure tone average < or = 50 dB and speech discrimination score > or = 50%) preservation was achieved in 10 of 10 patients immediately postoperatively, eight of 10 patients at 6 months, six of 10 patients at 1 year, and five of 10 at 2 years. Preservation of some measurable hearing was possible in all patients immediately after radiosurgery, in 84% and in more than half of patients at 2 years. Preoperative facial nerve function was preserved in 19 of 20 patients at 2 years after radiosurgery. All patients returned to their preoperative employment status within 2 to 5 days after radiosurgery. CONCLUSION: Stereotactic radiosurgery performed with current technology (multiple radiation isocenters and magnetic resonance imaging guidance) is a safe and effective management strategy for patients with small acoustic tumors. The risk of facial and trigeminal neuropathy after gamma knife radiosurgery is low, and useful hearing can be preserved in up to 50% of patients with useful preoperative hearing. Stereotactic radiosurgery is a valuable alternative strategy to surgical removal for many patients with newly diagnosed small acoustic tumors.

Cranial nerve preservation after stereotactic radiosurgery of intracanalicular acoustic tumors.

We reviewed our initial stereotactic radiosurgery experience in 10 patients with intracanalicular acoustic tumors managed by radiosurgery during a 5-year period. These patients constitute 4.7% of acoustic tumor patients who underwent Gamma Knife radiosurgery during this period. Tumor volume stabilization was achieved in 8. Two patients had initial growth followed by delayed growth arrest. Preservation of preoperative hearing was achieved in all patients in the immediate postoperative period and in 8 of 10 at 1 year. No patient had developed facial or trigeminal nerve dysfunction at the last follow-up, which varied from 3 to 64 months (mean 25 months). Tumor growth was delayed in 2 patients, but neither has required delayed microsurgical resection. All patients returned to their preoperative functional status within 3-5 days after radiosurgery. Stereotactic radiosurgery using the Gamma Knife is a safe and effective management strategy for intracanalicular acoustic tumor patients. Our initial results indicate that high cranial nerve preservation rates and a rapid return to previous activity and employment are benefits of radiosurgery.

Stereotactic radiosurgery for acoustic nerve tumors in patients with useful preoperative hearing: results at 2-year follow-up examination.

Twenty patients with acoustic nerve tumors (mean diameter < or = 30 mm) and useful preoperative hearing were examined 2 years after stereotactic radiosurgery to determine the effectiveness of the surgery in the control of tumor growth and the preservation of cranial nerve function. Results showed tumor volume stabilization (12 cases) or reduction (seven cases) was achieved in a total of 19 patients (95%). Useful hearing (defined as Gardner and Robertson Class I or II) preservation was obtained in 100% of cases immediately postoperatively, 50% at 6 months, and 45% at both 1 and 2 years. Two years after stereotactic radiosurgery, facial nerve function was preserved in 90% of patients and 75% continued to have normal trigeminal nerve function. All patients returned to and maintained their preoperative functional status within 3 to 5 days after radiosurgery. These findings indicate that stereotactic radiosurgery with multiple isocenters and narrow radiation beams is a safe and effective management strategy for progressive acoustic nerve tumors. Auditory, facial, and trigeminal nerve function can be preserved in most patients. Prevention of further growth and preservation of cranial nerve function appear to be satisfactory goals in the current management of patients with acoustic neuromas.

Facial nerve preservation and tumor control after gamma knife radiosurgery of unilateral acoustic tumors.

To assess the long-term risk of facial nerve dysfunction after unilateral acoustic tumor stereotactic radiosurgery, we retrospectively analyzed our initial experience in 98 unilateral acoustic tumor patients who were evaluated at least 2 years after treatment. This observation interval permits an analysis of both the risk of onset and the potential for recovery of facial nerve function. The overall risk of developing any degree of delayed transient or permanent postoperative facial neuropathy was 21.4% (21 of 98 patients). Only one patient undergoing radiosurgery alone had poor residual facial nerve dysfunction worse than House-Brackmann grade III. Normal facial nerve function (House-Brackmann grade 1) was preserved in 95% of patients with small tumors (10 mm or less petrous-pons dimension) and in 90% of patients who had useful hearing and normal facial function preoperatively. Normal facial function was preserved in all patients with intracanalicular acoustic tumors. The risk of delayed facial neuropathy was reduced by performing radiosurgery when tumors were small (1000 mm(3) or less), by enclosing the tumor within the 50% isodose volume, by using multiple small radiation isocenters, and by detailed identification of the tumor volume using stereotactic magnetic resonance imaging.