Stereotactic radiosurgery in the management of acoustic neuromas associated with neurofibromatosis Type 2

Object. Stereotactically guided radiosurgery is one of the primary treatmen t modalities for patients with acoustic neuromas (vestibular schwannomas). The goal of radiosurgery is to arrest tumor growth while preserving neurolo gical function. Patients with acoustic neuromas associated with neurofibrom atosis Type 2 (NF2) represent a special challenge because of the risk of co mplete deafness. To define better the tumor control rate and long-term func tional outcome, the authors reviewed their 10-year experience in treating t hese lesions. Methods. Forty patients underwent stereotactic radiosurgery at the Universi ty of Pittsburgh, 35 of them for solitary tumors. The other five underwent staged procedures for bilateral lesions (10 tumors: 45 total). Thirteen pat ients (with 29% of tumors) had undergone a median of two prior resections. The mean tumor volume at radiosurgery was 4.8 mi, and the mean tumor margin dose was 15 Gy (range 12-20 Gy). The overall tumor control rate was 98%. During the median follow-up period of 36 months, 16 tumors (36%) re greased, 28 (62%) remained unchanged, and one (2%) grew. In the 10 patients for whom more than 5 years of clinical an d neuroimaging follow-up results were available (median 92 months), five tu mors were smaller and five remained unchanged. Surgical resection was perfo rmed in three patients (7%) after radiosurgery; only one showed radiographi c evidence of progression. Useful hearing (Gardner-Robertson Class I or II) was preserved in six (43%) of 14 patients, and this rate improved to 67% a fter modifications made in 1992. Normal facial nerve function (House-Brackm ann Grade 1) was preserved in 25 (81%) of 31 patients. Normal trigeminal ne rve function was preserved in 34 (94%) of 36 patients. Conclusions. Stereotactically guided radiosurgery is a safe and effective t reatment for patients with acoustic tumors in the setting of NF2. The rate of hearing preservation may be better with radiosurgery than with other ava ilable techniques.