Gamma-Knife Radiosurgery for Vestibular Schwannoma

ABSTRACT

OBJECT The goals of radiosurgery include preservation of neurological function and prevention of tumor growth. We document the results of gamma-knife radio-surgery for vestibular schwannoma. METHOD AND OBJECT Eighty-two patients underwent stereotactic radiosurgery for an vestibular schwannoma from October, 1994 to December, 2000. Sixty-five of these patients were followed up for radiological and clinical evaluation. As pregamma-knife modality, surgical resection were done in 23 patients,and V-P shunt in 2 patients. Initial symptoms were headache(n=45), dizziness(n=16), tinnitus(n=17). While normal facial function(House-Brackmann grade 1) was present in 48 patients(73.8%), other patients showed grade 2 function in 8, grade 3 function in 7,and grade 4 function in 2. The Gardner/Robertson scale was used to code hearing function. Male to female ratio was 13. Mean tumor volume was 7.98cm3. Mean dose delivered to the tumor margin was 14.2Gy,and mean maximal dose was 28.3Gy. RESULTS: Mean follow-up duration of 19.9 months. Thirty-five showed decrease(53.8%) in size, 19 patients(29.2%) stationary, 3(4.6%) initial decrease follow up increase, 5(7.6%) initial increase follow up decrease,and 59 patients (90.8%) were well controlled. Two patients experienced transient facial neuropathy, one transient trigeminal neuropathy, and one transient hearing deterioration. After gamma-knife radiosurgery, ventriculoperitoneal shunt was done in 4 patients. CONCLUSIONS: Gamma-knife radiosurgery can be used to treat postoperative residual tumors as well as in patients with concomitant medical problems in patients with preserved hearing function. Gamma-knife radiosurgery is safe and effective method to treat small, medium sized(less than 3cm in extracanalicular diameter), intracanalicular vestibular schwannoma, associated with low rate of cranial neuropathy.