Gamma knife radiosurgery for trigeminal neuralgia

OBJECTIVE: The purpose of this study was to assess outcomes in patients treated with gamma knife radiosurgery for trigeminal neuralgia. METHODS: From 1997 to 2003, a total of 49 patients with trigeminal neuralgia underwent gamma knife radiosurgery. The trigeminal root entry zone immediately adjacent to the pons was targeted by use of a 4-mm collimator to deliver 40 Gy to the 50% isodose line (maximum dose, 80 Gy). Special care was taken to limit radiation dose to the adjacent pons to 12 Gy. Of the 49 study patients, all had undergone previous medical therapy, 8 (16%) had undergone microvascular decompression, 8 (16%) had undergone percutaneous rhizotomy, 2 (4%) had undergone linear accelerator-based radiosurgery, and 5 (10%) presented with multiple sclerosis. The median duration of symptoms was 6 years. There were 29 female patients (59%) and 20 male patients (41%). Facial pain outcomes were assessed by use of the Barrow Neurological Institute pain score. Other outcomes assessed included recurrence of symptoms and treatment toxicity. The median follow-up period was 49 months. RESULTS: At last evaluation, a total of 27 patients (61%) with idiopathic trigeminal neuralgia reported pain relief (scores of IIIb or less). This included 14 patients (32%) who reported complete pain relief when not receiving medications. Significant recurrence of pain after an initial interval of relief was reported by 10 patients (23%). Mean time to pain recurrence was 9.6 months (range, 2-36 mo). Mild to moderate facial numbness was experienced by 13 patients (29%), whereas 8 (18%) reported mild dysesthesias. CONCLUSION: Gamma knife radiosurgery established durable pain relief in 61% of patients with medically refractory idiopathic trigeminal neuralgia. A longer follow-up period is necessary to fully assess the incidence of late complications and recurrences.