Role of enhanced MRI in the follow-up of patients with medically refractory trigeminal neuralgia undergoing stereotactic radiosurgery using the gammaknife: Initial experience

Purpose: The purpose of this work was to evaluate the early posttreatment M R findings, and their clinical utility, in patients with trigeminal neuralg ia undergoing stereotactic radiosurgery using the gamma knife. Method: Twenty-six patients with medically refractory trigeminal neuralgia underwent stereotactic radiosurgery, A single dose of 70-90 Gy was administ ered to the proximal root entry zone (n = 21) or the retrogasserian portion (n = 5) of the trigeminal nerve. Posttreatment enhanced MRI and clinical a ssessment were performed at 3-6 months. Results: Five patients did not have radiologic follow-up. There were no cha nges identified in the treated trigeminal nerve or adjacent brainstem in 19 of 21 patients, Two patients with multiple sclerosis developed abnormal si gnal and enhancement in the brainstem and/or trigeminal nerve; neither had clinical complications. Onset of therapeutic effect ranged from 3 weeks to 3 months; 19 patients had a beneficial response. Conclusion: Results of enhanced MRI 3-6 months after stereotactic radiosurg ical treatment of trigeminal neuralgia do not correlate with the clinical r esponse. Because beneficial clinical responses or treatment failures are ap parent by 3 months, routine posttreatment MRI in these patients is not warr anted.