Radiosurgery is becoming more and more the first treatment modality for trigeminal neuralgia (TN).

     In the present study we present the treatment results of a large cohort of patients treated for TN using Gamma Knife® radiosurgery.

     Between 2002 and 2009, a total of 380 patients were treated. 70 patients were re-treated. The treatment parameters were highly consistent.

     80 Gray was delivered using a 4 mm collimator shot that was placed on the root entry zone, with the 40% isodose line touching the brainstem. For re-treatments 80 Gray was given on an anterior location on the cisternal trigeminal nerve, also in a highly consistent manner. The outcome on pain was evaluated using the Barrow Neurological Institute (BNI) pain scale. Kaplan-Meier curves for pain relief were made for all patients and for different subgroups, with pain scores 4 or 5 as endpoints.

     Short term (3 month) success rate was 92%, slowly decreasing over the first 2 years and leveling off at longer time intervals. The long term (5 year) success rate was 70 % for typical idiopathic TN. Different subgroups (multiple sclerosis, atypical pain, re-treatment, prior treatment with other modality) were found to have a significant worse outcome in terms of pain relief. The adverse effects were scored according to the BNI numbness score. Overall, 55 % of patients experienced some form of numbness, which developed slowly over time. 12 % found this to be somewhat bothersome, 2 % very bothersome. In patients that were previously treated with another surgical modality Gamma Knife treatment showed an additive effect on the numbness.

     This is a retrospective study.

     This study contains a large population with a long follow up after GKRS for TN, enabling a robust statistical analysis of pain relief, adverse effects and various prognostic factors.

     MS, prior treatment and atypical pain showed worse outcomes.