Anatomical considerations in Gamma Knife radiosurgery for idiopathic trigeminal neuralgia

Abstract

Objective: The authors conducted this study to present the long-term treatment outcomes (minimum 2 years) of Gamma knife radiosurgery(GKS) for trigeminal neuralgia(TN) and to demonstrate the correlation of treatment outcomes and the anatomical characteristics of TN. Methods: From 1997 to 2003, 44 consecutive patients suffering from medically intractable pain underwent GKS for TN. A single 4mm collimator was used with a median maximum dose of 80Gy (range 75~80Gy) prescribed to the root entry zone of the trigeminal nerve. Median follow up duration was 30 months (range 24~78 months). Anatomical measurements of trigeminal nerve in magnetic resonance images during GKS planning were correlated with clinical outcome. Results: Twenty-two patients (50%) achieved an excellent outcome (BNI grade I & II), 20 patients (45.5%) a good outcome (grade IIIa & IIIb), and only 2 patients (4.5%) a poor outcome (grade IV & V). Eleven patients (25.0%) experienced pain recurrence after initial pain relief. Smaller volume of trigeminal nerve area irradiated more than 40Gy was significantly correlated with excellent outcome in both univariate and multivariate analyses respectively (P=0.033 and 0.040). Conclusion: Anatomical considerations during the planning of GKS would be helpful for predicting clinical outcome in TN.