OBJECTIVE: To determine predictive factors for the successful treatment of trigeminal neuralgia with GKRS.
METHODS: Between 1999 and 2008, 777 GKRS procedures for patients with TN were performed at our institution. Evaluable follow-up data were obtained for 448 patients. Median follow-up time was 20.9 months (3-86 months). The mean maximum prescribed dose was 88 Gy (80-97 Gy). Dosimetric variables recorded included dorsal root entry zone dose (DREZ), pons maximum dose, dose to the petrous dural ridge, and the cisternal nerve length.
RESULTS: 86% of patients achieved BNI I-III pain scores by 3 months after GKRS, with 43% of patients achieving a BNI I pain score. 26% of patients reported post-treatment facial numbness. 28% of patients reported a post-GKRS procedure for relapsed pain and median time to next procedure was 4.4 years. Multivariate analysis revealed that the development of post-surgical numbness (OR 2.76, p=0.006) was the dominant factor predictive of efficacy. Longer cisternal nerve length (OR 0.85, p=0.005), prior radiofrequency ablation (OR 0.35, p=0.028), and diabetes (OR 0.38, p=0.013) predicted decreased efficacy. The mean dose delivered to the DREZ in patients who developed facial numbness (57.6 Gy) was more than the mean dose (47.3 Gy) to patients who did not develop numbness (p=0.02).
CONCLUSION: The development of post-GKRS facial numbness is a dominant factor that predicts for efficacy of GKRS. History of diabetes or previous RFA may portend worsened outcome.