Repeat Gamma Knife surgery for trigeminal neuralgia: long-term results

Abstract

The purpose of this study was to assess the long-term outcome achieved after repeat Gamma Knife surgery (GKS) for trigeminal neuralgia (TN) using a uniform treatment plan. Between 1985 and 2010, 53 patients underwent repeat GKS for refractory TN. In the initial GKS, which involved targeting the root entry zone of the trigeminal nerve, a maximal dose of 80 Gy was used with a 4-mm collimator so that the 50% isodose line abutted the pons. In the second GKS, the treatment plan consisted of a 70-Gy dose directed at a target 4-5 mm distal to the first target on the trigeminal nerve. The mean follow-up duration in these patients was 42 months. Outcomes were defined using the Marseille scale: excellent (Class I or II, no pain with or without medications), good (Class III or IV, ≥ 50% relief), and poor (Class V, < 50% relief). Trigeminal neuralgia pain was controlled (≥ 50% improvement with or without medications) after repeat GKS in 70% of patients at 1 year, 50% at 3 years, 50% at 5 years, and 50% at 10 years, as defined by a Kaplan-Meier analysis. A correlation was found between facial numbness and pain relief (p = 0.047). No difference was found between patients with Type 1 TN and those with Type 2 TN, and there was no correlation between the best relief obtained and long-term durability of relief from pain. Twenty-two patients (47.8%) described their trigeminal dysfunction in the following manner: numbness (45.6%), dry eye (10.9%), taste change (8.7%), or jaw weakness (2.2%). In only 8.7% of cases did the patient experience facial numbness that was regarded as bothersome. Repeat GKS for TN at the doses used provides substantial long-term relief. Treatment failure occurred up to 28 months after the second GKS. Facial numbness correlated with more durable pain relief after repeat GKS in this series.