Gamma Knife radiosurgery for relapsing trigeminal neuralgia following microvascular decompression

OBJECTIVE Gamma Knife radiosurgery (GKRS) is a treatment option for refractory trigeminal neuralgia (TN). However, there is a paucity of data regarding the effectiveness of GKRS for relapsing TN following microvascular decompression (MVD). The aim of this study was to characterize the response rate, complications, pain relief durability, and predictors of pain relapse for salvage GKRS following MVD for TN. METHODS A retrospective study of all patients who received GKRS for Burchiel type 1 TN (TN1) or type 2 TN (TN2) pain at Wake Forest University School of Medicine was conducted. Pain was measured using the Barrow Neurological Institute (BNI) pain intensity score. After an initial pain response of BNI scores I–III, a BNI score of IV or V constituted relapse. Durability of pain relief was characterized using the Kaplan-Meier estimator. Predictors of relapse were investigated using Cox regression models. Statistical significance was set at p < 0.05. RESULTS Of 2065 patients with TN1 or TN2, 59 had GKRS post-MVD. Forty-nine (83.1%) of these patients experienced a BNI pain score of I–III at the first follow-up post-GKRS. The median time to relapse was 1.75 years; freedom rates from relapse were 77%, 45.9%, and 30.7% at 1, 2, and 5 years, respectively. Radiofrequency ablation prior to MVD significantly decreased the likelihood of an initial response to salvage GKRS (Fisher’s exact test, p = 0.02). After controlling for baseline and clinical characteristics, facial numbness significantly decreased the likelihood of pain relapse (Cox regression, HR 0.15, 95% CI 0.03–0.73; p = 0.01). Conversely, a worse initial pain response significantly increased the likelihood of pain relapse (Cox regression, HR 3.64, 95% CI 1.02–12.95; p = 0.04). Pain relapse within 24 months of the original MVD did not predict durability of pain relief following salvage GKRS (Cox regression, HR 0.94, 95% CI 0.40–2.22; p = 0.89). The overall toxicity rate of salvage GKRS was 35.6%. CONCLUSIONS Salvage GKRS presents an effective, noninvasive option for recurring TN after MVD, with a comparable response rate to primary GKRS or MVD, and a favorable complications profile relative to salvage MVD. Patients with postoperative facial numbness and a better initial pain response may experience more durable pain relief following salvage GKRS.