Gamma Knife Radiosurgery for Idiopathic Trigeminal Neuralgia: Does the Status of Offending Vessels Influence Pain Control or Side Effects?

Objective To evaluate pain control and side effects after gamma knife radiosurgery (GKRS) for classical idiopathic trigeminal neuralgia (TN) with or without neurovascular compression (NVC). Methods This study included 47 patients with type 1 idiopathic TN and Barrow Neurological Institute (BNI) pain class IV or V who were treated with GKRS, with a maximum dose of 85 Gy targeting the root entry zone, as an initial treatment modality between January 2005 and March 2015. A retrospective analysis of NVC status, pain control, side effects, recurrence, and cross-sectional area was conducted. Results During follow-up (median, 21.5 months; range, 3–119 months), 36 of the 47 patients (76.6%) demonstrated good outcomes (i.e., improved to below BNI class IIIa). Twenty-two patients did not have NVC (group A) and 25 had NVC (group B). The rate of good outcomes did not differ significantly between the 2 groups (group A, 86.4% [19 of 22] vs. group B, 68% [17 of 25]; P = 0.138). The number of cases in BNI class I or II and the number of recurrences also did not differ significantly between the 2 groups (P = 0.532 and 0.786, respectively). The mean area was 8.64 ± 2.59 mm³ in nondeviated cases (n = 27) and 2.59 ± 1.68 mm³ in deviated (n = 10). Side effects were significantly more frequent in deviated cases (80% [8 of 10]) than in nondeviated cases (25.9% [7 of 27]; P = 0.003). Conclusions NVC is not a predictive factor for pain control after GKRS for the treatment of idiopathic TN. Side effects may occur more frequently in patients with NVC at the target coordinate when a root entry zone is used, but the subjective symptoms are not always bothersome.