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 mm(3) in nondeviated cases (n = 27) and 2.59 ± 1.68 mm(3) 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.