• Yong-Sin Hu, Cheng-Chia Lee, Wan-Yuo Guo, Chung-Jung Lin, Huai-Che Yang, Hsiu-Mei Wu, Kang-Du Liu, and Wen-Yuh Chung.
• Department of Radiology, Department of Neurosurgery, Taipei Veterans General Hospital, Taipei, Taiwan.
• Neurosurgery. 2019 Apr 1; 84 (4): 927-934.

BackgroundTrigeminal nerve atrophy and neurovascular compression (NVC) are frequently observed in classical trigeminal neuralgia (CTN).ObjectiveTo determine whether nerve characteristics contribute to Gamma Knife (Elekta AB, Stockholm, Sweden) surgery (GKS) outcomes in unilateral CTN without previous surgery.MethodsFrom 2006 to 2012, 67 patients with unilateral CTN without previous surgery received GKS with a maximal dose of 90 Gy delivered to the trigeminal nerve juxta brainstem. Two evaluators, blinded to the side of pain, analyzed the magnetic resonance images before GKS to obtain the parameters, including nerve cross-sectional area (CSA), vessel type of NVC, and site of NVC along the nerve. Correlations of the parameters with pain relief (Barrow Neurological Institute [BNI] grades I-IIIb) and recurrence (BNI grades VI-V) were made by using Cox regression and Kaplan-Meier analyses.ResultsThe median CSA of the symptomatic nerves was significantly smaller than that of the asymptomatic nerves (4.95 vs 5.9 mm2, P < .001). After adjustment for age and sex, larger nerve CSA was associated with lower initial pain relief (hazard ratio 0.81, P = .03) and lower pain recurrence after initial response (hazard ratio 0.58, P = .02). Patients with nerve atrophy (CSA of ≤ 4.4 mm2 after receiver operating characteristic curve analysis) had a lower 5-yr probability of maintaining pain relief after initial response than those without nerve atrophy (65% vs 86%, P = .04).ConclusionTrigeminal nerve atrophy may predict pain recurrence in patients with initial post-GKS relief of CTN. Arterial and proximal NVC are not predictive of GKS outcomes. Future studies are required to determine optimal treatments for long-term pain relief in patients with CTN and trigeminal nerve atrophy.Copyright © 2018 by the Congress of Neurological Surgeons.

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