Trigeminal nerve asymmetry in classic trigeminal neuralgia - pretreatment volumetry and clinical evaluation in patients irradiated by Leksell Gamma Knife.

OBJECTIVES: The etiology of classic trigeminal neuralgia (CTN) is still under debate and, together with neurovascular compression (NVC), other anatomical abnormalities have been considered, including differences of trigeminal nerve (TN) volume.

DESIGN: We evaluated the volumes of affected and non-affected nerves and the presence and type of NVC in large group of 84 CTN subjects prior to gamma knife treatment (GKS) on MR images. Correlation between affected nerve volume and NVC, treatment outcome and demographic characteristics were explored.

RESULTS: NVC was detected in 71% of affected nerves, 52% of non-affected nerves, and in 31% of subjects bilaterally. Lower trigeminal nerve volume was detected on the affected side (p<0.001, affected mean 34.9 mm3 ± 14.4 SD, non-affected mean 41.9 mm3 ± 17.7 SD), however, no correlation between affected nerve volume and the presence and type NVC, treatment outcome or demographic data was detected.

CONCLUSION: Our results suggest that NVC may trigger CTN in susceptible subjects but is not a reliable disease marker. Lower trigeminal nerve volume appears to manifest independently of NVC, and may represent nerve asymmetry rather than atrophy. No correlation between volumetry and clinical data was detected including treatment outcome after GKS.