MRI volumetry for the preoperative diagnosis of trigeminal neuralgia.

To assess whether quantitative measuring methods can help improve the reliability of MRI-based evaluations of the pathological role of a neurovascular conflict between an artery and the trigeminal nerve. In a prospective study, magnetic resonance images were obtained from 62 patients with unilateral facial pain and 50 healthy test subjects. In coronal T1- and T2-weighted sequences volume measurements were performed by regions of interest and compared intraindividually (healthy versus affected side in the patient populations and right versus left side in the group of test subjects) and on the basis of the different clinical pictures (t test for dependent and independent samples, p<0.05). In patients with trigeminal neuralgia, the affected nerve showed a smaller volume than the trigeminal nerve on the healthy side (p<0.001). Such a volume difference was noted neither in the other patients nor in the healthy test subjects. Quantitative MRI measurements allow a pathological neurovascular conflict to be distinguished from a nonpathological condition where an artery is in close proximity to the trigeminal nerve. The measured volume difference between the healthy and the affected nerve in patients with neuralgia is indicative of trigeminal nerve atrophy resulting from damage to the nerve.