Abstract: Objective　To provide the imaging basis on microstructure changing for the clinical diagnosis of trigeminal neuralgia.　Methods　There were 150 normal persons and 100 patients with primary trigeminal neuralgia selected by diffusion tensor imaging (DTI) scanning of the cranial brain, and all patients were unilateral. The patients were divided into group A  (close or contact group), group B (mild compression group), group C (severe compression group) and group D (compression deformation and atrophy group) according to the degree of lesion. The region of interest was divided into the cisternal segment of trigeminal nerve and the lesion site of trigeminal neuralgia at workstation, and the apparent diffusion coefficient (ADC) value and fractional anisotropy (FA) value of the region of interest were measured.  ADC values and FA values of different ages, sites, the affected and healthy sides of trigeminal neuralgia, and different lesions of the trigeminal cerebral cistern were compared.　Results　There was no statistical differences in other ADC values and FA values between the groups under 35 years old, 35~55 years old and over 55 years old except the ADC value at 6 mm and 9 mm from the brainstem (P＞0.05). Apart from the FA values at 6 mm and 9 mm, statistical differences in other FA values and ADC values between the 0 mm, 3 mm, 6 mm and 9 mm length from brainstem of the cisternal segment of trigeminal nerve were found (P＜0.05). statistical differences in the ADC values and FA values among the affected-side group, the healthy-side group of trigeminal neuralgia and the normal group were found(P＜0.05), and no statistical difference in ADC values and FA values between the healthy-side group of trigeminal neuralgia and normal group was found (P＞0.05). Statistical differences in ADC values and FA values among the A, B, C and D groups on the affected side of trigeminal neuralgia were found (P＜0.05).　Conclusions　The ADC values and FA values of the cisternal segment of trigeminal nerve are closely related to the age, position and the degree of vascular compression on the affected side of trigeminal neuralgia. DTI can provide an objective imaging diagnostic basis for the changes in the microstructure of the trigeminal cistern.

Key words: Trigeminal neuralgia, Cisternal segment of trigeminal nerve, Diffusion tensor imaging, MRI