Diffusion tensor imaging white matter fiber bundles in unmedicated bipolar disorder

Abstract

Objective To investigate the changes of white matter fiber bundles in patients with bipolar disorder depressive epoch. Methods Forty-two patients with unmedicated bipolar disorder (BD) depression and 59 age-, sex- and handedness-matched healthy controls who underwent DTI were recruited in the study. According to the Johns Hopkins University human white matter fiber bundle map, the white matter tissue of the brain was segmented into 20 acknowledged large fiber bundles. The PANDA software was used to calculate the four average diffusion properties of each white matter fiber bundle for each subject. Nonparametric substitution test was used to detect the difference of diffusion index between the two groups on these 20 white matter fiber bundles. Pearson correlation analysis was performed between FA values and RD values extracted from significantly different white matter fiber bundles and clinical indices. Results In comparison to the normal controls, BD patients had a significant decreased fractional anisotropy (FA) values in the left uncinate fasciculus (0.40±0.01 vs. 0.41±0.01, P=0.001) and the forceps minor (0.36±0.02 vs. 0.38±0.02, P<0.001). Additionally, the radial diffusivity values increased in the left uncinate fasciculus (6.57×10-4±2.41×10-5vs. 6.40×10-4±2.42×10-5, P=0.001 7). Pearson correlation analysis showed that there were no significant correlations among the clinical indices the FA values and AD values in the left uncinate fasciculus and forceps minor. Conclusions The patients with bipolar disorder in depression possibly have abnormal left uncinate fasciculus and the forceps minor. Key words: Bipolar disorder; Diffusion tensor imaging; White matter fiber bundle atlas; Uncinate fasciculus; Forceps minor