White Matter Microstructural Abnormalities and Cognitive Functions Assessment in First versus Multiple episodes of Euthymic Bipolar Cases

Abstract

Background: Recently, several studies have detected cognitive impairment and microstructural anomalies of white matter (WM) in bipolar disorder type I (BD-I). It is still unclear if these structural and cognitive anomalies in BD are progressive or static. Subjects and Methods: We investigated Diffusion Tensor Imaging (DTI) derived fractional anisotropy (FA) and cognitive functions in 40 cases with euthymic BD I, who were subdivided into 20 cases with single episode and another 20 cases with multiple episodes, and were further compared with 20 healthy controls. Four tracts bilaterally (cingulum, inferior longitudinal fasciculus, superior longitudinal fasciculus, and uncinate fasciculus) and three areas (left rostral anterior cingulate, right inferior frontal area, and right subgenual anterior cingulate) were studied. The findings were further correlated with cognitive functions (memory, executive functions, and sustained attention), which were assessed using Trail Making Test A and B, Wisconsin Card Sorting Test, Wechsler Memory Scale, and Continuous Performance Test). Results: Cases with BD I either with a single episode or multiple episodes showed deficits than the control group in all the selected regions except right subgenual anterior cingulate in comparison to controls. Also, more deficits were found as regards cognitive functions. On the other hand, cases with many episodes had lower FA than those with a single episode regarding seven regions of interest (left and right inferior longitudinal fasciculus, left and right superior longitudinal fasciculus, left uncinate fasciculus, right cingulum, and right inferior frontal area) as well as more impairment in executive functions and sustained attention which correlated with these white matter abnormalities. Discussion and Conclusion: The present findings indicate that white matter microstructural abnormalities and cognitive functions deficits could serve as state and trait markers in cases with BD I. The detected abnormalities could affect the future in early diagnosis and intervention, thus facilitating functional recovery in cases with BD I.