A systematic review of DTI studies in Bipolar Disorder

Includes bibliographical references.In the last decade, multiple diffusion tensor imaging (DTI) studies have revealed changes in the microstructure of white matter in bipolar disorder. The results are poorly replicated and inconsistent, however, with some authors suggesting a predominance of alterations in fronto-limbic white matter. Preliminary reading of the literature suggests that white matter changes as revealed by DTI may be more widespread throughout the brain. Two extant reviews have each been limited by including all affective disorders or by a methodology which ignores tracts and discards potentially meaningful data. This background in the review includes a detailed exposition of the main DTI techniques and shortcomings. The review aims to determine whether certain white matter tracts are affected preferentially in the brain, as opposed to more diffuse white matter involvement. It also aims to determine if there is an anterior-posterior gradient of abnormalities. This review systematically collates data relating to tract involvement as demonstrated by DTI, as well as data regarding anterior-posterior distribution of abnormalities. Medline and EMBASE databases are searched systematically to select original papers comparing a bipolar group with healthy controls, using DTI, in adults, and reporting at least fractional anisotropy (FA). Subject, scan and analysis characteristics are extracted. Details of affected tracts are collated, as is the y-axis (anterior/posterior) of the most affected ('peak') voxels