White Matter Microstructural Changes in Bipolar Disorder: A HARDI CSD Tractography Study

Louise Emsell¹, ², Alexander Leemans³, Wim Van Hecke⁴, ⁵, Camilla Langan², Gareth J. Barker⁶, Peter McCarthy², Stefan Sunaert¹, Dara Cannon², Colm McDonald²

Structural brain changes detected by diffusion tensor tractography have been reported in bipolar disorder. However the investigation of heterogeneous clinical populations and the limitations of the tensor model for tractography have resulted in contradictory findings. We used high angular resolution diffusion imaging and a constrained spherical deconvolution approach to improve tract delineation in crossing-fibre regions. We investigated anatomically defined subdivisions of the corpus callosum, cingulum and fornix in a sample of 35 prospectively confirmed euthymic bipolar 1 disorder patients and 44 healthy controls. We detected widespread reductions in fractional anisotropy and increases in diffusivity measures in patients compared to controls.