Reduced white matter axonal density in bipolar disorder using Neurite Orientation Dispersion and Density Imaging (NODDI)

Bipolar disorder is a serious psychiatric condition whose cause remains unknown. Previous diffusion MRI studies suggest white matter alterations may be involved, but standard diffusion tensor scalars provide limited information regarding potential pathophysiology. Here we used Neurite Orientation Dispersion and Density Imaging (NODDI) to examine select white matter bundles to provide additional information regarding changes in microstructure. We found that the uncinate fasciculus, cingulum hippocampus, and corpus callosum genu showed evidence of reduced axonal density, suggesting axonal loss or altered neurodevelopment. Additional work is necessary to determine how this pattern changes over time, and how it relates to mood lability.