White matter microstructure alterations in bipolar disorder

Genetic, neuropathologic and magnetic resonance imaging (MRI) findings support diffuse white matter cytoarchitecture disruption in bipolar disorder. In this study, diffusion weighted imaging (DWI) was applied to study cortical white matter microstructure organisation in 24 patients with DSM-IV bipolar disorder and 35 matched normal controls. DWI images were obtained using a 1.5 Tesla scanner and apparent diffusion coefficient (ADC) values were determined over regions of interest placed, bilaterally, in the frontal, temporal, parietal, and occipital white matter. Significantly increased ADC values were found in bipolar patients with respect to normal controls in right temporal lobe, left parietal lobe, and bilateral occipital lobes. ADC values did not associate significantly with age or with clinical variables (p>0.05). Diffuse cortical white matter alterations on DWI in bipolar disorder denote widespread disruption of white matter integrity and may be due to alterations of myelination and/or axonal integrity