White matter microstructural abnormalities in families multiply affected with bipolar I disorder: a diffusion tensor...

Area of Science:

• Neuroimaging
• Neuroscience
• Psychiatry

Background:

• White matter (WM) abnormalities are potential endophenotypic markers for bipolar disorder (BD).
• Previous diffusion tensor imaging (DTI) voxel-based analysis (VBA) linked widespread fractional anisotropy (FA) abnormalities to BD and genetic liability.
• This study further explores WM abnormalities using DTI tractography to investigate tracts involved in BD pathophysiology.

Purpose of the Study:

• To investigate the endophenotypic potential of white matter (WM) abnormalities in bipolar disorder (BD).
• To analyze specific white matter tracts implicated in the pathophysiology of BD using DTI tractography.
• To examine the effects of participant group and genetic liability on WM microstructure.

Main Methods:

• Diffusion magnetic resonance imaging (MRI) data from 19 BD patients, 21 unaffected relatives, and 18 healthy volunteers.
• DTI tractography applied to identify key tracts: cingulum, uncinate fasciculus (UF), superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), corpus callosum, and anterior limb of the internal capsule (ALIC).
• Regression analyses to assess group and genetic liability effects on fractional anisotropy (FA) and radial diffusivity (RD).

Main Results:

• Significant group effects on FA and RD in the cingulum, SLF, callosal splenium, and ILF, with reduced FA and increased RD in BD patients.
• Genetic liability correlated with decreased FA and increased RD in the UF.
• Genetic liability was also associated with decreased FA in the SLF among patients.

Conclusions:

• WM microstructural abnormalities in limbic, temporal, and callosal pathways are associated with BD.
• Alterations in the SLF and UF may serve as potential endophenotypic markers for BD risk.
• DTI tractography provides insights into the neural underpinnings of BD and genetic susceptibility.