A voxel-based diffusion tensor imaging study of white matter in bipolar disorder

Area of Science:

• Neuroimaging
• Neuroscience
• Psychiatry

Background:

• Bipolar disorder pathophysiology involves white matter abnormalities, including hyperintensities and volumetric alterations.
• Functional imaging suggests frontal cortico-subcortical pathway defects in bipolar disorder, but white matter integrity is understudied.
• Previous white matter studies in bipolar disorder are limited and often use manual region-of-interest methods.

Purpose of the Study:

• To compare white matter integrity, specifically fractional anisotropy (FA), between patients with bipolar disorder and healthy volunteers.
• To investigate the specific white matter tracts implicated in bipolar disorder using advanced neuroimaging techniques.

Main Methods:

• Voxelwise analysis of fractional anisotropy (FA) in white matter comparing 30 bipolar disorder patients and 38 healthy volunteers.
• Analysis of individual eigenvalues (axial and radial diffusivity) to understand FA group differences.
• Tractography on averaged diffusion tensor imaging data to identify affected white matter bundles.

Main Results:

• Patients with bipolar disorder exhibited significantly higher FA in right and left frontal white matter (p<0.001).
• Patients showed significantly lower FA in left cerebellar white matter (p<0.001).
• Group differences in axial and radial diffusivity contributed to altered FA in these regions.

Conclusions:

• White matter abnormalities in frontal and cerebellar regions are implicated in bipolar disorder.
• Affected tracts include the pontine crossing tract, corticospinal/corticopontine tracts, and thalamic radiation fibers.
• Findings support models implicating cortico-subcortical and cerebellar dysregulation in bipolar disorder pathogenesis and phenomenology.