Abnormal frontal white matter tracts in bipolar disorder: a diffusion tensor imaging study.

Area of Science:

• Neuroimaging
• Neuropsychiatry
• White Matter Integrity

Background:

• Prefrontal white matter integrity is hypothesized to be crucial in bipolar disorder pathophysiology.
• Previous morphometric studies have not consistently identified white matter changes in bipolar patients.
• Functional changes in bipolar disorder may stem from white matter tract dysconnectivity.

Purpose of the Study:

• To investigate prefrontal white matter integrity in bipolar disorder using diffusion tensor imaging (DTI).
• To test the hypothesis that reduced white matter tract integrity underlies prefrontal functional deficits in bipolar disorder.

Main Methods:

• Diffusion tensor imaging (DTI) was used to examine prefrontal white matter in nine bipolar disorder patients and nine healthy controls.
• Regions of interest (ROIs) were defined in prefrontal white matter at varying distances superior to the anterior commissure (AC).
• Fractional anisotropy (FA) and trace apparent diffusion coefficient (TADC) were compared between groups.

Main Results:

• Significantly reduced FA was observed in prefrontal white matter ROIs located 25 and 30 mm superior to the AC in bipolar disorder patients.
• Effect sizes for FA differences were medium to large across all ROIs.
• No significant differences in TADC were found between patient and control groups.

Conclusions:

• Findings suggest a loss of white matter bundle coherence in the prefrontal region of individuals with bipolar disorder.
• This compromised white matter integrity may contribute to the observed prefrontal cortical pathology in bipolar disorder.
• The results support a dysconnectivity model of bipolar disorder pathophysiology.