Volumetric, cortical thickness and white matter integrity alterations in bipolar disorder type I and II

Background: Bipolar disorder (BD) is a debilitating psychiatric disorder affecting millions of people worldwide with mean time to diagnosis estimated to be at least 10 years. Whilst many brain imaging studies have compared those with BD to controls, few have attempted to investigate differences between BD Type I and II and matched controls.

Methods: Thirty-one patients with BD (16 Type I and 15 Type II) and 31 matched healthy controls were MRI brain scanned with conventional T1-weighted and diffusion tensor imaging methods.

Results: There was significantly reduced regional brain volume and thickness among the BD subjects, but also between BD Type I when compared to Type II. White matter integrity also differed between the groups and BD severity correlated significantly with regional brain volume and thickness.

Limitations: Future investigations will consider length of time each BD patient had been diagnosed with BD, as well as assessing controls for family history of psychiatric illness, specifically BD. Similarly, genetic assessment will be conducted as well.

Conclusions: These findings suggest that there are not only regional brain volumetric, thickness and white matter integrity differences between BD and matched controls, but also between those with BD Type I and Type II, such that reduced regional brain volume may underlie BD Type I whereas white matter integrity is more altered in BD Type II.