Brain alterations evident in bipolar II disorder
medwireNews: Results from a combined voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) study show that patients with bipolar II disorder (BD II) have structural brain alterations compared with mentally healthy individuals.
However, these alterations are less pronounced than those previously observed in patients with BD I, "confirming reports that brain structure of [BD II] patients is less severely affected than that of [BD I] patients," say Elisa Ambrosi (Sapienza University, Rome, Italy) and team.
The findings come from a study of 20 euthymic BD II patients, aged between 18 and 65 years (mean age 41.9 years), and 21 mentally healthy controls.
There were no significant differences between the groups regarding age, gender, and handedness, but controls had received significantly more years of education than BD II patients, at a mean of 16 versus 13 years.
All of the participants underwent magnetic resonance imaging of the brain, with VBM and DTI used to assess between-group differences in gray and white matter volume.
The team found that, compared with controls, BD II patients showed localized gray matter volume reductions mainly in the right middle frontal gyrus (Brodmann area 8) and the right superior temporal gyrus (Brodmann area 22). There were no brain regions in which BD II patients showed greater gray matter volume than controls.
Regarding white matter, BD II patients showed significantly lower fractional anisotropy values than controls in all major white matter tracts studied, including cortico-cortical association tracts (ie, the uncinate, inferior fronto-occipital, inferior longitudinal, and superior longitudinal fasciculi), interhemispheric tracts, and limbic tracts.
The researchers note that education level did not correlate with any VBM or DTI measure.
Ambrosi and team conclude in the Journal of Affective Disorders: "Our preliminary combined VBM-DTI study found structural brain differences between [BD II] patients and HCs [healthy controls]; these differences are less pronounced than previously described differences between [BD I] patients and HCs.
"Further studies should seek to address some still unresolved issues, i.e., stability of alterations over time and their possible phase-relatedness, and their correlation with clinical and neuropsychological measures."
By Mark Cowen, Senior medwireNews Reporter