Bipolar disorder (BD) is a common and debilitating condition, often beginning in adolescence.
Converging evidence from genetic and neuroimaging studies indicates that white matter
abnormalities may be involved in BD. In this study, we investigated white matter structure
in adolescents with familial bipolar disorder using diffusion tensor imaging (DTI)
and a whole brain analysis.
We analyzed DTI images using tract-based spatial statistics (TBSS), a whole-brain
voxel-by-voxel analysis, to investigate white matter structure in 21 adolescents with
BD, who also were offspring of at least one parent with BD, and 18 age- and IQ-matched
control subjects. Fractional anisotropy (FA; a measure of diffusion anisotropy), trace
values (average diffusivity), and apparent diffusion coefficient (ADC; a measure of
overall diffusivity) were used as variables in this analysis. In a post hoc analysis,
we correlated between FA values, behavioral measures, and medication exposure.
Adolescents with BD had lower FA values than control subjects in the fornix, the left
mid-posterior cingulate gyrus, throughout the corpus callosum, in fibers extending
from the fornix to the thalamus, and in parietal and occipital corona radiata bilaterally.
There were no significant between-group differences in trace or ADC values and no
significant correlation between behavioral measures, medication exposure, and FA values.
Significant white matter tract alterations in adolescents with BD were observed in
regions involved in emotional, behavioral, and cognitive regulation. These results
suggest that alterations in white matter are present early in the course of disease
in familial BD.