US researchers have found significant white matter tract alterations in adolescent patients with bipolar disorder (BD) within pathways 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,” say Naama Barnea??”Goraly (Stanford University, California) and co-authors.

A number of studies indicate that white matter abnormalities are present in BD. To investigate further, the researchers analyzed diffusion tensor imaging (DTI) images using a whole-brain voxel-by-voxel analysis to investigate white matter structure in 21 adolescents with familial BD and 18 age- and intelligence quotient-matched healthy individuals.

BD patients had lower white matter fractional anisotropy (FA) values than healthy individuals within the limbic system (the fornix and the left mid-posterior cingulated gyrus), which has been hypothesized to contribute to the combination of affective, cognitive, and vegetative symptomatology in BD.

The researchers point out that the fornix findings in their study should be interpreted with caution due to the thin nature of the fornix, which could result in partial volume effects.

BD patients also had lower FA values than controls throughout the corpus callosum, in fibers extending from the fornix to the thalamus, and in parietal and occipital radiata bilaterally.

Barnea??”Goraly and team say that their finding of reduced FA in the corpus callosum is at odds with a previous study in adults, which “may indicate an abnormal maturation process in the corpus callosum occurring in individuals with BD, with lower FA in adolescence representing reduced coherence or aberrant myelination with increasing FA with age.”

No significant differences were seen between groups in apparent diffusion coefficient values, a measure of overall diffusivity. Furthermore, there were no significant correlations between behavioral measures or medication exposure and FA values.

“An intriguing and important follow-up study will be to investigate whether early treatment of BD normalizes the development of these pathways and if improvement of particular symptoms is associated with structural changes in regional white matter anatomy,” suggest the researchers.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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