Corpus callosum abnormalities in BD patients

By Mark Cowen, Senior MedWire Reporter

Patients with bipolar disorder show area reductions in the genu and isthmus subregions of the corpus callosum (CC) compared with mentally healthy controls, researchers report.

"The genu and the isthmus could be important areas in the connection of different brain structures, such as the frontal lobe, that are related to mood regulation, and this finding may provide an initial explanation for the mood dysregulation observed in bipolar patients," comment Fabiana Nery-Fernandes (Universidade Federal da Bahia, Salvador, Brazil) and colleagues.

The researchers also found that BD patients with a history of suicide attempts display greater levels of impulsivity, even during periods of euthymia, than those without such a history.

They studied associations between corpus callosum (CC) area, impulsivity, and suicidal behavior among 19 BD euthymic patients with a history of suicide attempts, 21 euthymic BD patients without such a history, and 22 mentally healthy controls.

All of the participants underwent magnetic resonance imaging (MRI) of the brain and were assessed for impulsivity using the Barratt Impulsiveness Scale (BIS-11).

Results from the MRI scans revealed no significant difference between BD patients with and without a history of suicide attempts regarding any CC subregion area measurements.

However, BD patients (as one group) had significantly smaller genu and isthmus measurements than controls, at 106.38 versus 114.71 mm² and 44.66 versus 51.67 mm², respectively.

The researchers also found that BD patients with a history of suicide attempts had significantly higher BIS-11 total, attention, and non-planning impulsivity scores than those without such a history and controls, at 67.3 versus 58.3 and 58.5, 20.5 versus 16.6 and 17.5, and 26.4 versus 22.1 and 23.1, respectively.

However, no correlations were observed between any subregion of the CC and BIS-11 total or subscale impulsivity scores.

Nery-Fernandes et al conclude in the Journal of Affective Disorders: "This report potentially provides evidence that a reduction in the CC area is present even in non-symptomatic bipolar patients, which may be evidence of a biological trait marker for BD.

"Furthermore, the study demonstrated that [BD patients with a history of suicide attempts] had higher impulsivity even during euthymia, which points to a sustained association between lifetime history of suicide attempts and impulsivity in BD."

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