Corpus callosum changes in euthymic bipolar affective disorder

Background Changes in corpus callosum area and thickness have been reported in bipolar disorder. Imaging and limited neuropathological data suggest possible abnormalities in myelination and/or glial function. Aims To compare corpus callosum area, thickness and magnetic resonance imaging (MRI) T-1 signal intensity in patients with bipolar disorder and healthy controls. Method A total of 48 patients with euthymic bipolar disorder and 46 healthy controls underwent MRI analysis of callosal midsagittal area, callosal thickness and T1 signal intensity. Results The bipolar group had smaller overall and subregional callosal areas and correspondingly reduced callosal width than the control group. Age correlated negatively with callosal area in the control group but not in the bipolar group. Signal intensity was higher in women than in men in both groups. Signal intensity was reduced in women, but not in men, in the bipolar group. Conclusions Observed differences probably relate to diagnosis rather than mood state and bipolar disorder appears to result in morphometric change that overrides changes seen in normal ageing. Intensity changes are consistent with possible altered myelination or glial function. A gender-dependent factor appears to operate and to interact with diagnosis.