Background: Neuroimaging studies have identified abnormalities in fronto-limbic brain regions of bipolar disorder (BD) probands. The aim of this study was to investigate anatomical brain abnormalities in BD and the effect of medications on volumes.
Methods: 128 healthy controls (HC, mean age 28.2±SD 21.28y; 80 females) and 77 BD patients (mean age 23.42±SD 21.62y; 54 females) were studied using 1.5T MRI with the Freesurfer Software Package (http://surfer.nmr.mgh.harvard.edu). We used ANCOVA to with age, sex, and intracranial volume as covariates to assess diagnosis and gender effects.
Results: Male BD patients had smaller left and right cerebral cortex, hippocampus and postcentral gyri (parietal lobe); left amygdala, caudal-middlefrontal volume (DLPFC) and precentral gyrus; right superior temporal sulcus banks, lingual volume (occipital lobe) with P<0.05 uncorrected. Among females, the supramarginal gyrus was smaller in the BD group compared to the HC. The right caudal anterior cingulate was larger, and part of the right thalamus smaller, in medicated compared to unmedicated BD.
Discussion: Our preliminary analysis found strong gender difference, with significant fronto-limbic volume reduction only in males, especially for hippocampus and amygdale, suggesting that volume alterations in males may represent a specific feature of the disorder and that effects of medication, when present, can be localized rather than generalized. The cingulate volumes were larger in medicated versus unmedicated BD, and this could possibly explain the lack of difference found for cingulate volumes in the comparison with HC.