Changes of cortical thickness and cortical surface area in patients with bipolar depression

Objective To investigate the changes of cortical thickness and surface area in patients with bipolar depression(BD), and to explore the relationship between abnormal changes in gray matter and clinical symptoms. Methods 28 BD patients and 28 healthy controls underwent T1-weighted MRI. The Freesurfer software was used to process the T1 images, which used a set of automated sequences to analyze cortical thickness and surface area on 66 regions (33 regions of each hemisphere), and the correlation with clinical features was also calculated. Results Compared with controls, BD patients showed thinner cortical thickness in left medial orbitofrontal cortex((2.40±0.12)mm vs (2.55±0.18)mm, P=1.2×10-3) and left rostral anterior cingulate((2.66±0.21)mm vs (2.88±0.27)mm, P=3.1×10-4), and smaller area of left cuneus((1 443.13±131.00)mm2vs (6 634.70±600.16)mm2, P=2.7×10-4)and right superior frontal gyrus((6 634.70±600.16)mm2vs (7 300.50±653.39)mm2, P=1.3×10-3). In addition, the negatively correlation was found between the cortical area of left cuneus and effective illness duration (r=-0.471, P=0.018), and the cortical thickness in left rostral anterior cingulate and total score of HAMD-17(17-item Hamilton Rating Scale for Depression)(r=-0.508, P=0.009). Conclusion There are abnormal altertion of cortical thickness and cortical areas of emotional circuit in bipolar depression, but the brain areas are not completely overlapping. Correlation analysis suggests that cortical thickness and area is related to different clinical features. Key words: Bipolar disorder; Cortical thickness; Cortical area; Structural MRI