AMYGDALA VOLUME IN DEPRESSED PATIENTS WITH BIPOLAR DISORDER ASSESSED USING HIGH RESOLUTION 3T MRI: THE IMPACT OF MEDICATION

Abstract MRI-based reports of both abnormally increased and decreased amygdala volume in bipolar disorder (BD) have surfaced in the literature. Two major methodological weaknesses characterizing extant studies are treatment with medication and inaccurate segmentation of the amygdala due to limitations in spatial and tissue contrast resolution. Here, we acquired high-resolution images (voxel size = 0.55 × 0.55 × 0.60 mm) using a GE 3T MRI scanner, and a pulse sequence optimized for tissue contrast resolution. The amygdala was manually segmented by one rater blind to diagnosis, using coronal images. Eighteen unmedicated (mean medication-free period 11 ± 10 months) BD subjects were age and gender matched with 18 healthy controls, and 17 medicated (lithium or divalproex) subjects were matched to 17 different controls. The unmedicated BD patients displayed smaller left and right amygdala volumes than their matched control group ( p p  = 0.051). Right and left amygdala volumes were larger ( p