Metabolic changes in the brain of patients with late-onset major depression.

Positron emission tomography (PET) with fluorodeoxyglucose-F18 was used to examine glucose metabolism in patients with late-onset major depression, all hospitalized non-responders to antidepressant medication. The three-dimensional stereotactic surface projection (3D-SSP) method provided 3D-SSP images and relative metabolic values with minimal partial volume effects. The 3D-SSP score map showed decreased relative metabolism in the prefontal, cingulate and parietal regions in both hemispheres, and in the temporal region on the right, and increased relative metabolism in the occipital pole, vermis, cerebellum, dorsal-frontal, central convexity areas and basal ganglia in both hemispheres in patients compared with controls. The ratio of the parietal to occipital values in right plus left hemispheres was significantly decreased. Correlation coefficients of the anterior cingulate-primary sensorimotor, posterior cingulate-primary sensorimotor and occipital-media frontal in both hemispheres, of the frontal-primary sensorimotor, occipital-parahippocampal, primary visual-medial frontal and parahippocampal-amygdala in the right, and the frontal-vermis, parietal-thalamus, temporal-vermis, occipital-putamen, primary visual-putamen, thalamus-vermis and thalamus-cerebellum in the left were significantly different in patients compared with controls. Patients with late-onset depression who were treatment non-responders showed alterations not only in limbic-cortical circuits, but also in a wider network of thalamo-cortical circuits.