Regional cerebral blood flow abnormalities associated with apathy and depression in Alzheimer disease

The aim of this study was to identify brain areas related to apathy or depression in patients with Alzheimer disease (AD). Eighty-one AD patients were enrolled in this prospective study. (99m)Tc-HMPAO single photon emission computed tomography was performed to evaluate regional cerebral blood flow (rCBF). According to the Neuropsychiatric Inventory subscores of apathy and depression, 9 patients were classified as clinically significant (cs) depressed and non-cs-apathetic (D+) groups and 9 were classified as cs-apathetic and non-cs-depressed (A+) groups. In addition, 18 patients were classified as age-matched and Mini-Mental State Examination-matched disease control groups (D-, A-). The significance of rCBF differences between groups and the correlation between rCBF and subscores in 81 AD patients were estimated by SPM (uncorrected P < 0.005) analysis. D+ patients had significantly lower perfusion in the right orbitofrontal and inferior frontal gyri than D- patients, whereas A+ patients had this in the right amygdala, temporal, posterior cingulate, right superior frontal, postcentral, and left superior temporal gyri than A- patients. The negatively correlated areas with depression subscores included the left inferior frontal and the right middle frontal gyri and those with apathy subscores included the right temporal and right medial frontal gyri. We suggest that this finding may indicate that apathy and depression in AD patients involve distinct functional circuits.