Depressive symptoms and regional cerebral blood flow in Alzheimer's disease

Depressive symptoms are common in patients with Alzheimer's disease (AD) and increase the caregiver burden, although the etiology and pathologic mechanism of depressive symptoms in AD patients remain unclear. In this study, we tried to clarify the cerebral blood flow (CBF) correlates of depressive symptoms in AD, excluding the effect of apathy and anxiety. Seventy-nine consecutive patients with AD were recruited from outpatient units of the Memory Clinic of Okayama University Hospital. The level of depressive symptoms was evaluated using the depression domain of the Neuropsychiatric Inventory (NPI). The patients underwent brain SPECT with 99mTc-ethylcysteinate dimer. After removing the effects of age, anxiety and apathy scores of NPI, and five subscales of Addenbrooke's Cognitive Examination-revised (ACE-R), correlation analysis of NPI depression scores showed a significant cluster of voxels in the left middle frontal gyrus (Brodmann area 9), similar to the areas in the simple correlation analysis. The dorsolateral prefrontal area is significantly involved in the pathogenesis of depressive symptoms in AD, and the area on the left side especially may be closely related to the depressive symptoms revealed by NPI.