A SINGLE-PHOTON EMISSION COMPUTERIZED-TOMOGRAPHY STUDY OF REGIONAL BRAIN-FUNCTION IN ELDERLY PATIENTS WITH MAJOR DEPRESSION AND WITH ALZHEIMER-TYPE DEMENTIA

The uptake, at rest, of Tc-99m-exametazime into different brain region s was compared using SPECT for 20 elderly subjects with major depressi ve disorder, 20 with Alzheimer-type dementia, and 30 age-matched norma l volunteers. Uptake was referred to calcarine-occipital cortex as a r eference sensory area. Cross-sectional differences between the three g roups were highly statistically significant, but reflected primarily t he reductions in cortical uptake in the Alzheimer group. A detailed co mparison of depressed patients and controls identified decrements in a nterior cingulate, temporal and frontal cortex and in caudate and thal amus in men only. These decrements were correlated with impairment of performance on a trail-making task, but were also associated with cont inuing treatment with antidepressants or benzodiazepines. However, mos t depressed patients had quantitatively normal scans for posterior par ietal association cortex, and this suggests that SPECT may find a limi ted role in the differential diagnosis of depression and dementia. The reduced brain function in some depressed patients may parallel the fi ndings from studies of brain structure in elderly depressives; there w as a weak association between good outcome at 6-18 months and increase d tracer uptake in subcortical areas.