Regional cerebral blood flow in the assessment of major depression and Alzheimer's disease in the early elderly.

BACKGROUND

Alzheimer's disease and major depression are representative diseases that present forgetfulness and a depressive mood. It is often difficult to make a differential diagnosis between the two in the initial phase.

AIM: To evaluate the differential diagnosis method using regional cerebral blood flow patterns with a three-dimensional stereotactic surface projection technique.

METHODS

Twenty early-elderly patients with mild and moderate forgetfulness were studied. Among them, 10 were diagnosed as having major depression (the MD group) and the other 10 as having Alzheimer's disease (the AD group). All patients underwent cerebral perfusion single photon emission computed tomography (SPECT) with [(123)I]iodoamphetamine. A z-score was calculated for each pixel of the cerebral surface. Twenty-one circular regions of interest (ROIs) were placed on the z-score map. The significance of the statistical difference in ROI values between the two groups was determined by using the two-sided Mann-Whitney U-test.

RESULTS

The z-scores for the lateral parietal, lateral temporal, bilateral precuneus and bilateral posterior cingulate gyrus were significantly reduced in the AD group compared with those in the MD group. The z-scores for the lateral frontal, left thalamus and bilateral medial frontal regions were significantly lower in the MD group than in the AD group.

CONCLUSION

Our study demonstrated a difference in regional cerebral blood flow patterns between the early elderly with Alzheimer's disease and those with major depression. All patients were classified into the appropriate categories using discriminant analysis and z-scores of frontal and parietal regions. Brain perfusion SPECT was a useful tool for the differential diagnosis between Alzheimer's disease and major depression.