SPECT patterns in probable Alzheimer's disease.

Abstract

The primary objective of this study was to test hypotheses about the relationship between HMPAO-SPECT findings and probable Alzheimer's disease (DAT) in a relatively large sample of patients diagnosed according to DSM-III-R. SPECT patterns of 20 controls and 116 DAT patients were investigated. Left and right frontal, temporal, parietal and occipital regions of the brain were rated as showing a hypoperfusion or not. A wide variety of patterns were found and these are described in detail below. In DAT patients, temporal and/or parietal regions were affected significantly more often (88%, p > 0.001) than frontal and/or occipital regions (70%). A bilateral temporoparietal pattern, which has been repeatedly reported as typical for DAT, was observed in 48% of DAT patients, but also in 25% of controls, and did not differentiate significantly between these two groups (p > 0.05). Conversely, more than three regions with hypoperfusion were observed significantly more often in DAT patients (48%, p < 0.01) than in controls (10%). In DAT patients, the number of regions with hypoperfusion correlated significantly with the score of the Mini Mental State Examination (MMSE, r = 0.33, p < 0.001). The frequency of at least one hypoperfusion was approximately equal in left and right hemispheres (77% vs. 73%, p = 0.2). The hypothesis that cognitive decline in DAT starts in the temporal regions was tested in 14 SPECT patterns showing only one region with hypoperfusion. In 12 of these patterns, a temporal region was in fact affected (p < 0.001). Whereas hypoperfusion in frontal areas was not accompanied by a significantly lower MMSE than when only temporoparietal regions were affected, MMSE scores were significantly lower when occipital regions were affected in addition to temporoparietal regions (p < 0.05). The clinical use of SPECT findings was tested in discriminating analyses with the MMSE and a delayed recall test as additional predictors of DAT. Whereas the MMSE and the delayed recall test differentiated significantly between DAT patients and controls, SPECT findings yielded no further differentiation. In conclusion, the theoretical and clinical implications of SPECT findings and their relationships to other physiological and psychological variables deserve further investigation.