Technetium HMPAO SPECT study in dementia with Lewy bodies, Alzheimer's disease and idiopathic Parkinson's disease

The aim of this, study was to compare the regional cerebral blood flow meas urements studied by SPECT in dementia with Lewy bodies (DLB) and Alzheimer' s disease (AD) to determine the contribution of SPECT to the differential d iagnosis of these two diseases. Methods: SPECT analysis with Tc-99m-hexamet hyl propyleneamine oxime (HMPAO) was performed in 20 patients with probable DLB, 20 patients with probable AD and 20 patients with idiopathic Parkinso n's disease (IPD). Ten pairs of regions of interest were analyzed. Tracer u ptake was expressed as a corticocerebellar activity ratio. Results: Compare d with IPD, in the DLB group there was a global decrease of HMPAO uptake in cortical regions of interest except in the posterior frontal and occipital regions; in the AP group there was limited left temporal and parietal hypo perfusion. In the DLB group, frontal HMPAO uptake was significantly lower t han in the AD group. Two predictive scores were established by a factorial discriminant analysis from six left Cortical indices (medial frontal, later al frontal, posterior frontal, temporoparietal, parietal and parietooccipit al) and the Mini-Mental State Examination,which correctly classified 53 of 60 patients (88%) (DLB, 18 of 20; AD, 16 of 20; IPD, 19 of 20). Conclusion: These findings indicate the presence of diffuse cortical abnormalities in LB and suggest that SPECT may be useful in discriminating in vivo DLB from AD, revealing mainly frontal hypoperfusion in the former group. We estimate that SPECT study increases the possibility of separating DLB and AD becaus e both disorders share different patterns of cerebral blood flow abnormalit y.