Dementia and functional cerebral imaging a reevaluation

New concepts which concerned especially the nosologic classification of dementia as for example Dementia with Lewy Bodies (DLB) incite to revalue the main characteristics of the regional cerebral blood flow measurements studied by SPECT in several forms of dementia. SPECT analysis with 99m-Technetium HMPAO (555 MBq) was performed to 20 patients with probable DLB, 20 patients with probable Alzheimer's disease (AD) and 20 patients with Fronto-Temporal dementia (FTD). Ten pairs of regions of interest were analysed. Tracer uptake was expressed as a cortico-cerebellar activity ratio. Statistical analysis of index of fixation was performed using an univariate analysis of variance, and a selection of significative ROIs was performed using two cut-off values (80 and 82.5 %). In the FTD group, a decrease of HMPAO uptake in frontal cortical regions of interest (internal, lateral and posterior) was observed. In the DLB group the decrease of HMPAO uptake was widespread and concerned all the cortical regions of interest except the posterior frontal and occipital regions. Finally in the AD group there was a limited temporal and parietal hypoperfusion more marked on the left side without frontal hypoperfusion. This last result was obtained whatever the cognitive impairment. Consequently it seems that the frontal hypoperfusion previously reported in AD groups was induced by the fact that patients with DLB were also included because the diagnosis was not established. In conclusion we estimate that SPECT studies could be used more often in clinical research especially for a classification approach of dementia. (authors)