REGIONAL CEREBRAL BLOOD-FLOW MEASURED BY TC-99M-HMPAO SPECT DIFFERS IN SUBGROUPS OF ALZHEIMERS-DISEASE

Alzheimer's disease (AD) is a heterogeneous entity. Identifying AD sub types might have impact in patients' response to different treatment s trategies. We designed a study to examine regional cerebral blood flow (rCBF) in AD subtypes. To identify AD subtypes, we performed a cluste r analysis including performance on memory, language, visuospatial, pr axic, and executive functions. The rCBF measured by Tc-99m-HMPAO SPECT was referred to the cerebellum. We examined 35 patients fulfilling th e NINCDS-ADRDA criteria of probable AD and 13 age and sex-matched heal thy cognitively intact controls. AD patients were at the early stage o f the disease, their mean Mini-Mental Status (MMS) score (S.D.) was 22 .5 (3.6). The cluster analysis revealed two AD subgroups: AD1 (N = 12) and AD2 (N = 23). The subgroups did not differ in age, sex, or global clinical severity as assessed by MMS and Brief Cognitive Rating Scale (BCRS). Both subgroups had equally impaired memory. The AD2 group was inferior to the AD1 group on verbal, visuospatial, praxic, and execut ive functions. The AD1 group showed reduced rCBF ratios in the tempora l and parietal cortices and the amygdala compared to controls. The AD2 group differed from controls in the rCBF ratios of frontal, temporal, parietal, occipital, basal ganglia, and amygdaloid regions bilateral and from AD1 in the rCBF ratios of frontal and temporal cortices. In A D patients, the rCBF ratios did not correlate with MMS or BCRS scores. In contrast, several significant correlations were found between decr eases rCBF ratios and impairment of memory and other cognitive functio ns. In conclusion, a cluster analysis on neuropsychological test perfo rmance identified two AD subgroups that differed on the neuropsycholog ical profile and on the rCBF in spite of similar global clinical sever ity.