HETEROGENEITY OF NEOCORTICAL CEREBRAL BLOOD-FLOW DEFICITS IN DEMENTIAOF THE ALZHEIMER-TYPE - A [TC-99M]-D,L-HMPAO SPECT STUDY

Regional cerebral blood flow (rCBF) was measured with high resolution brain dedicated single photon emission computer tomography (SPECT) and [Tc-99m]-d,l-hexamethyl-propylene-amineoxime (HMPAO) in 25 patients w ith probable Alzheimer's disease and in 25 control subjects, selected according to rigorous inclusion and exclusion criteria. The aim was to analyse the topography of rCBF deficits in individual patients. In th e group of patients with Alzheimer's disease as a whole, global CBF wa s reduced, but a factorial analysis of variance did not show dispropor tionate reduction of rCBF in any brain region. A parametric analysis o f the rCBF data in individual patients was carried out with reference to normal values for internal rCBF ratios and to 13 different abnormal rCBF patterns. These theoretical patterns were predefined by showing significant hypoperfusion in at least one, or in any relevant combinat ion of two, three, or four, of four major brain regions (a left and ri ght frontal and a left and right posterior region). All patients with Alzheimer's disease and none of the control subjects had an abnormal r CBF pattern. Eleven of the 13 different patterns were seen in the pati ents. Frontal changes were seen in 19 (76%) of the patients, more ofte n than previously reported. No single Alzheimer's disease pattern coul d be derived from our data. The number of regions with hypoperfusion, but not the presence of frontal changes, correlated significantly with the duration of disease. It is concluded that a clinical diagnosis of probable Alzheimer's disease is associated with heterogeneous pattern s of rCBF deficits as measured with SPECT and [(TC)-T-99m]-d,l-HMPAO. This heterogeneity may reflect different stages of the disease or cogn itive subtypes and help explain published discrepancies concerning the topography of hypoperfusion in Alzheimer's disease. An analysis of in dividual rCBF data may add important information in the investigation of diseases with heterogeneous effects on the brain.