Morphologic (CT) and functional (rCBF-SPECT) correlates in Alzheimer's disease.

Thirty-five patients with a clinical diagnosis of probable Alzheimer's disease underwent computed tomography (CT) and regional cerebral blood flow (rCBF) studies using single photon emission computed tomography (SPECT). Two sets of images in each subject were scored for the extent of structure and function changes. Thirty-four of 35 patients had various degrees of atrophy on CT, 33 of whom also had perfusion deficits of varying severity. One patient with normal CT had perfusion deficits, and another patient with a normal perfusion pattern had changes on CT. Regional perfusion deficits on SPECT were seen with and without associated changes on CT. Correlations were studied between CT and SPECT scores using Spearman's rank correlation coefficients. While regional scores on CT and SPECT did not significantly correlate, the total and left hemisphere scores on two sets of images showed fair correlations (r = 0.425 and r = 0.535, respectively, P less than 0.01). The correlations between cognitive performance in patients as assessed on Mini-Mental State Examination (MMSE) and CAM-COG and perfusion scores were highly significant while CT scores showed lower correlations. These findings suggest that the relationship between structural and functional changes in Alzheimer's disease is not straightforward and that the extent of changes in function as assessed by regional cerebral blood flow studies is a reliable measure of deficits in cognitive function.