Short-term longitudinal evaluation of cerebral blood flow in mild Alzheimer's disease

The aim of this study was to estabilish whether subtle changes in regional cerebral blood flow (rCBF) can be detected in patients with mild Alzheimer's disease (AD) over a period as short as three months. Aprospective evaluation of rCBF changes with HMPAO SPECT at baseline and after 3 and 6 months was carried out. Standard clinical dementia tests were performed in parallel. The study enrolled 13 patients with mild probable AD from an outpatient memory clinic. SPECT data collected at baseline and after three months were compared using Statistical Parametric Mapping (SPM). Significant clusters of rCBF decrement in the medial part of the temporal lobe in both hemispheres, in the orbital part of the right frontal lobe and in the inferior part of the right parietal lobe were observed. No significant differences were found using a region of interest (ROI) analysis. After six months SPM analysis showed larger clusters of significant decrement in the same areas. ROI analysis was now sensitive to the rCBF changes and significant differences were shown in all brain regions except the temporal lobes. SPM analysis of SPECT data can detect significant changes in rCBF in mild AD over a short time interval. This method might be of potential advantage for the early diagnosis of AD and for its differentiation from stable cognitive impairments.