Cerebral blood flow abnormality in clinically diagnosed Alzheimer's disease patients with or without amyloid β accumulation on positron emission tomography

Background The detection of amyloid β accumulation might be useful in confirming the diagnosis of Alzheimer's disease in clinically suspected cases. However, confirmation of the disease by a positron emission tomography scan is not always available. Aim We measured the cerebral blood flow in clinically suspected Alzheimer's disease cases, and compared the findings between amyloid-positive and -negative cases. Methods At the Osaka City University Hospital, patients with “probable or possible Alzheimer's disease” were enrolled. In addition, “healthy volunteers” with no subjective decline in cognitive function or in cognitive tests were evaluated as controls. A positron emission tomography scan with Pittsburgh compound B as a tracer was utilized to detect amyloid accumulation. Results In the healthy control cases aged >60 years, a positive rate of amyloid increased steeply with age. In contrast, an amyloid-positive rate decreased with age in the clinically suspected Alzheimer's disease cases aged >60 years. The Mini-Mental State Examination score was higher and the disease duration was longer in the amyloid-negative group than in the positive group, suggesting a slower progression of dementia in the amyloid-negative patients, though the tendency failed to reach the statistical significance. Cerebral blood flow decrease was classified into four patterns. Typical Alzheimer's disease patterns were found exclusively in the amyloid-positive group, whereas frontal dominant and temporal dominant were more frequently found in the amyloid-negative group. Conclusion Even in the era of amyloid imaging, cerebral blood flow measurement can help differentiate Alzheimer's disease from other diseases causing apparent Alzheimer's disease-type cognitive impairment.