BRAIN FDG-PET IN MILD COGNITIVE IMPAIRMENT: A RETROSPECTIVE LONGITUDINAL STUDY

Abstract

Brain metabolism alteration represents one of the earlier neuroimaging biomarkers of dementia. This study aimed to verify the predictive role of FDG-PET in differential diagnosis in a cohort of Mild Cognitive Impairment (MCI) patients. Seventy-four MCI patients underwent brain F18-FDG-PET and clinical and neuropsychological follow-up for about two years and a half. Statistical comparisons of FDG-PET scans at baseline were compared between patients who convert to dementia (MCI-D), to Alzheimer’s type Dementia (MCI-AD) or to Fronto-Temporal Dementia (MCI-FTD) and those who remained Stable MCI. Compared with Stable MCI, MCI-D patients at baseline presented hypometabolism in the left superior, middle and inferior temporal gyri and an higher metabolism in the left postcentral gyrus, putamen and in the right insula and claustrum. MCI-AD patients had hypometabolism in the left middle and inferior temporal gyri and a suspected increased metabolism in the bilateral postcentral gyri, in the right precentral gyrus, insula and in the left lentiform nucleus. MCI-FTD showed hypometabolism in the right inferior, middle, superior frontal gyri and inferior, middle and superior temporal gyri. In the prodromal phase, compared with stable MCI, AD was characterized by temporal hypometabolic activity indicating synaptic dysfunction and by higher sub-cortical metabolic activity as possible expression of compensatory mechanisms, whereas FTD by hypometabolic frontal and temporal regions. In MCI patients, FDG-PET is not only an excellent and early diagnostic biomarker, but also a good tool to describe neurobiological correlates of dementia subtypes in time.