Single and Multiple Domain Amnestic MCI: two sides of the same coin?

Abstract

Background. Amnestic Mild Cognitive Impairment (aMCI) is considered a transition stage between normal aging and Alzheimer's disease (AD). Two main clinical subtypes of aMCI have been identified: 1) aMCI single domain (aMCI-SD), with isolated episodic memory impairments, and 2) aMCI multiple domain (aMCI-MD), with episodic memory impairments and deficits in one or more other cognitive domains. Aims.To map the pattern of gray matter (GM) atrophy associated with aMCI-SD, aMCIMD and mild AD. Methods. A group of aMCI-SD, aMCI-MD characterized by executive function disorders, mild AD patients and cognitively unimpaired age-matched subjects underwent a comprehensive neuropsychological assessment and a high-definition MR brain scan. Voxel-based morphometry (VBM) analysis was used to characterize the GM tissue loss in each patient group, and the common pattern of GM atrophy in aMCI-SD and aMCIMD. Results. The results revealed that aMCI-SD and aMCI-MD are characterized by a common pattern of GM atrophy within the medial temporal cortex, predisposing to AD and correlating with the severity of verbal memory symptoms. Moreover, the pattern of GM atrophy observed in aMCI-SD, aMCI-MD and mild AD revealed that, from an anatomical point of view, these three clinical syndromes could represent three severity points along the continuum between normal aging and AD.