AMCI delay recall performance is associated with white and grey matter abnormalities in the left hippocampal formation: A DTI and cortical thickness study

Abstract

assessing its relationships with brain imaging AD PET markers, ie. s-amyloid deposition and glucose hypometabolism, in cognitively normal elderly (NE) and patients with mild cognitive impairment (MCI) and AD. Methods: Seventeen NE and 13 patients (MCI1 + AD) from the IMAP project*, and twenty-two MCI2 patients from another cohort with an 18-months follow-up allowing to identify 9 converters to AD, were included. All subjects underwent neuropsychological testing including a self-assessment of cognitive deficits scale and episodic memory tests. A delta-score corresponding to the subjective-objective memory discrepancy was used as a measure of awareness of memory deficits (lowest scores 1⁄4 underestimation of deficits 1⁄4 anosognosia). Subjects also had a 18F-FDG-PET scan (all subjects) and a 18F-AV-45-PET scan (IMAP subjects only). Voxel-wise correlations were computed between the delta-score and PET images using SPM. Results: Within the NE, the delta-score was positively correlated with s-amyloid in the orbito-frontal cortex, while no correlation was found with cerebral metabolism. By contrast, the delta-score was not correlated to s-amyloid within the pooled MCI1 and AD group, while it was related to cerebral metabolism in the temporal pole and orbito-frontal cortex within the patient groups (MCI1-AD and MCI2). Moreover, in MCI2 patients, the delta-score tended to decrease over the 18 months, and was significantly lower in converters than in non-converters. Conclusions: A hypothetical characterisation of the evolution of memory awareness in the course of AD is illustrated in the Fig.1. At a presymptomatic stage, our results outlined a progressive increase in subjective deficits with growing s-amyloid burden. Then, at the MCI stage, with the progression of metabolic alterations, patients may start losing insight of their cognitive impairment.These results provide additional evidence (1) within the earliest stages, that subjective cognitive impairment could be a prodromal sign of MCI and AD, and (2) within the symptomatic stage, that anosognosia could be an early symptom characteristic of AD.