Longitudinal study of amnesic patients at high risk for Alzheimer's disease: clinical, neuropsychological and magnetic resonance spectroscopy features.

BACKGROUND/AIMS To prospectively follow up a group of amnesic patients at risk for Alzheimer's disease (AD), to characterize a group of patients whose features were intermediate between amnesic mild cognitive impairment (aMCI) and probable AD, prodromal AD (Prd-AD), and to investigate if these patients were at higher risk for AD conversion. METHODS A total of 109 subjects were assessed by neuropsychological evaluation and by 1H magnetic resonance spectroscopy (1H-MRS): 27 controls, and 16 aMCI, 34 probable AD and 32 Prd-AD patients. RESULTS Episodic memory and frontal test scores resulted lower in Prd-AD compared to aMCI patients. Prd-AD patients obtained significantly higher scores than AD ones in language, perception, praxis and frontal functions. Although Prd-AD and AD patients had distinct 1H-MRS features from aMCI ones, there were no 1H-MRS differences between Prd-AD and AD patients. The AD annual conversion rate after 1 year of follow-up for Prd-AD (57.1%) was higher than in aMCI patients (20%; p<0.01). A logistic regression, in which all amnesic patients were treated as a single group, showed that the Visual Memory Test was a significant neuropsychological predictor for AD conversion. CONCLUSIONS Prd-AD patients are a clinically distinguishable group, with distinct neuropsychological and 1H-MRS features and a higher conversion rate to probable AD than aMCI patients.