Medial temporal lobe atrophy on MRI scans and the diagnosis of Alzheimer disease

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Abstract

Background:

Despite convenience, accessibility, and strong correlation to severity of Alzheimer disease (AD) pathology, medial temporal lobe atrophy (MTA) has not been used as a criterion in the diagnosis of prodromal and probable AD.

Methods:

Using a newly validated visual rating system, mean MTA scores of three bilateral medial temporal lobe structures were compared for subjects with no cognitive impairment (NCI) (n = 117), nonamnestic mild cognitive impairment (MCI) (n = 46), amnestic MCI (n = 45), and probable AD (n = 53). Correlations between MTA scores and neuropsychological test scores at baseline, and predictors of change in diagnosis at 1-year follow-up were evaluated.

Results:

With NCI as the reference group, a mean MTA cut score of 1.33 yielded an optimal sensitivity/specificity of 85%/82% for probable AD subjects and 80%/82% for amnestic MCI subjects. MTA and Clinical Dementia Rating Sum of Boxes scores at baseline were independent and additive predictors of diagnosis at baseline, and of transition from NCI to MCI or from MCI to dementia at 1-year follow-up.

Conclusion:

Medial temporal lobe atrophy (MTA) scores 1) distinguish probable Alzheimer disease (AD) and amnestic mild cognitive impairment (MCI) subjects from nonamnestic MCI and no cognitive impairment (NCI) subjects, 2) help predict diagnosis at baseline, and 3) predict transition from NCI to MCI and from MCI to probable AD. MTA scores should be used as a criterion in the clinical diagnosis of AD.

GLOSSARY

AD = Alzheimer disease; ADRDA = Alzheimer's Disease and Related Disorders Association; aMCI = amnestic mild cognitive impairment; ANOVA = analysis of variance; CDRSB = Clinical Dementia Rating Sum of Boxes; ERC = entorhinal cortex; FADRC-CC = Florida Alzheimer's Disease Research Center–Clinical Core; HPC = hippocampus; HR = hazard ratio; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; MTA = medial temporal lobe atrophy; MTL = medial temporal lobe; NACC = National Alzheimer's Coordinating Center; naMCI = nonamnestic mild cognitive impairment; NCI = no cognitive impairment; NINCDS = National Institute of Neurological and Communicative Disorders and Stroke; NS = not significant; PRC = perirhinal cortex; VRS = visual rating system.

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