Background: The most characteristic symptom of Alzheimer's disease (AD) is episodic memory impairment, which is closely associated with atrophy of the entorhinal cortex. Meanwhile, atypical symptoms are more frequent in early-onset AD than in late-onset AD, suggesting that the former subtype has less atrophy in the entorhinal cortex. Therefore, we investigated whether the degree of atrophy in the entorhinal cortex is different between the two subtypes of AD using the voxel-based specific regional analysis system for AD (VSRAD) targeting this region.
Methods: The subjects consisted of 198 patients with AD. They were divided into two groups, that is, the early-onset AD group with the onset under age 65 years (n = 18) and the late-onset AD group with the onset at age 65 years or over (n = 180). The degree of atrophy in the entorhinal cortex was quantified by application of the VSRAD to magnetic resonance imaging data, and a Z-score >2 was defined as significant atrophy according to previous studies.
Results: The early-onset group had significantly lower Z-scores than the late-onset group (mean ± SD: 1.83 ± 0.92 vs 2.90 ± 1.40, p < 0.01). The analysis of covariance with possible confounding factors as covariates also showed that Z-scores were significantly lower in the early-onset group than in the late-onset group (p < 0.01). The proportion of patients with atrophy was significantly lower in the early-onset group than in the late-onset group (44% vs 71%, p < 0.05).
Conclusions: The present study using the VSRAD suggests that early-onset AD shows less atrophy in the entorhinal cortex than late-onset AD.
Copyright © 2012 John Wiley & Sons, Ltd.