Cortical thinning in verbal, visual, and both memory-predominant mild cognitive impairment.

The amnestic form of mild cognitive impairment (aMCI) is likely a precursor of Alzheimer disease (AD). Both verbal and visual memory tests are used in the diagnosis of aMCI; however, it is unknown which type of test is superior at predicting the underlying pathologic changes associated with AD. In this study, we compared the topography of cortical thinning among 3 subtypes of patients with aMCI: 33 patients with predominant verbal memory impairment (verbal-aMCI), 35 with predominant visual memory impairment (visual-aMCI), and 56 with both verbal and visual memory-predominant impairment (both-aMCI), and 143 patients with normal cognition. As a result, patients with verbal-aMCI showed cortical thinning in the left anterior and medial temporal regions compared with individuals with normal cognition, while those with visual-aMCI did not show significant cortical thinning. The cortical thinning areas of both-aMCI group overlapped those of verbal-aMCI but were more widespread involving the bilateral temporal regions. These findings suggest that the verbal-aMCI and both-aMCI are more likely to be a precursor of AD than visual-aMCI, and that both-aMCI may be more advanced subtype than verbal-aMCI on the spectrum from MCI to AD.