Does posterior cortical atrophy on MRI discriminate between Alzheimer's disease, dementia with Lewy bodies, and normal aging?

Background: Previous studies suggest that posterior cortical atrophy may be a useful marker for early onset Alzheimer's disease (AD). Dementia with Lewy bodies (DLB) is associated with less temporal lobe atrophy than AD, though posterior cortical atrophy may be greater. Therefore, we assessed whether visual rating scales for assessing posterior atrophy (PA), medial temporal lobe atrophy (MTA), and ventricular enlargement (VEn) aid in the discrimination between AD, DLB, and normal aging. Methods: T1-weighted MRI scans acquired at 3 Tesla were visually rated for PA (range 0-3), MTA (range 0-4), and VEn (range 0-3) in older subjects with AD (n = 36), DLB (n = 35), and healthy controls (n = 35). The diagnostic utility of MTA, PA, and VEn visual ratings in distinguishing AD and DLB from controls as well as AD from DLB was investigated. Results: Significantly higher MTA ratings were associated with AD and DLB compared to controls (p < 0.001). MTA ratings were greater in AD relative to DLB (U = 384.5, p = 0.004). For PA ratings, scores did not differ between groups (p = 0.20). VEn ratings were significantly higher in AD and DLB compared to controls (p = 0.003), but similar between AD and DLB (U = 384.5, p = 0.4). Conclusions: Unlike findings reported in younger subjects, visual ratings for PA are not a reliable marker at older ages for distinguishing AD from controls, or for distinguishing DLB from AD. However, visual ratings of MTA and VEn may be useful markers in distinguishing both AD and DLB from older subjects without dementia.