Abstract
Medial temporal lobe atrophy (MTA) is a recognized marker of Alzheimer's disease (AD), however, it can be prominent in frontotemporal lobar degeneration (FTLD). There is an increasing awareness that posterior atrophy (PA) is important in AD and may aid the differentiation of AD from FTLD. Visual rating scales are a convenient way of assessing atrophy in a clinical setting. In this study, 2 visual rating scales measuring MTA and PA were used to compare atrophy patterns in 62 pathologically-confirmed AD and 40 FTLD patients. Anatomical correspondence of MTA and PA was assessed using manually-delineated regions of the hippocampus and posterior cingulate gyrus, respectively. Both MTA and PA scales showed good inter- and intrarater reliabilities (kappa > 0.8). MTA scores showed a good correspondence with manual hippocampal volumes. Thirty percent of the AD patients showed PA in the absence of MTA. Adding the PA to the MTA scale improved discrimination of AD from FTLD, and early-onset AD from normal aging. These results underline the importance of considering PA in AD diagnosis, particularly in younger patients where medial temporal atrophy may be less conspicuous.
Highlights
Alzheimer’s disease (AD) is the most common cause of dementia (Hebert et al, 2003)
Of the 44 sporadic cases, 33 patients had an age at onset Ͻ 65 years (EOAD), whereas 11 had an age at onset of Ն 65 years (LOAD)
All of the familial AD subjects had an amnestic presentation during life
Summary
Alzheimer’s disease (AD) is the most common cause of dementia (Hebert et al, 2003). Frontotemporal lobar degeneration (FTLD), less prevalent overall, is almost as common as AD in patients under the age of 65 years (Harvey et al, 2003; Ratnavalli et al, 2002). AD and FTLD may present with overlapping symptoms, in particular in the early stages of the disease. Less common “atypical” forms of AD have been described in which memory is not the primary deficit. These patients may present with visuospatial and visuoperceptual problems (Benson et al, 1988), while others present with behavioral symptoms (Johnson et al, 1999; Taylor et al, 2008), yet others have predominantly language difficulties (Gorno-Tempini et al, 2008). Patients with FTLD pathology may present with a range of different clinical symptoms, most commonly categorized
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