Alzheimer and frontotemporal pathology in subsets of primary progressive aphasia.
OBJECTIVE
To identify predictors of Alzheimer's disease (AD) versus frontotemporal lobar degeneration pathology in primary progressive aphasia (PPA), and determine whether the AD pathology is atypically distributed to fit the aphasic phenotype.


METHODS
Neuropsychological and neuropathological analyses of 23 consecutive PPA autopsies. All had qualitative determination of neurofibrillary tangle (NFT) density. Additional quantitation was done in four of the PPA/AD cases and four AD cases with the typical amnestic dementia of the Alzheimer type.


RESULTS
The sample contained mostly logopenic, agrammatic, and mixed forms of PPA. All six agrammatics had frontotemporal lobar degeneration (five of six with tauopathy). Seven of the 11 logopenics had AD. In logopenics, lower memory scores increased the probability of AD, but there were exceptions. The PPA/AD group showed predominance of entorhinal NFT typical of the amnestic dementia of the Alzheimer type. In the small subgroup examined quantitatively, neocortical NFTs were more numerous in the left hemisphere of PPA/AD. However, the asymmetry was low and inconsistent. Neuritic plaques did not display consistent asymmetry. Apolipoprotein E4, a major risk factor for typical AD, did not predict AD pathology in PPA.


CONCLUSIONS
Subtyping PPA helps to predict AD versus frontotemporal lobar degeneration pathology at the group level. However, our results and the literature also indicate that no clinical predictor is completely reliable in individual patients. The inconsistent concordance of NFT distribution with the asymmetric atrophy and the nonamnestic phenotype also raises the possibility that the AD markers encountered at autopsy in PPA may not always reflect the nature of the initiating neurodegenerative process.
Mesulam
Marsel
M
Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. mmesulam@northwestern.edu
Wicklund
Alissa
A
Johnson
Nancy
N
Rogalski
Emily
E
Léger
Gabriel C
GC
Rademaker
Alfred
A
Weintraub
Sandra
S
Bigio
Eileen H
EH
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D018888:Aphasia, Primary Progressive / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D001284:Atrophy / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D015415:Biomarkers; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D003704:Dementia / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D003937:Diagnosis, Differential; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D016874:Neurofibrillary Tangles / Q000473:pathology; D009474:Neurons / Q000473:pathology*; D010641:Phenotype
D015415:Biomarkers