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Neuroimaging correlates of pathologically defined subtypes of Alzheimer's disease: a case-control study.

ABSTRACT: Three subtypes of Alzheimer's disease (AD) have been pathologically defined on the basis of the distribution of neurofibrillary tangles: typical AD, hippocampal-sparing AD, and limbic-predominant AD. Compared with typical AD, hippocampal-sparing AD has more neurofibrillary tangles in the cortex and fewer in the hippocampus, whereas the opposite pattern is seen in limbic-predominant AD. We aimed to determine whether MRI patterns of atrophy differ between these subtypes and whether structural neuroimaging could be a useful predictor of pathological subtype at autopsy.We identified patients who had been followed up in the Mayo Clinic Alzheimer's Disease Research Center (Rochester, MN, USA) or in the Alzheimer's Disease Patient Registry (Rochester, MN, USA) between 1992 and 2005. To be eligible for inclusion, participants had to have had dementia, AD pathology at autopsy (Braak stage ?IV and intermediate to high probability of AD), and an ante-mortem MRI. Cases were assigned to one of three pathological subtypes--hippocampal-sparing, limbic-predominant, and typical AD--on the basis of neurofibrillary tangle counts in hippocampus and cortex and ratio of hippocampal to cortical burden, without reference to neuronal loss. Voxel-based morphometry and atlas-based parcellation were used to compare patterns of grey matter loss between groups and with age-matched control individuals. Neuroimaging was obtained at the time of first presentation. To summarise pair-wise group differences, we report the area under the receiver operator characteristic curve (AUROC).Of 177 eligible patients, 125 (71%) were classified as having typical AD, 33 (19%) as having limbic-predominant AD, and 19 (11%) as having hippocampal-sparing AD. Most patients with typical (98 [78%]) and limbic-predominant AD (31 [94%]) initially presented with an amnestic syndrome, but fewer patients with hippocampal-sparing AD (eight [42%]) did. The most severe medial temporal atrophy was recorded in patients with limbic-predominant AD, followed by those with typical disease, and then those with hippocampal-sparing AD. Conversely, the most severe cortical atrophy was noted in patients with hippocampal-sparing AD, followed by those with typical disease, and then limbic-predominant AD. The ratio of hippocampal to cortical volumes allowed the best discrimination between subtypes (p<0·0001; three-way AUROC 0·52 [95% CI 0·47-0·52]; ratio of AUROC to chance classification 3·1 [2·8-3·1]). Patients with typical AD and non-amnesic initial presentation had a significantly higher ratio of hippocampal to cortical volumes (median 0·045 [IQR 0·035-0·056]) than did those with an amnesic presentation (0·041 [0·031-0·057]; p=0·001).Patterns of atrophy on MRI differ across the pathological subtypes of AD. MRI regional volumetric analysis can reliably track the distribution of neurofibrillary tangle pathology and can predict pathological subtype of AD at autopsy.US National Institutes of Health (National Institute on Aging).

SUBMITTER: Whitwell JL

PROVIDER: S-EPMC3490201 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Neuroimaging correlates of pathologically defined subtypes of Alzheimer's disease: a case-control study.

Whitwell Jennifer L JL Dickson Dennis W DW Murray Melissa E ME Weigand Stephen D SD Tosakulwong Nirubol N Senjem Matthew L ML Knopman David S DS Boeve Bradley F BF Parisi Joseph E JE Petersen Ronald C RC Jack Clifford R CR Josephs Keith A KA

The Lancet. Neurology 20120903 10

<h4>Background</h4>Three subtypes of Alzheimer's disease (AD) have been pathologically defined on the basis of the distribution of neurofibrillary tangles: typical AD, hippocampal-sparing AD, and limbic-predominant AD. Compared with typical AD, hippocampal-sparing AD has more neurofibrillary tangles in the cortex and fewer in the hippocampus, whereas the opposite pattern is seen in limbic-predominant AD. We aimed to determine whether MRI patterns of atrophy differ between these subtypes and whet ...[more]

PMID: 22951070

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Project description:Neurofibrillary pathology has a stereotypical progression in Alzheimer's disease (AD) that is encapsulated in the Braak staging scheme; however, some AD cases are atypical and do not fit into this scheme. We aimed to compare clinical and neuropathological features between typical and atypical AD cases.AD cases with a Braak neurofibrillary tangle stage of more than IV were identified from a brain bank database. By use of thioflavin-S fluorescence microscopy, we assessed the density and the distribution of neurofibrillary tangles in three cortical regions and two hippocampal sectors. These data were used to construct an algorithm to classify AD cases into typical, hippocampal sparing, or limbic predominant. Classified cases were then compared for clinical, demographic, pathological, and genetic characteristics. An independent cohort of AD cases was assessed to validate findings from the initial cohort.889 cases of AD, 398 men and 491 women with age at death of 37-103 years, were classified with the algorithm as hippocampal sparing (97 cases [11%]), typical (665 [75%]), or limbic predominant (127 [14%]). By comparison with typical AD, neurofibrillary tangle counts per 0.125 mm(2) in hippocampal sparing cases were higher in cortical areas (median 13, IQR 11-16) and lower in the hippocampus (7.5, 5.2-9.5), whereas counts in limbic-predominant cases were lower in cortical areas (4.3, 3.0-5.7) and higher in the hippocampus (27, 22-35). Hippocampal sparing cases had less hippocampal atrophy than did typical and limbic-predominant cases. Patients with hippocampal sparing AD were younger at death (mean 72 years [SD 10]) and a higher proportion of them were men (61 [63%]), whereas those with limbic-predominant AD were older (mean 86 years [SD 6]) and a higher proportion of them were women (87 [69%]). Microtubule-associated protein tau (MAPT) H1H1 genotype was more common in limbic-predominant AD (54 [70%]) than in hippocampal sparing AD (24 [46%]; p=0.011), but did not differ significantly between limbic-predominant and typical AD (204 [59%]; p=0.11). Apolipoprotein E (APOE) ?4 allele status differed between AD subtypes only when data were stratified by age at onset. Clinical presentation, age at onset, disease duration, and rate of cognitive decline differed between the AD subtypes. These findings were confirmed in a validation cohort of 113 patients with AD.These data support the hypothesis that AD has distinct clinicopathological subtypes. Hippocampal sparing and limbic-predominant AD subtypes might account for about 25% of cases, and hence should be considered when designing clinical, genetic, biomarker, and treatment studies in patients with AD.US National Institutes of Health via Mayo Alzheimer's Disease Research Center, Mayo Clinic Study on Aging, Florida Alzheimer's Disease Research Center, and Einstein Aging Study; and State of Florida Alzheimer's Disease Initiative.

Project description:Lobar cerebral microbleeds (CMBs) in Alzheimer's disease (AD) are associated with cerebral amyloid angiopathy (CAA) due to vascular amyloid beta (Aβ) deposits. However, the relationship between lobar CMBs and clinical subtypes of AD remains unknown. Here, we enrolled patients with early- and late-onset amnestic dominant AD, logopenic variant of primary progressive aphasia (lvPPA) and posterior cortical atrophy (PCA) who were compatible with the AD criteria. We then examined the levels of cerebrospinal fluid (CSF) biomarkers [Aβ1-42, Aβ1-40, Aβ1-38, phosphorylated tau 181 (P-Tau), total tau (T-Tau), neurofilament light chain (NFL), and chitinase 3-like 1 protein (YKL-40)], analyzed the number and localization of CMBs, and measured the cerebral blood flow (CBF) volume by 99mTc-ethyl cysteinate dimer single photon emission computerized tomography (99mTc ECD-SPECT), as well as the mean cortical standard uptake value ratio by 11C-labeled Pittsburgh Compound B-positron emission tomography (11C PiB-PET). Lobar CMBs in lvPPA were distributed in the temporal, frontal, and parietal lobes with the left side predominance, while the CBF volume in lvPPA significantly decreased in the left temporal area, where the number of lobar CMBs and the CBF volumes showed a significant inversely correlation. The CSF levels of NFL in lvPPA were significantly higher compared to the other AD subtypes and non-demented subjects. The numbers of lobar CMBs significantly increased the CSF levels of NFL in the total AD patients, additionally, among AD subtypes, the CSF levels of NFL in lvPPA predominantly were higher by increasing number of lobar CMBs. On the other hand, the CSF levels of Aβ1-38, Aβ1-40, Aβ1-42, P-Tau, and T-Tau were lower by increasing number of lobar CMBs in the total AD patients. These findings may suggest that aberrant brain hypoperfusion in lvPPA was derived from the brain atrophy due to neurodegeneration, and possibly may involve the aberrant microcirculation causing by lobar CMBs and cerebrovascular injuries, with the left side dominance, consequently leading to a clinical phenotype of logopenic variant.

Project description:Alzheimer's disease (AD) can be classified based on the relative density of neurofibrillary tangles (NFTs) in the hippocampus and association cortices into three subtypes: typical AD, hippocampal-sparing AD (HpSp AD), and limbic-predominant AD (LP AD). AD subtypes not only have pathologic, but also demographic, clinical, and genetic differences. Neurofibrillary tangle-predominant dementia (NFTD), a disorder with NFTs relatively restricted to limbic structures, shares this feature with LP AD raising the possibility that NFTD is a variant of AD. The objective criteria for pathologic diagnosis of NFTD are not available. A goal of this study was to design a mathematical algorithm that could diagnose NFTD from NFT and senile plaque (SP) counts in hippocampus and association cortices, analogous to that used to subtype AD. Moreover, we aimed to compare pathologic, demographic, clinical, and genetic features of NFTD (n = 18) with LP AD (n = 19), as well as the other AD subtypes, typical AD (n = 52) and HpSp AD (n = 17). Using digital microscopy, we confirmed that burden of phospho-tau (CP13) and of an NFT conformational epitope (Ab39) correlated with NFT densities and showed expected patterns across AD subtypes. HpSp AD had the highest and LP AD had the lowest burden of cortical CP13 and Ab39 immunoreactivity. On the other hand, cortical β-amyloid burden did not significantly differ between AD subtypes. Semi-quantitative assessment of SPs in the basal ganglia did show HpSp AD to have significantly more frequent presence of SPs compared to typical AD, which was more frequent than LP AD. Compared to LP AD, NFTD had an older age at disease onset and shorter disease duration, as well as lower Braak NFT stage. NFTs and SPs on thioflavin-S fluorescent microscopy, as well as CP13, Ab39, and Aβ immunoreactivities were very low in the frontal cortex of NFTD, differentiating NFTD from AD subtypes, including LP AD. MAPT H1H1 genotype frequency was high (~70 %) in NFTD and LP AD, and similar to typical AD, while APOE ε4 carrier state was low in NFTD. While it shares clinical similarities with regard to female sex predominance, onset in advanced age, and a slow cognitive decline, NFTD has significant pathologic differences from LP AD, suggesting that it may not merely be a variant of AD.

Project description:ObjectiveTo study the molecular connection among cardiovascular diseases (CVD) subtypes defined by the International Classification of Diseases (ICD) version 10 (ICD-10).MethodsBoth phenotypic data and genotypic data used in this study were obtained from the UK Biobank. A total of 380 083 participants aged between 40 and 69 years were included. Those without any cardiovascular disease (either no ICD-10 code at all or no ICD-10 code containing letter I) were assigned to the control group. The five CVD subtypes were: ischaemic heart diseases (IHD), pulmonary heart disease and diseases of pulmonary circulation (PHD), cerebrovascular diseases (CRB), diseases of arteries, arterioles and capillaries (AAC), diseases of veins, lymphatic vessels and lymph nodes, and diseases not elsewhere classified (VLL). We first performed a genome-wide association study (GWAS) for each of the five subtypes. We summarized novel loci using genome-wide significance threshold P=5×10-8. Next, we used linkage disequilibrium score regression (LDSC) method to assess genetic correlation among the five subtypes. Lastly, we applied mendelian randomization (MR) approach to assess the causal relationship among the subtypes. The particular software that we used was generalised summary-data-based mendelian randomisation (GSMR).ResultsThrough GWAS, we identified hundreds of genome-wide significant SNPs: 672 for IHD, 241 for PHD, 31 for CRB, 48 for AAC, and 193 for VLL. By comparing with published literature, we found 28 novel loci, for PHD (n=14), CRB (n =7) and AAC (n =7). Eight of these 28 loci were rare, where the lead SNP had minor allele frequency (MAF) less than 1%. LDSC analyses indicated IHD had significant genetic correlation with VLL (P=2.52×10-7), PHD (P=3.77×10-3) and AAC (P=4.90×10-3), respectively. Bidrectional GSMR analyses showed that IHD had a positive causal relationship with VLL (P=7.40×10-5) and AAC (P=1.50×10-3), while reverse causality was not supported.ConclusionThis study adopted an innovative approach to study the molecular connection among CVD subtypes that are defined by ICD. We identified potentially positive genetic correlation and causal effects among some of these subtypes. Research along this line will provide scientific insights and serve as a guidance for future ICD standards.

Dataset Information

Neuroimaging correlates of pathologically defined subtypes of Alzheimer's disease: a case-control study.

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Neuroimaging correlates of pathologically defined subtypes of Alzheimer's disease: a case-control study.

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