Josephs, Keith A.

Abstract Alzheimer’s disease can present clinically with either the typical amnestic phenotype or with atypical phenotypes, such as logopenic progressive aphasia and posterior cortical atrophy. We have recently described longitudinal patterns of flortaucipir PET uptake and grey matter atrophy in the atypical phenotypes, demonstrating a longitudinal regional disconnect between flortaucipir accumulation and brain atrophy. However, it is unclear how these longitudinal patterns differ from typical Alzheimer’s disease, to what degree flortaucipir and atrophy mirror clinical phenotype in Alzheimer’s disease, and whether optimal longitudinal neuroimaging biomarkers would also differ across phenotypes. We aimed to address these unknowns using a cohort of 57 participants diagnosed with Alzheimer’s disease (18 with typical amnestic Alzheimer’s disease, 17 with posterior cortical atrophy and 22 with logopenic progressive aphasia) that had undergone baseline and 1-year follow-up MRI and flortaucipir PET. Typical Alzheimer’s disease participants were selected to be over 65 years old at baseline scan, while no age criterion was used for atypical Alzheimer’s disease participants. Region and voxel-level rates of tau accumulation and atrophy were assessed relative to 49 cognitively unimpaired individuals and among phenotypes. Principal component analysis was implemented to describe variability in baseline tau uptake and rates of accumulation and baseline grey matter volumes and rates of atrophy across phenotypes. The capability of the principal components to discriminate between phenotypes was assessed with logistic regression. The topography of longitudinal tau accumulation and atrophy differed across phenotypes, with key regions of tau accumulation in the frontal and temporal lobes for all phenotypes and key regions of atrophy in the occipitotemporal regions for posterior cortical atrophy, left temporal lobe for logopenic progressive aphasia and medial and lateral temporal lobe for typical Alzheimer’s disease. Principal component analysis identified patterns of variation in baseline and longitudinal measures of tau uptake and volume that were significantly different across phenotypes. Baseline tau uptake mapped better onto clinical phenotype than longitudinal tau and MRI measures. Our study suggests that optimal longitudinal neuroimaging biomarkers for future clinical treatment trials in Alzheimer’s disease are different for MRI and tau-PET and may differ across phenotypes, particularly for MRI. Baseline tau tracer retention showed the highest fidelity to clinical phenotype, supporting the important causal role of tau as a driver of clinical dysfunction in Alzheimer’s disease.

AbstractObjectiveTo assess the relationships between MRI volumetry and [18F]flortaucipir PET of typical and atypical clinical phenotypes of Alzheimer’s disease, by genarian (age by decade).MethodsFive‐hundred and sixty‐four participants including those with typical (n = 86) or atypical (n = 80) Alzheimer’s dementia and normal controls (n = 398) underwent apolipoprotein E genotyping, MRI, flortaucipir, and 11C‐PiB; all 166 Alzheimer’s participants were beta‐amyloid positive and all controls were beta‐amyloid negative. Grey matter volume and flortaucipir standard uptake value ratios were calculated for hippocampus, entorhinal cortex, and neocortex. Ratios of hippocampal‐to‐neocortical and entorhinal‐to‐neocortical volume and flortaucipir uptake were also calculated. Linear regression models assessed relationships among regional volume, flortaucipir uptake, and ratios and phenotypes, within three genarians (50–59, 60–69, and 70+). Voxel‐level analyses were also performed.ResultsFor 50–59 greater medial temporal atrophy and flortaucipir uptake was observed in the typical compared with atypical phenotype. The typical phenotype also showed greater frontal neocortex uptake with the voxel‐level analysis. For 60–69 and 70+ there was greater hippocampal volume loss in the typical compared with atypical phenotype while only the 60–69, but not the 70+ group, showed a difference in hippocampal flortaucipir uptake. We also observed a pattern for higher neocortical flortaucipir uptake to correlate with younger age decade for both phenotypes.InterpretationMRI volumetry versus flortaucipir PET relationships differ across Alzheimer’s clinical phenotypes, and also within phenotype across age decades. This suggests that there is potential risk of masked effects by not accounting for genarian in participants with beta‐amyloid and tau‐positive biomarker defined Alzheimer’s disease.

Prominent behavioral changes and language dysfunction are features of frontotemporal lobar degeneration (FTLD) but can also occur in AD. Recently, application of TAR DNA‐binding protein 43 (TDP‐43) antibody has been shown to be useful for demonstrating the pathologic lesions of FTLD‐U and FTLD‐MND. Since these cases might represent combined disorders (FTD and AD), we studied the utility of TDP‐43 staining to demonstrate inclusion bodies in brains of patients with clinical features of frontal or temporal lobe dysfunction but with autopsy features of AD. METHODS: Eight patients from 1998 to 2005 were identified, including 1 with combined pathologic features of FTLD‐U (previously identified with anti‐ubiquitin staining) and mild AD (Braak stage IV). Sections of hippocampus and frontal and temporal lobes were stained with anti‐TDP‐43 antibody (Proteintech Group). RESULTS: Of the 8 patients, 1 had advanced AD (Braak stage VI) and scattered TDP‐43 positive cytoplasmic inclusions in hippocampal dentate granular cells and frontal and temporal neocortical neurons. The previously identified patient with combined FTLD‐U and mild AD also had TDP‐43 positive cytoplasmic and nuclear inclusions. CONCLUSION: TDP‐43 aids in the identification of case with dual pathologies, particularly in advanced AD where inclusion may be masked by overwhelming AD pathology.

Frontotemporal lobar degeneration (FTLD) and motor neuron disease (MND) are considered separate diseases; yet, they can overlap (FTLD‐MND), affecting predominantly lower motor neurons. We reviewed all cases of FTLD‐MND (N=25) to determine if lower MND is a consistent feature. We identified 2 cases (8%) with pure upper MND or primary lateral sclerosis (PLS). Detailed neuropathological examination was conducted. Case 1: a 63‐year‐old man with 7‐years of executive dysfunction, aphasia, and choking. Family history was negative. Neurological examination 1‐year prior to death revealed spasticity and extensor plantar responses, without extrapyramidal or lower MND signs. Case 2: a 69‐year‐old man with 6‐years of expressive aphasia and apraxia. Family history was negative. Neurological examination 4‐years prior to death reveled asymmetric ideomotor apraxia and parkinsonism, but no signs of upper or lower MND. Brain weights were 1140 and 930 grams, respectively. Histological examination revealed neuronal loss and gliosis of motor cortex, severe in case 1 and mild‐to‐moderate in case 2, as well as neuronal loss and gliosis in frontotemporal and parietal (case 2 only) neocortices. Activated microglial and myelin stains revealed corticospinal tract destruction to the level of the medullary pyramids. The hypoglossal nuclei were preserved. Neither ubiquitin nor TDP‐43 immunohistochemistry identified intraneuronal inclusions. Case 1 also had features of tangle dominant dementia. FTLD with pure upper MND or PLS is rare, but does exist. Unlike in typical FTLD‐MND were disease duration is 2‐3 years, those with FTLD‐PLS seem to have longer illness duration and, hence, better prognosis. Further genetic studies are needed to determine if FTLD‐PLS is a variant of FTLD‐MND or a separate disease entity.

Background: Transactive response DNA-binding protein of 43 kDa (TDP-43) is associated with hippocampal atrophy in Alzheimer’s disease (AD), but whether the association is modified by other factors is unknown. Objective: To evaluate whether the associations between TDP-43 and hippocampal volume and atrophy rate are affected by age, gender, apolipoprotein E ( APOE) ɛ4, Lewy bodies (LBs), amyloid-β (Aβ), or Braak neurofibrillary tangle (NFT) stage. Methods: In this longitudinal neuroimaging-clinicopathological study of 468 cases with AD neuropathological changes (Aβ-positive) that had completed antemortem head MRI, we investigated how age, gender, APOE ɛ4, presence of LBs, Aβ, TDP-43, and Braak NFT stages are associated with hippocampal volumes and rates of atrophy over time. We included field strength in the models since our cohort included 1.5T and 3T scans. We then determined whether the associations between hippocampal atrophy and TDP-43 are modified by these factors using mixed effects models. Results: Older age, female gender, APOE ɛ4, higher field strength, higher TDP-43, and Braak NFT stages were associated with smaller hippocampi. Rate of atrophy was greater with higher TDP-43 and Braak NFT stage, but lower in older patients. The association of TDP-43 with greater rate of atrophy was enhanced in APOE ɛ4 carriers ( p = 0.04). Conclusion: Neurodegenerative effects of TDP-43 seem to be independent of most factors except perhaps APOE in cases with AD neuropathological changes. TDP-43 and tau appear to behave independently of one another.

AbstractIntroductionFrontotemporal dementia disorders (FTDs) are heterogeneous phenotypical behavioral and language disorders usually associated with frontal and/or temporal lobe degeneration. We investigated their incidence in a population‐based cohort.MethodsUsing a records‐linkage system, we identified all patients with a diagnostic code for dementia in Olmsted County, MN, 1995–2010, and confirmed the diagnosis of FTD. A behavioral neurologist verified the clinical diagnosis and determined phenotypes.ResultsWe identified 35 FTDs cases. Overall, the incidence of FTDs was 4.3/100,000/year (95% CI: 2.9, 5.7). Incidence was higher in men (6.3/100,000, 95% CI 3.6, 9.0) than women (2.9/100,000; 95% CI: 1.3, 4.5); we observed an increased trend over time (B = 0.83, 95% CI: 0.54, 1.11, P < .001). At autopsy, clinical diagnosis was confirmed in eight (72.7%) cases.DiscussionWe observed an increased incidence and trends of FTDs over time. This may reflect a better recognition by clinicians and improvement of clinical criteria and diagnostic tools.

Purpose The primary aim was to examine the utility of the Western Aphasia Battery–Revised (WAB-R; Kertesz, 2007 ) for classifying variants of primary progressive aphasia (PPA). Traditional WAB-R metrics of Aphasia Quotient (AQ), subtest scores, WAB-R classification, and several novel metrics were examined. A secondary aim was to examine these same WAB-R metrics in individuals with primary progressive apraxia of speech (PPAOS). Method A retrospective analysis of WAB-R records from 169 participants enrolled in a study of neurodegenerative speech and language disorders was conducted. PPA/PPAOS classification was determined by consensus review of speech, language, and cognitive profiles. Scores on each of the WAB-R subtests were obtained to derive AQ, WAB-R aphasia profile, and 3 ratios reflecting relative performance on subtests. Results Mean AQ was significantly higher in the PPAOS group compared to all PPA variants except primary fluent aphasia. AQ above the normal cutoff was observed for 20% of participants with PPA. Significant main effects of group were noted for each of the subtests. Follow-up comparisons most frequently discriminated PPAOS, primary agrammatic aphasia (PAA), and logopenic progressive aphasia. Primary fluent aphasia and semantic dementia (SD) subtest scores were less distinctive, with the exception of Naming for SD, which was significantly lower than for PAA and PPAOS. When the WAB-R AQ detected aphasia, a classification of anomic aphasia was most frequently observed; this pattern held true for each of the PPA variants. The mean Information Content:Naming ratio was highest for SD, and the mean Comprehension:Fluency ratio was highest for PAA. Conclusions In the current study, AQ underestimated the presence of PPA and WAB-R classification did not distinguish among PPA classification determined by consensus. Performance on individual subtests and relative performance across subtests demonstrated inconsistent alignment with PPA classification. We conclude the WAB-R in isolation is inadequate to detect or characterize PPA. We instead suggest utilizing the WAB-R as 1 component of a comprehensive language and motor speech assessment when PPA is suspected.