Citations

Abstract Primary four-repeat tauopathies are characterized by depositions of the four-repeat isoform of the microtubule binding protein, tau. The two most common sporadic four-repeat tauopathies are progressive supranuclear palsy and corticobasal degeneration. Because tau PET tracers exhibit poor binding affinity to four-repeat pathology, determining how well in vivo MRI findings relate to underlying pathology is critical to evaluating their utility as surrogate markers to aid in diagnosis and as outcome measures for clinical trials. We studied the relationship of cross-sectional imaging findings, such as MRI volume loss and diffusion tensor imaging white matter tract abnormalities, to tau histopathology in four-repeat tauopathies. Forty-seven patients with antemortem 3 T MRI volumetric and diffusion tensor imaging scans plus post-mortem pathological diagnosis of a four-repeat tauopathy (28 progressive supranuclear palsy; 19 corticobasal degeneration) were included in the study. Tau lesion types (pretangles/neurofibrillary tangles, neuropil threads, coiled bodies, astrocytic lesions) were semiquantitatively graded in disease-specific cortical, subcortical and brainstem regions. Antemortem regional volumes, fractional anisotropy and mean diffusivity were modelled using linear regression with post-mortem tau lesion scores considered separately, based on cellular type (neuronal versus glial), or summed (total tau). Results showed that greater total tau burden was associated with volume loss in the subthalamic nucleus (P = 0.001), midbrain (P < 0.001), substantia nigra (P = 0.03) and red nucleus (P = 0.004), with glial lesions substantially driving the associations. Decreased fractional anisotropy and increased mean diffusivity in the superior cerebellar peduncle correlated with glial tau in the cerebellar dentate (P = 0.04 and P = 0.02, respectively) and red nucleus (P < 0.001 for both). Total tau and glial pathology also correlated with increased mean diffusivity in the midbrain (P = 0.02 and P < 0.001, respectively). Finally, increased subcortical white matter mean diffusivity was associated with total tau in superior frontal and precentral cortices (each, P = 0.02). Overall, results showed clear relationships between antemortem MRI changes and pathology in four-repeat tauopathies. Our findings show that brain volume could be a useful surrogate marker of tau pathology in subcortical and brainstem regions, whereas white matter integrity could be a useful marker of tau pathology in cortical regions. Our findings also suggested an important role of glial tau lesions in the pathogenesis of neurodegeneration in four-repeat tauopathies. Thus, development of tau PET tracers selectively binding to glial tau lesions could potentially uncover mechanisms of disease progression.

The objective of this study was to characterize network-level changes in nonfluent/agrammatic Primary Progressive Aphasia (agPPA) and Primary Progressive Apraxia of Speech (PPAOS) with graph theory (GT) measures derived from scalp electroencephalography (EEG) recordings. EEGs of 15 agPPA and 7 PPAOS patients were collected during relaxed wakefulness with eyes closed (21 electrodes, 10–20 positions, 256 Hz sampling rate, 1–200 Hz bandpass filter). Eight artifact-free, non-overlapping 1024-point epochs were selected. Via Brainwave software, GT weighted connectivity and minimum spanning tree (MST) measures were calculated for theta and upper and lower alpha frequency bands. Differences in GT and MST measures between agPPA and PPAOS were assessed with Wilcoxon rank-sum tests. Of greatest interest, Spearman correlations were computed between behavioral and network measures in all frequency bands across all patients. There were no statistically significant differences in GT or MST measures between agPPA and PPAOS. There were significant correlations between several network and behavioral variables. The correlations demonstrate a relationship between reduced global efficiency and clinical symptom severity (e.g., parkinsonism, AOS). This preliminary, exploratory study demonstrates potential for EEG GT measures to quantify network changes associated with degenerative speech–language disorders.

Background: Alzheimer’s disease can present atypically as a progressive dysexecutive syndrome (dAD), an entity that preferentially affects younger individuals and is frequently misdiagnosed, highlighting the imperative for additional research. Objective: The objective of this study is to characterize the clinical, antemortem neuroimaging, and postmortem neuropathologic features of two cases of young-onset dAD who displayed evidence of Lewy body disease (LBD) co-pathology at autopsy. Methods: Clinical histories, antemortem MRI and PET imaging, and postmortem neuropathologic data were reviewed for each patient. Case Descriptions/Results: Canonical features of dAD were observed in both cases, including progressive and predominant impairment in tasks related to working memory and cognitive flexibility, a lack of major behavioral/personality changes, and evidence of abnormal amyloid and tau deposition by antemortem amyloid and tau PET and postmortem neuropathology. Relative sparing of hippocampal involvement was observed in both individuals, in keeping with many cases of clinically atypical AD. One of the patients developed subtle parkinsonian signs as well as paranoia and irritability in the years prior to passing. In both cases, transitional (brainstem and limbic) LBD co-pathology was observed at autopsy. Discussion: Although LBD co-pathology is not uncommon in AD overall, the presence of LBD pathology in these young-onset cases of dAD (including a case with apparent symptomatic correlate) warrants further investigation for broader frequency and underlying pathophysiology. Conclusion: A better understanding of which specific young-onset AD phenotypes are associated with LBD co-pathology would have important implications for counseling, treatment, clinical trial enrollment, and knowledge on disease mechanisms.

ABSTRACT Background and Objective Patients with dementia with Lewy bodies (DLB) may have overlapping Alzheimer's disease pathology. We investigated the longitudinal rate of tau accumulation and its association with neurodegeneration and clinical disease progression in DLB. Methods Consecutive patients with probable DLB (n = 22) from the Mayo Clinic Alzheimer's Disease Research Center and age‐matched and sex‐matched cognitively unimpaired controls (CU; n = 22) with serial magnetic resonance imaging and flortaucipir positron emission tomography scans within an average of 1.6 years were included. Regional annualized rates of flortaucipir uptake standardized uptake value ratios (SUVr) were calculated. Regional annualized rates of cortical volume change were measured with the Tensor Based Morphometry–Syn algorithm. Results The annual increase of flortaucipir SUVr was greater in the middle and superior occipital, fusiform, and inferior parietal cortices in DLB (mean: 0.017, 0.019, 0.019, and 0.015, respectively) compared with the CU (mean: −0.006, −0.009, −0.003, and − 0.005, respectively; P < 0.05). In patients with DLB (but not the CU), a longitudinal increase in flortaucipir SUVr was associated with longitudinal cortical atrophy rates in the lateral occipital and inferior temporoparietal cortices, hippocampus, and the temporal pole as well as a concurrent decline on Mini‐Mental State Examination and Clinical Dementia Rating–Sum of Boxes in the lateral occipital and the fusiform cortices. Conclusions Tau accumulation was faster in DLB compared with the CU, with increased accumulation rates in the lateral occipital and temporoparietal cortices. These increased rates of tau accumulation were associated with neurodegeneration and faster disease progression in DLB. Tau may be a potential treatment target in a subset of patients with DLB. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Abstract Mild cognitive impairment with the core clinical features of dementia with Lewy bodies is recognized as a prodromal stage of dementia with Lewy bodies. Although grey matter atrophy has been demonstrated in prodromal dementia with Lewy bodies, longitudinal rates of atrophy during progression to probable dementia with Lewy bodies are unknown. We investigated the regional patterns of cross-sectional and longitudinal rates of grey matter atrophy in prodromal dementia with Lewy bodies, including those who progressed to probable dementia with Lewy bodies. Patients with mild cognitive impairment with at least one core clinical feature of dementia with Lewy bodies (mean age = 70.5; 95% male), who were enrolled in the Mayo Clinic Alzheimer’s Disease Research Center and followed for at least two clinical evaluations and MRI examinations, were included (n = 56). A cognitively unimpaired control group (n = 112) was matched 2:1 to the patients with mild cognitive impairment by age and sex. Patients either remained stable (n = 28) or progressed to probable dementia with Lewy bodies (n = 28) during a similar follow-up period and pathologic confirmation was available in a subset of cases (n = 18). Cross-sectional and longitudinal rates of grey matter atrophy were assessed using voxel-based and atlas-based region of interest analyses. At baseline, prodromal dementia with Lewy bodies was characterized by atrophy in the nucleus basalis of Meynert both in those who remained stable and those who progressed to probable dementia with Lewy bodies (P &lt; 0.05 false discovery rate corrected). Increase in longitudinal grey matter atrophy rates were widespread, with greatest rates of atrophy observed in the enthorhinal and parahippocampal cortices, temporoparietal association cortices, thalamus and the basal ganglia, in mild cognitive impairment patients who progressed to probable dementia with Lewy bodies at follow-up (P &lt; 0.05 false discovery rate corrected). Rates of inferior temporal atrophy were associated with greater rates of worsening on the clinical dementia rating–sum of boxes. Seventeen of the 18 (94%) autopsied cases had Lewy body disease. Results show that atrophy in the nucleus basalis of Meynert is a feature of prodromal dementia with Lewy bodies regardless of proximity to progression to probable dementia with Lewy bodies. Longitudinally, grey matter atrophy progresses in regions with significant cholinergic innervation, in alignment with clinical disease progression, with widespread and accelerated rates of atrophy in patients who progress to probable dementia with Lewy bodies. Given the prominent neurodegeneration in the cholinergic system, patients with prodromal dementia with Lewy bodies may be candidates for cholinesterase inhibitor treatment.

AbstractBackgroundFrontotemporal dementia spectrum disorders (FTD) display complex neuropathological substrates and poor clinicopathological correlations, which hinders therapy development. Plasma P‐tau217 is an emerging tool to screen for Alzheimer’s disease (AD) pathology and may have diagnostic value in FTD.MethodPlasma P‐tau217 was measured cross‐sectionally by electrochemiluminescence in FTD patients referred to ALLFTD from ARTFL (n = 628, 45.7% female, median age 66 ± 12 years). P‐tau217 differences by baseline phenotype, disease severity and genotype were determined with non‐parametric tests and general linear models. Associations between P‐tau217 and measures of disease severity and neuropsychological performance were determined with linear regressions corrected for age, sex, phenotype and APOE.ResultThe sample included 33% behavioral variant FTD, 23.6% primary progressive aphasia (PPA), 28.5% atypical parkinsonism, 1.6% amnestic dementia (AmDem), 2.8% FTD/motoneuron disease, 3% mild cognitive/behavioral impairment and 7.5% healthy controls. Only 1.6% carried FTD‐causing mutations. P‐tau217 was not related to age (r = 0.034, 95%CI ‐0.03 – 0.12, p = 0.4). Compared to controls (0.18 ± 0.07 pg/mL), P‐tau217 was elevated only in AmDem (0.58 ± 0.9 pg/mL, p = 0.001) and logopenic PPA (lvPPA, 0.71 ± 0.62 pg/mL p < 0.001). P‐tau217 ≥ 0.42 pg/mL effectively discriminated AmDem and lvPPA from all other phenotypes (AUC 0.87, 95%CI 0.77 – 0.96, p = 0.001, 77% sensitivity, 92% specificity). AmDem (60%) and lvPPA (91.7%) had the highest prevalence of high (≥ 0.42 pg/mL) P‐tau217, and the highest prevalence of APOE4 (AmDem 40%, lvPPA 63.6%). APOE4 carriers (0.23 ± 0.22 pg/mL) had higher P‐tau217, than non‐carriers (0.19 ± 0.09 pg/mL), regardless of phenotype (APOE effect p = .002, APOE x phenotype, p = 0.44). P‐tau217 was associated with worse clinical severity, mood, memory and executive function, but not with worse motor symptoms or social cognition.ConclusionWhen FTD is suspected, high plasma P‐tau217 is strongly associated with amnestic dementia and logopenic PPA phenotypes. Pending completion of ongoing neuropathological, CSF and molecular neuroimaging analyses, the data support the use of plasma P‐tau217 to identify atypical AD as a cause or AD as a co‐pathology contributing to FTD clinical presentation.

AbstractBackgroundIn animal models of Alzheimer’s disease (AD), aerobic exercise favorably modified the accumulation, degradation, and removal of Aβ and tau. However, human mechanistic randomized controlled trials (RCTs) are limited with mixed findings on hippocampal volume and biofluid Aβ and tau. Hence, an objective of the FIT‐AD Trial was to examine the effects of 6‐month aerobic exercise on magnetic resonance imaging (MRI) biomarkers in community‐dwelling older adults with AD dementia.MethodThe FIT‐AD Trial was a pilot RCT that first qualified participants for the main exercise study eligibility and then for MRI. Participants were randomized to moderate intensity cycling or low intensity stretching for 20‐50 minutes, 3 times a week for six months on a 2:1 ratio with three age strata (66‐75, 76‐85, and 85+ years of age) and followed up for another six months. MRI biomarkers included hippocampal volume, temporal meta‐regions of interest cortical thickness, white matter hyperintensity (WMH) volume, and network failure quotient (NFQ) measured at baseline, six months, and 12 months.ResultSixty participants met MRI eligibility, but one was excluded when this participant’s baseline MRI failed quality control. Among the 59 remaining participants, 38 were randomized to cycling and 21 to stretching. The sample characteristics (n=59) were 77.3±6.3 years old with 15.6±2.9 years of education and 53% men. Both groups experienced significant declines in hippocampal volume (2.64% in cycling vs. 2.89% in stretching) and cortical thickness (0.94% vs. 1.54%) over six months and over 12 months (hippocampal volume: 4.47% vs. 3.84%; cortical thickness: 2.27% vs. 1.79%). These declines didn’t differ between groups. WMH volume increased significantly, but the cycling group increased >50% less than stretching (10.9% vs. 24.5% over six months [f=4.47, p=.04]; 12.1% vs. 27.6% over 12 months [f=5.88, p=.02]). NFQ didn’t change significantly over time nor differed between group.ConclusionAerobic exercise may reduce hippocampal volume and cortical thickness declines during the intervention period; however, its effects are likely to be small and dose‐dependent and reverse after the intervention stops. Aerobic exercise is effective on reducing WMH progression but has no effect on NFQ.

AbstractBackgroundIn longitudinal tau (flortaucipir) positron emission tomography (PET), a reliable method to detect a tau accumulation while minimizing a random variability is crucial. Variability can be a problem especially in the early stages of tau pathology in which only small regions and low levels of accumulation may exist relative to the range of random noise fluctuation.MethodWe recruited 76 participants who had serial scans for a total of 234 tau PET scans. In this cohort we tested a PET signal measurement method we developed called the “overlap index” (OI). The OI was calculated by identifying voxels that have elevated tau PET signal that overlap on two successive tau PET scans in the same participant (Figure 1). This analysis procedure tests the hypothesis that voxel‐wise, elevated‐uptake consistency might be more sensitive for early detection of tau tangles than standard ROI based measures. We compared OI to ROI based measures for early detection of increasing tau PET signal and detection clinical progression. A meta ROI used in this analysis included the amygdala, entorhinal cortex, fusiform, parahippocampal, and inferior temporal and middle temporal gyri.ResultOI showed regional progression of tau in the temporal lobe followed by increases throughout the brain at relatively low standardized uptake value ratio (SUVr) levels (Figure 2A and B). The topographical pattern of OI was in agreement in some respects with the sequential appearance of tau aggregation (Figure 2B and C). The high‐OI group (OI>0.5) had a significantly higher ΔSUVr compared to the low‐OI group (OI<0.5) (Figure 3A and B). OI identified subjects that did or didn’t have tau accumulation within meta SUVr subgroups even when below the meta ROI SUVr threshold. OI was associated with early clinical disease stage progression vs meta‐ROI SUVr measures (Figure 3C‐E).ConclusionIn this study, we found that OI tau PET measurement was able to quantify voxel‐wise consistency using a set of serial scans. OI may detect earlier tau tangle accumulation and earlier disease progression than standard SUVr measurements in tau PET.

AbstractBackgroundBlood neurofilament light chain (NfL) is a robust predictor of phenoconversion in familial frontotemporal lobar degeneration (fFTLD). The comparative value of CSF NfL and other CSF markers of degeneration in fFTLD remains unexplored.MethodFLTD‐causing mutation carriers were recruited through ALLFTD (n = 113, 56.6% female, mean age 48.1 ± 13 years; 29 C9orf72, 16 GRN, 34 MAPT, 34 mutation non‐carriers) and prospectively evaluated for 3 years. Baseline CSF was analyzed for NfL, phosphorylated neurofilament heavy chain (p‐NfH), tau, phosphorylated tau181 (p‐tau) and neurogranin using fit‐for‐purpose immunoassays. Mixed effect linear models, with random slopes, corrected for age, sex, genotype and total intracranial volume related CSF biomarkers to longitudinal clinical variables.ResultNfL (β = 0.64, p < 0.001), p‐NfH (β = 0.68, p < 0.001) and tau (β = 0.46, p < 0.001) correlated with age. There were no differences in biomarker concentrations by phenotype or severity, except for higher NfL and p‐NfH in full phenotype, compared to prodromal disease and asymptomatic carriers. Low neurogranin (β = ‐0.39, p < 0.001), low p‐tau (β = ‐0.33, p < 0.001) and high NfL (β = 0.42, p < 0.001) correlated with worse baseline disease severity measured by the CDR® Dementia Staging Instrument plus behavior and language domains from the National Alzheimer’s Disease Coordinating Center FTLD module sum of boxes (CDR®+NACC‐FTLDsb), and with other measures of global cognition, instrumental and daily function, and frontal and temporal brain volumes. Regardless of genotype, the predicted annualized rate of CDR®+NACC‐FTLDsb score worsenings per higher baseline CSF biomarker Log pg/mL were tau: 3.0 ± 0.2, NfL: 2.8 ± 0.2 and p‐NfH: 2.8 ± 0.2. High tau, NfL and p‐NfH also predicted worsening in other measures of global cognition and instrumental and daily function. Neurogranin and p‐tau did not predict clinical decline.ConclusionCSF tau, p‐tau, neurogranin, NfL and p‐NfH reflect important aspects of disease severity in fFTLD. In contrast to Alzheimer’s disease, low p‐tau and neurogranin are inversely related to clinical severity, which suggests a distinctive pathophysiological process and has implications for therapeutic development. CSF NfL, p‐NfH and tau have strong prognostic value in fFTLD.