Senjem, Matthew L.

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.

AbstractBackgroundElevated systolic blood pressure (SBP) and diastolic blood pressure (DBP) are risk factors for white matter (WM) injury associated with cognitive decline and dementia. White matter hyperintensities (WMH) on MRI, markers of WM injury, increase with aging and are more common in women than in men after the age of 60. We examined SBP and DBP in relation to WMH volume and diffusion MRI measures of WM integrity in postmenopausal women.MethodWomen (n=144) with median age of 67 (range 58‐72) and of good cardiovascular health who were previously enrolled in the multi‐site randomized clinical trial, Kronos Early Estrogen Prevention Study (KEEPS), participated in the present observational KEEPS Continuation Study. SBP, DBP, and MRI data were collected approximately 9 years after the end of KEEPS menopausal hormones versus placebo 4‐year interventions. WM integrity was assessed with WMH volume measurements (log transformed) on structural MRI and with measures of WM microstructure on diffusion MRI. Multiple linear regression analyses, adjusted for age, were used to test for associations of SBP and DBP with MRI measures.ResultThe median SBP was 128 (range 86‐180) and DBP was 77 (range 47‐106). Higher SBP (r=0.332;p=0.015) and DBP (r=0.346;p=0.007) were associated with higher WMH volumes. Among the WM tracts, higher SBP was associated with lower fractional anisotropy (FA) in lateral orbitofrontal gyrus WM (r=0.198;p=0.039) and sagittal stratum (r=0.226;p=0.043), and higher DBP was associated with lower FA in the superior occipital gyrus WM (r=0.370;p=0.045). Higher SBP and DBP were associated with higher mean diffusivity (MD) in the external capsule [(r=0.311;p=0.007);(r=375;p<0.001)] and the fronto‐occipital fasciculus [(r=0.286;p=0.016); (r=0.303;p=0.008)]. Furthermore, higher DBP was associated with higher MD in the anterior corona radiata (r=0.233;p=0.039), internal capsule (r=0.303;p=0.042), and the middle (r=0.275; p=0.03) and superior frontal gyrus (r=0.269;p=0.03) WM.ConclusionElevated SBP and DBP measurements are associated with greater WM injury in postmenopausal women. In particular, the frontal lobe WM and its connecting tracts may be more vulnerable to elevation in SBP and DBP. Whether BP control reduces the risk for WM injury, a risk factor for dementia, in post‐menopausal women warrants study.

AbstractBackgroundAlzheimer’s disease biomarkers of tau pathology may be assessed by both CSF and PET. Cross‐sectional associations between CSF phosphorylated tau (p‐tau) and tau PET have been studied and regional tau PET SUVR has been shown to have similar diagnostic performance as CSF p‐tau. The association between CSF p‐tau and longitudinal tau PET has not been studied. CSF measures may be thought of as a result of the imbalance of influx vs efflux of soluble tau, whereas, tau PET reflects total tau accumulation into insoluble aggregates to date. We therefore hypothesize that baseline CSF p‐tau may be a leading indicator of future tau PET accumulation.MethodWe identified Mayo Clinic Study of Aging (MCSA) and Mayo Alzheimer’s Disease Research Center (ADRC) participants with diagnoses of cognitively unimpaired, mild cognitive impairment, and amnestic dementia who had CSF p‐tau (Elecsys p‐tau [181P]) and subsequent serial tau PET (flortaucipir) exams. The first tau PET scan was within 3 years of the CSF p‐tau collection. A longitudinal pipeline with two‐compartment partial volume correction was used to measure change in tau PET in a temporal‐lobe meta‐ROI (amygdala, fusiform, middle/inferior temporal, entorhinal, and parahippocampal regions) with a composite reference region (eroded supratentorial white matter, pons, and whole cerebellum). Spearman correlation was used to assess the association between CSF p‐tau and annual percent change in tau PET. A linear mixed effects model was fit to assess the association adjusting for age and sex.ResultThe study included 143 participants (76% cognitively unimpaired) (). CSF p‐tau was significantly associated with annual percent change in tau PET overall (Spearman R=0.19, p=0.023) () and after adjusting for age and sex (p<0.001) (). There was nonlinearity in the CSF p‐tau effect, with higher values (>20 pg/mL) having a greater association with annual change in tau PET than lower values.ConclusionIn a group of cognitively unimpaired and impaired participants, CSF p‐tau predicted subsequent tau PET accumulation rate. A threshold effect is suggested with subsequent tau PET accumulation primarily in participants with elevated CSF p‐tau levels near the Mayo threshold of 22 pg/mL.

AbstractBackgroundWhite matter (WM) 11C‐Pittsburgh compound‐B (PiB) and 18F‐Flutemetamol (FMT) uptake is increasingly being used as a reference region to calculate the standard uptake value ratios (SUVr) in longitudinal amyloid‐β PET studies. PiB uptake is lower in WM hyperintensities (WMH) in older adults. Furthermore, WM PiB uptake increases with aging. Our objective was to determine whether a similar variation in WM uptake exists with an 18F‐ligand FMT.MethodA cohort of cognitively unimpaired (CU) older adults with median (range) age of 67 (61, 83) years (N=31), and younger adults with median (range) age of 38 (30, 48) years (N=30) from the community responding to a study advertisement underwent MRI, PiB and FMT PET. MRI‐FLAIR images were segmented into WMH and normal appearing white matter (NAWM) and registered to the T1‐weighted image. PiB and FMT PET images were registered to the T1‐weighted image. PiB and FMT SUVrs from the WMH and NAWM compartments were calculated using cerebellar crus uptake as a reference.ResultWMH PiB SUVr and NAWM PiB SUVr were lower in the younger compared to the older adults (p<0.001). WMH FMT SUVr and NAWM FMT SUVr were lower in younger compared to older adults (p<0.001). PiB SUVr was lower than FMT SUVr both in younger and older adults in both WMH and NAWM compartments (p<0.001). In both age groups, PiB SUVr and FMT SUVr in WMH was lower than NAWM (p<0.001). AUROC analysis demonstrated no difference between PiB versus FMT SUVr in differentiating WMH from NAWM in younger and older adults.ConclusionWMH and NAWM SUVRs are higher with FMT than PiB, however both PiB and FMT show a similar topographic pattern of uptake in the WM with higher uptake in NAWM compared to WMH. Aging is associated with a decrease in myelin integrity and increase of WMH volume. Higher WMH and NAWM PiB and FMT uptake in the older compared to younger adults suggests that additional aging‐related mechanisms are influencing WM PET tracer uptake. Age and WMH volume should be considered when WM uptake is used as a reference region for the evaluation of cortical uptake of both PiB and FMT.

Abstract Dementia and mortality rates rise inexorably with age and consequently interact. However, because of the major logistical difficulties in accounting for both outcomes in a defined population, very little work has examined how risk factors and biomarkers for incident dementia are influenced by competing mortality. The objective of this study was to examine long-term associations between amyloid PET, APOE ɛ4, sex, education and cardiovascular/metabolic conditions, and hazard and absolute risk of dementia and mortality in individuals without dementia at enrolment. Participants were enrolled in the Mayo Clinic Study of Aging, a population-based study of cognitive ageing in Olmsted County, MN, USA. All were without dementia and were age 55–92 years at enrolment and were followed longitudinally. Predictor variables were amyloid PET, APOE ɛ4 status, sex, education, cardiovascular/metabolic conditions and age. The main outcomes were incident dementia and mortality. Multivariable, multi-state models were used to estimate mortality and incident dementia rates and absolute risk of dementia and mortality by predictor variable group. Of the 4984 participants in the study, 4336 (87%) were cognitively unimpaired and 648 (13%) had mild cognitive impairment at enrolment. The median age at enrolment was 75 years; 2463 (49%) were women. The median follow-up time was 9.4 years (7.5 years after PET). High versus normal amyloid (hazard ratio 2.11, 95% confidence interval 1.43–2.79), APOE ɛ4 (women: hazard ratio 2.24, 95% confidence interval 1.80–2.77; men: hazard ratio 1.37, 95% confidence interval 1.09–1.71), older age and two additional cardiovascular/metabolic conditions (hazard ratio 1.37, 95% confidence interval 1.22–1.53) were associated with the increased hazard of dementia (all P &lt; 0.001). Among APOE ɛ4 carriers with elevated amyloid, remaining lifetime risk of dementia at age 65 years was greater in women [74% (95% confidence interval 65–84%) high and 58% (95% confidence interval 52–65%) moderate amyloid], than men [62% (95% confidence interval 52–73%) high and 44% (95% confidence interval 35–53%) moderate amyloid]. Overall, the hazard and absolute risk of dementia varied considerably by predictor group. The absolute risk of dementia associated with predictors characteristic of Alzheimer’s disease was greater in women than men while at the same time the combination of APOE ɛ4 non-carrier with normal amyloid was more protective in women than men. This set of findings may be attributed in part to different biological effects and in part to lower mortality rates in women.

AbstractBackgroundThe Neurodegenerative Research Group (NRG) at Mayo clinic has followed patients with degenerative speech and/or language disorders for over a decade. In this presentation I will present data from this cohort to inform a broader discussion about the importance of apraxia of speech (AOS) and its subtypes, heterogeneity within the agrammatic PPA variant, and perils of mixed phenotypes.MethodWe reviewed the NRG database to identify patients who initially presented with isolated (PPAOS), AOS in conjunction with agrammatic aphasia (AOS‐PAA), isolated agrammatic aphasia (PAA), and patients who had PAA or AOS overlapping with another degenerative diagnosis. Data from the following clinical instruments were abstracted: WAB AQ (aphasia severity), UPDRS III (parkinsonism), WAB Praxis (ideomotor apraxia), and the MoCA (cognitive ability). We assessed the effect of baseline diagnosis and AOS subtype on these outcomes over time using Bayesian linear mixed effects models. We qualitatively reviewed longitudinal diagnostic trajectories. Preliminary analyses were done on available autopsy data.ResultPAA was associated with greater aphasia at baseline and more rapid decline; PPAOS was associated with normal language at baseline and slow decline; and PAA‐AOS with intermediate baseline aphasia and decline. However, for those with AOS longitudinal decline differed based on AOS subtype: prosodic PPAOS was associated with the slowest decline and phonetic PAA‐AOS with the fastest. Some patients met criteria for non‐PPA disorders during follow up. However, compared to patients who met criteria for these disorders at enrollment, the speech/language‐first patients remained qualitatively distinct, and neither resembled the cases that were mixed at onset. Preliminary autopsy data suggests that AOS is predictive of tau and that the specific tauopathy may be related to the initial syndrome and AOS subtype.ConclusionThe differences between PAA, PAA‐AOS and PPAOS suggest that these disorders should not be lumped. In fact, the longitudinal trajectories are sufficiently different that doing so would add noise to observational and interventional studies. Instead, more detailed phenotyping, including AOS subtype, can aid prognostication and may improve prediction of the underlying pathology. Finally, caution should be exercised when considering PPAOS and PPA patients for other FTLD diagnostic categories.

AbstractBackgroundOptimizing software to measure Flortaucipir (AV‐1451) tau PET SUVR change‐over‐time is crucial for longitudinal observational studies and potential trials of anti‐tau agents. Ideal measurements should have good repeatability (low noise), and should clearly separate clinical cognitive groups.MethodWe compared 456 software methods varying in their use of: two major packages, each with cross‐sectional and longitudinal variants (FreeSurfer and an in‐house pipeline using SPM12, MCALT, and ANTs); three temporal‐lobe target regions (each with/without adjacent WM); seven reference regions; five PVC methods; and two statistics (mean vs. median). We used linear mixed‐effects models to compare methods using scans from 88 Mayo Clinic participants (46 cognitively impaired, 42 impaired, excluding those with symptoms inconsistent with the AD pathology imaged by Flortaucipir), each with three visits with PET and MRI. From these models, we calculated two criteria for each pipeline: relative measurement error (residual from the linear mixed model), and the t‐statistic for testing differences in group‐wise rates of change (which has a Cohen’s d interpretation of effect size for longitudinal data). We plotted both criteria orthogonally, then ranked methods overall according to the average of their ranks on both individual criteria.ResultMethods using the entorhinal cortex target region performed poorly in both criteria (Figure 1). The top 10 methods by the combined criteria (top‐left in Figure 2) all used the Mayo SPM12‐based pipeline with an eroded supratentorial WM (eSWM) or composite (eSWM + pons + cerebellum) reference region. Among them, 9/10 used the longitudinal variant, 8/10 used 2‐compartment PVC, and 7/10 used median. Altogether, our results favored SUVR methods with a longitudinal design (simultaneously calculating all time‐points), a temporal‐lobe meta‐ROI including adjacent WM, a composite reference region, 2‐class voxel‐based (Meltzer) PVC, and median statistics. Methods using GTM‐Tau PVC (Baker et al., Data in Brief, 2017) had the highest group separation but relatively large measurement error, giving them ranks 197 and 199 out of 456 with the joint (average rank) criteria.ConclusionCompared with popular FreeSurfer‐based methods (ranks 176, 258; Figure 2), our top‐ranked approaches approximately halved error in SUVR measurements while maintaining or improving group separation.

We present the case of a cognitively unimpaired 77-year-old man with elevated, asymmetric, and longitudinally increasing Flortaucipir tau PET despite normal (visually negative) amyloid PET. His atypical tau PET signal persisted and globally increased in a follow-up scan five years later. Across eight years of observations, temporoparietal atrophy was observed consistent with tau PET patterns, but he retained the cognitively unimpaired classification. Altogether, his atypical tau PET signal is not explained by any known risk factors or alternative pathologies, and other imaging findings were not remarkable. He remains enrolled for further observation.

Abstract Normal brain aging is accompanied by patterns of functional and structural change. Alzheimer's disease (AD), a representative neurodegenerative disease, has been linked to accelerated brain aging at respective age ranges. Here, we developed a deep learning-based brain age prediction model using fluorodeoxyglucose (FDG) PET and structural MRI and tested how the brain age gap relates to degenerative cognitive syndromes including mild cognitive impairment, AD, frontotemporal dementia, and Lewy body dementia. Occlusion analysis, performed to facilitate interpretation of the model, revealed that the model learns an age- and modality-specific pattern of brain aging. The elevated brain age gap in dementia cohorts was highly correlated with the cognitive impairment and AD biomarker. However, regions generating brain age gaps were different for each diagnosis group of which the AD continuum showed similar patterns to normal aging in the CU.

AbstractBackgroundDysphagia is a common symptom of progressive supranuclear palsy often leading to aspiration pneumonia and death.ObjectiveThe aim of this study was to examine how impairments of the oral and pharyngeal phases of the swallow and airway incursion during liquid swallows relate to gray and white matter integrity.MethodsThirty‐eight participants with progressive supranuclear palsy underwent videofluorographic swallowing assessment and structural and diffusion tensor head magnetic resonance imaging. Penalized linear regression models assessed relationships between swallowing metrics and regional gray matter volumes and white matter fractional anisotropy and mean diffusivity.ResultsOral phase impairments were associated with reduced superior parietal volumes and abnormal diffusivity in parietal and sensorimotor white matter, posterior limb of the internal capsule, and superior longitudinal fasciculus. Pharyngeal phase impairments were associated with disruption to medial frontal lobe, corticospinal tract, and cerebral peduncle. No regions were predictive of airway incursion.ConclusionsDifferential patterns of neuroanatomical impairment corresponded to oral and pharyngeal phase swallowing impairments. © 2021 International Parkinson and Movement Disorder Society