Ahlskog, J. Eric

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.

AbstractBackgroundMagnetic resonance brainstem measurements are useful structural biomarkers in the Richardson's syndrome variant of progressive supranuclear palsy (PSP). However, it is unclear how these biomarkers differ across the phenotypic spectrum of PSP and how they relate to underlying pathology.ObjectiveThe aim of this study was to compare brainstem imaging measures across clinical variants of PSP and determine sensitivity and specificity based on pathologically diagnosed cases.MethodsA total of 153 patients with PSP who represented eight clinical variants were recruited at Mayo Clinic (Rochester, MN, USA) and underwent structural magnetic resonance imaging (MRI). Midbrain and pons area and superior and middle cerebellar peduncle width measurements were performed, and midbrain/pons ratio and Magnetic Resonance Parkinsonism Index (MRPI) were calculated. Among the 43 patients who later died, PSP pathology was confirmed in 29, whereas 14 had other pathology.ResultsBrainstem measurements varied across PSP clinical variants and were most abnormal in PSP‐Richardson's syndrome and frontal variants, followed by PSP‐corticobasal, PSP‐speech/language, and PSP‐parkinsonism variants. All these variants showed abnormalities compared with controls. The PSP‐gait freezing variant and patients with prominent corticospinal tract signs showed normal brainstem measures. Among cases with confirmed PSP pathology, the midbrain area, midbrain/pons ratio, and MRPI were all more abnormal compared to those with other pathologies, with best differentiation obtained with the MRPI (sensitivity = 83%; specificity = 85%).ConclusionsMRI brainstem measures show utility as diagnostic biomarkers across PSP clinical variants and have the potential to be useful in predicting underlying pathology. © 2021 International Parkinson and Movement Disorder Society

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

AbstractBackgroundSeveral studies have proposed a role for infections to induce an inflammatory response triggering Parkinson's disease. This remains controversial and the influence of severe infections on other α‐synucleinopathies (Dementia with Lewy Bodies, Parkinson's disease dementia, and Multiple System Atrophy) has not been adequately investigated.ObjectivesTo assess the association between hospitalization‐required infections or sepsis and risk of clinically diagnosed α‐synucleinopathies.MethodsUsing the medical records‐linkage system (Rochester Epidemiology Project), we identified all α‐synucleinopathy cases of in Olmsted County (1991–2010). Cases were matched by symptom‐onset age and sex to controls. We reviewed complete medical records to detect hospital‐required infections or sepsis preceding clinical‐motor onset of α‐synucleinopathies. We used conditional logistic regression to calculate the odds ratio of all α‐synucleinopathies, adjusting for medications, coffee, and smoking.ResultsThere was no association between infection‐related hospitalization (odds ratio: 1.05; 95% confidence interval: 0.78–1.40; P = 0.76) or sepsis (odds ratio: 0.86; 95% confidence interval: 0.40–1.85; P = 0.70) and all α‐synucleinopathies in multivariable analyses. We did not identify any associations after stratifying for type of α‐synucleinopathy, sex, and age at clinical‐motor onset. We analyzed sepsis separately with similar results.ConclusionWe did not observe any associations between infections leading to hospitalization or sepsis and development of any α‐synucleinopathies. © 2020 International Parkinson and Movement Disorder Society

Background: Few studies have investigated the incidence of PSP and CBS in the population. Objective: To examine the incidence of and trends in progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) in a population-based cohort of residents of Olmsted County, MN. Methods: We used the 1991-2005 population-based, Olmsted County Parkinsonism-cohort study, defined via the Rochester Epidemiology Project. A movement-disorder specialist reviewed medical records, to confirm PSP and CBS diagnoses. Results: We identified 21 patients with these diagnoses 1991-2005 : 18 (85.7%), PSP; 3 (14.3%), CBS. The median diagnosis age was 78 (range: 66-88). 13/21 (62.0%) were male. MRI was performed pre-diagnosis in 11 patients (8 PSP and 3 CBD); 10 showed atrophy consistent with clinical diagnoses. We observed concordance between clinical and pathological diagnoses in two PSP patients who underwent autopsy. Combined incidence for PSP and CBS in Olmsted County was 3.1 per 100,000 person-years (2.6 per 100,000 person-years, PSP; 0.4 per 100,000 person-years, CBS). Incidence was higher in men (4.5, 95% CI, 2.0-7.0) than women (1.8, 95% CI, 0.5-2.9). A combined, significant trend of increasing incidence was observed between 1991 and 2005 (B=0.69, 95% CI 0.42, 0.96, p<0.001). Median time from symptom onset to death among both groups was 6 years (range PSP, 1-10 years; range CBS, 3-8 years). Conclusions: The combined incidence for PSP and CBS was 3.1 per 100,000 person-years, higher in men than women. We observed a significant increase in both PSP and CBS, likely due to advancing imaging technology and improved diagnostic ability among physicians.