Long-duration progressive supranuclear palsy: clinical course and pathological underpinnings

Progressive supranuclear palsy: Neuropathology, clinical presentation, diagnostic challenges, management, and emerging therapies

Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized by the accumulation of 4R-tau protein aggregates in various brain regions. PSP leads to neuronal loss, gliosis, and tau-positive inclusions, such as neurofibrillary tangles, tufted astrocytes, and coiled bodies. These pathological changes mainly affect the brainstem and the basal ganglia, resulting in distinctive MRI features, such as the hummingbird and morning glory signs. PSP shows clinical heterogeneity and presents as different phenotypes, the most classical of which is Richardson's syndrome (PSP-RS). The region of involvement and the mode of atrophy spread can further distinguish subtypes of PSP. PSP patients can experience various signs and symptoms, such as postural instability, supranuclear ophthalmoplegia, low amplitude fast finger tapping, and irregular sleep patterns. The most common symptoms of PSP are postural instability, falls, vertical gaze palsy, bradykinesia, and cognitive impairment. These features often overlap with those of Parkinson's disease (PD) and other Parkinsonian syndromes, making the diagnosis challenging. PSP is an essential clinical topic to research because it is a devastating and incurable disease. However, there are still many gaps in knowledge about its pathophysiology, diagnosis, and treatment. Several clinical trials are underway to test noveltherapies that target tau in various ways, such as modulating its post-translational modifications, stabilizing its interaction with microtubules, or enhancing its clearance by immunotherapy. These approaches may offer new hope for slowing down the progression of PSP. In this review, we aim to provide an overview of the current knowledge on PSP, from its pathogenesis to its management. We also discuss the latest advances and future directions in PSP research.

Contribution of MRI for the Early Diagnosis of Parkinsonism in Patients with Diagnostic Uncertainty

BACKGROUND

International clinical criteria are the reference for the diagnosis of degenerative parkinsonism in clinical research, but they may lack sensitivity and specificity in the early stages.

OBJECTIVES

To determine whether magnetic resonance imaging (MRI) analysis, through visual reading or machine-learning approaches, improves diagnostic accuracy compared with clinical diagnosis at an early stage in patients referred for suspected degenerative parkinsonism.

MATERIALS

Patients with initial diagnostic uncertainty between Parkinson's disease (PD), progressive supranuclear palsy (PSP), and multisystem atrophy (MSA), with brain MRI performed at the initial visit (V1) and available 2-year follow-up (V2), were included. We evaluated the accuracy of the diagnosis established based on: (1) the international clinical diagnostic criteria for PD, PSP, and MSA at V1 ("Clin1"); (2) MRI visual reading blinded to the clinical diagnosis ("MRI"); (3) both MRI visual reading and clinical criteria at V1 ("MRI and Clin1"), and (4) a machine-learning algorithm ("Algorithm"). The gold standard diagnosis was established by expert consensus after a 2-year follow-up.

RESULTS

We recruited 113 patients (53 with PD, 31 with PSP, and 29 with MSA). Considering the whole population, compared with clinical criteria at the initial visit ("Clin1": balanced accuracy, 66.2%), MRI visual reading showed a diagnostic gain of 14.3% ("MRI": 80.5%; P = 0.01), increasing to 19.2% when combined with the clinical diagnosis at the initial visit ("MRI and Clin1": 85.4%; P < 0.0001). The algorithm achieved a diagnostic gain of 9.9% ("Algorithm": 76.1%; P = 0.08).

CONCLUSION

Our study shows the use of MRI analysis, whether by visual reading or machine-learning methods, for early differentiation of parkinsonism. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Histologic tau lesions and magnetic resonance imaging biomarkers differ across two progressive supranuclear palsy variants

Progressive supranuclear palsy is a neurodegenerative disease characterized by the deposition of four-repeat tau in neuronal and glial lesions in the brainstem, cerebellar, subcortical and cortical brain regions. There are varying clinical presentations of progressive supranuclear palsy with different neuroimaging signatures, presumed to be due to different topographical distributions and burden of tau. The classic Richardson syndrome presentation is considered a subcortical variant, whilst progressive supranuclear palsy with predominant speech and language impairment is considered a cortical variant, although the pathological underpinnings of these variants are unclear. In this case-control study, we aimed to determine whether patterns of regional tau pathology differed between these variants and whether tau burden correlated with neuroimaging. Thirty-three neuropathologically confirmed progressive supranuclear palsy patients with either the Richardson syndrome (n = 17) or speech/language (n = 16) variant and ante-mortem magnetic resonance imaging were included. Tau lesion burden was semi-quantitatively graded in cerebellar, brainstem, subcortical and cortical regions and combined to form neuronal and glial tau scores. Regional magnetic resonance imaging volumes were converted to Z-scores using 33 age- and sex-matched controls. Diffusion tensor imaging metrics, including fractional anisotropy and mean diffusivity, were calculated. Tau burden and neuroimaging metrics were compared between groups and correlated using linear regression models. Neuronal and glial tau burden were higher in motor and superior frontal cortices in the speech/language variant. In the subcortical and brainstem regions, only the glial tau burden differed, with a higher burden in globus pallidus, subthalamic nucleus, substantia nigra and red nucleus in Richardson's syndrome. No differences were observed in the cerebellar dentate and striatum. Greater volume loss was observed in the motor cortex in the speech/language variant and in the subthalamic nucleus, red nucleus and midbrain in Richardson's syndrome. Fractional anisotropy was lower in the midbrain and superior cerebellar peduncle in Richardson's syndrome. Mean diffusivity was greater in the superior frontal cortex in the speech/language variant and midbrain in Richardson's syndrome. Neuronal tau burden showed associations with volume loss, lower fractional anisotropy and higher mean diffusivity in the superior frontal cortex, although these findings did not survive correction for multiple comparisons. Results suggest that a shift in the distribution of tau, particularly neuronal tau, within the progressive supranuclear palsy network of regions is driving different clinical presentations in progressive supranuclear palsy. The possibility of different disease epicentres in these clinical variants has potential implications for the use of imaging biomarkers in progressive supranuclear palsy.

Correlation between clinical and neuropathological subtypes of progressive supranuclear palsy

INTRODUCTION

Progressive supranuclear palsy (PSP) is characterized by pathology prominently in the basal ganglia, the tegmentum of the brainstem, and the frontal cortex. However, pathology varies according to clinical features. This study aimed to statistically verify the correspondence between the clinical and pathological subtypes of PSP.

METHODS

We identified patients with a pathological diagnosis of PSP and classified the eight clinical subtypes of the Movement Disorders Society criteria for the clinical diagnosis of PSP (MDS-PSP criteria) into the Richardson, Akinesia, and Cognitive groups. We used anti-phosphorylated tau antibody immunostaining to semi-quantitatively evaluate neurofibrillary tangles (NFTs) and coiled bodies/threads (CB/Ths) in the globus pallidus, subthalamic nucleus, and midbrain tegmentum. In the frontal cortex, tufted astrocytes (TAs) and CB/Ths were assessed on a 3-point scale. We compared the pathology among the three groups, recorded the phenotypes ranked the second and lower in the multiple allocation extinction rule and examined whether the pathology changed depending on applying each phenotype.

RESULTS

The Richardson group exhibited severe NFTs and CB/Ths in the midbrain tegmentum. The Akinesia group showed severe NFTs in the globus pallidus. The Cognitive group had severe TAs and CB/Ths in the frontal cortex. TAs and CB/Ths in the frontal cortex correspond to behavioral variant frontotemporal dementia, and supranuclear vertical oculomotor palsy.

CONCLUSION

These clinical symptoms may reflect the distribution of tau pathologies in PSP.

Association of Structural Forms of 17q21.31 with the Risk of Progressive Supranuclear Palsy and MAPT Sub-haplotypes

Importance

The chromosome 17q21.31 region, containing a 900 Kb inversion that defines H1 and H2 haplotypes, represents the strongest genetic risk locus in progressive supranuclear palsy (PSP). In addition to H1 and H2, various structural forms of 17q21.31, characterized by the copy number of α, β, and γ duplications, have been identified. However, the specific effect of each structural form on the risk of PSP has never been evaluated in a large cohort study.

Objective

To assess the association of different structural forms of 17q.21.31, defined by the copy numbers of α, β, and γ duplications, with the risk of PSP and MAPT sub-haplotypes.

Design setting and participants

Utilizing whole genome sequencing data of 1,684 (1,386 autopsy confirmed) individuals with PSP and 2,392 control subjects, a case-control study was conducted to investigate the association of copy numbers of α, β, and γ duplications and structural forms of 17q21.31 with the risk of PSP. All study subjects were selected from the Alzheimer's Disease Sequencing Project (ADSP) Umbrella NG00067.v7. Data were analyzed between March 2022 and November 2023.

Main outcomes and measures

The main outcomes were the risk (odds ratios [ORs]) for PSP with 95% CIs. Risks for PSP were evaluated by logistic regression models.

Results

The copy numbers of α and β were associated with the risk of PSP only due to their correlation with H1 and H2, while the copy number of γ was independently associated with the increased risk of PSP. Each additional duplication of γ was associated with 1.10 (95% CI, 1.04-1.17; P = 0.0018) fold of increased risk of PSP when conditioning H1 and H2. For the H1 haplotype, addition γ duplications displayed a higher odds ratio for PSP: the odds ratio increases from 1.21 (95%CI 1.10-1.33, P = 5.47 × 10-5) for H1β1γ1 to 1.29 (95%CI 1.16-1.43, P = 1.35 × 10-6) for H1β1γ2, 1.45 (95%CI 1.27-1.65, P = 3.94 × 10-8) for H1β1γ3, and 1.57 (95%CI 1.10-2.26, P = 1.35 × 10-2) for H1β1γ4. Moreover, H1β1γ3 is in linkage disequilibrium with H1c (R2 = 0.31), a widely recognized MAPT sub-haplotype associated with increased risk of PSP. The proportion of MAPT sub-haplotypes associated with increased risk of PSP (i.e., H1c, H1d, H1g, H1o, and H1h) increased from 34% in H1β1γ1 to 77% in H1β1γ4.

Conclusions and relevance

This study revealed that the copy number of γ was associated with the risk of PSP independently from H1 and H2. The H1 haplotype with more γ duplications showed a higher odds ratio for PSP and were associated with MAPT sub-haplotypes with increased risk of PSP. These findings expand our understanding of how the complex structure at 17q21.31 affect the risk of PSP.

Differentiating progressive supranuclear palsy from other movement disorders using transcranial sonography: a systematic review and meta-analysis

Progressive supranuclear palsy (PSP) is an atypical parkinsonism that presents with different phenotypes. There are still no validated diagnostic biomarkers for early diagnosis of PSP. Transcranial sonography (TCS) is a promising tool in the differential diagnosis of parkinsonian disorders; however, there are no systematic investigations about the application of TCS in PSP patients. Therefore, we performed a systematic review and meta-analysis to discuss the role of TCS in diagnosing PSP by systematically searching PubMed, Cochrane Library, Chinese National Knowledge Infrastructure and Wan Fang databases. Of 66 obtained records, 16 articles, including 366 patients with PSP, were included. Our results showed the estimated random-effects pooled prevalence of substantia nigra hyperechogenicity in patients with PSP was 22% (95% CI 12-32%), lenticular nucleus hyperechogenicity was 70% (95% CI 52-82%), and enlarged third ventricle was 71% (95% CI 55-85%). Additionally, a normal echogenicity substantia nigra in TCS showed 70% sensitivity (95% CI 56-81%) and 86% specificity (95% CI 75-86%) to differentiate PSP from Parkinson's disease. In conclusion, TCS is an important supplementary biomarker for diagnosing PSP. At the same time, the diagnostic value of TCS in discriminating PSP from other atypical parkinsonism and between different PSP phenotypes needs further exploration.

Whole-Genome Sequencing Analysis Reveals New Susceptibility Loci and Structural Variants Associated with Progressive Supranuclear Palsy

Background

Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease characterized by the accumulation of aggregated tau proteins in astrocytes, neurons, and oligodendrocytes. Previous genome-wide association studies for PSP were based on genotype array, therefore, were inadequate for the analysis of rare variants as well as larger mutations, such as small insertions/deletions (indels) and structural variants (SVs).

Method

In this study, we performed whole genome sequencing (WGS) and conducted association analysis for single nucleotide variants (SNVs), indels, and SVs, in a cohort of 1,718 cases and 2,944 controls of European ancestry. Of the 1,718 PSP individuals, 1,441 were autopsy-confirmed and 277 were clinically diagnosed.

Results

Our analysis of common SNVs and indels confirmed known genetic loci at MAPT, MOBP, STX6, SLCO1A2, DUSP10, and SP1, and further uncovered novel signals in APOE, FCHO1/MAP1S, KIF13A, TRIM24, TNXB, and ELOVL1. Notably, in contrast to Alzheimer's disease (AD), we observed the APOE ε2 allele to be the risk allele in PSP. Analysis of rare SNVs and indels identified significant association in ZNF592 and further gene network analysis identified a module of neuronal genes dysregulated in PSP. Moreover, seven common SVs associated with PSP were observed in the H1/H2 haplotype region (17q21.31) and other loci, including IGH, PCMT1, CYP2A13, and SMCP. In the H1/H2 haplotype region, there is a burden of rare deletions and duplications (P = 6.73×10-3) in PSP.

Conclusions

Through WGS, we significantly enhanced our understanding of the genetic basis of PSP, providing new targets for exploring disease mechanisms and therapeutic interventions.

ApoE4 expression disrupts tau uptake, trafficking, and clearance in astrocytes

Tauopathies are a collection of neurodegenerative diseases characterized by the accumulation of pathogenic aggregates of the microtubule-associated protein tau. Despite the prevalence and diversity of tau astrogliopathy in tauopathies, the interactions between astrocytes and tau in the brain, and the influence of neurodegenerative genetic risk factors like the apolipoprotein E4 (apoE4) isoform, are largely unknown. Here, we leveraged primary and immortalized astrocytes expressing humanized apoE isoforms to characterize the mechanisms by which astrocytes interact with and eliminate extracellular tau, and the influence of apoE genotype on these processes. Our work indicates that astrocytes rapidly internalize, process, and release tau via an exosomal secretory mechanism under physiological conditions. However, we found that apoE4 disrupted these processes in comparison to apoE3, resulting in an astrocytic phenotype prone to intracellular tau accumulation. Furthermore, exposure to repetitive mild traumatic brain injuries exacerbated the apoE4-induced impairments in tau processing and elimination by astrocytes in apoE4 targeted-replacement mice. The diminished ability of apoE4 astrocytes to eliminate extracellular tau can lead to an accumulation of pathogenic tau, which induces mitochondrial dysfunction, as demonstrated by our studies. In total, our findings suggest that the apoE4 isoform lowers the threshold of astrocytic resilience to pathogenic tau, rendering them susceptible to bioenergetic deficits in the early stages of neurodegenerative diseases such as traumatic brain injury, potentially contributing to neurological decline.

Clinical and neuroimaging features of the progressive supranuclear palsy- corticobasal degeneration continuum

PURPOSE OF REVIEW

The aim of this study was to discuss how recent work has increased our understanding of progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). The investigation of large and autopsy-confirmed cohorts, imaging modalities to assess different aspects of pathophysiology, clinical phenotypes and the application of advanced machine learning techniques, have led to recent advances in the field that will be discussed.

RECENT FINDINGS

Literature over the past 18 months will be discussed under the following themes: studies assessing how different neuroimaging modalities can improve the diagnosis of PSP and CBD from other neurodegenerative and parkinsonian disorders, including the investigation of pathological targets such as tau, iron, neuromelanin and dopamine and cholinergic systems; work improving our understanding of clinical, neuroanatomical and pathological heterogeneity in PSP and CBD; and work using advanced neuroimaging tools to investigate patterns of disease spread, as well as biological mechanisms potentially driving spread through the brain in PSP and CBD.

SUMMARY

The findings help improve the imaging-based diagnosis of PSP and CBD, allow more targeted prognostic estimates for patients accounting for phenotype or disease, and will aid in the development of appropriate and better-targeted disease biomarkers for clinical treatment trials.

Progressive supranuclear palsy's economical burden: the use and costs of healthcare resources in a large health provider in Israel

BACKGROUND

Progressive supranuclear palsy (PSP) is a rare and fatal neurodegenerative movement disorder with no disease modifying therapy currently available. Data on the costs associated with PSP are scarce. This study aims to assess the direct medical expenditure of patients with PSP (PwPSP) throughout disease course.

METHODS

This retrospective cohort study is based on the data of a large state-mandated health provider in Israel. We identified PwPSP who were initially diagnosed between 2000 and 2017. Each PwPSP was randomly matched to three health-plan members without PSP by birth-year, sex, and socioeconomic status. Healthcare resources' utilization and related costs were assessed.

RESULTS

We identified 88 eligible PwPSP and 264 people in the reference group; mean age at diagnosis was 72.6 years (SD = 8.4) and 53.4% were female. The annual direct costs of PwPSP have risen over time, reaching US$ 21,637 in the fifth year and US$ 36,693 in the tenth year of follow-up vs US$ 8910 in the year prior diagnosis. Compared to people without PSP, PwPSP had substantially higher medical expenditure during the years prior- and post-index date.

CONCLUSION

The present study demonstrates higher economic burden, which increases with time, in PwPSP as compared to those without.

Longitudinal clinical decline and baseline predictors in progressive supranuclear palsy

INTRODUCTION

Progressive supranuclear palsy (PSP) is associated with several clinical variants defined based on ocular motor dysfunction, postural instability, akinesia, and cognitive dysfunction, although little is known about how these features progress over time. We aimed to assess the evolution of these core clinical features across variants and assess baseline clinical and neuroimaging predictors of progression.

METHODS

Ninety-three PSP patients were recruited by the Neurodegenerative Research Group, Mayo Clinic, and underwent two visits 1-year apart, with baseline MRI and [18F]flortaucipir PET. We compared baseline and annualized rates of clinical change on the PSP Rating Scale (total, ocular motor, gait/midline scores) and Montreal Cognitive Assessment, across PSP-Richardson's, PSP-Cortical and PSP-Subcortical variants and assessed relationships between rates of change and baseline regional imaging.

RESULTS

Ocular motor scores differed across groups at baseline and follow-up, with lowest scores observed in PSP-subcortical, but no differences were observed in rate of change across groups. PSP Rating Scale total and gait/midline scores differed across groups at follow-up and in rates of change, with PSP-subcortical showing the least impairment and slowest progression. Greatest cognitive impairment was observed in PSP-Cortical. Sample size estimates for treatment trials differed across PSP variants. Greater baseline flortaucipir uptake, but not volume, of midbrain and motor cortex correlated with faster rates of clinical decline.

CONCLUSION

The PSP Rating Scale and its subscores might be useful markers for the prognostic stratification of PSP variants. Flortaucipir imaging at baseline may help predict rate of decline.

Epidemiology of Progressive Supranuclear Palsy: Real World Data from the Second Largest Health Plan in Israel

Progressive supranuclear palsy (PSP) is a rare and fatal neurodegenerative movement disorder and no disease modifying therapy (DMT) is currently available. This study aims to assess the epidemiology of PSP in Israel and to describe its clinical features. This retrospective analysis identified patients with PSP between 2000 and 2018 over the age of 40 years at first diagnosis (index date). We identified 209 patients with ≥1 diagnosis of PSP. Of those, 88 patients satisfied the inclusion criteria with a mean age at diagnosis of 72 years (SD = 8) and 53% were female. The 2018 prevalence and incidence rates were 5.3 and 1 per 100,000 persons, respectively. Median survival time was 4.9 years (95% CI 3.6–6.1) and median time from initial symptom to diagnosis was 4.2 years. The most common misdiagnoses were Parkinson’s disease, cognitive disorder and depression. The present study demonstrates that the clinic-epidemiological features of PSP in Israel are similar to PSP worldwide. In light of PSP’s rarity, investigation of PSP cohorts in different countries may create a proper platform for upcoming DMT trials.