Sensitivity and Specificity of Diagnostic Criteria for Progressive Supranuclear Palsy

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.

Added value of FDG-PET for detection of progressive supranuclear palsy

BACKGROUND

Diagnostic criteria for progressive supranuclear palsy (PSP) include midbrain atrophy in MRI and hypometabolism in [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) as supportive features. Due to limited data regarding their relative and sequential value, there is no recommendation for an algorithm to combine both modalities to increase diagnostic accuracy. This study evaluated the added value of sequential imaging using state-of-the-art methods to analyse the images regarding PSP features.

METHODS

The retrospective study included 41 PSP patients, 21 with Richardson's syndrome (PSP-RS), 20 with variant PSP phenotypes (vPSP) and 46 sex- and age-matched healthy controls. A pretrained support vector machine (SVM) for the classification of atrophy profiles from automatic MRI volumetry was used to analyse T1w-MRI (output: MRI-SVM-PSP score). Covariance pattern analysis was applied to compute the expression of a predefined PSP-related pattern in FDG-PET (output: PET-PSPRP expression score).

RESULTS

The area under the receiver operating characteristic curve for the detection of PSP did not differ between MRI-SVM-PSP and PET-PSPRP expression score (p≥0.63): about 0.90, 0.95 and 0.85 for detection of all PSP, PSP-RS and vPSP. The MRI-SVM-PSP score achieved about 13% higher specificity and about 15% lower sensitivity than the PET-PSPRP expression score. Decision tree models selected the MRI-SVM-PSP score for the first branching and the PET-PSPRP expression score for a second split of the subgroup with normal MRI-SVM-PSP score, both in the whole sample and when restricted to PSP-RS or vPSP.

CONCLUSIONS

FDG-PET provides added value for PSP-suspected patients with normal/inconclusive T1w-MRI, regardless of PSP phenotype and the methods to analyse the images for PSP-typical features.

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.

Patterns of brain volume and metabolism predict clinical features in the progressive supranuclear palsy spectrum

Progressive supranuclear palsy (PSP) is a neurodegenerative tauopathy that presents with highly heterogenous clinical syndromes. We perform cross-sectional data-driven discovery of independent patterns of brain atrophy and hypometabolism across the entire PSP spectrum. We then use these patterns to predict specific clinical features and to assess their relationship to phenotypic heterogeneity. We included 111 patients with PSP (60 with Richardson syndrome and 51 with cortical and subcortical variant subtypes). Ninety-one were used as the training set and 20 as a test set. The presence and severity of granular clinical variables such as postural instability, parkinsonism, apraxia and supranuclear gaze palsy were noted. Domains of akinesia, ocular motor impairment, postural instability and cognitive dysfunction as defined by the Movement Disorders Society criteria for PSP were also recorded. Non-negative matrix factorization was used on cross-sectional MRI and fluorodeoxyglucose-positron emission tomography (FDG-PET) scans. Independent models for each as well as a combined model for MRI and FDG-PET were developed and used to predict the granular clinical variables. Both MRI and FDG-PET were better at predicting presence of a symptom than severity, suggesting identification of disease state may be more robust than disease stage. FDG-PET predicted predominantly cortical abnormalities better than MRI such as ideomotor apraxia, apraxia of speech and frontal dysexecutive syndrome. MRI demonstrated prediction of cortical and more so sub-cortical abnormalities, such as parkinsonism. Distinct neuroanatomical foci were predictive in MRI- and FDG-PET-based models. For example, vertical gaze palsy was predicted by midbrain atrophy on MRI, but frontal eye field hypometabolism on FDG-PET. Findings also differed by scale or instrument used. For example, prediction of ocular motor abnormalities using the PSP Saccadic Impairment Scale was stronger than with the Movement Disorders Society Diagnostic criteria for PSP oculomotor impairment designation. Combination of MRI and FDG-PET demonstrated enhanced detection of parkinsonism and frontal syndrome presence and apraxia, cognitive impairment and bradykinesia severity. Both MRI and FDG-PET patterns were able to predict some measures in the test set; however, prediction of global cognition measured by Montreal Cognitive Assessment was the strongest. MRI predictions generalized more robustly to the test set. PSP leads to neurodegeneration in motor, cognitive and ocular motor networks at cortical and subcortical foci, leading to diverse yet overlapping clinical syndromes. To advance understanding of phenotypic heterogeneity in PSP, it is essential to consider data-driven approaches to clinical neuroimaging analyses.

A Blinded Evaluation of Brain Morphometry for Differential Diagnosis of Atypical Parkinsonism

BACKGROUND

Advanced imaging techniques have been studied for differential diagnosis between PD, MSA, and PSP.

OBJECTIVES

This study aims to validate the utility of individual voxel-based morphometry techniques for atypical parkinsonism in a blinded fashion.

METHODS

Forty-eight healthy controls (HC) T1-WI were used to develop a referential dataset and fit a general linear model after segmentation into gray matter (GM) and white matter (WM) compartments. Segmented GM and WM with PD (n = 96), MSA (n = 18), and PSP (n = 20) were transformed into z-scores using the statistics of referential HC and individual voxel-based z-score maps were generated. An imaging diagnosis was assigned by two independent raters (trained and untrained) blinded to clinical information and final diagnosis. Furthermore, we developed an observer-independent index for ROI-based automated differentiation.

RESULTS

The diagnostic performance using voxel-based z-score maps by rater 1 and rater 2 for MSA yielded sensitivities: 0.89, 0.94 (95% CI: 0.74-1.00, 0.84-1.00), specificities: 0.94, 0.80 (0.90-0.98, 0.73-0.87); for PSP, sensitivities: 0.85, 0.90 (0.69-1.00, 0.77-1.00), specificities: 0.98, 0.94 (0.96-1.00, 0.90-0.98). Interrater agreement was good for MSA (Cohen's kappa: 0.61), and excellent for PSP (0.84). Receiver operating characteristic analysis using the ROI-based new index showed an area under the curve (AUC): 0.89 (0.77-1.00) for MSA, and 0.99 (0.98-1.00) for PSP.

CONCLUSIONS

These evaluations provide support for the utility of this imaging technique in the differential diagnosis of atypical parkinsonism demonstrating a remarkably high differentiation accuracy for PSP, suggesting potential use in clinical settings in the future.

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.

Monash-Alfred protocol for assessment of atypical parkinsonian syndromes (MAP-APS)

Introduction

Atypical parkinsonian syndromes (APS) are rare neurodegenerative syndromes for which parkinsonism is one significant feature. APS includes progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and corticobasal syndrome (CBS). The diagnosis of APS remains reliant on clinical features with no available diagnostic or prognostic biomarker. Clinical scales remain the gold standard assessment measures in clinical trials and research. The lack of standardised approach for research cohorts has contributed to shortcomings in disease understanding and limits collaboration between researchers. The primary objectives of this study are to (1) establish an assessment protocol for parkinsonian syndromes and (2) to implement it at a single site to establish the viability and utility of populating a clinical and biological databank of patients with APS.

Methods

The Monash Alfred Protocol for Assessment of APS was devised by expert consensus within a broad multidisciplinary team. Eligible patients are diagnosed as possible or probable PSP, MSA or CBS by a consultant neurologist with expertise in movement disorders. Participants will be assessed at recruitment and then annually for up to 3 years; individuals within 5 years of index symptom onset will also undergo a once-off 6-month assessment.

Ethics and dissemination

Each participant or their legally authorised representative will provide informed written consent prior to commencement of the study. Data will be stored on a locally hosted Research Electronic Data Capture database.

Trial registration number

Australian New Zealand Clinical Trials Registry (ANZCTN 12622000923763).

New Perspectives in Radiological and Radiopharmaceutical Hybrid Imaging in Progressive Supranuclear Palsy: A Systematic Review

Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized by four-repeat tau deposition in various cell types and anatomical regions, and can manifest as several clinical phenotypes, including the most common phenotype, Richardson's syndrome. The limited availability of biomarkers for PSP relates to the overlap of clinical features with other neurodegenerative disorders, but identification of a growing number of biomarkers from imaging is underway. One way to increase the reliability of imaging biomarkers is to combine different modalities for multimodal imaging. This review aimed to provide an overview of the current state of PSP hybrid imaging by combinations of positron emission tomography (PET) and magnetic resonance imaging (MRI). Specifically, combined PET and MRI studies in PSP highlight the potential of [18F]AV-1451 to detect tau, but also the challenge in differentiating PSP from other neurodegenerative diseases. Studies over the last years showed a reduced synaptic density in [11C]UCB-J PET, linked [11C]PK11195 and [18F]AV-1451 markers to disease progression, and suggested the potential role of [18F]RO948 PET for identifying tau pathology in subcortical regions. The integration of quantitative global and regional gray matter analysis by MRI may further guide the assessment of reduced cortical thickness or volume alterations, and diffusion MRI could provide insight into microstructural changes and structural connectivity in PSP. Challenges in radiopharmaceutical biomarkers and hybrid imaging require further research targeting markers for comprehensive PSP diagnosis.

α-Synuclein seed amplification assay as a diagnostic tool for parkinsonian disorders

INTRODUCTION

Synucleinopathies such as Parkinson's disease (PD) and multiple system atrophy (MSA) can be challenging to diagnose due to the symptom overlap with, for example, atypical parkinsonisms like progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Seed amplification assays (SAA), developed for the detection of α-synuclein (αSyn) aggregates in CSF, have been successful when used as a biomarker evaluation for synucleinopathies. In this study, we investigated the potential of this assay to not only detect αSyn seeds in CSF, but also discriminate between movement disorders.

METHODS

The αSyn-SAA was tested in a Scandinavian cohort composed of 129 CSF samples from patients with PD (n = 55), MSA (n = 27), CBD (n = 7), and PSP (n = 16), as well as healthy controls (HC, n = 24).

RESULTS

The αSyn seed amplification assay (αSyn-SAA) was able to correctly identify all PD samples as positive (sensitivity of 100%) while also discriminating the PD group from HC (70.8% specificity, p < 0.0001) and tauopathies [CBD (71% specificity) and PSP (75% specificity), p < 0.0001)]. The αSyn-SAA was also able to identify almost all MSA samples as positive for αSyn aggregation (sensitivity of 92.6%). In general, this assay is able to discriminate between the synucleinopathies and tauopathies analyzed herein (p < 0.0001) despite the overlapping symptoms in these diseases.

CONCLUSION

These findings suggest the αSyn-SAA is a useful diagnostic tool for differentiating between different parkinsonian disorders, although further optimization may be needed.

Investigating differences in young- and late-onset progressive supranuclear palsy

BACKGROUND

The impact of age of onset on the presentation of progressive supranuclear palsy phenotypes is not well studied. We hypothesized that there is difference in presentation and phenotype between young- and late-onset PSP.

OBJECTIVES

Our aim was to compare phenotypes and rate of change in disability between young-onset PSP (YOPSP) and late-onset PSP (LOPSP).

METHODS

Retrospective data of patients seen in the Rossy PSP Centre from March 2014 to April 2022 with clinical diagnosis of PSP as per the MDS 2017 diagnostic criteria were examined. We used cut-off age of 65 years to categorize the patients into YOPSP and LOPSP. We compared the prevalence of phenotypes, presenting symptoms, and MDS core criteria between the two groups. The severity of disease between the two groups was measured using PSP-RS.

RESULTS

We found 107 patients with clinical diagnosis of PSP as per MDS criteria, a third were defined as YOPSP. PSP speech/language (SL) phenotype was more prevalent in YOPSP (18% vs 0%, p < 0.001). Aphasia was significantly higher in YOPSP (16% vs 1.4%, p = 0.03). The speech and language dysfunction (C1) core criteria were more prevalent in YOPSP (33.3% vs 12.2%, p = 0.05). Longitudinal analysis of PSP-RS showed worsening of bulbar total score at 6 months in YOPSP (t (38) = 2.87; p = 0.05).

CONCLUSION

Our study revealed that YOPSP are more likely to present with a speech and language variant. Our results highlight that age of onset may predict PSP phenotypes, which holds both clinical and prognostic importance.

Omics profile of iPSC-derived astrocytes from Progressive Supranuclear Palsy (PSP) patients

INTRODUCTION

Progressive Supranuclear Palsy (PSP) is a neurodegenerative tauopathy and, to date, the pathophysiological mechanisms in PSP that lead to Tau hyperphosphorylation and neurodegeneration are not clear. In some brain areas, Tau pathology in glial cells appears to precede Tau aggregation in neurons. The development of a model using astrocyte cell lines derived from patients has the potential to identify molecules and pathways that contribute to early events of neurodegeneration. We developed a model of induced pluripotent stem cells (iPSC)-derived astrocytes to investigate the pathophysiology of PSP, particularly early events that might contribute to Tau hyperphosphorylation, applying omics approach to detect differentially expressed genes, metabolites, and proteins, including those from the secretome.

METHODS

Skin fibroblasts from PSP patients (without MAPT mutations) and controls were reprogrammed to iPSCs, further differentiated into neuroprogenitor cells (NPCs) and astrocytes. In the 5th passage, astrocytes were harvested for total RNA sequencing. Intracellular and secreted proteins were processed for proteomics experiments. Metabolomics profiling was obtained from supernatants only.

RESULTS

We identified hundreds of differentially expressed genes. The main networks were related to cell cycle re-activation in PSP. Several proteins were found exclusively secreted by the PSP group. The cellular processes related to the cell cycle and mitotic proteins, TriC/CCT pathway, and redox signaling were enriched in the secretome of PSP. Moreover, we found distinct sets of metabolites between PSP and controls.

CONCLUSION

Our iPSC-derived astrocyte model can provide distinct molecular signatures for PSP patients and it is useful to elucidate the initial stages of PSP pathogenesis.

Automatic covariance pattern analysis outperforms visual reading of 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET) in variant progressive supranuclear palsy

BACKGROUND

To date, studies on positron emission tomography (PET) with 18 F-fluorodeoxyglucose (FDG) in progressive supranuclear palsy (PSP) usually included PSP cohorts overrepresenting patients with Richardson's syndrome (PSP-RS).

OBJECTIVES

To evaluate FDG-PET in a patient sample representing the broad phenotypic PSP spectrum typically encountered in routine clinical practice.

METHODS

This retrospective, multicenter study included 41 PSP patients, 21 (51%) with RS and 20 (49%) with non-RS variants of PSP (vPSP), and 46 age-matched healthy controls. Two state-of-the art methods for the interpretation of FDG-PET were compared: visual analysis supported by voxel-based statistical testing (five readers) and automatic covariance pattern analysis using a predefined PSP-related pattern.

RESULTS

Sensitivity and specificity of the majority visual read for the detection of PSP in the whole cohort were 74% and 72%, respectively. The percentage of false-negative cases was 10% in the PSP-RS subsample and 43% in the vPSP subsample. Automatic covariance pattern analysis provided sensitivity and specificity of 93% and 83% in the whole cohort. The percentage of false-negative cases was 0% in the PSP-RS subsample and 15% in the vPSP subsample.

CONCLUSIONS

Visual interpretation of FDG-PET supported by voxel-based testing provides good accuracy for the detection of PSP-RS, but only fair sensitivity for vPSP. Automatic covariance pattern analysis outperforms visual interpretation in the detection of PSP-RS, provides clinically useful sensitivity for vPSP, and reduces the rate of false-positive findings. Thus, pattern expression analysis is clinically useful to complement visual reading and voxel-based testing of FDG-PET in suspected PSP. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Smaller and Denser Speech Graphs in Nondemented Patients with Progressive Supranuclear Palsy

The well-established semantic fluency test measures the ability to produce a sequence of spoken words from a particular category within a limited period of time. Like patients with Parkinson's disease (PD), patients with progressive supranuclear palsy (PSP) tend to produce fewer correct words than age-matched healthy adults. This study further examined the difference between patients with PSP and PD in their semantic fluency performance using a graph theory-based approach. Twenty-nine patients with PSP Richardson's syndrome (PSP-RS), thirty-eight patients with PD, and fifty-one healthy controls (HC) were recruited. All participants completed a standard semantic fluency test (animals). Their verbal responses were recorded, transcripted, and transformed into directed speech graphs. The speech graphs of the PSP-RS group showed higher density, shorter diameter, and shorter average shortest path than those of the PD and HC groups. It indicates that the PSP-RS group produced smaller and denser speech graphs than the PD and HC groups. In the PSP-RS group, moreover, the average shortest paths of the speech graphs correlated with the severity of motor symptoms. This study shows the potential of the graph theory-based approach in distinguishing the semantic fluency performance of nondemented patients with PSP-RS and PD.

Clinical features of progressive supranuclear palsy

Background

Progressive supranuclear palsy (PSP) is a clinically heterogenous atypical parkinsonian syndrome. Therefore, early recognition and correct diagnosis of PSP is challenging but essential. This study aims to characterize the clinical manifestations, magnetic resonance imaging (MRI), and longitudinal MRI changes of PSP in China.

Method

Clinical and MRI presentations were compared among 150 cases with PSP. Then the longitudinal MRI changes among 20 patients with PSP were further explored. Additionally, a series of midbrain-based MRI parameters was compared between PSP-P and PD.

Results

Throughout the course of the disease, there were differences in the symptoms of the fall and hand tremor between the PSP-RS and PSP-P. There were significant differences in the six midbrain-based MRI parameters between the PSP-RS and the PSP-P, including hummingbird sign, midbrain diameter, midbrain to pons ratio (MTPR), midbrain area, midbrain area to pons area ratio (Ma/Pa), and midbrain tegmental length (MBTegm). Longitudinal MRI studies revealed that the annual rel.ΔMTPR and rel.Δ (Ma/Pa) for PSP were 5.55 and 6.52%, respectively; additionally, PSP-RS presented a higher decline rate than PSP-P. Moreover, MTPR ≤0.56, midbrain diameter ≤ 0.92, midbrain area ≤ 1.00, and third ventricle width ≤ 0.75 could identify PSP-P from PD.

Conclusion

PSP-P differs from PSP-RS regarding clinical manifestations, MRI, and longitudinal MRI changes. MRI parameters could be potential imaging markers to identify PSP-P from PD.

Magnetic resonance imaging in the diagnosis of progressive supranuclear palsy: A case report and review of literature

Key Clinical Message

Progressive supranuclear palsy (PSP) has many clinical features overlapping with other Parkinson syndromes and differentiation on clinical ground is difficult. This case highlights how a brain MRI can help diagnose PSP in settings with limited resources where histological diagnosis is difficult.

Abstract

Progressive supranuclear palsy (PSP) may be challenging to diagnose due to its widely acknowledged clinical complexity and challenges with diagnosis confirmation, particularly in resource-poor settings where the ability to obtain confirmatory tests is highly complicated, leading to an inaccurate or incomplete diagnosis of PSP. This paper discusses using brain magnetic resonance imaging (MRI) to diagnose PSP, and a review of relevant literature addresses the diagnostic value of MRI in PSP.

Low clinical sensitivity and unexpectedly high incidence for neuropathologically diagnosed progressive supranuclear palsy

The objective of this study was to determine the prevalence, incidence, and clinical diagnostic accuracy for neuropathologically diagnosed progressive supranuclear palsy (PSP) with data from a longitudinal clinicopathological study using Rainwater criteria to define neuropathological PSP. Of 954 autopsy cases, 101 met Rainwater criteria for the neuropathologic diagnosis of PSP. Of these, 87 were termed clinicopathological PSP as they also had either dementia or parkinsonism or both. The prevalence of clinicopathologically defined PSP subjects in the entire autopsy dataset was 9.1%, while the incidence rate was estimated at 780 per 100 000 persons per year, roughly 50-fold greater than most previous clinically determined PSP incidence estimates. A clinical diagnosis of PSP was 99.6% specific but only 9.2% sensitive based on first examination, and 99.3% specific and 20.7% sensitive based on the final clinical exam. Of the clinicopathologically defined PSP cases, 35/87 (∼40%) had no form of parkinsonism at first assessment, while this decreased to 18/83 (21.7%) at final assessment. Our study confirms a high specificity but low sensitivity for the clinical diagnosis of PSP. The low clinical sensitivity for PSP is likely primarily responsible for previous underestimates of the PSP population incidence rate.

Uncovering spatiotemporal patterns of atrophy in progressive supranuclear palsy using unsupervised machine learning

To better understand the pathological and phenotypic heterogeneity of progressive supranuclear palsy and the links between the two, we applied a novel unsupervised machine learning algorithm (Subtype and Stage Inference) to the largest MRI data set to date of people with clinically diagnosed progressive supranuclear palsy (including progressive supranuclear palsy-Richardson and variant progressive supranuclear palsy syndromes). Our cohort is comprised of 426 progressive supranuclear palsy cases, of which 367 had at least one follow-up scan, and 290 controls. Of the progressive supranuclear palsy cases, 357 were clinically diagnosed with progressive supranuclear palsy-Richardson, 52 with a progressive supranuclear palsy-cortical variant (progressive supranuclear palsy-frontal, progressive supranuclear palsy-speech/language, or progressive supranuclear palsy-corticobasal), and 17 with a progressive supranuclear palsy-subcortical variant (progressive supranuclear palsy-parkinsonism or progressive supranuclear palsy-progressive gait freezing). Subtype and Stage Inference was applied to volumetric MRI features extracted from baseline structural (T1-weighted) MRI scans and then used to subtype and stage follow-up scans. The subtypes and stages at follow-up were used to validate the longitudinal consistency of subtype and stage assignments. We further compared the clinical phenotypes of each subtype to gain insight into the relationship between progressive supranuclear palsy pathology, atrophy patterns, and clinical presentation. The data supported two subtypes, each with a distinct progression of atrophy: a 'subcortical' subtype, in which early atrophy was most prominent in the brainstem, ventral diencephalon, superior cerebellar peduncles, and the dentate nucleus, and a 'cortical' subtype, in which there was early atrophy in the frontal lobes and the insula alongside brainstem atrophy. There was a strong association between clinical diagnosis and the Subtype and Stage Inference subtype with 82% of progressive supranuclear palsy-subcortical cases and 81% of progressive supranuclear palsy-Richardson cases assigned to the subcortical subtype and 82% of progressive supranuclear palsy-cortical cases assigned to the cortical subtype. The increasing stage was associated with worsening clinical scores, whilst the 'subcortical' subtype was associated with worse clinical severity scores compared to the 'cortical subtype' (progressive supranuclear palsy rating scale and Unified Parkinson's Disease Rating Scale). Validation experiments showed that subtype assignment was longitudinally stable (95% of scans were assigned to the same subtype at follow-up) and individual staging was longitudinally consistent with 90% remaining at the same stage or progressing to a later stage at follow-up. In summary, we applied Subtype and Stage Inference to structural MRI data and empirically identified two distinct subtypes of spatiotemporal atrophy in progressive supranuclear palsy. These image-based subtypes were differentially enriched for progressive supranuclear palsy clinical syndromes and showed different clinical characteristics. Being able to accurately subtype and stage progressive supranuclear palsy patients at baseline has important implications for screening patients on entry to clinical trials, as well as tracking disease progression.

Using Downgaze Palsy Progression Rate to Model Survival in Progressive Supranuclear Palsy-Richardson Syndrome

BACKGROUND

Rapid development of downgaze palsy, the most specific symptom of progressive supranuclear palsy (PSP), has been associated with shorter survival in small studies.

OBJECTIVE

We hypothesized that the progression rate of downgaze palsy and other disease features could predict survival if assessed soon after the onset of downgaze palsy in a large data set.

METHODS

We used a longitudinal database of 414 patients with probable PSP-Richardson syndrome from 1994 to 2020. The data set comprised demographics and, for each visit, 28 PSP Rating Scale (PSPRS) items and PSP stage scores. We calculated the rate of progression of each PSPRS item as its item score when the downgaze item first reached 1 or more (on a 0-4 scale) divided by disease duration at that point. Multivariate Cox regression was applied to identify variables independently associated with survival. We also explored the progression pattern of total PSPRS and downgaze palsy scores with disease course.

RESULTS

Independently associated with shorter survival were older onset age and faster progression of downgaze palsy, dysphagia for liquids, difficulty in returning to seat, and PSP stage. Patients with survival duration within 1 year of the median survival (6.58 years) showed approximately linear progression of the PSPRS score and downgaze palsy score during years 2 through 6 of the disease course.

CONCLUSIONS

Older onset age and faster progression of downgaze palsy and several axial features are associated with shorter survival. The disease typically progresses in approximately linear fashion during years 2 through 6. These results may aid study design and patient counseling. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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.

Clinical, cognitive, and morphometric profiles of progressive supranuclear palsy phenotypes

The International Parkinson's and Movement Disorder Society (MDS) criteria for progressive supranuclear palsy (PSP) have broadened the clinical spectrum of the disease and established phenotypic characterization according to the predominant manifestation at onset. The objective of this study is to describe clinical/cognitive and imaging features of a monocentric cohort of PSP patients, highlighting different patterns of functional disability according to the assigned phenotype. We retrospectively reviewed clinical/imaging data of 53 PSP patients diagnosed with probable PSP according to the MDS criteria and 40 age/sex-matched healthy controls (HCs). Neurological/neuropsychological assessments were performed using standardized scales, as well as comprehensive magnetic resonance imaging (MRI) morphometric measurements. In our cohort, there were 24/53 PSP-RS (Richardson's syndrome), 13/53 PSP-P (Parkinsonism), 7/53 PSP-PGF (Progressive gait freezing), and 9/53 PSP-Cog (Cognitive impairment). PSP-Cog presented the worst motor profiles, the highest percentages of dementia and impaired functional autonomy; 4/9 PSP-Cog and 2/7 PSP-PGF died. PSP-P had the lowest motor/cognitive burden. All MRI parameters had good discriminative efficacy vs. HCs, with P/M 2.0 discriminating PSP-PGF from PSP-RS and PSP-Cog. We highlighted discrete clinical and imaging patterns that best characterize different PSP phenotypes. PSP-Cog and PSP-PGF/RS manifest greater incidence of dementia and motor disability, respectively, while PSP-P has a more benign course. The identification of different phenotypes may be the expression of different progression patterns requiring tailored approaches in terms of follow-up and treatment. These findings support the concept of discrete patterns of Tau pathology within the PSP spectrum and encourage research for phenotype-specific outcome measures.

Performance of [18F]RO948 PET, MRI and CSF neurofilament light in the differential diagnosis of progressive supranuclear palsy

INTRODUCTION

The diagnosis of progressive supranuclear palsy (PSP) is often challenging since PSP may clinically resemble other neurodegenerative disorders. Recently, the tau PET tracer [¹⁸F]RO948, a potential new biomarker for PSP, was developed. The aim of this study was to determine the ability of three different biomarkers, including [¹⁸F]RO948 PET, to distinguish PSP patients from healthy controls and from patients with α-synucleinopathies.

METHODS

Patients with PSP (n = 23), α-synucleinopathies (n = 47) and healthy controls (n = 61) were included from the BioFINDER-2 study. [¹⁸F]RO948 standardized uptake value ratios (SUVR), magnetic resonance imaging midbrain/pons ratio, and cerebrospinal fluid neurofilament light (NfL) levels were compared between diagnostic groups individually and in combination.

RESULTS

[¹⁸F]RO948 PET SUVR in the globus pallidus, NfL, and midbrain/pons area ratios were all able to differentiate PSP patients from controls and from patients with α-synucleinopathies ([¹⁸F]RO948 [mean ± SD]: controls 1.24 ± 0.22; PSP 1.47 ± 0.4; PD 1.18 ± 0.2; DLB 1.25 ± 0.24, p < 0.05), (NfL pg/mL [mean ± SD]: controls 1055 ± 569; PSP 2197 ± 1010; PD 1038 ± 416; DLB 1548 ± 687, p < 0.001) and (midbrain/pons ratio [mean ± SD]: controls 0.46 ± 0.07; PSP 0.34 ± 0.09; PD 0.43 ± 0.06; DLB 0.40 ± 0.07, p < 0.01). Receiver operating characteristic (ROC) analyses indicated that combining the three biomarkers resulted in the highest area under the ROC values (0.94 [0.88-1.00]) for separating controls from PSP and (0.92 [0.85-0.99]) for separating PSP from α-synucleinopathies.

CONCLUSIONS

All studied biomarkers could individually separate PSP from controls and α-synucleinopathies patients at a group level. The optimal prediction models included NfL and midbrain/pons ratio for separating controls from PSP and all three biomarkers for separating PSP from α-synucleinopathies.

Analysis of Parkinson's Disease Using an Imbalanced-Speech Dataset by Employing Decision Tree Ensemble Methods

Parkinson's disease (PD) currently affects approximately 10 million people worldwide. The detection of PD positive subjects is vital in terms of disease prognostics, diagnostics, management and treatment. Different types of early symptoms, such as speech impairment and changes in writing, are associated with Parkinson disease. To classify potential patients of PD, many researchers used machine learning algorithms in various datasets related to this disease. In our research, we study the dataset of the PD vocal impairment feature, which is an imbalanced dataset. We propose comparative performance evaluation using various decision tree ensemble methods, with or without oversampling techniques. In addition, we compare the performance of classifiers with different sizes of ensembles and various ratios of the minority class and the majority class with oversampling and undersampling. Finally, we combine feature selection with best-performing ensemble classifiers. The result shows that AdaBoost, random forest, and decision tree developed for the RUSBoost imbalanced dataset perform well in performance metrics such as precision, recall, F1-score, area under the receiver operating characteristic curve (AUROC) and the geometric mean. Further, feature selection methods, namely lasso and information gain, were used to screen the 10 best features using the best ensemble classifiers. AdaBoost with information gain feature selection method is the best performing ensemble method with an F1-score of 0.903.

Clinicopathological features of progressive supranuclear palsy with asymmetrical atrophy of the superior cerebellar peduncle

Progressive supranuclear palsy (PSP) can be diagnosed despite the presence of asymmetrical parkinsonism depending on the clinical diagnostic criteria. Some studies have reported that atrophy of the superior cerebellar peduncle (SCP) is more frequent in PSP than in Parkinson's disease. There have also been reports of PSP cases with an asymmetrically atrophic SCP. Therefore, we analyzed 48 specimens from consecutive autopsy cases that were neuropathologically diagnosed as PSP to investigate the laterality of brain lesions, including the SCP. We measured the width of the SCP and evaluated the laterality of atrophy. We semi-quantitatively evaluated neuronal loss, atrophy/myelin pallor, and tau pathology in three steps. Asymmetrical atrophy of the SCP was present in seven (14.6%) of 48 cases. The atrophic side of the SCP corresponded to the dominant side of the tau pathology in the cerebellar dentate nucleus. It was opposite to the dominant side of the myelin pallor and tau pathology in the red nucleus and of the tau pathology in the central tegmental tract and inferior olivary nucleus, coinciding with the neurologically systematic anatomy of the Guillain-Mollaret triangle. Neurodegeneration of PSP can progress asymmetrically from one side to the initially intact side in PSP with an initial predominance of Richardson's syndrome, progressive gait freezing, ocular motor dysfunction, parkinsonism, or corticobasal syndrome. To our knowledge, no previous study has reported asymmetrical PSP neuropathology; this is the first study to report the presence of PSP cases with asymmetrical SCP atrophy and systematically asymmetrical degeneration of the Guillain-Mollaret triangle.

Cortical atrophy distinguishes idiopathic normal-pressure hydrocephalus from progressive supranuclear palsy: A machine learning approach

INTRODUCTION

Progressive supranuclear palsy (PSP) and idiopathic normal pressure hydrocephalus (iNPH) share several clinical and radiological features, making the differential diagnosis challenging. In this study, we aimed to differentiate between these two diseases using a machine learning approach based on cortical thickness and volumetric data.

METHODS

Twenty-three iNPH patients, 50 PSP patients and 55 control subjects were enrolled. All participants underwent a brain 3T-MRI, and cortical thickness and volumes were extracted using Freesurfer 6 on T1-weighted images and compared among groups. Finally, the performance of a machine learning approach with random forest using the extracted cortical features was investigated to differentiate between iNPH and PSP patients.

RESULTS

iNPH patients showed cortical thinning and volume loss in the frontal lobe, temporal lobe and cingulate cortex, and thickening in the superior parietal gyrus in comparison with controls and PSP patients. PSP patients only showed mild thickness and volume reduction in the frontal lobe, compared to control subjects. Random Forest algorithm distinguished iNPH patients from controls with AUC of 0.96 and from PSP patients with AUC of 0.95, while a lower performance (AUC 0.76) was reached in distinguishing PSP from controls.

CONCLUSION

This study demonstrated a more severe and widespread cortical involvement in iNPH than in PSP, possibly due to the marked lateral ventricular enlargement which characterizes iNPH. A machine learning model using thickness and volumetric data led to accurate differentiation between iNPH and PSP patients, which may help clinicians in the differential diagnosis and in the selection of patients for shunt procedures.

Automated Detection of Speech Timing Alterations in Autopsy-Confirmed Nonfluent/Agrammatic Variant Primary Progressive Aphasia

BACKGROUND AND OBJECTIVES

Motor speech function, including speech timing, is a key domain for diagnosing nonfluent/agrammatic variant primary progressive aphasia (nfvPPA). Yet, standard assessments use subjective, specialist-dependent evaluations, undermining reliability and scalability. Moreover, few studies have examined relevant anatomo-clinical alterations in patients with pathologically confirmed diagnoses. This study overcomes such caveats using automated speech timing analyses in a unique cohort of autopsy-proven cases.

METHODS

In a cross-sectional study, we administered an overt reading task and quantified articulation rate, mean syllable and pause duration, and syllable and pause duration variability. Neuroanatomical disruptions were assessed using cortical thickness and white matter (WM) atrophy analysis.

RESULTS

We evaluated 22 persons with nfvPPA (mean age: 67.3 years; 13 female patients) and confirmed underlying 4-repeat tauopathy, 15 persons with semantic variant primary progressive aphasia (svPPA; mean age: 66.5 years; 8 female patients), and 10 healthy controls (HCs; 70 years; 5 female patients). All 5 speech timing measures revealed alterations in persons with nfvPPA relative to both the HC and svPPA groups, controlling for dementia severity. The articulation rate robustly discriminated individuals with nfvPPA from HCs (area under the ROC curve [AUC] = 0.95), outperforming specialist-dependent perceptual measures of dysarthria and apraxia of speech severity. Patients with nfvPPA exhibited structural abnormalities in left precentral and middle frontal as well as bilateral superior frontal regions, including their underlying WM. The articulation rate correlated with atrophy of the left pars opercularis and supplementary/presupplementary motor areas. Secondary analyses showed that, controlling for dementia severity, all measures yielded greater deficits in patients with nfvPPA and corticobasal degeneration (nfvPPA-CBD, n = 12) than in those with progressive supranuclear palsy pathology (nfvPPA-PSP, n = 10). The articulation rate robustly discriminated between individuals in each subgroup (AUC = 0.82). More widespread cortical thinning was observed for the nfvPPA-CBD than the nfvPPA-PSP group across frontal regions.

DISCUSSION

Automated speech timing analyses can capture specific markers of nfvPPA while potentially discriminating between patients with different tauopathies. Thanks to its objectivity and scalability; this approach could support standard speech assessments.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that automated speech analysis can accurately differentiate patients with nonfluent PPA from normal controls and patients with semantic variant PPA.

Magnetic Resonance Planimetry in the Differential Diagnosis between Parkinson’s Disease and Progressive Supranuclear Palsy

The clinical differential diagnosis between Parkinson’s disease (PD) and progressive supranuclear palsy (PSP) is often challenging. The description of milder PSP phenotypes strongly resembling PD, such as PSP-Parkinsonism, further increased the diagnostic challenge and the need for reliable neuroimaging biomarkers to enhance the diagnostic certainty. This review aims to summarize the contribution of a relatively simple and widely available imaging technique such as MR planimetry in the differential diagnosis between PD and PSP, focusing on the recent advancements in this field. The development of accurate MR planimetric biomarkers, together with the implementation of automated algorithms, led to robust and objective measures for the differential diagnosis of PSP and PD at the individual level. Evidence from longitudinal studies also suggests a role of MR planimetry in predicting the development of the PSP clinical signs, allowing to identify PSP patients before they meet diagnostic criteria when their clinical phenotype can be indistinguishable from PD. Finally, promising evidence exists on the possible association between MR planimetric measures and the underlying pathology, with important implications for trials with new disease-modifying target therapies.

Clinical Spectrum of Tauopathies

Tauopathies are both clinical and pathological heterogeneous disorders characterized by neuronal and/or glial accumulation of misfolded tau protein. It is now well understood that every pathologic tauopathy may present with various clinical phenotypes based on the primary site of involvement and the spread and distribution of the pathology in the nervous system making clinicopathological correlation more and more challenging. The clinical spectrum of tauopathies includes syndromes with a strong association with an underlying primary tauopathy, including Richardson syndrome (RS), corticobasal syndrome (CBS), non-fluent agrammatic primary progressive aphasia (nfaPPA)/apraxia of speech, pure akinesia with gait freezing (PAGF), and behavioral variant frontotemporal dementia (bvFTD), or weak association with an underlying primary tauopathy, including Parkinsonian syndrome, late-onset cerebellar ataxia, primary lateral sclerosis, semantic variant PPA (svPPA), and amnestic syndrome. Here, we discuss clinical syndromes associated with various primary tauopathies and their distinguishing clinical features and new biomarkers becoming available to improve in vivo diagnosis. Although the typical phenotypic clinical presentations lead us to suspect specific underlying pathologies, it is still challenging to differentiate pathology accurately based on clinical findings due to large phenotypic overlaps. Larger pathology-confirmed studies to validate the use of different biomarkers and prospective longitudinal cohorts evaluating detailed clinical, biofluid, and imaging protocols in subjects presenting with heterogenous phenotypes reflecting a variety of suspected underlying pathologies are fundamental for a better understanding of the clinicopathological correlations.

Genetics of progressive supranuclear palsy in a Chinese population

BACKGROUND

Genetics plays an important role in progressive supranuclear palsy (PSP) and remains poorly understood. A detailed literature search identified 19 PSP-associated genes: MAPT, LRRK2, LRP10, DCTN1, GRN, NPC1, PARK, TARDBP, TBK1, BSN, GBA, STX6, EIF2AK3, MOBP, DUSP10, SLCO1A2, RUNX2, CXCR4, and APOE. To date, genetic studies on PSP have focused on Caucasian population. The gaps in PSP genetic study on East Asian populations need to be filled.

METHODS

Exon and flanking regions of the PSP-associated genes were sequenced in 104 patients with PSP and 488 healthy controls. Common variant-based association analysis and gene-based association tests of rare variants were performed using PLINK 1.9 and the sequence kernel association test-optimal, respectively. Additionally, the association of APOE and MAPT genotypes with PSP was evaluated. The above association analyses were repeated among probable PSP patients. Finally, PLINK 1.9 was used to test variants associated with the onset age of PSP.

RESULTS

A rare non-pathogenic variant of MAPT (c.425C > T,p.A142V) was detected in a PSP patient. No common variants were significantly associated with PSP. In both the rare-variant and the rare-damaging-variant groups, the combined effect for GBA reached statistical significance (p = 1.43 × 10^-3, p = 4.98 × 10^-4). The result between APOE, MAPT genotypes and PSP risk were inconsistent across all PSP group and probably PSP group.

CONCLUSIONS

The pathogenic variant in MAPT were uncommon in PSP patients. Moreover, GBA gene was likely to increase the risk of PSP, and GBA-associated diseases were beyond α-synucleinopathies. The association between APOE, MAPT and PSP is still unclear among the non-Caucasian population.

Progressive supranuclear palsy and corticobasal degeneration: novel clinical concepts and advances in biomarkers

BACKGROUND

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are sporadic adult-onset primary tauopathies clinically classified among the atypical parkinsonian syndromes. They are intrinsically related with regard to their clinical features, pathology, biochemistry, and genetic risk factors.

OBJECTIVES

This review highlights the current knowledge on PSP and CBD, focusing on evolving clinical concepts, new diagnostic criteria, and advances in biomarkers.

METHODS

We performed a non-systematic literature review through the PubMed database. The search was restricted to articles written in English, published from 1964 to date.

RESULTS

Clinicopathologic and in vivo biomarkers studies have broadened PSP and CBD clinical phenotypes. They are now recognized as a range of motor and behavioral syndromes associated with underlying 4R-tauopathy neuropathology. The Movement Disorders Society PSP diagnostic criteria included clinical variants apart from the classical description, increasing diagnostic sensitivity. Meanwhile, imaging biomarkers have explored the complexity of symptoms and pathological processes related to corticobasal syndrome and CBD.

CONCLUSIONS

In recent years, several prospective or clinicopathologic studies have assessed clinical, radiological, and fluid biomarkers that have helped us gain a better understanding of the complexity of the 4R-tauopathies, mainly PSP and CBD.

Development and Validation of Automated Magnetic Resonance Parkinsonism Index 2.0 to Distinguish Progressive Supranuclear Palsy‐Parkinsonism From Parkinson's Disease

Background

Differentiating progressive supranuclear palsy‐parkinsonism (PSP‐P) from Parkinson's disease (PD) is clinically challenging.

Objective

This study aimed to develop an automated Magnetic Resonance Parkinsonism Index 2.0 (MRPI 2.0) algorithm to distinguish PSP‐P from PD and to validate its diagnostic performance in two large independent cohorts.

Methods

We enrolled 676 participants: a training cohort (n = 346; 43 PSP‐P, 194 PD, and 109 control subjects) from our center and an independent testing cohort (n = 330; 62 PSP‐P, 171 PD, and 97 control subjects) from an international research group. We developed a new in‐house algorithm for MRPI 2.0 calculation and assessed its performance in distinguishing PSP‐P from PD and control subjects in both cohorts using receiver operating characteristic curves.

Results

The automated MRPI 2.0 showed excellent performance in differentiating patients with PSP‐P from patients with PD and control subjects both in the training cohort (area under the receiver operating characteristic curve [AUC] = 0.93 [95% confidence interval, 0.89–0.98] and AUC = 0.97 [0.93–1.00], respectively) and in the international testing cohort (PSP‐P versus PD, AUC = 0.92 [0.87–0.97]; PSP‐P versus controls, AUC = 0.94 [0.90–0.98]), suggesting the generalizability of the results. The automated MRPI 2.0 also accurately distinguished between PSP‐P and PD in the early stage of the diseases (AUC = 0.91 [0.84–0.97]). A strong correlation (r = 0.91, P < 0.001) was found between automated and manual MRPI 2.0 values.

Conclusions

Our study provides an automated, validated, and generalizable magnetic resonance biomarker to distinguish PSP‐P from PD. The use of the automated MRPI 2.0 algorithm rather than manual measurements could be important to standardize measures in patients with PSP‐P across centers, with a positive impact on multicenter studies and clinical trials involving patients from different geographic regions. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Autopsy Validation of the Diagnostic Accuracy of 123I-Metaiodobenzylguanidine Myocardial Scintigraphy for Lewy Body Disease

BACKGROUND AND OBJECTIVES

¹²³I-meta-iodobenzyl-guanidine (¹²³I-MIBG) myocardial scintigraphy is employed as a diagnostic imaging test to differentiate Lewy body diseases (LBDs), including Parkinson's disease and dementia with Lewy bodies, from other similar diseases. However, its diagnostic accuracy lacks validation compared with that of the gold standard. We aimed to validate the diagnostic accuracy of ¹²³I-MIBG myocardial scintigraphy for LBD against autopsy, the gold standard.

METHODS

This retrospective, cross-sectional study included consecutive autopsy patients from the Brain Bank for Aging Research who had undergone ¹²³I-MIBG myocardial scintigraphy. We compared the ¹²³I-MIBG myocardial scintigraphy findings with autopsy findings. Furthermore, the proportion of residual tyrosine hydroxylase (TH)-immunoreactive sympathetic fibers in the anterior wall of the left ventricle was investigated to assess the condition of the cardiac sympathetic nerves assumed to cause reduced ¹²³I-MIBG uptake in LBDs.

RESULTS

We analyzed the data of 56 patients (30 with pathologically confirmed LBDs and 26 without LBD pathology). Compared with the neuropathological diagnosis, the early heart-to-mediastinum (H/M) ratio had a sensitivity and specificity of 70.0% (95% confidence interval [CI]: 50.6-85.3%) and 96.2% (95% CI: 80.4-99.9%), respectively. The delayed H/M ratio had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 92.3% (95% CI: 74.9-99.1%), respectively. The washout rate had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 84.6% (95% CI: 65.1-95.6%), respectively. The proportion of residual TH-immunoreactive cardiac sympathetic fibers strongly correlated with the amount of cardiac ¹²³I-MIBG uptake when assessed with early and delayed H/M ratio values (correlation coefficient: 0.75 and 0.81, respectively; p < 0.001).

DISCUSSION

This clinicopathological validation study revealed that ¹²³I-MIBG myocardial scintigraphy could robustly differentiate LBDs from similar diseases. Abnormal ¹²³I-MIBG myocardial scintigraphy findings strongly support the presence of LBD and cardiac sympathetic denervation. However, LBD pathology should not necessarily be excluded by normal myocardial scintigraphy results, especially when other biomarkers suggest the presence of comorbid Alzheimer's disease pathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that ¹²³I-MIBG myocardial scintigraphy accurately identifies patients with LBD.

Differential Diagnosis of Rare Subtypes of Progressive Supranuclear Palsy and PSP-Like Syndromes—Infrequent Manifestations of the Most Common Form of Atypical Parkinsonism

Presently, there is increasing interest in rare PSP (progressive supranuclear palsy) variants, including PSP-PGF (PSP-progressive gait freezing), PSP-PI (PSP-postural instability), PSP-OM (PSP-ocular motor dysfunction), PSP-C (PSP-predominant cerebellar ataxia), PSP-CBS (PSP-corticobasal syndrome), PSP-SL (PSP-speech/language disorders), and PSP-PLS (PSP-primary lateral sclerosis). Diagnosis of these subtypes is usually based on clinical symptoms, thus thorough examination with anamnesis remains a major challenge for clinicians. The individual phenotypes often show great similarity to various neurodegenerative diseases and other genetic, autoimmune, or infectious disorders, manifesting as PSP-mimicking syndromes. At the current stage of knowledge, it is not possible to isolate a specific marker to make a definite ante-mortem diagnosis. The purpose of this review is to discuss recent developments in rare PSP phenotypes and PSP-like syndromes.

Is the Phenotype Designation by PSP-MDS Criteria Stable Throughout the Disease Course and Consistent With Tau Distribution?

Introduction

The MDS-PSP criteria have shown high sensitivity for the PSP diagnosis, but do not discriminate the phenotype diversity. Our purpose was to search for anatomopathological differences among PSP phenotypes resulting from the application of the MDS-PSP criteria comparing with the previous ones.

Methods

Thirty-four PSP cases from a single brain bank were retrospectively classified according to the criteria used by Respondek et al. in 2014 and the PSP-MDS criteria at 3 years (MDS-3y), 6 years (MDS-6y) and at the last clinical evaluation before death (MDS-last). Semiquantitative measurement of total, cortical and subcortical tau load was compared. For comparative analysis, PSP-Richardson syndrome and PSP postural instability were grouped (PSP-RS/PI) as well as the PSP atypical cortical phenotypes (PSP-Cx).

Results

Applying the Respondek's criteria, PSP phenotypes were distributed as follow: 55.9% PSP-RS/PI, 26.5% PSP-Cx, 11.8% PSP-Parkinsonism (PSP-P), and 5.9% PSP-Cerebellum. PSP-RS/PI and PSP-Cx had a higher total tau load than PSP-P; PSP-Cx showed a higher cortical tau load than PSP-RS/PI and PSP-P; and PSP-RS/PI had a higher subcortical tau load than PSP-P. Applying the MDS-3y, MDS-6y and MDS-last criteria; the PSP-RS/PI group increased (67.6, 70.6 and 70.6% respectively) whereas the PSP-Cx group decreased (8.8, and 8.8 and 11.8%). Then, only differences in total and subcortical tau burden between PSP-RS/PI and PSP-P were observed.

Interpretation

After the retrospective application of the new MDS-PSP criteria, total and subcortical tau load is higher in PSP-RS/PI than in PSP-P whereas no other differences in tau load between phenotypes were found, as a consequence of the loss of phenotypic diversity.

Longitudinal changes of early motor and cognitive symptoms in progressive supranuclear palsy: the OxQUIP study

BACKGROUND

Progressive supranuclear palsy (PSP) is a rare neurodegenerative condition characterised by a range of motor and cognitive symptoms. Very little is known about the longitudinal change in these symptoms over time. Moreover, the effectiveness of clinical scales to detect early changes in PSP is still a matter of debate.

OBJECTIVE

We aimed to determine longitudinal changes in PSP features using multiple closely spaced follow-up time points over a period of 2 years. Methods 28 healthy control and 28 PSP participants, with average time since onset of symptoms of 1.9 years, were prospectively studied every 3 months for up to 24 months. Changes from baseline scores were calculated at each follow-up time point using multiple clinical scales to identify longitudinal progression of motor and cognitive symptoms.

RESULTS

The Montreal Cognitive Assessment, but not the Mini-Mental State Examination, detected cognitive decline at baseline. Both scales revealed poor longitudinal sensitivity to clinical change in global cognitive symptoms. Conversely, the Movement Disorders Society Unified Parkinson's disease Rating Scale - part III and the PSP Rating Scale (PSPRS) reliably detected motor decline less than 2 years after disease onset. The 'Gait/Midline' PSPRS subscore consistently declined over time, with the earliest change being observed 6 months after baseline assessment.

CONCLUSION

While better cognitive screening tools are still needed to monitor cognitive decline in PSP, motor decline is consistently captured by clinical rating scales. These results support the inclusion of multiple follow-up time points in longitudinal studies in the early stages of PSP.

Autopsy Validation of Progressive Supranuclear Palsy-Predominant Speech/Language Disorder Criteria

BACKGROUND

Progressive supranuclear palsy (PSP) may present as a speech/language disorder (PSP-SL).

OBJECTIVE

We assessed pathological correlates of patients with PSP-SL who retained the suggestive of PSP-SL (s.o. PSP-SL) diagnosis versus those who progressed to possible/probable (poss./prob.) PSP.

METHODS

Thirty-four prospectively recruited patient with s.o. PSP-SL completed comprehensive speech/language and neurological assessments longitudinally, died, and underwent autopsy.

RESULTS

Twelve patients (35%) evolved to poss./prob PSP, while 22 (65%) remained as s.o. PSP-SL. Pathological diagnoses differed across the groups (P = 0.025). Patients with s.o. PSP-SL had four different neuropathologies (corticobasal degeneration [59%], PSP [13%], Pick's disease [14%], and frontotemporal lobar degeneration with TDP-43 [14%]), while all patients with poss./prob. PSP had a 4R-tauopathy (PSP [67%] and corticobasal degeneration [33%]). Development of poss./prob. PSP increased the chance of having PSP pathology by 2.38 times.

CONCLUSIONS

PSP-SL is associated with heterogenous pathologies. Evolution of PSP-SL into poss./prob. PSP is more predictive of underlying PSP pathology than s.o. PSP-SL. © 2021 International Parkinson and Movement Disorder Society.

Depression and Apathy across Different Variants of Progressive Supranuclear Palsy

BACKGROUND

Apathy and depression commonly occur in patients with progressive supranuclear palsy (PSP)-Richardson's syndrome variant; depression often requiring treatment. Little is known, however, about apathy and depression among other PSP variants.

METHODS

We prospectively studied 97 newly diagnosed PSP patients. All were classified into a PSP variant using the 2017 Movement Disorder Society-PSP criteria and administered the Geriatric Depression and Apathy Evaluation Scales. Differences in apathy and depression frequency and severity across six variants, and secondarily across PSP-Richardson's syndrome, PSP-Cortical and PSP-Subcortical, were analyzed using ANCOVA and linear regression adjusting for disease severity.

RESULTS

Depression (55%) was more common than apathy (12%). PSP-Speech/Language (PSP-SL) variant had the lowest depression frequency (13%) and lower depression scores than the other variants. No differences in apathy frequency/severity were identified.

CONCLUSION

PSP-SL patients may have less depression compared to PSP-Richardson's syndrome and other PSP variants.

Brainstem Biomarkers of Clinical Variant and Pathology in Progressive Supranuclear Palsy

BACKGROUND

Magnetic 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.

OBJECTIVE

The 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.

METHODS

A 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.

RESULTS

Brainstem 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%).

CONCLUSIONS

MRI 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.

Cardiovascular autonomic dysfunction is associated with executive dysfunction and poorer quality of life in progressive supranuclear palsy-Richardson's syndrome

BACKGROUND

Autonomic dysfunction in progressive supranuclear palsy (PSP) is not uncommon but is easily neglected.

OBJECTIVE

We evaluated blood pressure (BP) profiles in PSP patients and aimed to determine the associations between BP variability and cognition and quality of life.

METHODS

Consecutive patients diagnosed with PSP were enrolled in this cross-sectional study. All patients underwent 24-hour ambulatory blood pressure monitoring, office blood pressure measurements, and comprehensive clinical assessments.

RESULTS

We enrolled 31 PSP patients. Ten (32.3%) patients presented with reverse dipping, 10 (32.3%) presented with reduced dipping, and 11 (35.5%) presented with normal dipping. Additionally, 19 (61.3%) patients had supine hypertension, and no patients had orthostatic hypotension. In the entire PSP cohort, the Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS III) score, Scales for Outcomes in Parkinson's Disease-Autonomic (SCOPA-AUT) score, and daytime systolic BP (SBP) standard deviation explained 61.5% (adjusted R²) of the variance in Parkinson's Disease Questionnaire-39 (PDQ-39) scores. In the PSP with Richardson's syndrome group, the daytime SBP coefficient of variation and Mini-Mental State Examination score accounted for 33.9% of the variance in Frontal Assessment Battery scores. The MDS-UPDRS III score, 24-hour SBP coefficient of variation, and SCOPA-AUT score explained 77.6% of the variance in PDQ-39 scores.

CONCLUSIONS

Greater BP variability was associated with executive dysfunction and poorer quality of life in patients with PSP. A high prevalence of abnormal dipping patterns indicated circadian disruption in patients with PSP.

Corticospinal tract abnormalities and ventricular dilatation: A transdiagnostic comparative tractography study

BACKGROUND

Microstructural alterations of corticospinal tract (CST) have been found in idiopathic normal pressure hydrocephalus (iNPH). No study, however, investigated the effect of ventricular dilatation on CST in Progressive Supranuclear Palsy (PSP).

OBJECTIVE

The aim of this study was to investigate CST diffusion profile in a large cohort of PSP patients with and without ventricular dilatation.

METHODS

Twenty-three iNPH patients, 87 PSP patients and 26 controls were enrolled. Evans index (EI) and ventricular volume (VV) were measured in all patients. CST tractography was performed to calculate FA, MD, AxD and RD in six different anatomical regions: medulla oblungata (MO), pons (P), cerebral peduncle (CP), posterior limb of internal capsule (PLIC), corona radiata (CR), subcortical white matter (SWM). ANCOVA was used for comparing CST diffusion profiles between the groups and association between CST microstructural metrics and measures of ventricular dilatation (EI and VV) was assessed.

RESULTS

Thirty-three PSP patients had ventricular dilatation (EI > 0.30, PSP-vd) while 54 PSP patients had normal ventricular system (EI ≤ 0.30, PSP-wvd). iNPH patients had the most marked FA and AxD increase in PLIC and CR of CST followed by PSP-vd, PSP-wvd and controls; RD was altered only in iNPH. A strong correlation was found between CST diffusion metrics and EI or VV.

CONCLUSIONS

Our findings confirm the microstructural changes of CST in iNPH patients and demonstrate for the first time similar alterations in PSP-vd patients, suggesting a crucial role of ventricular dilatation in the mechanical compression of CST.

Evolving concepts in progressive supranuclear palsy and other 4-repeat tauopathies

Tauopathies are classified according to whether tau deposits predominantly contain tau isoforms with three or four repeats of the microtubule-binding domain. Those in which four-repeat (4R) tau predominates are known as 4R-tauopathies, and include progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, globular glial tauopathies and conditions associated with specific MAPT mutations. In these diseases, 4R-tau deposits are found in various cell types and anatomical regions of the brain and the conditions share pathological, pathophysiological and clinical characteristics. Despite being considered 'prototype' tauopathies and, therefore, ideal for studying neuroprotective agents, 4R-tauopathies are still severe and untreatable diseases for which no validated biomarkers exist. However, advances in research have addressed the issues of phenotypic overlap, early clinical diagnosis, pathophysiology and identification of biomarkers, setting a road map towards development of treatments. New clinical criteria have been developed and large cohorts with early disease are being followed up in prospective studies. New clinical trial readouts are emerging and biomarker research is focused on molecular pathways that have been identified. Lessons learned from failed trials of neuroprotective drugs are being used to design new trials. In this Review, we present an overview of the latest research in 4R-tauopathies, with a focus on progressive supranuclear palsy, and discuss how current evidence dictates ongoing and future research goals.

"Parkinson's disease" on the way to progressive supranuclear palsy: a review on PSP-parkinsonism

Progressive supranuclear palsy (PSP) is a progressive atypical parkinsonian syndrome characterised by postural instability, supranuclear ophthalmoplegia, dysarthria, dysphagia, executive dysfunction and other features. This clinical presentation represents the classic PSP-Richardson syndrome (PSP-RS). However, several other clinical subtypes have been recognised, including PSP-parkinsonism (PSP-P), probably the second most common PSP variant. Unlike PSP-RS, PSP-P often presents with an asymmetric onset, tremor and a moderate initial response to levodopa, especially during the first years of the disease, thus resembling Parkinson's disease (PD). It runs a more favourable course, but over time, PSP-P may evolve clinically into PSP-RS. Therefore, it may seem that PSP-P stands clinically between PD and PSP. There are several peculiarities that can distinguish PSP-P from these entities. As there is lack of systematic reviews on PSP-P in the literature, we decided to summarise all the necessary data about the epidemiology, clinical picture, neuroimaging, genetics and other aspects of this PSP variant in order to provide complete information for the reader.

Progressive supranuclear palsy with marked ventricular dilatation mimicking normal pressure hydrocephalus

BACKGROUND

Progressive supranuclear palsy (PSP) patients can show ventricular enlargement mimicking normal pressure hydrocephalus (NPH). The aim of this study was to distinguish PSP patients with marked ventricular dilatation (PSP-vd) from those with normal ventricular system and to evaluate the coexistence of NPH in PSP-vd patients.

METHODS

One hundred three probable PSP patients, 18 definite NPH patients, and 41 control subjects were enrolled in the study. Evans index (EI) > 0.32 associated with callosal angle (CA) < 100° was used to identify PSP-vd patients. Automated ventricular volumetry (AVV) and Magnetic Resonance Hydrocephalic Index (MRHI) were performed on T1-weighted MR images to evaluate the presence of NPH in PSP-vd patients.

RESULTS

Twelve (11.6%) out of 103 PSP patients had both abnormal EI and CA values (PSP-vd). In two of these 12 patients, AVV and MRHI values suggested PSP + NPH. In the remaining 10 PSP-vd patients, AVV and MRHI values were higher than PSP patients with normal ventricular system and controls, but lower than PSP + NPH and NPH patients, suggesting a non-hydrocephalic ventricular enlargement.

DISCUSSION

Our study provides evidence that the combination of EI and CA biomarkers allowed to identify PSP patients with marked ventricular dilatation mimicking NPH. Only a few of these patients had PSP + NPH. Recognition of these PSP patients with enlarged ventricles can positively impact the care of this disease, helping clinicians to identify patients with PSP + NPH who could benefit from shunt procedure and avoid surgery in those with enlarged ventricles without NPH.

Safety and efficacy of anti-tau monoclonal antibody gosuranemab in progressive supranuclear palsy: a phase 2, randomized, placebo-controlled trial

A randomized, double-blind, placebo-controlled, 52-week study (no. NCT03068468) evaluated gosuranemab, an anti-tau monoclonal antibody, in the treatment of progressive supranuclear palsy (PSP). In total, 486 participants dosed were assigned to either gosuranemab (n = 321) or placebo (n = 165). Efficacy was not demonstrated on adjusted mean change of PSP Rating Scale score at week 52 between gosuranemab and placebo (10.4 versus 10.6, P = 0.85, primary endpoint), or at secondary endpoints, resulting in discontinuation of the open-label, long-term extension. Unbound N-terminal tau in cerebrospinal fluid decreased by 98% with gosuranemab and increased by 11% with placebo (P < 0.0001). Incidences of adverse events and deaths were similar between groups. This well-powered study suggests that N-terminal tau neutralization does not translate into clinical efficacy.

Potential roles of gut microbiota and microbial metabolites in Parkinson's disease

Parkinson's disease (PD) is a complicated neurodegenerative disease attributed to multifactorial changes. However, its pathological mechanism remains undetermined. Accumulating evidence has revealed the emerging functions of gut microbiota and microbial metabolites, which can affect both the enteric nervous system and the central nervous system via the microbiota-gut-brain axis. Accordingly, intestinal dysbiosis might be closely associated with PD. This review explores alterations to gut microbiota, correlations with clinical manifestations of PD, and briefly probes the underlying mechanisms. Next, the highly controversial roles of microbial metabolites including short-chain fatty acids (SCFAs), H₂ and H₂S are discussed. Finally, the pros and cons of the current treatments for PD, including those targeting microbiota, are assessed. Advancements in research techniques, further studies on levels of specific strains and longitudinal prospective clinical trials are urgently needed for the identification of early diagnostic markers and the development of novel therapeutic approaches for PD.