Pathological Validation of the MDS Criteria for the Diagnosis of Multiple System Atrophy

An update on multiple system atrophy

PURPOSE OF REVIEW

Multiple system atrophy (MSA) is a rapidly progressive synucleinopathy characterized by autonomic failure, parkinsonism, and cerebellar ataxia. Here, we provide an update on α-synuclein's role in MSA pathophysiology and review the new Movement Disorders Society (MDS) diagnostic criteria and the utility of α-synuclein-based biomarkers. We also highlight ongoing efforts toward clinical trial readiness and review potential disease-modifying therapies undergoing clinical trials.

RECENT FINDINGS

A role of urinary tract infections in triggering α-synuclein aggregation and contribution of genes implicated in oligodendroglial development have been suggested in the MSA pathophysiology. The clinically probable MSA category of the new diagnostic criteria shows improved accuracy in early disease stages. Predictors of phenoconversion from pure autonomic failure to MSA are now better defined. Alpha-synuclein strains in CSF and serum, phosphorylated α-synuclein deposits in the skin, and brain α-synuclein pathology visualized using PET ligand [18F]ACI-12589 are emerging as valuable diagnostic tools. Clinical trials in MSA investigate drugs targeting α-synuclein aggregation or preventing α-synuclein expression, along with stem cell and gene therapies to halt disease progression.

SUMMARY

New MSA diagnostic criteria and α-synuclein-based biomarkers may enhance diagnostic accuracy while promising therapies are in development to address disease progression.

Neuropathologic Validation and Diagnostic Accuracy of Presynaptic Dopaminergic Imaging in the Diagnosis of Parkinsonism

BACKGROUND AND OBJECTIVES

Degeneration of the presynaptic nigrostriatal dopaminergic system is one of the main biological features of Parkinson disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), which can be measured using single-photon emission CT imaging for diagnostic purposes. Despite its widespread use in clinical practice and research, the diagnostic properties of presynaptic nigrostriatal dopaminergic (DAT) imaging in parkinsonism have never been evaluated against the diagnostic gold standard of neuropathology. The aim of this study was to evaluate the diagnostic parameters of DAT imaging compared with pathologic diagnosis in patients with parkinsonism.

METHODS

Retrospective cohort study of patients with DAT imaging for the investigation of a clinically uncertain parkinsonism with brain donation between 2010 and 2021 to the Queen Square Brain Bank (London). Patients with DAT imaging for investigation of pure ataxia or dementia syndromes without parkinsonism were excluded. Those with a pathologic diagnosis of PD, MSA, PSP, or CBD were considered presynaptic dopaminergic parkinsonism, and other pathologies were considered postsynaptic for the analysis. DAT imaging was performed in routine clinical practice and visually classified by hospital nuclear medicine specialists as normal or abnormal. The results were correlated with neuropathologic diagnosis to calculate diagnostic accuracy parameters for the diagnosis of presynaptic dopaminergic parkinsonism.

RESULTS

All of 47 patients with PD, 41 of 42 with MSA, 68 of 73 with PSP, and 6 of 10 with CBD (sensitivity 100%, 97.6%, 93.2%, and 60%, respectively) had abnormal presynaptic dopaminergic imaging. Eight of 17 patients with presumed postsynaptic parkinsonism had abnormal scans (specificity 52.9%).

DISCUSSION

DAT imaging has very high sensitivity and negative predictive value for the diagnosis of presynaptic dopaminergic parkinsonism, particularly for PD. However, patients with CBD, and to a lesser extent PSP (of various phenotypes) and MSA (with predominant ataxia), can show normal DAT imaging. A range of other neurodegenerative disorders may have abnormal DAT scans with low specificity in the differential diagnosis of parkinsonism. DAT imaging is a useful diagnostic tool in the differential diagnosis of parkinsonism, although clinicians should be aware of its diagnostic properties and limitations.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that DAT imaging does not accurately distinguish between presynaptic dopaminergic parkinsonism and non-presynaptic dopaminergic parkinsonism.

Heterozygous APTX mutation associated with atypical multiple system atrophy-like phenotype: A case report

We describe here a 73-year-old patient presenting with atypical MSA-P-like phenotype carrying a monoallelic p. W279X mutation in the APTX gene, which causes ataxia with oculomotor apraxia type 1 (AOA1) when in homozygous state. We hypothesize that rare monoallelic APTX variants could modulate MSA risk and phenotype.

Multiple system atrophy: an update and emerging directions of biomarkers and clinical trials

Multiple system atrophy is a rare, debilitating, adult-onset neurodegenerative disorder that manifests clinically as a diverse combination of parkinsonism, cerebellar ataxia, and autonomic dysfunction. It is pathologically characterized by oligodendroglial cytoplasmic inclusions containing abnormally aggregated α-synuclein. According to the updated Movement Disorder Society diagnostic criteria for multiple system atrophy, the diagnosis of clinically established multiple system atrophy requires the manifestation of autonomic dysfunction in combination with poorly levo-dopa responsive parkinsonism and/or cerebellar syndrome. Although symptomatic management of multiple system atrophy can substantially improve quality of life, therapeutic benefits are often limited, ephemeral, and they fail to modify the disease progression and eradicate underlying causes. Consequently, effective breakthrough treatments that target the causes of disease are needed. Numerous preclinical and clinical studies are currently focusing on a set of hallmarks of neurodegenerative diseases to slow or halt the progression of multiple system atrophy: pathological protein aggregation, synaptic dysfunction, aberrant proteostasis, neuronal inflammation, and neuronal cell death. Meanwhile, specific biomarkers and measurements with higher specificity and sensitivity are being developed for the diagnosis of multiple system atrophy, particularly for early detection of the disease. More intriguingly, a growing number of new disease-modifying candidates, which can be used to design multi-targeted, personalized treatment in patients, are being investigated, notwithstanding the failure of most previous attempts.

Early Screening for the Parkinson Variant of Multiple System Atrophy: A 6-Item Score

BACKGROUND

A 4-item score based on ≥2 features out of orthostatic hypotension, overactive bladder, urinary retention and postural instability was previously shown to early distinguish the Parkinson-variant of multiple system atrophy (MSA-P) from Parkinson's disease (PD) with 78% sensitivity and 86% specificity.

OBJECTIVES

To replicate and improve the 4-item MSA-P score.

METHODS

We retrospectively studied 161 patients with early parkinsonism [ie, ≤2 years disease duration or no postural instability, aged 64 (57; 68) years, 44% females] and a diagnosis of clinically established MSA-P (n = 38) or PD (n = 123) after ≥24 months follow-up.

RESULTS

The 4-item MSA-P score had a 92% sensitivity and 78% specificity for a final MSA-P diagnosis. By including dopaminergic responsiveness and postural deformities into a 6-item score (range: 0-6), reaching ≥3 points at early disease identified MSA-P patients with 89% sensitivity and 98% specificity.

CONCLUSIONS

The 6-item MSA-P score is a cost-effective tool to pinpoint individuals with early-stage MSA-P.

Recent Advances in Clinical Trials in Multiple System Atrophy

PURPOSE OF REVIEW

This review summarizes previous and ongoing neuroprotection trials in multiple system atrophy (MSA), a rare and fatal neurodegenerative disease characterized by parkinsonism, cerebellar, and autonomic dysfunction. It also describes the preclinical therapeutic pipeline and provides some considerations relevant to successfully conducting clinical trials in MSA, i.e., diagnosis, endpoints, and trial design.

RECENT FINDINGS

Over 30 compounds have been tested in clinical trials in MSA. While this illustrates a strong treatment pipeline, only two have reached their primary endpoint. Ongoing clinical trials primarily focus on targeting α-synuclein, the neuropathological hallmark of MSA being α-synuclein-bearing glial cytoplasmic inclusions. The mostly negative trial outcomes highlight the importance of better understanding underlying disease mechanisms and improving preclinical models. Together with efforts to refine clinical measurement tools, innovative statistical methods, and developments in biomarker research, this will enhance the design of future neuroprotection trials in MSA and the likelihood of positive outcomes.

Case-Fatality Rate in Parkinson's Disease: A Nationwide Registry Study

BACKGROUND

Patients with Parkinson's disease (PD) may have an increased risk of mortality, but robust estimates are lacking.

OBJECTIVE

To compare mortality rates nationally between patients with PD and controls.

METHODS

The case-fatality rates of Finnish PD patients diagnosed in 2004-2018 (n = 23,688; 57% male, mean age at diagnosis = 71 years) and randomly selected sex- and age-matched control subjects (n = 94,752) were compared using data from national registries. The median follow-up duration was 5.8 years (max 17 years).

RESULTS

The case-fatality rate in patients with PD was higher than that in matched controls (HR 2.29; 95% CI 2.24-2.33; P < 0.0001). Excess fatality among PD patients was already present at 1 year from diagnosis and then plateaued at 29% at 12 years after diagnosis. The long-term relative hazard of death in PD patients vs. matched controls did not differ based on sex. Patients with early-onset PD (age at diagnosis <50 years old) had the highest relative hazard of death (HR 3.36) compared to matched control subjects, and the relative hazard decreased with higher age at diagnosis. The seven-year excess risk of death decreased during the study period, especially in men. In patients with PD, male sex, increasing age, and increasing comorbidity burden were associated with an increased risk of death.

CONCLUSIONS

An increased risk of death among PD patients was evident from early on. The increase in risk was greatest among young-onset patients. The excess risk in early PD declined during the study period, particularly in men. The reasons for this are unknown.

Validation Study of the MDS Criteria for the Diagnosis of Multiple System Atrophy in the Mayo Clinic Brain Bank

BACKGROUND AND OBJECTIVE

The second consensus criteria in 2008 have been used in diagnosing multiple system atrophy (MSA). The International Parkinson and Movement Disorder Society (MDS) proposed new diagnostic criteria for MSA in 2022. This study aimed to compare the diagnostic accuracy between these 2 criteria and validate the clinical utility of the newly proposed criteria for MSA.

METHODS

We conducted a retrospective autopsy cohort study of consecutive patients with a clinical or pathologic diagnosis of MSA from the Mayo Clinic brain bank between 1998 and 2021. We studied 352 patients (250 pathologically diagnosed MSA and 102 non-MSA); MDS criteria and the second consensus criteria were applied. The sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic curves were compared between these criteria. Comparison was conducted between clinical subtypes and among clinically challenging cases (those with different clinical diagnoses or those with suspected but undiagnosed MSA before death). We also used machine learning algorithm, eXtreme Gradient Boosting, to identify clinical features contributing diagnostic performance.

RESULTS

The sensitivity and specificity of clinically established and probable MSA by the MDS criteria were 16% and 99% and 64% and 74%, respectively. The sensitivity and specificity of probable MSA and possible MSA by the second consensus criteria were 72% and 52% and 93% and 21%, respectively. The AUC of MDS clinically probable MSA was the highest (0.69). The diagnostic performance did not differ between clinical subtypes. In clinically challenging cases, MDS clinically established MSA maintained high specificity and MDS clinically probable MSA demonstrated the highest AUC (0.62). MRI findings contributed to high specificity. In addition, combining core clinical features with 2 or more from any of the 13 supporting features and the absence of exclusion criteria also yielded high specificity. Among supporting features, rapid progression was most important for predicting MSA pathology.

DISCUSSION

The MDS criteria showed high specificity with clinically established MSA and moderate sensitivity and specificity with clinically probable MSA. The observation that high specificity could be achieved with clinical features alone suggests that MSA diagnosis with high specificity is possible even in areas where MRI is not readily available.

Quantitative cellular changes in multiple system atrophy brains

Multiple system atrophy (MSA) is a neurodegenerative disorder characterised by a combined symptomatology of parkinsonism, cerebellar ataxia, autonomic failure and corticospinal dysfunction. In brains of MSA patients, the hallmark lesion is the aggregation of misfolded alpha-synuclein in oligodendrocytes. Even though the underlying pathological mechanisms remain poorly understood, the evidence suggests that alpha-synuclein aggregation in oligodendrocytes may contribute to the neurodegeneration seen in MSA. The primary aim of this review is to summarise the published stereological data on the total number of neurons and glial cell subtypes (oligodendrocytes, astrocytes and microglia) and volumes in brains from MSA patients. Thus, we include in this review exclusively the reports of unbiased quantitative data from brain regions including the neocortex, nuclei of the cerebrum, the brainstem and the cerebellum. Furthermore, we compare and discuss the stereological results in the context of imaging findings and MSA symptomatology. In general, the stereological results agree with the common neuropathological findings of neurodegeneration and gliosis in brains from MSA patients and support a major loss of nigrostriatal neurons in MSA patients with predominant parkinsonism (MSA-P), as well as olivopontocerebellar atrophy in MSA patients with predominant cerebellar ataxia (MSA-C). Surprisingly, the reports indicate only a minor loss of oligodendrocytes in sub-cortical regions of the cerebrum (glial cells not studied in the cerebellum) and negligible changes in brain volumes. In the past decades, the use of stereological methods has provided a vast amount of accurate information on cell numbers and volumes in the brains of MSA patients. Combining different techniques such as stereology and diagnostic imaging (e.g. MRI, PET and SPECT) with clinical data allows for a more detailed interdisciplinary understanding of the disease and illuminates the relationship between neuropathological changes and MSA symptomatology.

Diagnostic utility of movement disorder society criteria for multiple system atrophy

Background

The 2008 criteria for the diagnosis of multiple system atrophy (MSA) has been widely used for more than 10 years, but the sensitivity is low, particularly for patients in the early stage. Recently, a new MSA diagnostic criteria was developed.

Objective

The objective of the study was to assess and compare the diagnostic utility of the new movement disorder society (MDS) MSA criteria with the 2008 MSA criteria.

Methods

This study included patients diagnosed with MSA between January 2016 and October 2021. All patients underwent regular face-to-face or telephonic follow-ups every year until October 2022. A total of 587 patients (309 males and 278 females) were retrospectively reviewed to compare the diagnostic accuracy of the MDS MSA criteria to that of the 2008 MSA criteria (determined by the proportion of patients categorized as established or probable MSA). Autopsy is the gold standard diagnosis of MSA, which is not available in clinical practice. Thus, we applied the 2008 MSA criteria at the last review as the reference standard.

Results

The sensitivity of the MDS MSA criteria (93.2%, 95% CI = 90.5-95.2%) was significantly higher than that of the 2008 MSA criteria (83.5%, 95% CI = 79.8-86.6%) (P < 0.001). Additionally, the sensitivity of the MDS MSA criteria was maintained robustly across different subgroups, defined by diagnostic subtype, disease duration, and the type of symptom[s] at onset. Importantly, the specificities were not significantly different between the MDS MSA criteria and the 2008 MSA criteria (P > 0.05).

Conclusion

The present study demonstrated that the MDS MSA criteria exhibited good diagnostic utility for MSA. The new MDS MSA criteria should be considered as a useful diagnostic tool for clinical practice and future therapeutic trials.