A Review on the Clinical Diagnosis of Multiple System Atrophy

The genetic landscape of sporadic adult-onset degenerative ataxia: a multi-modal genetic study of 377 consecutive patients from the longitudinal multi-centre SPORTAX cohort

BACKGROUND

While most sporadic adult-onset neurodegenerative diseases have only a minor monogenic component, given several recently identified late adult-onset ataxia genes, the genetic burden may be substantial in sporadic adult-onset ataxias. We report systematic mapping of the genetic landscape of sporadic adult-onset ataxia in a well-characterised, multi-centre cohort, combining several multi-modal genetic screening techniques, plus longitudinal natural history data.

METHODS

Systematic clinico-genetic analysis of a prospective longitudinal multi-centre cohort of 377 consecutive patients with sporadic adult-onset ataxia (SPORTAX cohort), including clinically defined sporadic adult-onset ataxia of unknown aetiology (SAOA) (n = 229) and 'clinically probable multiple system atrophy of cerebellar type' (MSA-Ccp) (n = 148). Combined GAA-FGF14 (SCA27B) and RFC1 repeat expansion screening with next-generation sequencing (NGS) was complemented by natural history and plasma neurofilament light chain analysis in key subgroups.

FINDINGS

85 out of 377 (22.5%) patients with sporadic adult-onset ataxia carried a pathogenic or likely pathogenic variant, thereof 67/229 (29.3%) patients with SAOA and 18/148 (12.2%) patients meeting the MSA-Ccp criteria. This included: 45/377 (11.9%) patients with GAA-FGF14≥250 repeat expansions (nine with MSA-Ccp), 17/377 (4.5%) patients with RFC1 repeat expansions (three with MSA-Ccp), and 24/377 (6.4%) patients with single nucleotide variants (SNVs) identified by NGS (six with MSA-Ccp). Five patients (1.3%) were found to have two relevant genetic variants simultaneously (dual diagnosis).

INTERPRETATION

In this cohort of sporadic adult-onset ataxia, a cohort less likely to have a monogenic cause, a substantial burden of monogenic variants was identified, particularly GAA-FGF14 and RFC1 repeat expansions. This included a substantial share of patients meeting the MSA-Ccp criteria, suggesting a reduced specificity of this clinical diagnosis and potential co-occurrence of MSA-C plus a second, independent genetic condition. These findings have important implications for the genetic work-up and counselling of patients with sporadic ataxia, even when presenting with MSA-like features. With targeted treatments for genetic ataxias now on the horizon, these findings highlight their potential utility for these patients.

FUNDING

This work was supported by the Clinician Scientist programme "PRECISE.net" funded by the Else Kröner-Fresenius-Stiftung (to DM, AT, CW, OR, and MS), by the Deutsche Forschungsgemeinschaft (as part of the PROSPAX project), and by the Canadian Institutes of Health Research and the Fondation Groupe Monaco. Support was also provided by Humboldt Research Fellowship for Postdocs and the Hertie-Network of Excellence in Clinical Neuroscience and a Fellowship award from the Canadian Institutes of Health Research.

Sphingolipidoses: expanding the spectrum of α-synucleinopathies

Although α-synuclein pathology is typically associated with Lewy body diseases and multiple systems atrophy, increasing evidence indicates that it also occurs in a group of lysosomal storage disorders termed sphingolipidoses caused by the incomplete degradation, and subsequent accumulation, of a class of lipids termed sphingolipids. Notably, a number of genes that cause sphingolipidoses are also risk genes for Lewy body diseases, suggesting aetiological links between these distinct disorders. In the present review, we discuss the sphingolipidoses in which α-synuclein pathology has been reported: Gaucher disease, Krabbe disease, metachromatic leukodystrophy, Tay-Sachs disease and Anderson-Fabry disease, and describe the characteristic clinical and pathological features of these disorders, in addition to the evidence suggesting α-synuclein pathology occurs in these disorders. Finally, we evaluate the pathological mechanisms that underlie these rare disorders, with particular attention to how the enzymatic deficiency, substrate accumulation, or both, could contribute to the genesis of α-synuclein pathology and the implications of this for Lewy body diseases.

Comparing a BCI communication system in a patient with Multiple System Atrophy, with an animal model

Paralysis affects many people worldwide, and the people affected often suffer from impaired communication. We developed a microelectrode-based Brain-Computer Interface (BCI) for enabling communication in patients affected by paralysis, and implanted it in a patient with Multiple System Atrophy (MSA), a neurodegenerative disease that causes widespread neural symptoms including paralysis. To verify the effectiveness of the BCI system, it was also tested by implanting it in a non-human primate (NHP). Data from the human and NHP were used to train binary classifiers two different types of machine learning models: a Linear Discriminant Analysis (LDA) model, and a Long Short-Term Memory (LSTM)-based Artificial Neural Network (ANN). The LDA model performed at up to 72.7 % accuracy for binary decoding in the human patient, however, performance was highly variable and was much lower on most recording days. The BCI system was able to accurately decode movement vs non-movement in the NHP (accuracy using LDA: 82.7 ± 3.3 %, LSTM: 83.7 ± 2.2 %, 95 % confidence intervals), however it was not able to with recordings from the human patient (accuracy using LDA: 47.0 ± 5.1 %, LSTM: 44.6 ± 9.9 %, 95 % confidence intervals). We discuss how neurodegenerative diseases such as MSA can impede BCI-based communication, and postulate on the mechanisms by which this may occur.

A challenging case presentation of multiple system atrophy cerebellar type: A rare case report from Somalia

Multiple system atrophy is a rare and quickly progressing neurological condition characterized by autonomic failure, parkinsonism, or cerebellar ataxia. It is classified into two subtypes: MSA with predominant parkinsonism (MSA-P) and MSA with predominant cerebellar ataxia (MSA-C). We are presenting here a 54-year-old male with parkinsonism, ataxia, and dysarthria. He was diagnosed with parkinson disease and was given a maximum dose of levodopa but has not responded. After a close neurological evaluation with magnetic resonance imaging of the brain, which shows atrophy of the cerebellum and a brainstem with a hot cross bun sign of the pons, suggestive of multiple system atrophy, he was diagnosed with multiple system atrophy cerebellar type, which is the first time to have this diagnosis in Somalia, which is a low-resource country.

SARS-CoV-2 Infection and Alpha-Synucleinopathies: Potential Links and Underlying Mechanisms

Alpha-synuclein (α-syn) is a 140-amino-acid, intrinsically disordered, soluble protein that is abundantly present in the brain. It plays a crucial role in maintaining cellular structures and organelle functions, particularly in supporting synaptic plasticity and regulating neurotransmitter turnover. However, for reasons not yet fully understood, α-syn can lose its physiological role and begin to aggregate. This altered α-syn disrupts dopaminergic transmission and causes both presynaptic and postsynaptic dysfunction, ultimately leading to cell death. A group of neurodegenerative diseases known as α-synucleinopathies is characterized by the intracellular accumulation of α-syn deposits in specific neuronal and glial cells within certain brain regions. In addition to Parkinson's disease (PD), these conditions include dementia with Lewy bodies (DLBs), multiple system atrophy (MSA), pure autonomic failure (PAF), and REM sleep behavior disorder (RBD). Given that these disorders are associated with α-syn-related neuroinflammation-and considering that SARS-CoV-2 infection has been shown to affect the nervous system, with COVID-19 patients experiencing neurological symptoms-it has been proposed that COVID-19 may contribute to neurodegeneration in PD and other α-synucleinopathies by promoting α-syn misfolding and aggregation. In this review, we focus on whether SARS-CoV-2 could act as an environmental trigger that facilitates the onset or progression of α-synucleinopathies. Specifically, we present new evidence on the potential role of SARS-CoV-2 in modulating α-syn function and discuss the causal relationship between SARS-CoV-2 infection and the development of parkinsonism-like symptoms.

Improvements in clinical signs and symptoms of Parkinson's disease using photobiomodulation: a five-year follow-up

BACKGROUND

Parkinson's disease is a progressive neurodegenerative disease characterized by clinical motor signs and non-motor symptoms that severely impact quality of life. There is an urgent need for therapies that might slow, halt or even reverse the progression of existing symptoms or delay the onset of new symptoms. Photobiomodulation is a therapy that has shown potential to alleviate some symptoms of Parkinson's disease in animal studies and in small clinical trials.

OBJECTIVE

To assess long-term effectiveness of photobiomodulation therapy in a cohort of Parkinson's disease individuals after five years of continuing therapy.

METHODS

Eight participants of the initial 12 in a previously published study agreed to be reassessed after five years. Seven of these participants had continued home-based, self-applied photobiomodulation therapy three times per week for five years. One participant had discontinued treatment after one year. Participants were assessed for a range of clinical motor signs, including MDS-UPDRS-III, measures of mobility and balance. Cognition was assessed objectively, and quality of life and sleep quality were assessed using self-reported questionnaires. A Wilcoxon Signed Ranks test was used to evaluate change in outcome measures between baseline (before treatment) and after five years, with the alpha value set to 0.05.

RESULTS

Of the seven participants who had continued photobiomodulation therapy, one had a preliminary diagnosis of multisystem atrophy and was excluded from the group analysis. For the remaining six participants, there was a significant improvement in walk speed, stride length, timed up-and-go tests, tests of dynamic balance, and cognition compared to baseline and nonsignificant improvements in all other measures, apart from MDS-UPDRS-III, which was unchanged and one measure of static balance (single leg stance, standing on the unaffected leg with eyes open) which declined. Five of six participants either improved or showed no decline in MDS-UPDRS-III score and most participants showed improvement or no decline in all other outcome measures. No adverse effects of the photobiomodulation therapy were reported.

CONCLUSIONS

This study provides a signal that photobiomodulation therapy might safely reduce important clinical motor signs and non-motor symptoms in some Parkinson's disease patients, with improvements maintained over several years. Home-based photobiomodulation therapy has the potential to complement standard therapies to manage symptoms and potentially delay Parkinson's symptom progression.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, registration number ACTRN12618000038291p, registered on 12/01/2018.

Multiple system atrophy: Diagnostic challenges and a proposed diagnostic algorithm

Multiple system atrophy (MSA) is a heterogenous condition, presenting with core clinical features of autonomic dysfunction, parkinsonism, and/or cerebellar ataxia. The presence of alpha-synuclein glial cytoplasmic inclusion is the hallmark of MSA. It shares a common pathological origin with Parkinson's disease (PD) and Lewy body dementia (DLB) and they are collectively grouped as "synucleinopathies." The pathological synuclein protein is now well- recognized in skin biopsies of these patients. Besides the pathological findings, radiological investigation is a useful diagnostic tool. Brain MRI helps rule out other etiologies, and findings like the "Hot-cross bun" sign, "putaminal atrophy," and "infratentorial findings" can assist with the diagnosis of MSA. Cardiac MIBG scan, autonomic testing, urodynamic studies can help differentiate MSA from other conditions. Although diagnostic tools are available for MSA diagnosis, clarity is needed on when to use these tests. We suggest a diagnostic algorithm to navigate the use of these tests. However, this algorithm is not intended to replace the use of current MDS diagnostic criteria of MSA.

Multiple System Atrophy Masquerading as Drug-Resistant Orthostatic Hypotension

A 54-year-old male presented with a two-year history of recurrent syncope. Although he was treated with droxidopa and amezinium metilsulfate, his syncope was drug-resistant. Blood tests, cardiac evaluation and brain computed tomography (CT) were unremarkable. As his Schellong test was positive, orthostatic hypotension and syncope were the tentative diagnoses. Upon evaluating the patient neurologically while carefully avoiding syncope induction, mild cerebellar ataxia was observed. However, a brain magnetic resonance imaging (MRI) scan revealed a possible "cross sign" in the pons. Subsequent dopamine transporter single-photon emission computed tomography (DAT-SPECT) showed reduced uptake in the basal ganglia. Based on these findings, a clinical diagnosis of probable multiple system atrophy of the cerebellar type (MSA-C) was made, and treatment with taltirelin hydrate was initiated. This case underscores the importance of considering multiple system atrophy (MSA) in patients with persistent orthostatic hypotension and syncope, even before more obvious neurodegenerative symptoms emerge.

The potential of phosphorylated α-synuclein as a biomarker for the diagnosis and monitoring of multiple system atrophy

INTRODUCTION

Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disorder characterized by the presence of glial cytoplasmic inclusions (GCIs) containing aggregated α-synuclein (α-Syn). Accurate diagnosis and monitoring of MSA present significant challenges, which can lead to potential misdiagnosis and inappropriate treatment. Biomarkers play a crucial role in improving the accuracy of MSA diagnosis, and phosphorylated α-synuclein (p-syn) has emerged as a promising biomarker for aiding in diagnosis and disease monitoring.

METHODS

A literature search was conducted on PubMed, Scopus, and Google Scholar using specific keywords and MeSH terms without imposing a time limit. Inclusion criteria comprised various study designs including experimental studies, case-control studies, and cohort studies published only in English, while conference abstracts and unpublished sources were excluded.

RESULTS

Increased levels of p-syn have been observed in various samples from MSA patients, such as red blood cells, cerebrospinal fluid, oral mucosal cells, skin, and colon biopsies, highlighting their diagnostic potential. The α-Syn RT-QuIC assay has shown sensitivity in diagnosing MSA and tracking its progression. Meta-analyses and multicenter investigations have confirmed the diagnostic value of p-syn in cerebrospinal fluid, demonstrating high specificity and sensitivity in distinguishing MSA from other neurodegenerative diseases. Moreover, combining p-syn with other biomarkers has further improved the diagnostic accuracy of MSA.

CONCLUSION

The p-syn stands out as a promising biomarker for MSA. It is found in oligodendrocytes and shows a correlation with disease severity and progression. However, further research and validation studies are necessary to establish p-syn as a reliable biomarker for MSA. If proven, p-syn could significantly contribute to early diagnosis, disease monitoring, and assessing treatment response.

Distinct forebrain regions define a dichotomous astrocytic profile in multiple system atrophy

The growing recognition of a dichotomous role of astrocytes in neurodegenerative processes has heightened the need for unraveling distinct astrocytic subtypes in neurological disorders. In multiple system atrophy (MSA), a rare, rapidly progressing atypical Parkinsonian disease characterized by increased astrocyte reactivity. However the specific contribution of astrocyte subtypes to neuropathology remains elusive. Hence, we first set out to profile glial fibrillary acidic protein levels in astrocytes across the human post mortem motor cortex, putamen, and substantia nigra of MSA patients and observed an overall profound astrocytic response. Matching the post mortem human findings, a similar astrocytic phenotype was present in a transgenic MSA mouse model. Notably, MSA mice exhibited a decreased expression of the glutamate transporter 1 and glutamate aspartate transporter in the basal ganglia, but not the motor cortex. We developed an optimized astrocyte isolation protocol based on magnetic-activated cell sorting via ATPase Na+/K+ transporting subunit beta 2 and profiled the transcriptomic landscape of striatal and cortical astrocytes in transgenic MSA mice. The gene expression profile of astrocytes in the motor cortex displayed an anti-inflammatory signature with increased oligodendroglial and pro-myelinogenic expression pattern. In contrast, striatal astrocytes were defined by elevated pro-inflammatory transcripts accompanied by dysregulated genes involved in homeostatic functions for lipid and calcium metabolism. These findings provide new insights into a region-dependent, dichotomous astrocytic response-potentially beneficial in the cortex and harmful in the striatum-in MSA suggesting a differential role of astrocytes in MSA-related neurodegenerative processes.

Neurofilament light chain in spinal fluid and plasma in multiple system atrophy: a prospective, longitudinal biomarker study

PURPOSE

There is a critical need for reliable diagnostic biomarkers as well as surrogate markers of disease progression in multiple system atrophy (MSA). Neurofilament light chain (NfL) has been reported to potentially meet those needs. We therefore sought to explore the value of NfL in plasma (NfL-p) in contrast to cerebrospinal fluid (NfL-c) as a diagnostic marker of MSA, and to assess NfL-p and NfL-c as markers of clinical disease progression.

METHODS

Well-characterized patients with early MSA (n = 32), Parkinson's disease (PD; n = 21), and matched controls (CON; n = 15) were enrolled in a prospective, longitudinal study of synucleinopathies with serial annual evaluations. NfL was measured using a high-sensitivity immunoassay, and findings were assessed by disease category and relationship with clinical measures of disease progression.

RESULTS

Measurements of NfL-c were highly reproducible across immunoassay platforms (Pearson, r = 0.99), while correlation between NfL-c and -p was only moderate (r = 0.66). NfL was significantly higher in MSA compared with CON and PD; the separation was essentially perfect for NfL-c, but there was overlap, particularly with PD, for NfL-p. While clinical measures of disease severity progressively increased over time, NfL-c and -p remained at stable elevated levels within subjects across serial measurements. Neither change in NfL nor baseline NfL were significantly associated with changes in clinical markers of disease severity.

CONCLUSIONS

These findings confirm NfL-c as a faithful diagnostic marker of MSA, while NfL-p showed less robust diagnostic value. The significant NfL elevation in MSA was found to be remarkably stable over time and was not predictive of clinical disease progression.

Diagnosing multiple system atrophy: current clinical guidance and emerging molecular biomarkers

Multiple system atrophy (MSA) is a rare and progressive neurodegenerative disorder characterized by motor and autonomic dysfunction. Accurate and early diagnosis of MSA is challenging due to its clinical similarity with other neurodegenerative disorders, such as Parkinson's disease and atypical parkinsonian disorders. Currently, MSA diagnosis is based on clinical criteria drawing from the patient's symptoms, lack of response to levodopa therapy, neuroimaging studies, and exclusion of other diseases. However, these methods have limitations in sensitivity and specificity. Recent advances in molecular biomarker research, such as α-synuclein protein amplification assays (RT-QuIC) and other biomarkers in cerebrospinal fluid and blood, have shown promise in improving the diagnosis of MSA. Additionally, these biomarkers could also serve as targets for developing disease-modifying therapies and monitoring treatment response. In this review, we provide an overview of the clinical syndrome of MSA and discuss the current diagnostic criteria, limitations of current diagnostic methods, and emerging molecular biomarkers that offer hope for improving the accuracy and early detection of MSA.

Genetic modifiers of synucleinopathies-lessons from experimental models

α-Synuclein is a pleiotropic protein underlying a group of progressive neurodegenerative diseases, including Parkinson's disease and dementia with Lewy bodies. Together, these are known as synucleinopathies. Like all neurological diseases, understanding of disease mechanisms is hampered by the lack of access to biopsy tissues, precluding a real-time view of disease progression in the human body. This has driven researchers to devise various experimental models ranging from yeast to flies to human brain organoids, aiming to recapitulate aspects of synucleinopathies. Studies of these models have uncovered numerous genetic modifiers of α-synuclein, most of which are evolutionarily conserved. This review discusses what we have learned about disease mechanisms from these modifiers, and ways in which the study of modifiers have supported ongoing efforts to engineer disease-modifying interventions for synucleinopathies.

Glutathione Depletion and MicroRNA Dysregulation in Multiple System Atrophy: A Review

Multiple system atrophy (MSA) is a rare neurodegenerative disease characterized by parkinsonism, cerebellar impairment, and autonomic failure. Although the causes of MSA onset and progression remain uncertain, its pathogenesis may involve oxidative stress via the generation of excess reactive oxygen species and/or destruction of the antioxidant system. One of the most powerful antioxidants is glutathione, which plays essential roles as an antioxidant enzyme cofactor, cysteine-storage molecule, major redox buffer, and neuromodulator, in addition to being a key antioxidant in the central nervous system. Glutathione levels are known to be reduced in neurodegenerative diseases. In addition, genes regulating redox states have been shown to be post-transcriptionally modified by microRNA (miRNA), one of the most important types of non-coding RNA. miRNAs have been reported to be dysregulated in several diseases, including MSA. In this review, we focused on the relation between glutathione deficiency, miRNA dysregulation and oxidative stress and their close relation with MSA pathology.