Riluzole in patients with hereditary cerebellar ataxia: a randomised, double-blind, placebo-controlled trial

Efficacy and safety of riluzole for treating motor function in rare dyskinesia syndromes: a systematic review with meta-analysis

OBJECTIVES

We conducted a systematic review and meta-analysis to evaluate the clinical effectiveness and safety of riluzole to treat neurodegenerative dyskinesia in patients, using the Cochrane collaboration guidelines.

METHODS

We searched databases including Medline, Embase, and Cochrane without any language filters. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used as a guideline, and the study protocol was registered in PROSPERO (CRD42022354627).

RESULTS

Eleven studies involving 1376 patients were included. There was a significant overall effect of riluzole on changes in motor function scores. However, the level of heterogeneity was I2 = 74%. In the subgroup analyses, there were no significant effects of riluzole on motor scores in hereditary ataxia, Parkinson's disease, or Huntington's disease. In the sensitivity analysis, there were no significant effects of riluzole on motor function scores. Furthermore, there were no significant differences in adverse events between the riluzole and placebo groups.

CONCLUSIONS

Although riluzole may not have significant efficacy for improving motor function in neurodegenerative dyskinesia syndromes compared with placebo, it seems to have an acceptable safety profile. Moreover, it may be effective for hereditary ataxia syndromes, although there was a relatively small effect size and limited quality of evidence.

The importance of synthetic pharmacotherapy for recessive cerebellar ataxias

INTRODUCTION

The last decade has witnessed major breakthroughs in identifying novel genetic causes of hereditary ataxias, deepening our understanding of disease mechanisms, and developing therapies for these debilitating disorders.

AREAS COVERED

This article reviews the currently approved and most promising candidate pharmacotherapies in relation to the known disease mechanisms of the most prevalent autosomal recessive ataxias. Omaveloxolone is an Nrf2 activator that increases antioxidant defense and was recently approved for treatment of Friedreich ataxia. Its therapeutic effect is modest, and further research is needed to find synergistic treatments that would halt or reverse disease progression. Promising approaches include upregulation of frataxin expression by epigenetic mechanisms, direct protein replacement, and gene replacement therapy. For ataxia-telangiectasia, promising approaches include splice-switching antisense oligonucleotides and small molecules targeting oxidative stress, inflammation, and mitochondrial function. Rare recessive ataxias for which disease-modifying therapies exist are also reviewed, emphasizing recently approved therapies. Evidence supporting the use of riluzole and acetyl-leucine in recessive ataxias is discussed.

EXPERT OPINION

Advances in genetic therapies for other neurogenetic conditions have paved the way to implement feasible approaches with potential dramatic benefits. Particularly, as we develop effective treatments for these conditions, we may need to combine therapies, consider newborn testing for pre-symptomatic treatment, and optimize non-pharmacological approaches.

A combination of chlorzoxazone and folic acid improves recognition memory, anxiety and depression in SCA3-84Q mice

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is reported to be the most common type of autosomal dominant cerebellar ataxia (ADCA). SCA3 patients suffer from a progressive decline in motor coordination and other disease-associated symptoms. Moreover, recent studies have reported that SCA3 patients also exhibit symptoms of cerebellar cognitive affective syndrome (CCAS). We previously observed signs of CCAS in mouse model of SCA3. Particularly, SCA3-84Q mice suffer from anxiety, recognition memory decline, and also exhibit signs of low mood and aversion to activity. Here we studied the effect of long-term injections of SK channels activator chlorzoxazone (CHZ) together and separately with the folic acid (FA) on the cerebellar Purkinje cell (PC) firing and histology, and also on the motor and cognitive functions as well as mood alterations in SCA3-84Q hemizygous transgenic mice. We realized that both CHZ and CHZ-FA combination had similar positive effect on pure cerebellum impairments including PC firing precision, PC histology, and motor performance in SCA3-84Q mice. However, only the CHZ-FA combination, but not CHZ, had significantly ameliorated the signs of anxiety and depression, and also noticeably improved recognition memory in SCA3-84Q mice. Our results suggest that the combination therapy for both ataxia and non-motor symptoms is required for the complex treatment of ADCA.

Video-Based Kinematic Analysis of Movement Quality in a Phase 3 Clinical Trial of Troriluzole in Adults with Spinocerebellar Ataxia: A Post Hoc Analysis

INTRODUCTION

Traditional methods for assessing movement quality rely on subjective standardized scales and clinical expertise. This limitation creates challenges for assessing patients with spinocerebellar ataxia (SCA), in whom changes in mobility can be subtle and varied. We hypothesized that a machine learning analytic system might complement traditional clinician-rated measures of gait. Our objective was to use a video-based assessment of gait dispersion to compare the effects of troriluzole with placebo on gait quality in adults with SCA.

METHODS

Participants with SCA underwent gait assessment in a phase 3, double-blind, placebo-controlled trial of troriluzole (NCT03701399). Videos were processed through a deep learning pose extraction algorithm, followed by the estimation of a novel gait stability measure, the Pose Dispersion Index, quantifying the frame-by-frame symmetry, balance, and stability during natural and tandem walk tasks. The effects of troriluzole treatment were assessed in mixed linear models, participant-level grouping, and treatment group-by-visit week interaction adjusted for age, sex, baseline modified Functional Scale for the Assessment and Rating of Ataxia (f-SARA), and time since diagnosis.

RESULTS

From 218 randomized participants, 67 and 56 participants had interpretable videos of a tandem and natural walk attempt, respectively. At Week 48, individuals assigned to troriluzole exhibited significant (p = 0.010) improvement in tandem walk Pose Dispersion Index versus placebo {adjusted interaction coefficient: 0.584 [95% confidence interval (CI) 0.137 to 1.031]}. A similar, nonsignificant trend was observed in the natural walk assessment [coefficient: 1.198 (95% CI - 1.067 to 3.462)]. Further, lower baseline Pose Dispersion Index during the natural walk was significantly (p = 0.041) associated with a higher risk of subsequent falls [adjusted Poisson coefficient: - 0.356 [95% CI - 0.697 to - 0.014)].

CONCLUSION

Using this novel approach, troriluzole-treated subjects demonstrated improvement in gait as compared to placebo for the tandem walk. Machine learning applied to video-captured gait parameters can complement clinician-reported motor assessment in adults with SCA. The Pose Dispersion Index may enhance assessment in future research. TRIAL REGISTRATION-CLINICALTRIALS.

GOV IDENTIFIER

NCT03701399.

Specific Biomarkers in Spinocerebellar Ataxia Type 3: A Systematic Review of Their Potential Uses in Disease Staging and Treatment Assessment

Spinocerebellar ataxia type 3 (SCA3) is the most common type of disease related to poly-glutamine (polyQ) repeats. Its hallmark pathology is related to the abnormal accumulation of ataxin 3 with a longer polyQ tract (polyQ-ATXN3). However, there are other mechanisms related to SCA3 progression that require identifying trait and state biomarkers for a more accurate diagnosis and prognosis. Moreover, the identification of potential pharmacodynamic targets and assessment of therapeutic efficacy necessitates valid biomarker profiles. The aim of this review was to identify potential trait and state biomarkers and their potential value in clinical trials. Our results show that, in SCA3, there are different fluid biomarkers involved in neurodegeneration, oxidative stress, metabolism, miRNA and novel genes. However, neurofilament light chain NfL and polyQ-ATXN3 stand out as the most prevalent in body fluids and SCA3 stages. A heterogeneity analysis of NfL revealed that it may be a valuable state biomarker, particularly when measured in plasma. Nonetheless, since it could be a more beneficial approach to tracking SCA3 progression and clinical trial efficacy, it is more convenient to perform a biomarker profile evaluation than to rely on only one.

Long-Term Follow-Up before and during Riluzole Treatment in Six Patients from Two Families with Spinocerebellar Ataxia Type 7

BACKGROUND

Currently no curative treatment exists for spinocerebellar ataxias (SCAs). Riluzole repurposing was proposed as a symptomatic treatment in different types of cerebellar ataxia. We report a long-term-follow up under riluzole treatment in SCA type 7.

METHODS

Six patients received Riluzole 50 mg twice daily on a compassionate use program for a mean of 4.8 years (range 3.5-9). We measured ataxia onset and progression through the Scale for the Assessment and Rating of Ataxia (SARA), and collected extensive ophthalmological data before and after Riluzole treatment. Electrocardiogram and laboratory profile for drug safety were performed every six months.

RESULTS

Riluzole treatment showed no effect on visual function in two patients with an advanced retinal damage. Improvements of visual function occurred in four patients followed by ophthalmologic stability up to 5 years after starting treatment. Two patients had a less steep deterioration of ataxia after treatment compared to pre-treatment, during the first 2,5 years of therapy. One showed soon after therapy an improvement of the SARA score, and then overall stability lasting 3,5 years, followed by ataxia worsening. One visually impaired patient without neurological impairment did not worse until the last visit after 3,5 years of follow-up. The remaining 2 patients showed an improvement of SARA scores soon after therapy, and an overall stability lasting respectively 5 and 3 years. No adverse event was registered during the observation period.

DISCUSSION

This study suggests a possible beneficial action of Riluzole in SCA7 and provides a detailed description of the ophthalmologic profile of these patients.

Ataxic hemiparesis: a narrative review for clinical practice in rehabilitation

BACKGROUND

Ataxic hemiparesis (AH) is a well-recognized clinical lacunar stroke syndrome, characterized by paresis with ataxia on the same side of the body. It affects patients with stroke involving the basal ganglia, pons, internal capsule, corona radiata, and thalamus. In the past, lacunar syndrome denotes good functional recovery with low mortality and morbidity rate. However, recent evidence suggests AH has an association with more debilitating outcomes in the long term.

OBJECTIVE

To provide a comprehensive narrative review of published literatures on the topics related with AH and update clinical practice including rehabilitation.

METHODS

Literature review was performed by using the keywords "Subcortical Ataxia," "Lacunar Stroke," "Diaschisis", and "Ataxic Hemiparesis" on PubMed and Google Scholar Engines from 1978 to 2022. All papers published in English were reviewed and manual search of references from retrieved literature was performed for other relevant articles.

RESULTS

A comprehensive review was carried out on the following topics: neuroanatomical localization, pathogenesis, clinical features and clinical assessment scales, pharmacological and non-pharmacological modalities for ataxia treatment, prognosis, and outcome.

CONCLUSION

AH imposes significant challenges on stroke survivors when it comes to remediation of balance and coordination. It is associated with increased risk of mortality, stroke recurrence, and dementia. Though application of the concept of neuroplasticity and the utilization of repetitive transcranial magnetic stimulation have shown early promising results, further research is needed to establish the practice guidelines for rehabilitation of patients with AH.

Spinocerebellar ataxias: from pathogenesis to recent therapeutic advances

Spinocerebellar ataxia is a phenotypically and genetically heterogeneous group of autosomal dominant-inherited degenerative disorders. The gene mutation spectrum includes dynamic expansions, point mutations, duplications, insertions, and deletions of varying lengths. Dynamic expansion is the most common form of mutation. Mutations often result in indistinguishable clinical phenotypes, thus requiring validation using multiple genetic testing techniques. Depending on the type of mutation, the pathogenesis may involve proteotoxicity, RNA toxicity, or protein loss-of-function. All of which may disrupt a range of cellular processes, such as impaired protein quality control pathways, ion channel dysfunction, mitochondrial dysfunction, transcriptional dysregulation, DNA damage, loss of nuclear integrity, and ultimately, impairment of neuronal function and integrity which causes diseases. Many disease-modifying therapies, such as gene editing technology, RNA interference, antisense oligonucleotides, stem cell technology, and pharmacological therapies are currently under clinical trials. However, the development of curative approaches for genetic diseases remains a global challenge, beset by technical, ethical, and other challenges. Therefore, the study of the pathogenesis of spinocerebellar ataxia is of great importance for the sustained development of disease-modifying molecular therapies.

Content Validity of the Modified Functional Scale for the Assessment and Rating of Ataxia (f-SARA) Instrument in Spinocerebellar Ataxia

The functional Scale for the Assessment and Rating of Ataxia (f-SARA) assesses Gait, Stance, Sitting, and Speech. It was developed as a potentially clinically meaningful measure of spinocerebellar ataxia (SCA) progression for clinical trial use. Here, we evaluated content validity of the f-SARA. Qualitative interviews were conducted among individuals with SCA1 (n = 1) and SCA3 (n = 6) and healthcare professionals (HCPs) with SCA expertise (USA, n = 5; Europe, n = 3). Interviews evaluated symptoms and signs of SCA and relevance of f-SARA concepts for SCA. HCP cognitive debriefing was conducted. Interviews were recorded, transcribed, coded, and analyzed by ATLAS.TI software. Individuals with SCA1 and 3 reported 85 symptoms, signs, and impacts of SCA. All indicated difficulties with walking, stance, balance, speech, fatigue, emotions, and work. All individuals with SCA1 and 3 considered Gait, Stance, and Speech relevant f-SARA concepts; 3 considered Sitting relevant (42.9%). All HCPs considered Gait and Speech relevant; 5 (62.5%) indicated Stance was relevant. Sitting was considered a late-stage disease indicator. Most HCPs suggested inclusion of appendicular items would enhance clinical relevance. Cognitive debriefing supported clarity and comprehension of f-SARA. Maintaining current abilities on f-SARA items for 1 year was considered meaningful for most individuals with SCA1 and 3. All HCPs considered meaningful changes as stability in f-SARA score over 1-2 years, 1-2-point change in total f-SARA score, and deviation from natural history. These results support content validity of f-SARA for assessing SCA disease progression in clinical trials.

Polyglutamine disorders: Pathogenesis and potential drug interventions

Polyglutamine/poly(Q) diseases are a group nine hereditary neurodegenerative disorders caused due to abnormally expanded stretches of CAG trinucleotide in functionally distinct genes. All human poly(Q) diseases are characterized by the formation of microscopically discernable poly(Q) positive aggregates, the inclusion bodies. These toxic inclusion bodies are responsible for the impairment of several cellular pathways such as autophagy, transcription, cell death, etc., that culminate in disease manifestation. Although, these diseases remain largely without treatment, extensive research has generated mounting evidences that various events of poly(Q) pathogenesis can be developed as potential drug targets. The present review article briefly discusses the key events of disease pathogenesis, model system-based investigations that support the development of effective therapeutic interventions against pathogenesis of human poly(Q) disorders, and a comprehensive list of pharmacological and bioactive compounds that have been experimentally shown to alleviate poly(Q)-mediated neurotoxicity. Interestingly, due to the common cause of pathogenesis, all poly(Q) diseases share etiology, thus, findings from one disease can be potentially extrapolated to other poly(Q) diseases as well.

Potential Benefit of Channel Activators in Loss-of-Function Primary Potassium Channelopathies Causing Heredoataxia

Potassium channels (KCN) are transmembrane complexes that regulate the resting membrane potential and the duration of action potentials in cells. The opening of KCN brings about an efflux of K+ ions that induces cell repolarization after depolarization, returns the transmembrane potential to its resting state, and enables for continuous spiking ability. The aim of this work was to assess the role of KCN dysfunction in the pathogenesis of hereditary ataxias and the mechanisms of action of KCN opening agents (KCO). In consequence, a review of the ad hoc medical literature was performed. Among hereditary KCN diseases causing ataxia, mutated Kv3.3, Kv4.3, and Kv1.1 channels provoke spinocerebellar ataxia (SCA) type 13, SCA19/22, and episodic ataxia type 1 (EA1), respectively. The K+ efflux was found to be reduced in experimental models of these diseases, resulting in abnormally prolonged depolarization and incomplete repolarization, thereby interfering with repetitive discharges in the cells. Hence, substances able to promote normal spiking activity in the cerebellum could provide symptomatic benefit. Although drugs used in clinical practice do not activate Kv3.3 or Kv4.3 directly, available KCO probably could ameliorate ataxic symptoms in SCA13 and SCA19/22, as verified with acetazolamide in EA1, and retigabine in a mouse model of hypokalemic periodic paralysis. To summarize, ataxia could possibly be improved by non-specific KCO in SCA13 and SCA19/22. The identification of new specific KCO agents will undoubtedly constitute a promising therapeutic strategy for these diseases.

Ataxia Rating Scales Reflect Patient Experience: an Examination of the Relationship Between Clinician Assessments of Cerebellar Ataxia and Patient-Reported Outcomes

Ataxia rating scales are observer administered clinical outcome assessments (COAs) of the cerebellar motor syndrome. It is not known whether these COAs mirror patient experience of their disease. Here we test the hypothesis that ataxia COAs are related to and reflect patient reported symptoms and impact of illness. A concept library of symptoms and activities impacted by ataxia was created by reviewing (a) concept elicitation data from surveys completed by 147 ataxia patients and 80 family members and (b) cognitive debrief data from focus groups of 17 ataxia patients used to develop the Patient Reported Outcome Measure of Ataxia. These findings were mapped across the items on 4 clinical measures of ataxia (SARA, BARS, ICARS and FARS). Symptoms reported most commonly related to balance, gait or walking, speech, tremor and involuntary movements, and vision impairment. Symptoms reported less frequently related to hand coordination, loss of muscle control, dizziness and vertigo, muscle discomfort or pain, swallowing, and incontinence. There was a mosaic mapping of items in the observer-derived ataxia COAs with the subjective reports by ataxia patients/families of the relevance of these items to their daily lives. Most COA item mapped onto multiple real-life manifestations; and most of the real-life impact of disease mapped onto multiple COA items. The 4 common ataxia COAs reflect patient reported symptoms and impact of illness. These results validate the relevance of the COAs to patients' lives and underscore the inadvisability of singling out any one COA item to represent the totality of the patient experience.

Physical Activity and Fitness Levels of Individuals With Ataxia: A Cross-Sectional Study

OBJECTIVE

To investigate physical activity levels of individuals with ataxia and correlate fitness to ataxia severity.

DESIGN

An observational study SETTING: An outpatient ataxia clinic in a large, tertiary, urban hospital in the US.

PARTICIPANTS

Individuals with cerebellar ataxia (N=42).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

Participants were classified as sedentary or physically active using the International Physical Activity Questionnaire-Short Form (IPAQ-SF). Maximal oxygen consumption (V̇o2max) as an indicator of fitness level was measured, and ataxia severity was determined by the Scale for the Assessment and Rating of Ataxia (SARA). Mixed effect models were used to correlate ataxia severity to fitness levels.

RESULTS

Most participants (28 out of 42) lived sedentary lifestyles, and these individuals had poor fitness levels (only 67.3% of their predicted measure). The main barriers to physical activity included lack of energy, lack of time, and fear of falling. There were no differences in age, sex, disease type, disease duration, ataxia severity, fatigue level, and medication use between sedentary and active groups. Measures of V̇o2max, maximal work, maximal heart rate, and anerobic threshold demonstrated statistically significant differences between groups whereas maximal respiratory rate and expired ventilation/carbon dioxide production were similar between groups. When adjusting for age, sex, functional mobility status, and disease duration, ataxia severity was inversely correlated with fitness level in the sedentary group. There was no relationship between ataxia severity and fitness level in the 14 individuals who were physically active.

CONCLUSIONS

Lower fitness levels were associated with more ataxia symptoms in the sedentary group. This relationship was not seen in individuals who were more active. Given the poor health outcomes associated with low fitness, physical activity should be encouraged in this population.

A chlorzoxazone-folic acid combination improves cognitive affective decline in SCA2-58Q mice

Spinocerebellar ataxia type 2 (SCA2) is a polyglutamine disorder caused by a pathological expansion of CAG repeats in ATXN2 gene. SCA2 is accompanied by cerebellar degeneration and progressive motor decline. Cerebellar Purkinje cells (PCs) seem to be primarily affected in this disorder. The majority of the ataxia research is focused on the motor decline observed in ataxic patients and animal models of the disease. However, recent evidence from patients and ataxic mice suggests that SCA2 can also share the symptoms of the cerebellar cognitive affective syndrome. We previously reported that SCA2-58Q PC-specific transgenic mice exhibit anxiolytic behavior, decline in spatial memory, and a depressive-like state. Here we studied the effect of the activation of the small conductance calcium-activated potassium channels (SK channels) by chlorzoxazone (CHZ) combined with the folic acid (FA) on the PC firing and also motor, cognitive and affective symptoms in SCA2-58Q mice. We realized that CHZ-FA combination improved motor and cognitive decline as well as ameliorated mood alterations in SCA2-58Q mice without affecting the firing rate of their cerebellar PCs. Our results support the idea of the combination therapy for both ataxia and non-motor symptoms in ataxic mice without affecting the firing frequency of PCs.

Autosomal dominant cerebellar ataxias: new genes and progress towards treatments

Dominantly inherited spinocerebellar ataxias (SCAs) are associated with phenotypes that range from pure cerebellar to multisystemic. The list of implicated genes has lengthened in the past 5 years with the inclusion of SCA37/DAB1, SCA45/FAT2, SCA46/PLD3, SCA47/PUM1, SCA48/STUB1, SCA50/NPTX1, SCA25/PNPT1, SCA49/SAM9DL, and SCA27B/FGF14. In some patients, co-occurrence of multiple potentially pathogenic variants can explain variable penetrance or more severe phenotypes. Given this extreme clinical and genetic heterogeneity, genome sequencing should become the diagnostic tool of choice but is still not available in many clinical settings. Treatments tested in phase 2 and phase 3 studies, such as riluzole and transcranial direct current stimulation of the cerebellum and spinal cord, have given conflicting results. To enable early intervention, preataxic carriers of pathogenic variants should be assessed with biomarkers, such as neurofilament light chain and brain MRI; these biomarkers could also be used as outcome measures, given that clinical outcomes are not useful in the preataxic phase. The development of bioassays measuring the concentration of the mutant protein (eg, ataxin-3) might facilitate monitoring of target engagement by gene therapies.

Advances in cerebellar disorders: pre-clinical models, therapeutic targets, and challenges

INTRODUCTION

Cerebellar ataxias (CAs) represent neurological disorders with multiple etiologies and a high phenotypic variability. Despite progress in the understanding of pathogenesis, few therapies are available so far. Closing the loop between preclinical studies and therapeutic trials is important, given the impact of CAs upon patients' health and the roles of the cerebellum in multiple domains. Because of a rapid advance in research on CAs, it is necessary to summarize the main findings and discuss future directions.

AREAS COVERED

We focus our discussion on preclinical models, cerebellar reserve, the therapeutic management of CAs, and suitable surrogate markers. We searched Web of Science and PubMed using keywords relevant to cerebellar diseases, therapy, and preclinical models.

EXPERT OPINION

There are many symptomatic and/or disease-modifying therapeutic approaches under investigation. For therapy development, preclinical studies, standardization of disease evaluation, safety assessment, and demonstration of clinical improvements are essential. Stage of the disease and the level of the cerebellar reserve determine the goals of the therapy. Deficits in multiple categories and heterogeneity of CAs may require disease-, stage-, and symptom-specific therapies. More research is needed to clarify how therapies targeting the cerebellum influence both basal ganglia and the cerebral cortex, poorly explored domains in CAs.

Experimental Treatment with Edaravone in a Mouse Model of Spinocerebellar Ataxia 1

Edaravone is a mitochondrially targeted drug with a suggested capability to modify the course of diverse neurological diseases. Nevertheless, edaravone has not been tested yet in the context of spinocerebellar ataxia 1 (SCA1), an incurable neurodegenerative disease characterized mainly by cerebellar disorder, with a strong contribution of inflammation and mitochondrial dysfunction. This study aimed to address this gap, exploring the potential of edaravone to slow down SCA1 progression in a mouse knock-in SCA1 model. SCA1^154Q/2Q and healthy SCA1^2Q/2Q mice were administered either edaravone or saline daily for more than 13 weeks. The functional impairments were assessed via a wide spectrum of behavioral assays reflecting motor and cognitive deficits and behavioral abnormalities. Moreover, we used high-resolution respirometry to explore mitochondrial function, and immunohistochemical and biochemical tools to assess the magnitude of neurodegeneration, inflammation, and neuroplasticity. Data were analyzed using (hierarchical) Bayesian regression models, combined with the methods of multivariate statistics. Our analysis pointed out various previously documented neurological and behavioral deficits of SCA1 mice. However, we did not detect any plausible therapeutic effect of edaravone on either behavioral dysfunctions or other disease hallmarks in SCA1 mice. Thus, our results did not provide support for the therapeutic potential of edaravone in SCA1.

Novel Therapeutic Approaches in Inherited Neuropathies: A Systematic Review

The management of inherited neuropathies relies mostly on the treatment of symptoms. In recent years, a better understanding of the pathogenic mechanisms that underlie neuropathies has allowed for the development of disease-modifying therapies. Here, we systematically review the therapies that have emerged in this field over the last five years. An updated list of diseases with peripheral neuropathy as a clinical feature was created based on panels of genes used clinically to diagnose inherited neuropathy. This list was extended by an analysis of published data by the authors and verified by two experts. A comprehensive search for studies of human patients suffering from one of the diseases in our list yielded 28 studies that assessed neuropathy as a primary or secondary outcome. Although the use of various scales and scoring systems made comparisons difficult, this analysis identified diseases associated with neuropathy for which approved therapies exist. An important finding is that the symptoms and/or biomarkers of neuropathies were assessed only in a minority of cases. Therefore, further investigation of treatment efficacy on neuropathies in future trials must employ objective, consistent methods such as wearable technologies, motor unit indexes, MRI or sonography imaging, or the use of blood biomarkers associated with consistent nerve conduction studies.

Therapeutic Strategies for Spinocerebellar Ataxia Type 1

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder that affects one or two individuals per 100,000. The disease is caused by an extended CAG repeat in exon 8 of the ATXN1 gene and is characterized mostly by a profound loss of cerebellar Purkinje cells, leading to disturbances in coordination, balance, and gait. At present, no curative treatment is available for SCA1. However, increasing knowledge on the cellular and molecular mechanisms of SCA1 has led the way towards several therapeutic strategies that can potentially slow disease progression. SCA1 therapeutics can be classified as genetic, pharmacological, and cell replacement therapies. These different therapeutic strategies target either the (mutant) ATXN1 RNA or the ataxin-1 protein, pathways that play an important role in downstream SCA1 disease mechanisms or which help restore cells that are lost due to SCA1 pathology. In this review, we will provide a summary of the different therapeutic strategies that are currently being investigated for SCA1.

Home Aerobic Training for Cerebellar Degenerative Diseases: a Randomized Controlled Trial

Balance training has shown some benefits in cerebellar ataxia whereas the effects of aerobic training are relatively unknown. To determine whether a phase III trial comparing home aerobic to balance training in ambulatory patients with cerebellar ataxia is warranted, we conducted a single-center, assessor-blinded, randomized controlled trial. Nineteen subjects were randomized to aerobic training and 17 subjects to balance training. The primary outcome was improvement in ataxia as measured by the Scale for the Assessment and Rating of Ataxia (SARA). Secondary outcomes included safety, training adherence, and balance improvements. There were no differences between groups at baseline. Thirty-one participants completed the trial, and there were no training-related serious adverse events. Compliance to training was over 70%. There was a mean improvement in ataxia symptoms of 1.9 SARA points (SD 1.62) in the aerobic group compared to an improvement of 0.6 points (SD 1.34) in the balance group. Although two measures of balance were equivocal between groups, one measure of balance showed greater improvement with balance training compared to aerobic training. In conclusion, this 6-month trial comparing home aerobic versus balance training in cerebellar ataxia had excellent retention and adherence to training. There were no serious adverse events, and training was not interrupted by minor adverse events like falls or back pain. There was a significant improvement in ataxia symptoms with home aerobic training compared to balance training, and a phase III trial is warranted. Clinical trial registration number: NCT03701776 on October 8, 2018.

Riluzole for treating spasticity in patients with chronic traumatic spinal cord injury: Study protocol in the phase ib/iib adaptive multicenter randomized controlled RILUSCI trial

BACKGROUND

Satisfactory treatment is often lacking for spasticity, a highly prevalent motor disorder in patients with spinal cord injury (SCI). Low concentrations of riluzole potently reduce the persistent sodium current, the post-SCI increase in which contributes to spasticity. The repurposing of this drug may therefore constitute a useful potential therapeutic option for relieving SCI patients suffering from chronic traumatic spasticity.

OBJECTIVE

RILUSCI is a phase 1b-2b trial designed to assess whether riluzole is a safe and biologically effective means of managing spasticity in adult patients with traumatic chronic SCI.

METHODS

In this multicenter double-blind trial, adults (aged 18-65 years) suffering from spasticity after SCI (target enrollment: 90 participants) will be randomly assigned to be given either a placebo or a recommended daily oral dose of riluzole for two weeks. The latter dose will be previously determined in phase 1b of the study by performing double-blind dose-finding tests using a Bayesian continuous reassessment method. The primary endpoint of the trial will be an improvement in the Modified Ashworth Score (MAS) or the Numerical Rating Score (NRS) quantifying spasticity. The secondary outcomes will be based on the safety and pharmacokinetics of riluzole as well as its impact on muscle spasms, pain, bladder dysfunction and quality of life. Analyses will be performed before, during and after the treatment and the placebo-controlled period.

CONCLUSION

To the best of our knowledge, this clinical trial will be the first to document the safety and efficacy of riluzole as a means of reducing spasticity in patients with chronic SCI.

TRIAL REGISTRATION

The clinical trial, which is already in progress, was registered on the ClinicalTrials.gov website on August 9, 2016 under the registration number NCT02859792.

TRIAL SPONSOR

Assistance Publique-Hôpitaux de Marseille.

Effects of cerebellar transcranial alternating current stimulation in cerebellar ataxia: study protocol for a randomised controlled trial

Background

Cerebellar ataxia (CA) is a movement disorder that can affect balance and gait, limb movement, oculomotor control, and cognition. Multiple system atrophy-cerebellar type (MSA-C) and spinocerebellar ataxia type 3 (SCA3) are the most common forms of CA, for which no effective treatment is currently available. Transcranial alternating current stimulation (tACS) is a non-invasive method of brain stimulation supposed to alter cortical excitability and brain electrical activity, modulating functional connectivity within the brain. The cerebellar tACS can modulate the cerebellar outflow and cerebellum-linked behavior and it is a proven safe technique for humans. Therefore, the aim of this study is to 1) examine whether cerebellar tACS improves ataxia severity and various non-motor symptoms in a homogeneous cohort of CA patients consisting of MSA-C and SCA3, 2) explore the time course of these effects, and 3) assess the safety and tolerance of cerebellar tACS in all participants.

Methods/design

This is a 2-week, triple-blind, randomised, sham-controlled study. 164 patients (MSA-C: 84, SCA3: 80) will be recruited and randomly assigned to either active cerebellar tACS or sham cerebellar tACS, in a 1:1 ratio. Patients, investigators, and outcome assessors are unaware of treatment allocation. Cerebellar tACS (40 min, 2 mA, ramp-up and down periods of 10s each) will be delivered over 10 sessions, distributed in two groups of five consecutive days with a two-day break in between. Outcomes are assessed after the tenth stimulation (T1), and after 1 month (T2) and 3 months (T3). The primary outcome measure is the difference between the active and sham groups in the proportion of patients with an improvement of 1.5 points in the Scale for the Assessment and Rating of Ataxia (SARA) score after 2 weeks of treatment. In addition, effects on a variety of non-motor symptoms, quality of life, and autonomic nerve dysfunctions are assessed via relative scales. Gait imbalance, dysarthria, and finger dexterity are objectively valued via relative tools. Finally, functional magnetic resonance imaging is performed to explore the possible mechanism of treatment effects.

Discussion

The results of this study will inform whether repeated sessions of active cerebellar tACS benefit CA patients and whether this form of non-invasive stimulation might be a novel therapeutic approach to consider in a neuro-rehabilitation setting.Clinical Trial Registration: ClinicalTrials.gov, identifier NCT05557786; https://www.clinicaltrials.gov/ct2/show/NCT05557786.

Pharmacotherapy for the management of the symptoms of Machado-Joseph Disease

INTRODUCTION

Machado-Joseph disease or spinocerebellar ataxia type 3 (SCA3/MJD) is the leading cause of autosomal dominant ataxia worldwide. This is a slowly progressive, but very disabling disorder. Ataxia is the main clinical feature, but additional motor and non-motor manifestations may be found. Many of these manifestations are amenable to pharmacological treatments, which may impact the quality of life of affected subjects.

AREAS COVERED

Authors review available literature on both disease-modifying and symptomatic pharmacological therapies for SCA3/MJD. Discussion is stratified into motor (ataxic and non-ataxic syndromes) and non-motor manifestations. Ongoing clinical trials and future perspectives are also discussed in the manuscript.

EXPERT OPINION

Symptomatic treatment is the mainstay of clinical care and should be tailored for each patient with SCA3/MJD. Management of ataxia is still a challenging task, but relief (at least partial) of dystonia, pain/cramps, fatigue, and sleep disorders is an achievable goal for many patients. Even though there are no disease-modifying treatments so far, recent advances in understanding the biology of disease and international collaborations of clinical researchers are now paving the way for a new era where more clinical trials will be available for this devastating disorder.

Electrophysiological Studies Support Utility of Positive Modulators of SK Channels for the Treatment of Spinocerebellar Ataxia Type 2

Spinocerebellar ataxia type 2 (SCA2) is an incurable hereditary disorder accompanied by cerebellar degeneration following ataxic symptoms. The causative gene for SCA2 is ATXN2. The ataxin-2 protein is involved in RNA metabolism; the polyQ expansion may interrupt ataxin-2 interaction with its molecular targets, thus representing a loss-of-function mutation. However, mutant ataxin-2 protein also displays the features of gain-of-function mutation since it forms the aggregates in SCA2 cells and also enhances the IP3-induced calcium release in affected neurons. The cerebellar Purkinje cells (PCs) are primarily affected in SCA2. Their tonic pacemaker activity is crucial for the proper cerebellar functioning. Disturbances in PC pacemaking are observed in many ataxic disorders. The abnormal intrinsic pacemaking was reported in mouse models of episodic ataxia type 2 (EA2), SCA1, SCA2, SCA3, SCA6, Huntington's disease (HD), and in some other murine models of the disorders associated with the cerebellar degeneration. In our studies using SCA2-58Q transgenic mice via cerebellar slice recording and in vivo recording from urethane-anesthetized mice and awake head-fixed mice, we have demonstrated the impaired firing frequency and irregularity of PCs in these mice. PC pacemaker activity is regulated by SK channels. The pharmacological activation of SK channels has demonstrated some promising results in the electrophysiological experiments on EA2, SCA1, SCA2, SCA3, SCA6, HD mice, and also on mutant CACNA1A mice. In our studies, we have reported that the SK activators CyPPA and NS309 converted bursting activity into tonic, while oral treatment with CyPPA and NS13001 significantly improved motor performance and PC morphology in SCA2 mice. The i.p. injections of chlorzoxazone (CHZ) during in vivo recording sessions converted bursting cells into tonic in anesthetized SCA2 mice. And, finally, long-term injections of CHZ recovered the precision of PC pacemaking activity in awake SCA2 mice and alleviated their motor decline. Thus, the SK activation can be used as a potential way to treat SCA2 and other diseases accompanied by cerebellar degeneration.

Use of Riluzole for the Treatment of Hereditary Ataxias: A Systematic Review

Ataxia is a constellation of symptoms that involves a lack of coordination, imbalance, and difficulty walking. Hereditary ataxia occurs when a person is born with defective genes, and this degenerative disorder may progress for several years. There is no effective cure for ataxia, so we need to search for new treatments. Recently, interest in riluzole in the treatment of ataxia has emerged. We conducted this systematic review to analyze the safety and efficacy of riluzole for treating hereditary ataxia in recent clinical trials. We conducted a systematic review using PubMed and Google Scholar as databases in search of this relationship. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) protocols to conduct this study. For inclusion criteria, we included full-text clinical trials on humans written in English and found three clinical trials. We excluded case reports, literature reviews, systematic reviews, and meta-analyses for this analysis. We aimed to evaluate the Scale for the Assessment and Rating of Ataxia (SARA) score, the International Cooperative Ataxia Rating Scale (ICARS) score, and the safety of the medication. Two out of the three clinical trials showed statistically significant clinical improvement in the ICARS and SARA scores, while the other trial did not show improvement in the clinical or radiological outcomes. The drug was safe in all clinical trials. Overall, the results of this analysis of riluzole for the treatment of hereditary ataxia are encouraging. Further clinical trials are needed to investigate the efficacy of riluzole on hereditary ataxia.

Differential Temporal Dynamics of Axial and Appendicular Ataxia in SCA3

Background

Disease severity in spinocerebellar ataxia type 3 (SCA3) is commonly defined by the Scale for the Assessment and Rating of Ataxia (SARA) sum score, but little is known about the contributions and progression patterns of individual items.

Objectives

To investigate the temporal dynamics of SARA item scores in SCA3 patients and evaluate if clinical and demographic factors are differentially associated with evolution of axial and appendicular ataxia.

Methods

In a prospective, multinational cohort study involving 11 European and 2 US sites, SARA scores were determined longitudinally in 223 SCA3 patients with a follow‐up assessment after 1 year.

Results

An increase in SARA score from 10 to 20 points was mainly driven by axial and speech items, with a markedly smaller contribution of appendicular items. Finger chase and nose‐finger test scores not only showed the lowest variability at baseline, but also the least deterioration at follow‐up. Compared with the full set of SARA items, omission of both tests would result in lower sample size requirements for therapeutic trials. Sex was associated with change in SARA sum score and appendicular, but not axial, subscore, with a significantly faster progression in men. Despite considerable interindividual variability, the average annual progression rate of SARA score was approximately three times higher in subjects with a disease duration over 10 years than in those within 10 years from onset.

Conclusion

Our findings provide evidence for a difference in temporal dynamics between axial and appendicular ataxia in SCA3 patients, which will help inform the design of clinical trials and development of new (etiology‐specific) outcome measures. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Consensus Paper: Strengths and Weaknesses of Animal Models of Spinocerebellar Ataxias and Their Clinical Implications

Spinocerebellar ataxias (SCAs) represent a large group of hereditary degenerative diseases of the nervous system, in particular the cerebellum, and other systems that manifest with a variety of progressive motor, cognitive, and behavioral deficits with the leading symptom of cerebellar ataxia. SCAs often lead to severe impairments of the patient's functioning, quality of life, and life expectancy. For SCAs, there are no proven effective pharmacotherapies that improve the symptoms or substantially delay disease progress, i.e., disease-modifying therapies. To study SCA pathogenesis and potential therapies, animal models have been widely used and are an essential part of pre-clinical research. They mainly include mice, but also other vertebrates and invertebrates. Each animal model has its strengths and weaknesses arising from model animal species, type of genetic manipulation, and similarity to human diseases. The types of murine and non-murine models of SCAs, their contribution to the investigation of SCA pathogenesis, pathological phenotype, and therapeutic approaches including their advantages and disadvantages are reviewed in this paper. There is a consensus among the panel of experts that (1) animal models represent valuable tools to improve our understanding of SCAs and discover and assess novel therapies for this group of neurological disorders characterized by diverse mechanisms and differential degenerative progressions, (2) thorough phenotypic assessment of individual animal models is required for studies addressing therapeutic approaches, (3) comparative studies are needed to bring pre-clinical research closer to clinical trials, and (4) mouse models complement cellular and invertebrate models which remain limited in terms of clinical translation for complex neurological disorders such as SCAs.

Recessive cerebellar and afferent ataxias - clinical challenges and future directions

Cerebellar and afferent ataxias present with a characteristic gait disorder that reflects cerebellar motor dysfunction and sensory loss. These disorders are a diagnostic challenge for clinicians because of the large number of acquired and inherited diseases that cause cerebellar and sensory neuron damage. Among such conditions that are recessively inherited, Friedreich ataxia and RFC1-associated cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) include the characteristic clinical, neuropathological and imaging features of ganglionopathies, a distinctive non-length-dependent type of sensory involvement. In this Review, we discuss the typical and atypical phenotypes of Friedreich ataxia and CANVAS, along with the features of other recessive ataxias that present with a ganglionopathy or polyneuropathy, with an emphasis on recently described clinical features, natural history and genotype-phenotype correlations. We review the main developments in understanding the complex pathology that affects the sensory neurons and cerebellum, which seem to be most vulnerable to disorders that affect mitochondrial function and DNA repair mechanisms. Finally, we discuss disease-modifying therapeutic advances in Friedreich ataxia, highlighting the most promising candidate molecules and lessons learned from previous clinical trials.

Quantitative evaluation of upper limb ataxia in spinocerebellar ataxias

Objective

To quantitatively evaluate upper limb ataxia using a novel pen‐like sensor device in patients with spinocerebellar ataxia (SCA) and to assess its validity, reliability, and sensitivity to disease progression.

Methods

We designed a cross‐sectional and longitudinal study of patients with SCA and healthy controls. Upper limb ataxia was evaluated using a device that measures the three‐dimensional position every 10 msec. Participants were instructed to move a pen‐like part of the device iteratively between two buttons. We evaluated the time, length, velocity, and variation coefficient of the stroke, and calculated the distortion index using the mean squared error. The following scales were also evaluated: Scale for the Assessment and Rating of Ataxia (SARA), the International Cooperative Ataxia Rating Scale (ICARS), and the nine‐hole pegboard test. Subjects were followed 12 months after the baseline evaluation.

Results

A total of 42 patients with SCA and 33 healthy controls were enrolled and evaluated. For all ataxia indices measured using the device there were significant differences between healthy controls and patients with SCA. Among the ataxia indices, the distortion index showed the strongest correlation with the SARA and ICARS upper limb score (Pearson's r = 0.647 and 0.722, respectively). Test–retest reliability was high for most of the ataxia indices. In the longitudinal analysis, the distortion index showed high standardized response mean and adjusted effect size, regardless of disease severity.

Interpretation

Our study demonstrated that the distortion index is a reliable functional marker that is sensitive to longitudinal change in patients with SCA.

Current and Emerging Treatment Modalities for Spinocerebellar Ataxias

INTRODUCTION

Spinocerebellar ataxias (SCA) are a group of rare neurodegenerative diseases that dramatically affect the lives of affected individuals and their families. Despite having a clear understanding of SCA's etiology, there are no current symptomatic or neuroprotective treatments approved by the FDA.

AREAS COVERED

Research efforts have greatly expanded the possibilities for potential treatments, including both pharmacological and non-pharmacological interventions. Great attention is also being given to novel therapeutics based in gene therapy, neurostimulation, and molecular targeting. This review article will address the current advances in the treatment of SCA and what potential interventions are on the horizon.

EXPERT OPINION

SCA is a highly complex and multifaceted disease family with the majority of research emphasizing symptomatic pharmacologic therapies. As pre-clinical trials for SCA and clinical trials for other neurodegenerative conditions illuminate the efficacy of disease modifying therapies such as AAV-mediated gene therapy and ASOs, the potential for addressing SCA at the pre-symptomatic stage is increasingly promising.

Riluzole, a glutamate modulator, slows cerebral glucose metabolism decline in patients with Alzheimer's disease

Dysregulation of glutamatergic neural circuits has been implicated in a cycle of toxicity, believed among the neurobiological underpinning of Alzheimer's disease. Previously, we reported preclinical evidence that the glutamate modulator riluzole, which is FDA approved for the treatment of amyotrophic lateral sclerosis, has potential benefits on cognition, structural and molecular markers of ageing and Alzheimer's disease. The objective of this study was to evaluate in a pilot clinical trial, using neuroimaging biomarkers, the potential efficacy and safety of riluzole in patients with Alzheimer's disease as compared to placebo. A 6-month phase 2 double-blind, randomized, placebo-controlled study was conducted at two sites. Participants consisted of males and females, 50 to 95 years of age, with a clinical diagnosis of probable Alzheimer's disease, and Mini-Mental State Examination between 19 and 27. Ninety-four participants were screened, 50 participants who met inclusion criteria were randomly assigned to receive 50 mg riluzole (n = 26) or placebo (n = 24) twice a day. Twenty-two riluzole-treated and 20 placebo participants completed the study. Primary end points were baseline to 6 months changes in (i) cerebral glucose metabolism as measured with fluorodeoxyglucose-PET in prespecified regions of interest (hippocampus, posterior cingulate, precuneus, lateral temporal, inferior parietal, frontal); and (ii) changes in posterior cingulate levels of the neuronal viability marker N-acetylaspartate as measured with in vivo proton magnetic resonance spectroscopy. Secondary outcome measures were neuropsychological testing for correlation with neuroimaging biomarkers and in vivo measures of glutamate in posterior cingulate measured with magnetic resonance spectroscopy as a potential marker of target engagement. Measures of cerebral glucose metabolism, a well-established Alzheimer's disease biomarker and predictor of disease progression, declined significantly less in several prespecified regions of interest with the most robust effect in posterior cingulate, and effects in precuneus, lateral temporal, right hippocampus and frontal cortex in riluzole-treated participants in comparison to the placebo group. No group effect was found in measures of N-acetylaspartate levels. A positive correlation was observed between cognitive measures and regional cerebral glucose metabolism. A group × visit interaction was observed in glutamate levels in posterior cingulate, potentially suggesting engagement of glutamatergic system by riluzole. In vivo glutamate levels positively correlated with cognitive performance. These findings support our main primary hypothesis that cerebral glucose metabolism would be better preserved in the riluzole-treated group than in the placebo group and provide a rationale for more powered, longer duration studies of riluzole as a potential intervention for Alzheimer's disease.

Safety and Efficacy of Acetyl-DL-Leucine in Certain Types of Cerebellar Ataxia: The ALCAT Randomized Clinical Crossover Trial

IMPORTANCE

Cerebellar ataxia is a neurodegenerative disease impairing motor function characterized by ataxia of stance, gait, speech, and fine motor disturbances.

OBJECTIVE

To investigate the efficacy, safety, and tolerability of the modified essential amino acid acetyl-DL-leucine in treating patients who have cerebellar ataxia.

DESIGN, SETTING, AND PARTICIPANTS

The Acetyl-DL-leucine on Cerebellar Ataxia (ALCAT) trial was an investigator-initiated, multicenter, double-blind, randomized, placebo-controlled, clinical crossover trial. The study was conducted at 7 university hospitals in Germany and Austria between January 25, 2016, and February 17, 2017. Patients were aged at least 18 years and diagnosed with cerebellar ataxia of hereditary (suspected or genetically confirmed) or nonhereditary or unknown type presenting with a total score of at least 3 points on the Scale for the Assessment and Rating of Ataxia (SARA). Statistical analysis was performed from April 2018 to June 2018 and January 2020 to March 2020.

INTERVENTIONS

Patients were randomly assigned (1:1) to receive acetyl-DL-leucine orally (5 g per day after 2 weeks up-titration) followed by a matched placebo, each for 6 weeks, separated by a 4-week washout, or vice versa. The randomization was done via a web-based, permuted block-wise randomization list (block size, 2) that was stratified by disease subtype (hereditary vs nonhereditary or unknown) and site.

MAIN OUTCOMES AND MEASURES

Primary efficacy outcome was the absolute change of SARA total score from (period-dependent) baseline to week 6.

RESULTS

Among 108 patients who were randomly assigned to sequence groups (54 patients each), 55 (50.9%) were female; the mean (SD) age was 54.8 (14.4) years; and the mean (SD) SARA total score was 13.33 (5.57) points. The full analysis set included 105 patients (80 patients with hereditary, 25 with nonhereditary or unknown cerebellar ataxia). There was no evidence of a difference in the mean absolute change from baseline to week 6 in SARA total scores between both treatments (mean treatment difference: 0.23 points [95% CI, -0.40 to 0.85 points]).

CONCLUSIONS AND RELEVANCE

In this large multicenter, double-blind, randomized, placebo-controlled clinical crossover trial, acetyl-DL-leucine in the investigated dosage and treatment duration was not superior to placebo for the symptomatic treatment of certain types of ataxia. The drug was well tolerated; and ALCAT yielded valuable information about the duration of treatment periods and the role of placebo response in cerebellar ataxia. These findings suggest that further symptom-oriented trials are needed for evaluating the long-term effects of acetyl-DL-leucine for well-defined subgroups of cerebellar ataxia.

TRIAL REGISTRATION

EudraCT 2015-000460-34.

Pharmacological and non-pharmacological management of spinocerebellar ataxia: A systematic review

Spinocerebellar ataxias (SCA) comprise a rare, genetic subgroup within the degenerative ataxias and are dominantly inherited, with up to 48 recognized genetic subtypes. While an updated review on the management of degenerative ataxia is published recently, an evidence-based review focussed on the management of SCA is lacking. Here, we reviewed the pharmacological and non-pharmacological management of SCA by conducting a systematic review on Medline Ovid and Scopus. Of 29,284 studies identified, 47 studies (pharmacological: n = 25; non-pharmacological: n = 22) that predominantly involved SCA patients were included. Twenty studies had a high risk of bias based on the Cochrane's Collaboration risk of bias tool. As per the European Federation of Neurological Societies 2004 guideline for therapeutic intervention, the remaining 27 studies were of Class I (n = 4) and Class II (n = 23) evidence. Only two therapies had Level A recommendations for the management of ataxia symptoms: riluzole and immediate in-patient neurorehabilitation. Ten therapies had Level B recommendations for managing ataxia symptoms and require further investigations with better study design. These include high dose valproate acid, branched-chain amino acid, intravenous trehalose; restorative rehabilitation using cycling regimen and videogame; and cerebellar stimulations using transcranial direct current stimulation and transcranial magnetic stimulation. Lithium and coaching on psychological adjustment received Level B recommendation for depressive symptoms and quality of life, respectively. Heterogeneous study designs, different genotypes, and non-standardized clinical measures alongside short duration and small sample sizes may hamper meaningful clinical translation. Therefore, rating of recommendations only serve as points of reference.

Association of the Level of Neurofilament Light With Disease Severity in Patients With Spinocerebellar Ataxia Type 2

BACKGROUND AND OBJECTIVES

Few biochemical markers have been identified in spinocerebellar ataxia type 2 (SCA2). This study aimed to determine the levels of neurofilament light (NfL) in patients with SCA2 and identify whether they were associated with disease severity.

METHODS

Participants were recruited from one medical center in China, and individuals with SCA2 were genetically diagnosed. NfL levels were assessed using the single molecule array method. Disease severity was evaluated using the Scale for the Assessment and Rating of Ataxia (SARA), the International Cooperative Ataxia Rating Scale (ICARS), and the Inventory of Non-Ataxia Symptoms (INAS). Cerebellum and brainstem volumes were calculated using neuroimaging measurements. We used Pearson's correlation and partial correlation for correlation analyses.

RESULTS

Forty-nine manifest patients with SCA2, 10 preclinical individuals with SCA2 and 92 controls were enrolled. A high consistency was identified between serum and CSF NfL (r = 0.868, p < 0.0001). In individuals with SCA2, levels of serum NfL were associated with disease severity (SARA, r = 0.425, p = 0.003; ICARS, r = 0.383, p = 0.009; INAS, r = 0.390, p = 0.007; cerebellum volume, r = - 0.393, p = 0.024) after adjustment for age. NfL levels were higher close to the expected age of onset in preclinical individuals with SCA2 (R ² = 0.43, p = 0.04).

DISCUSSION

Levels of serum NfL were correlated with disease intensity in individuals with SCA2, and were higher close to the estimated age of onset in preclinical SCA2. Therefore, NfL is a potential serum biomarker of disease severity in SCA2.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that elevated NfL levels are associated with disease severity in individuals with SCA2.

Blood Neurofilament Light Chain in Genetic Ataxia: A Meta-Analysis

BACKGROUND

No comprehensive meta-analysis has ever been performed to assess the value of neurofilament light chain (NfL) as a biomarker in genetic ataxia.

OBJECTIVE

We conducted a meta-analysis to summarize NfL concentration and evaluate its utility as a biomarker in genetic ataxia.

METHODS

Studies were included if they reported NfL concentration of genetic ataxia. We used log (mean ± SD) NfL to describe mean raw value of NfL. The effect size of NfL between genetic ataxia and healthy controls (HC) was expressed by mean difference. Correlation between NfL and disease severity was calculated.

RESULTS

We identified 11 studies of 624 HC and 1006 patients, here referred to as spinocerebellar ataxia (SCA1, 2, 3, 6, and 7), Friedreich ataxia (FRDA), and ataxia telangiectasia (A-T). The concentration of blood NfL (bNfL) elevated with proximity to expected onset, and progressively increased from asymptomatic to preclinical to clinical stage in SCA3. Compared with HC, bNfL levels were significantly higher in SCA1, 2, 3, and 7, FRDA, as well as A-T, and the difference increased with the advancing disease in SCA3. bNfL levels correlated with disease severity in SCA3. There was a significant correlation between bNfL and longitudinal progression in SCA3. Additionally, bNfL increased with age in HC, yet this is probably masked by higher disease-related effects on bNfL in genetic ataxia.

CONCLUSIONS

bNfL can be used as a potential biomarker to predict disease onset, severity, and progression of genetic ataxia. Reference-value setting of bNfL should be divided according to age. © 2021 International Parkinson and Movement Disorder Society.

Therapeutic Potential of Sodium Channel Blockers as a Targeted Therapy Approach in KCNA1-Associated Episodic Ataxia and a Comprehensive Review of the Literature

Introduction: Among genetic paroxysmal movement disorders, variants in ion channel coding genes constitute a major subgroup. Loss-of-function (LOF) variants in KCNA1, the gene coding for KV1.1 channels, are associated with episodic ataxia type 1 (EA1), characterized by seconds to minutes-lasting attacks including gait incoordination, limb ataxia, truncal instability, dysarthria, nystagmus, tremor, and occasionally seizures, but also persistent neuromuscular symptoms like myokymia or neuromyotonia. Standard treatment has not yet been developed, and different treatment efforts need to be systematically evaluated. Objective and Methods: Personalized therapeutic regimens tailored to disease-causing pathophysiological mechanisms may offer the specificity required to overcome limitations in therapy. Toward this aim, we (i) reviewed all available clinical reports on treatment response and functional consequences of KCNA1 variants causing EA1, (ii) examined the potential effects on neuronal excitability of all variants using a single compartment conductance-based model and set out to assess the potential of two sodium channel blockers (SCBs: carbamazepine and riluzole) to restore the identified underlying pathophysiological effects of KV1.1 channels, and (iii) provide a comprehensive review of the literature considering all types of episodic ataxia. Results: Reviewing the treatment efforts of EA1 patients revealed moderate response to acetazolamide and exhibited the strength of SCBs, especially carbamazepine, in the treatment of EA1 patients. Biophysical dysfunction of KV1.1 channels is typically based on depolarizing shifts of steady-state activation, leading to an LOF of KCNA1 variant channels. Our model predicts a lowered rheobase and an increase of the firing rate on a neuronal level. The estimated concentration dependent effects of carbamazepine and riluzole could partially restore the altered gating properties of dysfunctional variant channels. Conclusion: These data strengthen the potential of SCBs to contribute to functional compensation of dysfunctional KV1.1 channels. We propose riluzole as a new drug repurposing candidate and highlight the role of personalized approaches to develop standard care for EA1 patients. These results could have implications for clinical practice in future and highlight the need for the development of individualized and targeted therapies for episodic ataxia and genetic paroxysmal disorders in general.

Safety and Outcomes of Dentate Nucleus Deep Brain Stimulation for Cerebellar Ataxia

Cerebellar symptoms remain orphan of treatment options despite being prevalent and incapacitating. Investigate whether dentate nucleus deep brain stimulation (DN DBS) is safe and leads to improvements in cerebellar symptoms when compared to sham stimulation. This randomized double-blind crossover pilot trial enrolled five patients with spinocerebellar ataxia type 3 or post-lesion ataxia. Active or sham phases were randomly performed three months apart. The primary outcome was ataxia improvement as measured by the Scale for the Assessment and Rating of Ataxia (SARA) after the active compared to the sham period. Secondary outcome measures included safety and tolerability, the Fahn-Tolosa-Marin Tremor Rating Scale (FTMRS), quality of life measurements, and patients' global impression of change. The effects on ataxia were numerically better in four out of five patients after active versus sham stimulation. The composite SARA score did not change after comparing active to sham stimulation (8.6 ± 3.6 versus 10.1 ± 4.1; p = 0.223). The FTMRS showed significant improvement after active stimulation versus sham (18.0 ± 17.2 versus 22.2 ± 19.5; p = 0.039) as did patients' global impression of change (p = 0.038). The quality of life was not modified by stimulation (p = 0.337). DN DBS was well tolerated without serious adverse events. One patient had the electrode repositioned. DN DBS is a safe and well tolerated procedure that is effective in alleviating cerebellar tremor. In this small cohort of ataxic patients, DN DBS did not achieve statistical significance for ataxia improvement.

Effectiveness of Robotic Exoskeleton-Assisted Gait Training in Spinocerebellar Ataxia: A Case Report

Spinocerebellar ataxia (SCA) is a hereditary neurodegenerative disorder that presents as ataxia. Due to the decline in balance, patients with SCA often experience restricted mobility and a decreased quality of life. Thus, many studies have emphasized the importance of physiotherapies, including gait training, in SCA patients. However, few studies have examined the effectiveness of robotic gait training in SCA. Here, we report the therapeutic outcomes of exoskeleton-assisted gait training in a patient with SCA. A 23-year-old woman with SCA participated in a gait training program using a powered lower-limb robotic exoskeleton, ANGELLEGS. The 8-week training program consisted of standing training, weight-shifting exercises, and gait training. Several measures of general function, balance, gait, and cardiopulmonary function were applied before, after, and 4 weeks after the program. After the program, overall improvements were found on scales measuring balance and gait function, and these improvements remained at 4 weeks after the program. Cardiopulmonary function was also improved 4 weeks after the program. Robotic exoskeleton gait training can be a beneficial option for training balance, gait, and cardiopulmonary function in SCA.

Serum neurofilament light chain as a severity marker for spinocerebellar ataxia

Since the serum neurofilament light (NfL) chain is known as a promising biomarker in neurodegenerative diseases, we aimed to evaluate serum NfL as a biomarker indicating neuronal damage in autosomal-dominant (AD) spinocerebellar ataxia (SCA). We reviewed patients diagnosed with AD SCA in the outpatient clinic of Seoul National University Hospital's (SNUH) Department of Neurology between May and August of 2019. We reviewed the demographic data, clinical characteristics, Scale for the Assessment and Rating of Ataxia (SARA) score, and brain magnetic resonance imaging (MRI) scans. The serum NfL was measured by electrochemiluminescence (ECL) immunoassay. Forty-nine patients with AD SCA were reviewed and their serum NfL level was determined. The median serum NfL level (109.5 pg/mL) was higher than control (41.1 pg/mL) (p-value < 0.001). Among the AD SCA patients, there was a positive correlation between the serum NfL level and the trinucleotide repeat number (r = 0.47, p-value = 0.001), disease duration (r = 0.35, p-value = 0.019), disease duration/age × trinucleotide repeat number (r = 0.330, p-value = 0.021), and SARA score (n = 33; r = 0.37, p-value = 0.033). This study shows that serum NfL is elevated in AD SCA patients and correlates with clinical severity.

Human Induced Pluripotent Stem Cell-Based Modelling of Spinocerebellar Ataxias

Abstract

Dominant spinocerebellar ataxias (SCAs) constitute a large group of phenotypically and genetically heterogeneous disorders that mainly present with dysfunction of the cerebellum as their main hallmark. Although animal and cell models have been highly instrumental for our current insight into the underlying disease mechanisms of these neurodegenerative disorders, they do not offer the full human genetic and physiological context. The advent of human induced pluripotent stem cells (hiPSCs) and protocols to differentiate these into essentially every cell type allows us to closely model SCAs in a human context. In this review, we systematically summarize recent findings from studies using hiPSC-based modelling of SCAs, and discuss what knowledge has been gained from these studies. We conclude that hiPSC-based models are a powerful tool for modelling SCAs as they contributed to new mechanistic insights and have the potential to serve the development of genetic therapies. However, the use of standardized methods and multiple clones of isogenic lines are essential to increase validity and reproducibility of the insights gained.

Graphical Abstract

Spinocerebellar ataxia clinical trials: opportunities and challenges

The spinocerebellar ataxias (SCAs) are a group of dominantly inherited diseases that share the defining feature of progressive cerebellar ataxia. The disease process, however, is not confined to the cerebellum; other areas of the brain, in particular, the brainstem, are also affected, resulting in a high burden of morbidity and mortality. Currently, there are no disease‐modifying treatments for the SCAs, but preclinical research has led to the development of therapeutic agents ripe for testing in patients. Unfortunately, due to the rarity of these diseases and their slow and variable progression, there are substantial hurdles to overcome in conducting clinical trials. While the epidemiological features of the SCAs are immutable, the feasibility of conducting clinical trials is being addressed through a combination of strategies. These include improvements in clinical outcome measures, the identification of imaging and fluid biomarkers, and innovations in clinical trial design. In this review, we highlight current challenges in initiating clinical trials for the SCAs and also discuss pathways for researchers and clinicians to mitigate these challenges and harness opportunities for clinical trial development.

Phase I Single-Blinded Randomized Controlled Trial Comparing Balance and Aerobic Training in Degenerative Cerebellar Disease

INTRODUCTION

Primary deficits in individuals with cerebellar degeneration include ataxia, unstable gait, and incoordination. Balance training is routinely recommended to improve function whereas little is known regarding aerobic training.

OBJECTIVE

To determine the feasibility of conducting a randomized trial comparing balance and aerobic training in individuals with cerebellar degeneration.

DESIGN

Assessor blinded randomized control phase I trial.

SETTING

Assessments in medical center, home training.

PARTICIPANTS

Twenty participants with cerebellar degeneration were randomized to home balance or aerobic training.

INTERVENTION

Aerobic training consisted of 4 weeks of stationary bicycle training, five times per week for 30-minute sessions. Home balance training consisted of performing the same duration of easy, moderate, and/or hard exercises.

OUTCOME MEASURES

Scale for the Assessment and Rating of Ataxia (SARA), maximal oxygen consumption (VO2 max), Dynamic Gait Index, Timed Up and Go, gait speed.

RESULTS

All 20 participants completed assigned training with no major adverse events. Seven of each group attained target training duration, frequency, and intensity. Although both groups had significant improvements in ataxia severity, balance, and gait measures, there were greater improvements in individuals who performed aerobic training in ataxia severity and maximal oxygen consumption when compared to balance training. The effect size for these outcome measures was determined to be large, indicating a phase II trial comparing the benefits of aerobic and balance training was feasible and required 26 participants per group. Improvements in SARA score and VO2 max remained in the aerobic training group at 3 months posttraining, but these improvements were trending back to baseline. In contrast, all balance group measures for pretraining and 3 months posttraining were statistically similar.

CONCLUSIONS

A phase II trial comparing balance and aerobic training in individuals with cerebellar degeneration is feasible. Benefits trended back toward baseline after training stopped, although benefits of longer duration exercise programs still need to be determined.

[Adult-onset ataxias]

Adult-onset ataxias are clinically and etiologically heterogeneous disorders affecting the cerebellum and its afferent and efferent connections. Early symptoms are usually a progressive ataxia of gait and stance, followed by limb ataxia, cerebellar dysarthria and oculomotor disturbances. In addition, various neurological and non-neurological symptoms may occur. Hereditary, acquired, and sporadic degenerative ataxias are distinguished. A detailed medical history and clinical examination as well as cranial magnetic resonance imaging are essential for the diagnostic work-up; however, specific biochemical or genetic tests are often required to make a definitive diagnosis. Besides rehabilitative therapies, specific drugs or dietary recommendations are available for some types of ataxia. An early and precise diagnosis is important to avoid redundant diagnostics and for counselling of patients and their relatives.

Hydrophobic interactions between the HA helix and S4-S5 linker modulate apparent Ca2+ sensitivity of SK2 channels

AIM

Small-conductance Ca2+ -activated potassium (SK) channels are activated exclusively by increases in intracellular Ca2+ that binds to calmodulin constitutively associated with the channel. Wild-type SK2 channels are activated by Ca2+ with an EC50 value of ~0.3 μmol/L. Here, we investigate hydrophobic interactions between the HA helix and the S4-S5 linker as a major determinant of channel apparent Ca2+ sensitivity.

METHODS

Site-directed mutagenesis, electrophysiological recordings and molecular dynamic (MD) simulations were utilized.

RESULTS

Mutations that decrease hydrophobicity at the HA-S4-S5 interface lead to Ca2+ hyposensitivity of SK2 channels. Mutations that increase hydrophobicity result in hypersensitivity to Ca2+ . The Ca2+ hypersensitivity of the V407F mutant relies on the interaction of the cognate phenylalanine with the S4-S5 linker in the SK2 channel. Replacing the S4-S5 linker of the SK2 channel with the S4-S5 linker of the SK4 channel results in loss of the hypersensitivity caused by V407F. This difference between the S4-S5 linkers of SK2 and SK4 channels can be partially attributed to I295 equivalent to a valine in the SK4 channel. A N293A mutation in the S4-S5 linker also increases hydrophobicity at the HA-S4-S5 interface and elevates the channel apparent Ca2+ sensitivity. The double N293A/V407F mutations generate a highly Ca2+ sensitive channel, with an EC50 of 0.02 μmol/L. The MD simulations of this double-mutant channel revealed a larger channel cytoplasmic gate.

CONCLUSION

The electrophysiological data and MD simulations collectively suggest a crucial role of the interactions between the HA helix and S4-S5 linker in the apparent Ca2+ sensitivity of SK2 channels.

Investigating the Clinical Significance and Research Discrepancies of Balance Training in Degenerative Cerebellar Disease: A Systematic Review

OBJECTIVE

The aims of this study were to understand the clinical significance of balance training in degenerative cerebellar disease and to analyze inconsistencies among published data.

DESIGN

Five databases were searched from inception to October 8, 2019. Cochrane guidelines informed review methods, and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. The Australian National Health and Medical Research Council Evidence Hierarchy, PEDro scale, and Joanna Briggs Institute Critical Appraisal Tools were used to evaluate methodological quality. Outcome measures examined included ataxia severity, gait speed, and balance.

RESULTS

Fourteen articles were identified that met inclusion criteria. The quality of evidence was moderate to high, with recent articles being of higher quality. Nine of 12 articles showed statistical improvements in ataxia severity (reduction ranging from 1.4 to 2.8 in the Scale for the Assessment and Rating of Ataxia points), three of eight showed statistical improvements in gait speed (average increase of 0.1 m/sec), and six of nine showed improvements in balance measures (average increase of 1.75 in Berg Balance Scale and 1.5 in Dynamic Gait Index).

CONCLUSION

Most studies showed statistical and clinically significant ataxia severity improvements in subjects who performed balance training. The amount of balance challenge and frequency of training were important factors in determining the extent of training benefit. Gait speed may also improve if walking exercises are included in the balance training, but more studies need to be conducted. Balance measures statistically improved with training, but these improvements did not meet criteria for clinical significance.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Describe the cause(s) of discrepancies in the literature regarding the benefits of balance training in degenerative cerebellar disease; (2) Determine if benefits from balance training are clinically meaningful for individuals with cerebellar degeneration; and (3) Understand the best practices gleaned from the current literature regarding balance training for these diseases.

LEVEL

Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Emerging therapies in Friedreich's Ataxia

INTRODUCTION

Friedreich's ataxia (FRDA) is a progressive, neurodegenerative disease that results in gait and limb ataxia, diabetes, cardiac hypertrophy, and scoliosis. At the cellular level, FRDA results in the deficiency of frataxin, a mitochondrial protein that plays a vital role in iron homeostasis and amelioration of oxidative stress. No cure currently exists for FRDA, but exciting therapeutic developments which target different parts of the pathological cascade are on the horizon.

AREAS COVERED

Areas covered include past and emerging therapies for FRDA, including antioxidants and mitochondrial-related agents, nuclear factor erythroid-derived 2-related factor 2 (Nrf2) activators, deuterated polyunsaturated fatty acids, iron chelators, histone deacetylase (HDAC) inhibitors, trans-activator of transcription (TAT)-frataxin, interferon gamma (IFNγ), erythropoietin, resveratrol, gene therapy, and anti-sense oligonucleotides (ASOs), among others.

EXPERT OPINION

While drug discovery has been challenging, new and exciting prospective treatments for FRDA are currently on the horizon, including pharmaceutical agents and gene therapy. Agents that enhance mitochondrial function, such as Nrf2 activators, dPUFAs and catalytic antioxidants, as well as novel methods of frataxin augmentation and genetic modulation will hopefully provide treatment for this devastating disease.

Placebo response in degenerative cerebellar ataxias: a descriptive review of randomized, placebo-controlled trials

Placebo response in degenerative cerebellar ataxias (CAs) has never been studied despite the large number of randomized controlled trials (RCTs) that have been conducted. In this descriptive review, we aimed to examine the placebo response in patients with CAs. We performed a literature search on PubMed for RCTs on CAs that were published from 1977 to January 2020 and collected data on the changes from the baseline to the endpoint on various objective ataxia-associated clinical rating scales. We reviewed 56 clinical trials, finally including 35 parallel-group studies and excluding 21 cross-over studies. The included studies were categorized as follows: (1) studies showing significant improvements in one or more ataxia scales in the placebo groups (n = 3); (2) studies reporting individual placebo responders with improvements in one or more ataxia scales in the placebo groups (n = 5)-the overall proportion of placebo responders was 31.9%; (3) studies showing mean changes in the direction of improvement in at least one ataxia scale in the placebo groups, though not statistically significant (n = 19); (4) studies showing no placebo response in any of the ataxia scales in the placebo groups (n = 4); (5) studies where data on the placebo groups were unavailable (n = 9). This review demonstrated the placebo response in patients with CAs on various objective ataxia scales. Our study emphasizes that the placebo response should be considered when designing, analyzing, and interpreting clinical trials and in clinical practice in CA patients.