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Purpose: Although approximately 45% of adults with Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) are permanent wheelchair users, this sub population has been less studied. The purpose of this study was to document wheelchair mobility, motor performance, and participation in a cohort of adult wheelchair users with ARSACS., Methods: We recruited 36 manual and powered wheelchair users with ARSACS, aged between 34 and 64 years, for this cross-sectional study. Participants completed measures regarding wheelchair mobility (Wheelchair Skills Test Questionnaire [WST-Q-F], Wheelchair Use Confidence Scale [WheelCon-F] and Wheelchair Outcome Measure [WhOM-F]), motor performance (Scale for the Assessment and Rating of Ataxia [SARA], Disease Severity Index for adults with ARSACS [DSI-ARSACS], Upper Extremity Performance Test for the Elderly [TEMPA], Standardised Finger to Nose Test [SFNT], grip strength, pinch strength, Lower Extremity Motor Coordination Test [LEMOCOT], Berg Balance Scale [BBS], Timed Up and Go [TUG] and 10-meter Walk Test [10mWT]), and participation (Barthel Index, LSA-F and LIFE-H). Results were compared between age groups (≤49 years and ≥50 years), types of wheelchair used, and available reference values. Correlations were computed between wheelchair mobility, upper limb function, and participation., Results: Participants presented limitations regarding wheelchair skills, motor performance, and participation in daily activities. Despite preserved upper limb strength, wheelchair skills, upper and lower limb coordination, standing balance, and functional independence were generally more impaired after 50 years of age and among powered wheelchair users. Significant moderate correlations were found between wheelchair skills and self-efficacy, upper limb strength and coordination, and participation in daily and social activities., Conclusions: This study provided the first data sets describing specific characteristics of manual and powered wheelchair users with ARSACS. It supports a need to offer wheelchair skills training interventions to adults with ARSACS, which could increase their daily and social participation.IMPLICATIONS FOR REHABILITATIONAdult wheelchair users with ARSACS present with limited wheelchair skills, significantly impaired motor performance, and reduced participation that generally decreases with age. This profile may serve as comparative data for clinicians to anticipate disease progression.This study provides the first data on distinguishing characteristics between PWC users and MWC users with ARSACS. The main characteristics of PWC users include more severe functional limitations and motor impairments, as well as limited grip strength that contrasts with the general preservation of this function among other adults with ARSACS.There is a need to offer and evaluate wheelchair skills training interventions in the future for adults with ARSACS. The general preservation of grip and pinch strength observed in this population suggests a potential for improvement. Considering the associations found between wheelchair mobility and participation, such interventions may increase users' daily and social participation.

Background: The Scale for the Assessment and Rating of Ataxia (SARA) is a commonly used scale measuring the severity of cerebellar ataxia and is a candidate for outcome measurement in foreseeable clinical trials in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS). Documenting its psychometric properties in this population will accelerate clinical trial readiness. The objectives of this study were to document the content and construct validity, the internal consistency, and to explore the 2-year responsiveness and the 4-year interpretability of the SARA in ARSACS., Methods: The first phase of the study consisted of an international Delphi survey to document the content validity. The second phase consisted of a methodological study from the secondary analysis of a longitudinal study to document the construct validity in 69 participants. Responsiveness to change and interpretability of the SARA was explored among a sub-sample of participants (n = 32 and n = 16, respectively)., Results: The SARA demonstrates adequate content validity with possible influence of pyramidal and/or neuropathic involvement. It demonstrates excellent construct validity (r s  = 0.77-0.95) and internal consistency (Cronbach's α = 0.89). The responsiveness to change was not significant, and the interpretation of change score increased by 1.9 ± 2.5 falling below the minimal detectable change threshold of 3.06., Conclusions: The SARA has shown evidences of adequate content validity and excellent construct validity in ARSACS. Responsiveness to change and interpretability will need to be further documented among a larger sample over a longer period of time., (Copyright © 2020. Published by Elsevier B.V.)

Objective: To develop a disease-specific severity index for adults with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) (DSI-ARSACS) that considers the 3 components (pyramidal, cerebellar, neuropathic) of the disease, and to document its content validity, internal consistency, and construct validity., Methods: The Beta DSI-ARSACS (17 items) was developed based on literature review and expert inputs and then administered to 26 participants. Items reduction was based on Cronbach α and desirable criteria. Performance measures were administered to assess the construct validity of the final version of the DSI-ARSACS., Results: The final DSI-ARSACS have 8 items that can be easily performed during usual medical follow-up. The mean score was 19.6 ± 8.1 (range 6.0-35.5) and the Cronbach α was 0.912. The DSI-ARSACS score increased with disease stage and age ( p ≤ 0.001) and was closely correlated with other measures assessing similar construct (9-Hole Peg Test, 10-Meter Walk Test, Scale for the Assessment and Rating of Ataxia, Berg Balance Scale, Barthel Index) ( r s = 0.75-0.95, p < 0.01). A moderate but not significant correlation was found with the 6-Minute Walk test ( r s = -0.611, p = 0.108)., Conclusions: The DSI-ARSACS is a valid measure of disease severity for the adult ARSACS population that is able to distinguish between patients with different clinical profiles. Further documentation of metrologic properties is necessary, but these first results are promising., (© 2019 American Academy of Neurology.)

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS [MIM 270550]) is an early-onset neurodegenerative disorder caused by mutations in the SACS gene. Over 200 SACS mutations have been identified. Most mutations lead to a complete loss of a sacsin, a large 520 kD protein, although some missense mutations are associated with low levels of sacsin expression. We previously showed that Sacs knock-out mice demonstrate early-onset ataxic phenotype with neurofilament bundling in many neuronal populations. To determine if the preservation of some mutated sacsin protein resulted in the same cellular and behavioral alterations, we generated mice expressing an R272C missense mutation, a homozygote mutation found in some affected patients. Though Sacs R272C mice express 21% of wild type brain sacsin and sacsin is found in many neurons, they display similar abnormalities to Sacs knock-out mice, including the development of an ataxic phenotype, reduced Purkinje cell firing rates, and somatodendritic neurofilament bundles in Purkinje cells and other neurons. Together our results support that Sacs missense mutation largely lead to loss of sacsin function.

Objective: This paper introduces a novel assessment tool to provide clinicians with quantitative and more objective measures of upper limb coordination in patients suffering from Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS). The Virtual Peg Insertion Test (VPIT) involves manipulating an instrumented handle in order to move nine pegs into nine holes displayed in a virtual environment. The main outcome measures were the number of zero-crossings of the hand acceleration vector, as a measure of movement coordination and the total time required to complete the insertion of the nine pegs, as a measure of overall upper limb performance., Results: 8\9 patients with ARSACS were able to complete five repetitions with the VPIT. Patients were found to be significantly less coordinated and slower than age-matched healthy subjects (p<0.01). Performance of ARSACS patients was positively correlated with the Nine-Hole Peg Test (r=0.85, p<0.01) and with age (r=0.93, p<0.01), indicative of the degenerative nature of the disease., Conclusion(s): This study presents preliminary results on the use of a robotics and virtual reality assessment tool with ARSACS patients. Results highlight its potential to assess impaired coordination and monitor its progression over time., (Copyright © 2014 Elsevier B.V. All rights reserved.)

An increasing number of genes required for mitochondrial biogenesis, dynamics, or function have been found to be mutated in metabolic disorders and neurological diseases such as Leigh Syndrome. In a forward genetic screen to identify genes required for neuronal function and survival in Drosophila photoreceptor neurons, we have identified mutations in the mitochondrial methionyl-tRNA synthetase, Aats-met, the homologue of human MARS2. The fly mutants exhibit age-dependent degeneration of photoreceptors, shortened lifespan, and reduced cell proliferation in epithelial tissues. We further observed that these mutants display defects in oxidative phosphorylation, increased Reactive Oxygen Species (ROS), and an upregulated mitochondrial Unfolded Protein Response. With the aid of this knowledge, we identified MARS2 to be mutated in Autosomal Recessive Spastic Ataxia with Leukoencephalopathy (ARSAL) patients. We uncovered complex rearrangements in the MARS2 gene in all ARSAL patients. Analysis of patient cells revealed decreased levels of MARS2 protein and a reduced rate of mitochondrial protein synthesis. Patient cells also exhibited reduced Complex I activity, increased ROS, and a slower cell proliferation rate, similar to Drosophila Aats-met mutants., Competing Interests: The authors have declared that no competing interests exist.

Autosomal dominant sensory ataxia is a rare genetic condition that results in a progressive ataxia that is caused by degeneration of the posterior columns of the spinal cord. To date only two families have been clinically ascertained with this condition, both from Maritime Canada. We previously mapped both families to chromosome 8p12-8q12 and have now screened the majority of annotated protein-coding genes in the shared haplotype region by direct DNA sequencing. We have identified a putative pathogenic mutation in the gene encoding ring-finger protein RNF170, a potential ubiquitin ligase. This mutation is a rare non-synonymous change in a well-conserved residue and is predicted to be pathogenic by SIFT, PolyPhen, PANTHER and Align-GVD. Microinjection of wild-type or mutant orthologous messenger RNAs into zebrafish (Danio rerio) embryos confirmed that the mutation dominantly disrupts normal embryonic development. Together these results suggest that the mutation in RNF170 is causal for the sensory ataxia in these families.

The study of inherited retinal diseases has advanced our knowledge of the cellular and molecular mechanisms involved in sensory neural signaling. Dysfunction of two specific sensory modalities, vision and proprioception, characterizes the phenotype of the rare, autosomal-recessive disorder posterior column ataxia and retinitis pigmentosa (PCARP). Using targeted DNA capture and high-throughput sequencing, we analyzed the entire 4.2 Mb candidate sequence on chromosome 1q32 to find the gene mutated in PCARP in a single family. Employing comprehensive bioinformatic analysis and filtering, we identified a single-nucleotide coding variant in the feline leukemia virus subgroup C cellular receptor 1 (FLVCR1), a gene encoding a heme-transporter protein. Sanger sequencing confirmed the FLVCR1 mutation in this family and identified different homozygous missense mutations located within the protein's transmembrane channel segment in two other unrelated families with PCARP. To determine whether the selective pathologic features of PCARP correlated with FLVCR1 expression, we examined wild-type mouse Flvcr1 mRNA levels in the posterior column of the spinal cord and the retina via quantitative real-time reverse-transcriptase PCR. The Flvcr1 mRNA levels were most abundant in the retina, followed by the posterior column of the spinal cord and other brain regions. These results suggest that aberrant FLVCR1 causes a selective degeneration of a subpopulation of neurons in the retina and the posterior columns of the spinal cord via dysregulation of heme or iron homeostasis. This finding broadens the molecular basis of sensory neural signaling to include common mechanisms that involve proprioception and vision., (Copyright © 2010 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Leukodystrophies are a heterogeneous group of disorders associated with abnormal central nervous system white matter. The clinical features invariably include upper motor neuron signs and developmental regression with or without other neurological manifestations. The objective of this study was to characterize clinically and genetically a new form of childhood-onset leukodystrophy with ataxia and tremor. We recruited seven French-Canadian cases belonging to five families affected by an unknown form of childhood-onset leukodystrophy. Genome-wide scans (GWS) were performed using the Illumina Hap310 or Hap610 Bead Chip to identify regions of shared homozygosity that were further studied for linkage with STS markers. All cases presented between the ages of 1 and 5 years with spasticity along with other upper motor neuron signs, prominent postural tremor, and cerebellar signs. Though motor regression is a constant feature, cognitive functions are relatively preserved, even late in the course of the disease. The higher frequency of founder diseases in the French-Canadian population and the segregation in pedigrees are suggestive of a recessive mode of inheritance. By homozygosity mapping, we established linkage to a 12.6-Mb SNP-haplotyped region on chromosome 10q22.3-10q23.31 (maximum LOD score: 5.47). We describe an autosomal recessive childhood-onset leukodystrophy with ataxia and tremor mapping to a 12.6 Mb interval on chromosome 10q22.3-10q23.31. Identification of the mutated gene will allow precise diagnosis and genetic counseling and shed light on how its perturbed function leads to white matter abnormalities.

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset disorder caused by a (GCG)n trinucleotide repeat expansion in the poly(A) binding protein nuclear-1 (PABPN1) gene, which in turn leads to an expanded polyalanine tract in the protein. We generated transgenic mice expressing either the wild type or the expanded form of human PABPN1, and transgenic animals with the expanded form showed clear signs of abnormal limb clasping, muscle weakness, coordination deficits, and peripheral nerves alterations. Analysis of mitotic and postmitotic tissues in those transgenic animals revealed ubiquitinated PABPN1-positive intranuclear inclusions (INIs) in neuronal cells. This latter observation led us to test and confirm the presence of similar INIs in postmortem brain sections from an OPMD patient. Our results indicate that expanded PABPN1, presumably via the toxic effects of its polyalanine tract, can lead to inclusion formation and neurodegeneration in both the mouse and the human.

Senataxin recently was identified as the mutated gene in ataxia-oculomotor apraxia 2, which is characterized by ataxia, oculomotor apraxia, and increased alpha-fetoprotein levels. In this study, we evaluated 24 ataxic patients from 10 French-Canadian families. All cases have a homogeneous phenotype consisting of a progressive ataxia appearing between 2 and 20 (mean age, 14.8) years of age with associated dysarthria, saccadic ocular pursuit, distal amyotrophy, sensory and motor neuropathy, and increased alpha-fetoprotein levels but absence of oculomotor apraxia. Linkage disequilibrium was observed with markers in the ataxia-oculomotor apraxia 2 locus on chromosome 9q34. We have identified four mutations in senataxin in the French-Canadian population including two novel missense mutations: the 5927T-->G mutation changes the leucine encoded by codon 1976 to an arginine in the helicase domain (L1976R), and the 193G-->A mutation changes a glutamic acid encoded by codon 65 into a lysine in the N-terminal domain of the protein (E65K). The common L1976R mutation is shared by 17 of 20 (85%) carrier chromosomes. The study of this large French-Canadian cohort better defines the phenotype of this ataxia and presents two novel mutations in senataxin including the more common founder mutation in the French-Canadian population.

Mobility limitations, including a decrease in walking speed, are major issues for people with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Improving our understanding of factors influencing walking speed in ARSACS may inform the development of future interventions for gait rehabilitation and contribute to better clinical practices. The objective of the study was to identify the factors influencing the self-selected walking speed in adults with ARSACS. The dependent variable of this cross-sectional study was the self-selected speed and the factors (independent variables) were age, sex, balance, balance confidence, knee flexion and extension cocontraction indexes, lower limb coordination, passive range of motion of ankle dorsiflexion, knee and hip extension, and global spasticity. Multiple regression models were used to assess the relationships between walking speed and each factor individually. Six factors were significantly associated with walking speed and thus included in regression models. The models explained between 42.4 and 66.5% of the total variance of the self-selected walking speed. The factors that most influence self-selected walking speed are balance and lower limb coordination. In order of importance, the other factors that also significantly influence self-selected walking speed are ankle dorsiflexion range of motion, lower limb spasticity, knee extension range of motion, and confidence in balance. Balance and lower limb coordination should be targeted in rehabilitation interventions to maintain walking ability and functional independence as long as possible. The six factors identified should also be included in future studies to deepen our understanding of walking speed. [ABSTRACT FROM AUTHOR]

Background: Autosomal recessive spastic ataxia of Charlevoix‐Saguenay (ARSACS) and hereditary spastic paraplegia type 7 (SPG7) represent the most common genotypes of spastic ataxia (SPAX). To date, their magnetic resonance imaging (MRI) features have only been described qualitatively, and a pure neuroradiological differential diagnosis between these two conditions is difficult to achieve. Objectives: To test the performance of MRI measures to discriminate between ARSACS and SPG7 (as an index of common SPAX disease). Methods: In this prospective multicenter study, 3D‐T1‐weighted images of 59 ARSACS (35.4 ± 10.3 years, M/F = 33/26) and 78 SPG7 (54.8 ± 10.3 years, M/F = 51/27) patients of the PROSPAX Consortium were analyzed, together with 30 controls (45.9 ± 16.9 years, M/F = 15/15). Different linear and surface measures were evaluated. A receiver operating characteristic analysis was performed, calculating area under the curve (AUC) and corresponding diagnostic accuracy parameters. Results: The pons area proved to be the only metric increased exclusively in ARSACS patients (P = 0.02). Other different measures were reduced in ARSACS and SPG7 compared with controls (all with P ≤ 0.005). A cut‐off value equal to 1.67 of the pons‐to‐superior vermis area ratio proved to have the highest AUC (0.98, diagnostic accuracy 93%, sensitivity 97%) in discriminating between ARSACS and SPG7. Conclusions: Evaluation of the pons‐to‐superior vermis area ratio can discriminate ARSACS from other SPAX patients, as exemplified here by SPG7. Hence, we hereby propose this ratio as the Magnetic Resonance Index for the Assessment and Recognition of patients harboring SACS mutations (MRI‐ARSACS), a novel diagnostic tool able to identify ARSACS patients and useful for discriminating ARSACS from other SPAX patients undergoing MRI. © 2024 International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurologic disorder with generally well-known clinical manifestations. However, few studies assessed their progression rate using a longitudinal design. This study aimed to document the natural history of ARSACS over a 4-year period in terms of upper and lower limb functions, balance, walking capacity, performance in daily living activities, and disease severity. Forty participants were assessed on three occasions over 4 years. Participant performance was reported in raw data as well as in percentage from reference values to consider the normal aging process. Severe balance and walking capacity impairments were found, with a significant performance decrease over the 4 years. Balance reached a floor score of around 6 points on the Berg Balance Scale for participants aged >40 years, while other participants lost about 1.5 points per year. The mean loss in walking speed was 0.044 m/s per year and the mean decrease in the distance walked in 6 min was 20.8 m per year for the whole cohort. Pinch strength, balance, walking speed, and walking distance decreased over time even when reported in percentage from reference values. Major impairments and rapid progression rates were documented in the present study for upper limb coordination, pinch strength, balance, and walking capacity in the ARSACS population. A progression rate beyond the normal aging process was observed. These results provide fundamental insights regarding the disease prognosis that will help to better inform patients, develop specific rehabilitation programs, and improve trial readiness. [ABSTRACT FROM AUTHOR]

A pathogenic GAA repeat expansion in the first intron of the fibroblast growth factor 14 gene (FGF14) has been recently identified as the cause of spinocerebellar ataxia 27B (SCA27B). We herein screened 160 Greek index cases with late‐onset cerebellar ataxia (LOCA) for FGF14 repeat expansions using a combination of long‐range PCR and bidirectional repeat‐primed PCRs. We identified 19 index cases (12%) carrying a pathogenic FGF14 GAA expansion, a diagnostic yield higher than that of previously screened repeat‐expansion ataxias in Greek LOCA patients. The age at onset of SCA27B patients was 60.5 ± 12.3 years (range, 34–80). Episodic onset (37%), downbeat nystagmus (32%) and vertigo (26%) were significantly more frequent in FGF14 expansion‐positive cases compared to expansion‐negative cases. Beyond typical cerebellar signs, SCA27B patients often displayed hyperreflexia (47%) and reduced vibration sense in the lower extremities (42%). The frequency and phenotypic profile of SCA27B in Greek patients was similar to most other previously studied populations. We conclude that FGF14 GAA repeat expansions are the commonest known genetic cause of LOCA in the Greek population and recommend prioritizing testing for FGF14 expansions in the diagnostic algorithm of patients with LOCA. [ABSTRACT FROM AUTHOR]

Hereditary ataxias, especially when presenting sporadically in adulthood, present a particular diagnostic challenge owing to their great clinical and genetic heterogeneity. Currently, up to 75% of such patients remain without a genetic diagnosis. In an era of emerging disease‐modifying gene‐stratified therapies, the identification of causative alleles has become increasingly important. Over the past few years, the implementation of advanced bioinformatics tools and long‐read sequencing has allowed the identification of a number of novel repeat expansion disorders, such as the recently described spinocerebellar ataxia 27B (SCA27B) caused by a (GAA)•(TTC) repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene. SCA27B is rapidly gaining recognition as one of the most common forms of adult‐onset hereditary ataxia, with several studies showing that it accounts for a substantial number (9–61%) of previously undiagnosed cases from different cohorts. First natural history studies and multiple reports have already outlined the progression and core phenotype of this novel disease, which consists of a late‐onset slowly progressive pan‐cerebellar syndrome that is frequently associated with cerebellar oculomotor signs, such as downbeat nystagmus, and episodic symptoms. Furthermore, preliminary studies in patients with SCA27B have shown promising symptomatic benefits of 4‐aminopyridine, an already marketed drug. This review describes the current knowledge of the genetic and molecular basis, epidemiology, clinical features and prospective treatment strategies in SCA27B. [ABSTRACT FROM AUTHOR]

Ataxia due to an autosomal dominant intronic GAA repeat expansion in FGF14 [GAA- FGF14 ataxia, spinocerebellar ataxia 27B (SCA27B)] has recently been identified as one of the most common genetic late-onset ataxias. We here aimed to characterize its phenotypic profile, natural history progression, and 4-aminopyridine (4-AP) treatment response. We conducted a multi-modal cohort study of 50 GAA- FGF14 patients, comprising in-depth phenotyping, cross-sectional and longitudinal progression data (up to 7 years), MRI findings, serum neurofilament light (sNfL) levels, neuropathology, and 4-AP treatment response data, including a series of n -of-1 treatment studies. GAA- FGF14 ataxia consistently presented as late-onset [60.0 years (53.5–68.5), median (interquartile range)] pancerebellar syndrome, partly combined with afferent sensory deficits (55%) and dysautonomia (28%). Dysautonomia increased with duration while cognitive impairment remained infrequent, even in advanced stages. Cross-sectional and longitudinal assessments consistently indicated mild progression of ataxia [0.29 Scale for the Assessment and Rating of Ataxia (SARA) points/year], not exceeding a moderate disease severity even in advanced stages (maximum SARA score: 18 points). Functional impairment increased relatively slowly (unilateral mobility aids after 8 years in 50% of patients). Corresponding to slow progression and low extra-cerebellar involvement, sNfL was not increased relative to controls. Concurrent second diseases (including progressive supranuclear palsy neuropathology) represented major individual aggravators of disease severity, constituting important caveats for planning future GAA- FGF14 trials. A treatment response to 4-AP with relevance for everyday living was reported by 86% of treated patients. A series of three prospective n -of-1 treatment experiences with on/off design showed marked reduction in daily symptomatic time and symptom severity on 4-AP. Our study characterizes the phenotypic profile, natural history progression, and 4-AP treatment response of GAA- FGF14 ataxia. It paves the way towards large-scale natural history studies and 4-AP treatment trials in this newly discovered, possibly most frequent, and treatable late-onset ataxia. [ABSTRACT FROM AUTHOR]

Objective: The Scale for the Assessment and Rating of Ataxia (SARA) is the most widely applied clinical outcome assessment (COA) for genetic ataxias, but presents metrological and regulatory challenges. To facilitate trial planning, we characterize its responsiveness (including subitem‐level relations to ataxia severity and patient‐focused outcomes) across a large number of ataxias, and provide first natural history data for several of them. Methods: Subitem‐level correlation and distribution‐based analysis of 1,637 SARA assessments in 884 patients with autosomal recessive/early onset ataxia (370 with 2–8 longitudinal assessments) were complemented by linear mixed effects modeling to estimate progression and sample sizes. Results: Although SARA subitem responsiveness varied between ataxia severities, gait/stance showed a robust granular linear scaling across the broadest range (SARA < 25). Responsiveness was diminished by incomplete subscale use at intermediate or upper levels, nontransitions ("static periods"), and fluctuating decreases/increases. All subitems except nose‐finger showed moderate‐to‐strong correlations to activities of daily living, indicating that metric properties—not content validity—limit SARA responsiveness. SARA captured mild‐to‐moderate progression in many genotypes (eg, SYNE1‐ataxia: 0.55 points/yr, ataxia with oculomotor apraxia type 2: 1.14 points/yr, POLG‐ataxia: 1.56 points/yr), but no change in others (autosomal recessive spastic ataxia of Charlevoix‐Saguenay, COQ8A‐ataxia). Whereas sensitivity to change was optimal in mild ataxia (SARA < 10), it substantially deteriorated in advanced ataxia (SARA > 25; 2.7‐fold sample size). Use of a novel rank‐optimized SARA without subitems finger‐chase and nose‐finger reduces sample sizes by 20 to 25%. Interpretation: This study comprehensively characterizes COA properties and annualized changes of the SARA across and within a large number of ataxias. It suggests specific approaches for optimizing its responsiveness that might facilitate regulatory qualification and trial design. ANN NEUROL 2023;94:470–485 [ABSTRACT FROM AUTHOR]

Background: Autosomal dominant (AD) spinocerebellar ataxias (SCAs) encompass a large group of rare disorders, which occurs in individuals of different ethnic backgrounds. To date, demographics, and clinical descriptions of AD SCA in Canada are lacking. Methods: A retrospective chart review of patients with a genetically confirmed diagnosis of AD SCAs was performed at five tertiary centers across Canada in the provinces of Quebec, Alberta, and Ontario. Demographic, genetic, and clinical information were collected and analyzed. Results: A total of 203 patients with AD SCA were identified. Weighted estimated prevalence of AD SCA in three large Canadian provinces was calculated (2.25 cases per 100.000) which is in keeping with the figures documented worldwide. We found that the distribution of the most common SCA differed when comparing provinces. The most prevalent SCA diagnosis in Ontario was SCA3 (49%), while the most prevalent SCA diagnosis in Alberta and Quebec was SCA2 in 26% and 47%, respectively. SCA6 was the third most prevalent SCA subtype in Quebec (14%), which was not seen as commonly in other provinces. SCA1 was uncommonly seen in both Alberta and Quebec, despite being common in Ontario. Conclusions: In this largest Canadian study, we describe the prevalence, distribution, and clinical characteristics of AD SCA. We found that the distribution of the most common SCA differed in the three provinces studied. This finding reflects the heterogenous nature of the Canadian population. [ABSTRACT FROM AUTHOR]

Autosomal Recessive Spastic Ataxia of the Charlevoix Saguenay (ARSACS) is caused by mutation in the SACS gene resulting in loss of function of the protein sacsin. A key feature is the formation of abnormal bundles of neurofilaments (NF) in neurons and vimentin intermediate filaments (IF) in cultured fibroblasts, suggesting a role of sacsin in IF homeostasis. Sacsin contains a J domain (SacsJ) homologous to Hsp40, that can interact with Hsp70 chaperones. The SacsJ domain resolved NF bundles in cultured Sacs−/− neurons. Having studied the mechanism using NF assembled in vitro from purified NF proteins, we report that the SacsJ domain interacts with NF proteins to disassemble NFL filaments, and to inhibit their initial assembly. A cell-penetrating peptide derived from this domain, SacsJ-myc-TAT was efficient in disassembling NF bundles in cultured Sacs−/− motor neurons, restoring the NF network; however, there was some loss of vimentin IF and NF in cultured Sacs+/+ fibroblasts and motor neurons, respectively. These results suggest that sacsin through its SacsJ domain is a key regulator of NF and vimentin IF networks in cells. [ABSTRACT FROM AUTHOR]

To establish the reliability and construct validity of two French-Canadian versions of assessment tools for manual (MWC) and powered wheelchair (PWC) users with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS): the Wheelchair Skills Test Questionnaire (WST-Q-F) version 5.0 and the Wheelchair Use Confidence Scale (WheelCon-F) Short Form. We recruited 32 MWC and PWC users with ARSACS aged between 34 and 64 years. Participants completed measures twice within 2 weeks for test–retest reliability and to determine the standard error of measurement. Construct validity was established by verifying hypothesized relationships between wheelchair use scores and other variables regarding personal factors, body functions, and activities. Participants' scores were also compared with those of MWC and PWC users with other diagnoses to explore known-groups validity. Adequate to excellent test–retest reliability values were found for all questionnaires (intraclass correlation coefficients between 0.506 and 0.995). SEMs were acceptable, ranging from 3.3 to 9.1 on the WST-Q-F and from 0.7 to 1.2 on the WheelCon-F. Moderate to excellent correlations supported construct validity for the WST-Q-F and the WheelCon-F. Compared with other populations, adults with ARSACS reported limited wheelchair skills, but similar wheelchair confidence. The WST-Q-F and the WheelCon-F have excellent test–retest reliability, acceptable measurement errors, and support for construct validity in adults with ARSACS. This study was the first to evaluate these assessment tools in this population, and the results support a need to implement wheelchair skills training interventions in this population. The WST-Q-F version 5.0 and the WheelCon-F Short Form are reliable and valid assessment tools to measure manual and powered wheelchair skills and self-efficacy in adults with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The WST-Q-F version 5.0 and the WheelCon-F Short Form can be used to evaluate and describe wheelchair skills and wheelchair use self-efficacy in clinical practice and are recommended for future research in adults with ARSACS. These outcome tools may be especially useful to measure the effects of a wheelchair training program. [ABSTRACT FROM AUTHOR]

Background: This study aimed to describe lower limbs impairments, balance and activity limitations related to indoor mobility in adult walkers with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS).Results: Twenty-five participants were recruited with a mean age of 32.2 (± 10.4) years with 45.7% using a walking aid. There is a significant difference between participants with and without a walking aid in terms of lower limbs coordination, balance and mobility. Although participants who walk without a walking aid perform better than the others and they are below predictive or reference values. Despite significant mobility limitations, only mild spasticity and passive range of motion limitations were observed. However, there is a significant difference between unaffected individuals and participants with ARSACS for lower limb muscle cocontraction.Conclusions: Results show a high level of lower limb impairments, balance and mobility limitation in adults' participants with ARSACS that are still walking, including people not using a walking aid. One of the most original finding is the presence of excessive cocontraction and a relatively mild level of spasticity in the lower limbs muscles. Results of this study better circumscribes the impairments and activities that should be the focus of intervention including rehabilitation in ARSACS. [ABSTRACT FROM AUTHOR]

A biallelic pentanucleotide expansion in the RFC1 gene has been reported to be a common cause of late-onset ataxia. In the general population, four different repeat conformations are observed: wild type sequence AAAAG (11 repeats) and longer expansions of either AAAAG, AAAGG or AAGGG sequences. However only the biallelic AAGGG expansions were reported to cause late-onset ataxia. In this study, we aimed to assess the prevalence and nature of RFC1 repeat expansions in three cohorts of adult-onset ataxia cases: Brazilian (n = 23) and Canadian (n = 26) cases that are negative for the presence of variants in other known ataxia-associated genes, as well as a cohort of randomly selected Canadian cases (n = 128) without regard to a genetic diagnosis. We identified the biallelic AAGGG expansion in only one Brazilian family which presented two affected siblings, and in one Canadian case. We also observed two new repeat conformations, AAGAG and AGAGG, which suggests the pentanucleotide expansion sequence has a dynamic nature. To assess the frequency of these new repeat conformations in the general population, we screened 163 healthy individuals and observed the AAGAG expansion to be more frequent in cases than in control individuals. While additional studies will be necessary to asses the pathogenic impact of biallelic genotypes that include the novel expanded conformations, their occurrence should nonetheless be examined in future studies. [ABSTRACT FROM AUTHOR]

Background Objectives Methods Results Conclusions Autosomal recessive spastic ataxia of Charlevoix‐Saguenay (ARSACS) is a common recessive ataxia that is still underdiagnosed worldwide. An easily accessible diagnostic biomarker might help to diagnostically confirm patients presenting SACS variants of unknown significance (VUS) or atypical phenotypes.To detect sacsin in peripheral blood mononuclear cells (PBMCs) and to validate its diagnostic biomarker quality to discriminate biallelic SACS patients (including patients with VUS and/or atypical phenotypes) against healthy controls, non‐ARSACS spastic ataxia patients, and heterozygous SACS carriers.Sacsin protein levels in PBMCs were assessed in patients versus controls and validated in skin‐derived fibroblasts.Patients with biallelic SACS variants – including patients with VUS and/or atypical phenotypes – showed loss of sacsin in PBMCs, with discriminative performance against healthy, heterozygous, and non‐ARSACS controls. This included all investigated SACS missense variants. Also, C‐terminal variants escaping nonsense‐mediated decay, while not differing from controls in expression level, showed lower molecular weight in this assay.Assessing sacsin levels using PBMCs offers an easy, peripherally accessible diagnostic biomarker for ARSACS, with PBMCs being much less invasive and easier to handle than fibroblasts. Additionally, this might be a potential target‐engagement blood biomarker for sacsin‐increasing therapies. © 2024 International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Background: Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a recessive neurological disorder with cerebellar, pyramidal and neuropathic features. Natural history data are urgently needed to increase trial readiness. This study aimed to describe the clinical phenotype including dexterity, coordination, strength, mobility, balance, disease severity, participation, and quality of life observed in adults with ARSACS homozygous for the c.8844delT mutation.Methods: Cross-sectional study with comparisons between disease stages and with reference values. Outcome measures included Standardized Finger-to-Nose Test, Grip/pinch strength, LEMOCOT, Six-Minute Walk Test, 10-Meter Walk Test, Berg Balance Scale, Spastic Paraplegia Rating Scale, Scale for the Assessment and Rating of Ataxia, LIFE-H, and SF-12.Results: Twenty-eight participants were recruited with a mean age of 38.1 years. The majority presented with lower limb coordination and fine dexterity scores below three standard deviations compare to reference values, scored under predicted values for mobility measures and were at increased risk of fall. Participants at an earlier disease stage performed better than the others, but individual variability was observed.Conclusions: Results showed overall impaired motor performances and, even in a genetically homogeneous ARSACS population, an individual variability within disease stages. This study lays the foundation for a longitudinal study using quantified measurements. [ABSTRACT FROM AUTHOR]

Objective Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neuromuscular disease leading to several impairments, including decrease of lower limb coordination. The Lower Extremity Motor Coordination Test (LEMOCOT) is an outcome measure recently developed for stroke population. The aim of this study was to document: 1) intra- and interrater reliability; 2) the standard error of measurement and minimal detectable change; and 3) the construct validity of the measurements obtained with the LEMOCOT in the adult ARSACS population. Results The LEMOCOT has shown a good intra- and interrater reliability with an intraclass correlation coefficient ranging from 0.92 to 0.97 for both dominant and non-dominant side. The construct validity (hypothesis testing) is satisfying where LEMOCOT's score negatively correlated with participants' age ( r = − 0.74) and the score of the Scale for the Assessment and Rating of Ataxia ( r = − 0.86) and positively correlated with the balance and mobility tests ( r = 0.82 with the Berg Balance Scale, r = 0.61 with the Six-Minute Walk Test, r = 0.57 with the 10-Meter Walk Test). The LEMOCOT was also able to distinguish between patients according to disease stages. Conclusion The LEMOCOT is a valid and reliable tool to assess lower limb coordination in the ARSACS population for whom the lack of coordination is a common symptom. [ABSTRACT FROM AUTHOR]

Abstract Background and purpose Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) diagnosis is based on the presence of three main clinical features: 1) ataxia, 2) pyramidal involvement, and 3) axonal neuropathy. This study aimed to explore, among a cohort of adults with ARSACS, the prevalence of other signs and symptoms than those commonly describe in this disease and compare their prevalence between younger (<40 years) and older (≥40 years) participants. Methods A clinical interview based on a standardized questionnaire was conducted. It included the following items: memory and concentration problems, hearing impairment, epilepsy, spasms, choreathetosis, neuropathic pain, cramps and fecal incontinence. Results A total of 43 participants were interviewed, with a mean age of 38.9 years and 51.2% were men. Spasms (55.8%), cramps (53.5%), and concentration problems (39.5%) were the most frequent manifestations. Except for choreathetosis, which was present in only one participant, all other signs and symptoms were present in 9.3% to 29.3% of participants. Conclusions People with ARSACS may experience many other clinical manifestations than the most commonly described. This study is a preliminary step toward the development of a comprehensive evidence-based clinical care guideline for this population. Highlights • Spasms, cramps, concentration problems, and fecal incontinence were often present. • Lower limb neuropathic pain is more frequent than in the Canadian population. • Prevalence of epilepsy is also much higher than in the Canadian population. [ABSTRACT FROM AUTHOR]

Sacsin is a 520-kDa protein mutated in the early-onset neurodevelopmental and neurodegenerative disease autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The C terminus of the protein contains an HEPN (ẖigher ...ukaryotes and ...rokaryotes ṉucleotide-binding) domain of unknown function. Here, we determined the high-resolution 1.9-Å crystal structure of the HEPN domain from human sacsin. The structure is composed of five parallel α-helices with a large loop of several short helical segments. Two HEPN protomers assemble as a dimer to form a large positively charged cavity at the dimer interface that binds GTP and other nucleotides. The crystal structure reveals that the ARSACS N4549D mutation disrupts dimerization and protein folding. This study provides novel insights into the oligomerization state of sacsin and functions that are lost in mutations that cause ARSACS. [ABSTRACT FROM AUTHOR]