Consensus Paper: Ataxic Gait

Might patients with cerebellar ataxia benefit from the Computer Assisted Rehabilitation ENvironment (CAREN)? A pilot study focusing on gait and balance

Introduction: Ataxia is a neurological symptom that causes decreased balance, loss of coordination, and gait alterations. Innovative rehabilitation devices like virtual reality (VR) systems can provide task-oriented, repetitive and intensive training with multisensorial feedback, thus promoting neuroplastic processes. Among these VR technologies, the Computer Assisted Rehabilitation ENvironment (CAREN) associates a split belt treadmill on a 6-degrees of freedom platform with a 180° VR screen and a Vicon motion capture system to monitor patients' movements during training sessions. Methods: Eight patients affected by cerebellar ataxia were enrolled and received 20 sessions of CAREN training in addition to standard rehabilitation treatment. Each patient was evaluated at the beginning and at the end of the study with 3D gait analysis and clinical scales to assess balance, gait function and risk of falls. Results: We found improvements in kinematic, kinetic, and electromyographic parameters (as per pre-post- CAREN training), as well as in clinical outcomes, such as balance and risk of falls in ataxic patients. In addition, we found that trunk rotation improved, after CAREN intervention, approximating to the normative values. Discussion: Our results suggested that CAREN might be useful to improve specific biomechanical parameters of gait in ataxic patients.

Optimizing Rare Disease Gait Classification through Data Balancing and Generative AI: Insights from Hereditary Cerebellar Ataxia

The interpretability of gait analysis studies in people with rare diseases, such as those with primary hereditary cerebellar ataxia (pwCA), is frequently limited by the small sample sizes and unbalanced datasets. The purpose of this study was to assess the effectiveness of data balancing and generative artificial intelligence (AI) algorithms in generating synthetic data reflecting the actual gait abnormalities of pwCA. Gait data of 30 pwCA (age: 51.6 ± 12.2 years; 13 females, 17 males) and 100 healthy subjects (age: 57.1 ± 10.4; 60 females, 40 males) were collected at the lumbar level with an inertial measurement unit. Subsampling, oversampling, synthetic minority oversampling, generative adversarial networks, and conditional tabular generative adversarial networks (ctGAN) were applied to generate datasets to be input to a random forest classifier. Consistency and explainability metrics were also calculated to assess the coherence of the generated dataset with known gait abnormalities of pwCA. ctGAN significantly improved the classification performance compared with the original dataset and traditional data augmentation methods. ctGAN are effective methods for balancing tabular datasets from populations with rare diseases, owing to their ability to improve diagnostic models with consistent explainability.

Digital Motor Biomarkers of Cerebellar Ataxia Using an RGB-Depth Camera-Based Motion Analysis System

This study aimed to identify quantitative biomarkers of motor function for cerebellar ataxia by evaluating gait and postural control using an RGB-depth camera-based motion analysis system. In 28 patients with degenerative cerebellar ataxia and 33 age- and sex-matched healthy controls, motor tasks (short-distance walk, closed feet stance, and stepping in place) were selected from a previously reported protocol, and scanned using Kinect V2 and customized software. The Clinical Assessment Scale for the Assessment and Rating of Ataxia (SARA) was also evaluated. Compared with the normal control group, the cerebellar ataxia group had slower gait speed and shorter step lengths, increased step width, and mediolateral trunk sway in the walk test (all P < 0.001). Lateral sway increased in the stance test in the ataxia group (P < 0.001). When stepping in place, the ataxia group showed higher arrhythmicity of stepping and increased stance time (P < 0.001). In the correlation analyses, the ataxia group showed a positive correlation between the total SARA score and arrhythmicity of stepping in place (r = 0.587, P = 0.001). SARA total score (r = 0.561, P = 0.002) and gait subscore (ρ = 0.556, P = 0.002) correlated with mediolateral truncal sway during walking. These results suggest that the RGB-depth camera-based motion analyses on mediolateral truncal sway during walking and arrhythmicity of stepping in place are useful digital motor biomarkers for the assessment of cerebellar ataxia, and could be utilized in future clinical trials.

Gait Variability as a Potential Motor Marker of Cerebellar Disease-Relationship between Variability of Stride, Arm Swing and Trunk Movements, and Walking Speed

Excessive stride variability is a characteristic feature of cerebellar ataxias, even in pre-ataxic or prodromal disease stages. This study explores the relation of variability of arm swing and trunk deflection in relationship to stride length and gait speed in previously described cohorts of cerebellar disease and healthy elderly: we examined 10 patients with spinocerebellar ataxia type 14 (SCA), 12 patients with essential tremor (ET), and 67 healthy elderly (HE). Using inertial sensors, recordings of gait performance were conducted at different subjective walking speeds to delineate gait parameters and respective coefficients of variability (CoV). Comparisons across cohorts and walking speed categories revealed slower stride velocities in SCA and ET patients compared to HE, which was paralleled by reduced arm swing range of motion (RoM), peak velocity, and increased CoV of stride length, while no group differences were found for trunk deflections and their variability. Larger arm swing RoM, peak velocity, and stride length were predicted by higher gait velocity in all cohorts. Lower gait velocity predicted higher CoV values of trunk sagittal and horizontal deflections, as well as arm swing and stride length in ET and SCA patients, but not in HE. These findings highlight the role of arm movements in ataxic gait and the impact of gait velocity on variability, which are essential for defining disease manifestation and disease-related changes in longitudinal observations.

CRPD frontiers in movement disorders Therapeutics: From evidence to treatment and applications: Addressing Patients' Needs in the Management of the Ataxias

The genetic ataxias have no cures and no proven ways to delay progression (no disease-modifying therapies). The acquired ataxias may have treatments that address the underlying cause and may slow or stop progression, but will not reverse damage already sustained. The idiopathic ataxias (of unknown genetic or acquired cause) also have no proven disease-modifying therapies. However, for all patients with ataxia of any cause, there is always something that can be done to improve quality of life-treat associated symptoms, provide information and resources, counsel patient and family, help with insurance and disability concerns, be available to listen and answer the many questions they will have.

Quantitative Evaluation of Stance as a Sensitive Biomarker of Postural Ataxia Development in Preclinical SCA1 Mutation Carriers

The aim of this study was to determine the time between the first detection of postural control impairments and the evident manifestation of ataxia in preclinical SCA1 individuals. Twenty five preclinical SCA1 mutation carriers: 13 with estimated disease onset ≤ 6 years (SCA1 +) aged 27.8 ± 8.1 years; 12 with expected disease onset > 6 years (SCA1-) aged 26.6 ± 3.1 years and 26 age and sex matched healthy controls (HCs) underwent static posturography during 5 years of observation. The movements of the centre of feet pressure (COP) during quiet standing with eyes open (EO) and closed (EC) were quantified by calculating the mean radius (R), developed surface area (A) and mean COP movement velocity (V). Ataxia was evaluated by use of the Scale for Assessment and Rating of Ataxia (SARA).SCA1 + exhibited significantly worse quality of stance with EC vs. SCA1- (p < 0.05 for V) and HCs (p < 0.001) even 5 to 6 years before estimated disease onset. There were no statistically significant differences between SCA1- and HCs. A slow increase in Cohen's d effect size was observed for VEO up to the clinical manifestation of ataxia. VEO and AEC recorded in preclinical SCA1 individuals correlated slightly but statistically significantly with SARA (r = 0.47).The study confirms that static posturography detects COP sway changes in SCA1 preclinical gene carriers even 5 to 6 years before estimated disease onset. The quantitative evaluation of stance in preclinical SCA is a sensitive biomarker for the monitoring of the disease progression and may be useful in clinical trials.

Exploring the Therapeutic Effects and Mechanisms of Transcranial Alternating Current Stimulation on Improving Walking Ability in Stroke Patients via Modulating Cerebellar Gamma Frequency Band-a Narrative Review

The cerebellum plays an important role in maintaining balance, posture control, muscle tone, and lower limb coordination in healthy individuals and stroke patients. At the same time, the relationship between cerebellum and motor learning has been widely concerned in recent years. Due to the relatively intact structure preservation and high plasticity after supratentorial stroke, non-invasive neuromodulation targeting the cerebellum is increasingly used to treat abnormal gait in stroke patients. The gamma frequency of transcranial alternating current stimulation (tACS) is commonly used to improve motor learning. It is an essential endogenous EEG oscillation in the gamma range during the swing phase, and rhythmic movement changes in the gait cycle. However, the effect of cerebellar tACS in the gamma frequency band on balance and walking after stroke remains unknown and requires further investigation.

Quantitative Gait and Balance Outcomes for Ataxia Trials: Consensus Recommendations by the Ataxia Global Initiative Working Group on Digital-Motor Biomarkers

With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid, finely granulated, digital health measures are highly warranted to augment clinical and patient-reported outcome measures. Gait and balance disturbances most often present as the first signs of degenerative cerebellar ataxia and are the most reported disabling features in disease progression. Thus, digital gait and balance measures constitute promising and relevant performance outcomes for clinical trials.This narrative review with embedded consensus will describe evidence for the sensitivity of digital gait and balance measures for evaluating ataxia severity and progression, propose a consensus protocol for establishing gait and balance metrics in natural history studies and clinical trials, and discuss relevant issues for their use as performance outcomes.

Protracted CLN3 Batten disease in mice that genetically model an exon-skipping therapeutic approach

Genetic mutations that disrupt open reading frames and cause translation termination are frequent causes of human disease and are difficult to treat due to protein truncation and mRNA degradation by nonsense-mediated decay, leaving few options for traditional drug targeting. Splice-switching antisense oligonucleotides offer a potential therapeutic solution for diseases caused by disrupted open reading frames by inducing exon skipping to correct the open reading frame. We have recently reported on an exon-skipping antisense oligonucleotide that has a therapeutic effect in a mouse model of CLN3 Batten disease, a fatal pediatric lysosomal storage disease. To validate this therapeutic approach, we generated a mouse model that constitutively expresses the Cln3 spliced isoform induced by the antisense molecule. Behavioral and pathological analyses of these mice demonstrate a less severe phenotype compared with the CLN3 disease mouse model, providing evidence that antisense oligonucleotide-induced exon skipping can have therapeutic efficacy in treating CLN3 Batten disease. This model highlights how protein engineering through RNA splicing modulation can be an effective therapeutic approach.

Neurophysiology of cerebellar ataxias and gait disorders

There are numerous forms of cerebellar disorders from sporadic to genetic diseases. The aim of this chapter is to provide an overview of the advances and emerging techniques during these last 2 decades in the neurophysiological tests useful in cerebellar patients for clinical and research purposes. Clinically, patients exhibit various combinations of a vestibulocerebellar syndrome, a cerebellar cognitive affective syndrome and a cerebellar motor syndrome which will be discussed throughout this chapter. Cerebellar patients show abnormal Bereitschaftpotentials (BPs) and mismatch negativity. Cerebellar EEG is now being applied in cerebellar disorders to unravel impaired electrophysiological patterns associated within disorders of the cerebellar cortex. Eyeblink conditioning is significantly impaired in cerebellar disorders: the ability to acquire conditioned eyeblink responses is reduced in hereditary ataxias, in cerebellar stroke and after tumor surgery of the cerebellum. Furthermore, impaired eyeblink conditioning is an early marker of cerebellar degenerative disease. General rules of motor control suggest that optimal strategies are needed to execute voluntary movements in the complex environment of daily life. A high degree of adaptability is required for learning procedures underlying motor control as sensorimotor adaptation is essential to perform accurate goal-directed movements. Cerebellar patients show impairments during online visuomotor adaptation tasks. Cerebellum-motor cortex inhibition (CBI) is a neurophysiological biomarker showing an inverse association between cerebellothalamocortical tract integrity and ataxia severity. Ataxic gait is characterized by increased step width, reduced ankle joint range of motion, increased gait variability, lack of intra-limb inter-joint and inter-segmental coordination, impaired foot ground placement and loss of trunk control. Taken together, these techniques provide a neurophysiological framework for a better appraisal of cerebellar disorders.

Post-Traumatic Craniocervical Disorders From a Postural Control Perspective: A Narrative Review

Mild traumatic brain injury (mTBI) and whiplash injury (WI) may lead to long-term disabling consequences known as post-concussive syndrome (PCS) and whiplash-associated disorders (WADs). PCS and WAD patients commonly complain of conditions encompassing dizziness, vertigo, headache, neck pain, visual complaints, anxiety, and neurocognitive dysfunctions. A proper medical work-up is a priority in order to rule out any acute treatable consequences. However investigations may remain poorly conclusive. Gathered in the head and neck structures, the ocular sensorimotor, the vestibular, and the cervical proprioceptive systems, all involved in postural control, may be damaged by mTBI or WI. Their dysfunctions are associated with a wide range of functional disorders including symptoms reported by PCS and WAD patients. In addition, the stomatognathic system needs to be specifically assessed particularly when associated to WI. Evidence for considering the post-traumatic impairment of these systems in PCS and WAD-related symptoms is still lacking but seems promising. Furthermore, few studies have considered the assessment and/or treatment of these widely interconnected systems from a comprehensive perspective. We argue that further research focusing on consequences of mTBI and WI on the systems involved in the postural control are necessary in order to bring new perspective of treatment.

Digital Gait Biomarkers Allow to Capture 1-Year Longitudinal Change in Spinocerebellar Ataxia Type 3

Measures of step variability and body sway during gait have shown to correlate with clinical ataxia severity in several cross-sectional studies. However, to serve as a valid progression biomarker, these gait measures have to prove their sensitivity to robustly capture longitudinal change, ideally within short time frames (eg, 1 year). We present the first multicenter longitudinal gait analysis study in spinocerebellar ataxias. We performed a combined cross-sectional (n = 28) and longitudinal (1-year interval, n = 17) analysis in Spinocerebellar Ataxia type 3 subjects (including seven preataxic mutation carriers). Longitudinal analysis showed significant change in gait measures between baseline and 1-year follow-up, with high effect sizes (stride length variability: P = 0.01, effect size r_prb  = 0.66; lateral sway: P = 0.007, r_prb  = 0.73). Sample size estimation for lateral sway indicates a required cohort size of n = 43 for detecting a 50% reduction of natural progression, compared with n = 240 for the clinical ataxia score Scale for the Assessment and Rating of Ataxia (SARA). These measures thus present promising motor biomarkers for upcoming interventional studies. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.