Falls and spinal muscular atrophy: Exploring cause and prevention

Longitudinal Assessment of Timed Function Tests Over Time in Ambulatory Individuals with SMA Treated with Nusinersen

BACKGROUND

Ambulatory individuals with spinal muscular atrophy experience weakness and impairments of speed and endurance. This leads to decreased motor skill performance required for daily living including transitioning from floor to stand, climbing stairs, and traversing short and community distances. Motor function improvements have been reported in individuals receiving nusinersen, but changes in timed functional tests (TFTs) which assess shorter distance walking and transitions have not been well documented.

OBJECTIVE

To evaluate changes in TFT performance over the course of nusinersen treatment in ambulatory individuals with SMA and identify potential factors [age, SMN2 copy number, BMI, Hammersmith Functional Motor Scale expanded (HFMSE score), Peroneal Compound Motor Action Potential (CMAP) amplitude] associated with TFT performance.

METHODS

Nineteen ambulatory participants receiving nusinersen were followed from 2017 through 2019 (range: 0-900 days, mean 624.7 days, median 780 days); thirteen of 19 (mean age = 11.5 years) completed TFTs. The 10-meter walk/run test, time-to-rise from supine, time-to-rise from sitting, 4-stair climb, 6-minute walk test (6MWT), Hammersmith-Expanded and peroneal CMAP were assessed at each visit. Linear mixed-effects models were used to evaluate unadjusted and adjusted changes in these outcomes over time.

RESULTS

Apart from time to rise from sitting and from supine, all TFTs were found to improve over the course of treatment after adjusting for baseline age and BMI.

CONCLUSIONS

Improvement in TFTs over time in patients with SMA treated with nusinersen suggests that shorter TFTs may have value to assess individuals with SMA who have or later gain ambulatory function during treatment.

The Impact of "Fear of Falling" on Physical Performance, Balance, and Ambulation in Duchenne Muscular Dystrophy

OBJECTIVE

The aim of this study was to investigate falls and the fear of falling (FOF) in children with Duchenne muscular dystrophy (DMD) and to determine the relationships between the FOF and physical performance, balance, and ambulation.

METHODS

Thirty-eight ambulatory children with DMD were included in the study. The functional level, falling history, FOF, physical performance, balance, and ambulation were assessed by using Brooke Lower Extremity Functional Classification, History of Falls Questionnaire, Pediatric Fear of Falling Questionnaire (Ped-FOF), timed performance tests, Timed "Up and Go" (TUG) test, and North Star Ambulatory Assessment (NSAA), respectively.

RESULTS

Of the 38 children (mean age: 9.00 ± 2.03 years) 97.4% had a history of serious fall last year and 62.2% were injured due to this fall. The Ped-FOF score was 13.79 ± 7.20. Weak to moderate relations were determined between Ped-FOF and functional level (r = 0.33), frequency of falls (r = 0.41), duration of climbing 4-steps (r = 0.38), TUG (r = 0.36), and NSAA (r = -0.32) (p < 0.05).

CONCLUSION

Ambulatory children with better performance scores had lower levels of FOF despite their history of serious falls and injuries. FOF tends to increase as the symptoms of the disease progresses. Investigating the history of falls and FOF from the earliest period will guide to take precautions and make necessary interventions on time in treatment programs.

Development of a questionnaire to assess fear of falling in children with neuromuscular diseases

Fear of falling (FOF) indicates loss of confidence in the ability to perform daily living activities without falling. Although specific questionnaires do exist to assess FOF in different patient populations, any of them targets the pediatric patients with neuromuscular diseases which falling is a frequent symptom. This study aims to present the development of a self-report FOF questionnaire for children with neuromuscular diseases, pilot application of the questionnaire, and its preliminary psychometric properties. An International Classification of Functioning, Disability and Health (ICF)-based 'Pediatric Fear of Falling Questionnaire' for neuromuscular diseases (Ped-FOF) was created by the study team following the steps of developing an instrument. The questionnaire included 34 items which were organized based on the 'Activities and Participation' component of ICF-children and youth. Thirty children with Duchenne muscular dystrophy (DMD) were recruited to obtain preliminary reliability and validity results of the questionnaire. The mean Ped-FOF score of study population was 15.30 ± 7.03. According to the preliminary results, intraclass correlation coefficient was 0.715 [confidence interval (CI) 95%], and moderate correlations between Ped-FOF and functional performance and quality of life were determined (P < 0.05). Ped-FOF promises a practical assessment of FOF in pediatrics with neuromuscular diseases with understandable items that allow self-report of children. Ped-FOF also allows clinicians and therapists to assess FOF efficiently in limited clinical time. Its preliminary reliability and validity results are also sufficient to be used in DMD that falling is a frequent condition, which indicates that the use of questionnaire is promising in many other pediatric neuromuscular disorders.

Filling the gaps in knowledge translation: Physical therapy recommendations for individuals with spinal muscular atrophy compared to standard of care guidelines

This study describes the current landscape of physical therapy practice recommendations in the United States for children with spinal muscular atrophy (SMA) and their relationship to current SMA standard of care (SMA-SOC) guidelines. Pediatric physical therapists were surveyed to determine their knowledge of SMA-SOC guidelines, and the type, duration and frequency of intervention they recommend for children with SMA, as well as perceived barriers and facilitators to progress in physical therapy. Physical therapists recommend five key intervention areas for individuals with SMA; however discrepancies exist between the SOC recommended intervention parameters and respondents' reported frequency and duration of recommendations. After individuals with SMA initiated disease modifying pharmacotherapies, a majority of physical therapist respondents recommended increases in both frequency and duration of interventions. Nearly all respondents reported that familiarity with SOC guidelines was beneficial to their practice. The primary facilitator to progress was parent/caregiver support, while the primary barrier was limited access to resources. Variation in practice exists regarding care for those with SMA, particularly in the areas of frequency and duration of specific interventions. These findings can guide educational initiatives, identify future research needs and further inform SMA-SOC and best-practice rehabilitation management.

Falls in paediatric Charcot-Marie-Tooth disease: a 6-month prospective cohort study

OBJECTIVE

To prospectively study falls in children and adolescents with Charcot-Marie-Tooth disease (CMT).

DESIGN

Prospective cohort study.

SETTING

Neuromuscular outpatient clinic of a tertiary paediatric hospital.

PATIENTS

Sixty children and adolescents ('children') aged 4-18 years, 30 with CMT and 30 typically developing (TD).

MAIN OUTCOME MEASURES

Falls rate over 6 months and falls characteristics questionnaire.

RESULTS

Twenty-two children with CMT reported falling at least once in 6 months compared with eight TD children (CMT 2819 (0-1915), TD 31 (0-6) total falls (range)). Detailed falls characteristics were collected from 242 individual falls (CMT 216, TD 26). Injurious falls were reported by 19 children with CMT (74 falls) compared with 2 TD children (3 falls), with cuts, grazes and bruising most common. No fractures were sustained and no child required hospitalisation. However, 12 injuries from falls in children with CMT required management by a healthcare provider, versus none in TD children. Tripping was the most common mechanism of falls in both groups. Age was the strongest predictor of falls (ρ=-0.53, p=0.006) with all children (CMT and TD) aged <7 years falling. Balance was the strongest impairment-related predictor of falls (ρ=-0.47, p=0.02). The conservative estimate of risk of falls in children and adolescents with CMT was 33 times higher than their TD peers (incidence rate ratio=32.8, 95% CI 10.2 to 106.0).

CONCLUSIONS

Children and adolescents with CMT fall more often than TD peers and sustain more injuries when they fall.

Spinal muscular atrophy: journeying from bench to bedside

Spinal muscular atrophy (SMA) is a frequently fatal neuromuscular disorder and the most common inherited cause of infant mortality. SMA results from reduced levels of the survival of motor neuron (SMN) protein. Although the disease was first described more than a century ago, a precise understanding of its genetics was not obtained until the SMA genes were cloned in 1995. This was followed in rapid succession by experiments that assigned a role to the SMN protein in the proper splicing of genes, novel animal models of the disease, and the eventual use of the models in the pre clinical development of rational therapies for SMA. These successes have led the scientific and clinical communities to the cusp of what are expected to be the first truly promising treatments for the human disorder. Yet, important questions remain, not the least of which is how SMN paucity triggers a predominantly neuromuscular phenotype. Here we review how our understanding of the disease has evolved since the SMA genes were identified. We begin with a brief description of the genetics of SMA and the proposed roles of the SMN protein. We follow with an examination of how the genetics of the disease was exploited to develop genetically faithful animal models, and highlight the insights gained from their analysis. We end with a discussion of ongoing debates, future challenges, and the most promising treatments to have emerged from our current knowledge of the disease.

Performance of the timed "up & go" test in spinal muscular atrophy

INTRODUCTION

The timed "up & go" (TUG) test is a quick measure of balance and mobility. TUG scores correlate with clinical, functional, and strength assessment and decline linearly over time. Reliability and validity have not been tested in spinal muscular atrophy (SMA).

METHODS

Fifteen ambulatory SMA participants performed TUG testing and strength, functional, and clinical assessments. Intraclass correlation coefficients quantified test-retest reliability. Convergent validity was determined using Pearson correlation coefficients.

RESULTS

Test-retest reliability was excellent for all participants. TUG was associated significantly with total leg and knee flexor strength, as well as the Hammersmith Functional Motor Scale Expanded, the 10-meter walk/run, and 6-minute walk tests. TUG findings were not associated with knee extensor strength, pulmonary function, or fatigue.

CONCLUSIONS

In SMA, the TUG test is easily administered, reliable, and correlates with established outcome measures. TUG testing is a potentially useful outcome measure for clinical trials and a measure of disability in ambulatory patients with SMA.

Neurodegeneration in spinal muscular atrophy: from disease phenotype and animal models to therapeutic strategies and beyond

Of the numerous inherited diseases known to afflict the pediatric population, spinal muscular atrophy (SMA) is among the most common. It has an incidence of approximately one in 10,000 newborns and a carrier frequency of one in 50. Despite its relatively high incidence, SMA remains somewhat obscure among the many neurodegenerative diseases that affect humans. Nevertheless, the last two decades have witnessed remarkable progress in our understanding of the pathology, underlying biology and especially the molecular genetics of SMA. This has led to a genuine expectation within the scientific community that a robust treatment will be available to patients before the end of the decade. The progress made in our understanding of SMA and, therefore, towards a viable therapy for affected individuals is in large measure a consequence of the simple yet fascinating genetics of the disease. Nevertheless, important questions remain. Addressing these questions promises not only to accelerate the march towards a cure for SMA, but also to uncover novel therapies for related neurodegenerative disorders. This review discusses our current understanding of SMA, considers the challenges ahead, describes existing treatment options and highlights state-of-the-art research being conducted as a means to a better, safer and more effective treatment for the disease.