Changes in abilities over the initial 12 months of nusinersen treatment for type II SMA.

Several studies have shown the efficacy of new disease-modifying therapies in slowing down type II SMA progression using the Hammersmith Functional Motor Scale Expanded (HFMSE). This research aims to enhance understanding of activity changes across age groups post-nusinersen treatment using shift analysis, compared with untreated individuals. Retrospective data from the, international SMA consortium (iSMAc) dataset were analyzed, assessing individual item changes over 12 months. Shift analysis was used to determine the gain or loss of abilities, defining "gain" as a positive change between scores from 0 to either 1 or 2 and "loss" as a negative change from either 2 or 1 to 0. The cohort included 130 SMA II patients who underwent 12-month assessments from their first nusinersen dose, with age range between 0.6 and 49.6 years. One-third of the entire cohort experienced at least a loss in one activity, while 60% experienced a gain, particularly notable in children aged 2.5 to 5 years and 5 to 13 years. Overall, the study demonstrates a positive impact of nusinersen treatment on SMA II patients, showing a trend of increased activity gains and decreased probability of ability loss across different age groups.

Nonverbal Cognitive Skills in Children With Aicardi Goutières Syndrome.

BACKGROUND AND OBJECTIVES: Aicardi Goutières syndrome (AGS) is type I interferonopathy characterized by severe neurologic impairment. Although many children with AGS demonstrate motor and expressive language deficits, the magnitude of receptive language impairment is uncharacterized. We sought to characterize cognitive function in AGS-affected children using assessment tools with reduced dependence on motor abilities and compare cognitive testing outcomes with overall severity and parental assessment of adaptive behavior. METHODS: We performed a cross-sectional study. Children were recruited as part of the Myelin Disorders Biorepository Project at the Children's Hospital of Philadelphia. We included individuals with a confirmed diagnosis of AGS. We administered the Leiter International Performance Scale, third edition (Leiter-3), and the Vineland Adaptive Behavior Scale, third edition (VABS-3), in the context of research encounters. Motor skills were categorized by AGS Severity Scale mobility levels. Descriptive statistics and Spearman's rank correlation were used to compare assessments. Mann-Whitney and Kruskal-Wallis tests with correction with Dunn's multiple comparison test were used to compare test performance between mobility groups. RESULTS: Cognitive and adaptive behavior performance was captured in 57 children. The mean age at encounters was 8.51 (SD 5.15) years. The median (IQR) Leiter-3 score was 51 (interquartile range [IQR] 60), with administration failure in 20 of 57 (35%) individuals. On the VABS-3, the Motor Domain (median 29, IQR 36.25) was more impacted than the Communication (median 50, IQR 52), Daily Living Skills (median 52, IQR 31), and Socialization (median 54, IQR 40) Domains (p < 0.0001). The AGS Scale correlated with VABS-3 (r = 0.86, p < 0.0001) and Leiter-3 (r = 0.87, p < 0.0001). There was correlation between VABS-3 Domains and Leiter-3 (r-range 0.83-0.97). Gross motor and fine motor categories, respectively, correlated with VABS-3 (H = 39.37, p < 0.0001; U = 63, p < 0.0001) and Leiter-3 (H = 40.43, p < 0.0001; U = 66, p < 0.0001). Within each gross motor and fine motor category of the AGS Scale, a subset of children scored within normal IQ range. DISCUSSION: Parental assessment of function by the VABS-3 correlated with directly assessed performance measures. Our data underscore the potential value of VABS-3 and Leiter-3 as tools to assess psychometric function in AGS. With a deeper understanding of our patients' abilities, we can better guide clinicians and families to provide appropriate support and personalized interventions to empower children with leukodystrophies to maximize their communication and educational potential.

Beyond Contractures in Spinal Muscular Atrophy: Identifying Lower-Limb Joint Hypermobility.

Background: The natural history of spinal muscular atrophy (SMA) is well understood, with progressive muscle weakness resulting in declines in function. The development of contractures is common and negatively impacts function. Clinically, joint hypermobility (JH) is observed but is poorly described, and its relationship with function is unknown. Methods: Lower-limb ROM (range of motion) assessments of extension and flexion at the hip, knee, and ankle were performed. ROMs exceeding the published norms were included in the analysis. The functional assessments performed included the six-minute walk test (6 MWT) and the Hammersmith Functional Motor Scale-Expanded (HFMSE). Results: Of the 143 participants, 86% (n = 123) had at least one ROM measure that was hypermobile, and 22% (n = 32) had three or more. The HFMSE scores were inversely correlated with hip extension JH (r = -0.60, p = 0.21; n = 6) and positively correlated with knee flexion JH (r = 0.24, p = 0.02, n = 89). There was a moderate, inverse relationship between the 6 MWT distance and ankle plantar flexion JH (r = -0.73, p = 0.002; n = 15). Conclusions: JH was identified in nearly all participants in at least one joint in this study. Hip extension, knee flexion and ankle plantar flexion JH was associated with function. A further understanding of the trajectory of lower-limb joint ROM is needed to improve future rehabilitation strategies.

Disease Trajectories in the Revised Hammersmith Scale in a Cohort of Untreated Patients with Spinal Muscular Atrophy types 2 and 3.

Background: Spinal muscular atrophy (SMA) is a neuromuscular disorder characterised by progressive motor function decline. Motor function is assessed using several functional outcome measures including the Revised Hammersmith Scale (RHS). Objective: In this study, we present longitudinal trajectories for the RHS in an international cohort of 149 untreated paediatric SMA 2 and 3 patients (across 531 assessments collected between March 2015 and July 2019). Methods: We contextualise these trajectories using both the Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM). At baseline, this cohort included 50% females and 15% of patients had undergone spinal fusion surgery. Patient trajectories were modelled using a natural cubic spline with age, sex, and random effects for each patient. Results: RHS and HFMSE scores show similar trends over time in this cohort not receiving disease modifying therapies. The results confirm the strong correlation between the RHS and RULM previously observed in SMA types 2 and 3a. Scoliosis surgery is associated with a reduction of 3 points in the RHS, 4.5 points in the HFMSE for the SMA 2 population, and a reduction of 11.8 points in the RHS, and 13.4 points in the HFMSE for the SMA 3a populations. When comparing the RHS and RULM, there is a lower correlation in the type 3a's than the type 2 patients. In the SMA 2 population, there is no significant difference between the sexes in either the RHS or HFMSE trajectories. There is no significant difference in the RULM trajectory in the SMA 2 or 3a participants by sex. Conclusions: This study demonstrates that the RHS could be used in conjunction with other functional measures such as the RULM to holistically detect SMA disease progression. This will assist with fully understanding changes that occur with treatments, further defining trajectories and therapy outcomes.

Characterization of Fine Motor and Visual Motor Skills in Aicardi-Goutières Syndrome.

Aicardi-Goutières syndrome is a genetic inflammatory disorder resulting in dispersed neurologic dysfunction. Despite a recognition of overall motor impairment, fine and visual motor skills are undercharacterized. We hypothesize that there is a spectrum of fine and visual motor skills in the Aicardi-Goutières syndrome population as captured by a standard outcome measure, the Peabody Developmental Motor Scales (PDMS-2), which will be proportional to overall disease severity.In a cohort of 74 subjects, the Peabody Developmental Motor Scales-2 grasping and visual-motor integration subtests were administered concurrently with the Aicardi-Goutières syndrome Severity Scale (severe [range 0-3], moderate [range 4-8], and attenuated [range 9-11]). The cohort was also compared by genotype and performance as defined by raw scores. The distribution of Peabody Developmental Motor Scales-2 scores within a genotype was assessed by interquartile ranges (IQRs).Peabody Developmental Motor Scales-2 grasping and visual-motor integration performance was the least variable in the TREX1-cohort (IQR: 10.00-12.00) versus the SAMHD1 and IFIH1 cohorts (IQR: 51.00-132.00 and 48.50-134.00, respectively). Neurologic severity highly correlated with both fine and visual motor skills (Spearman correlation: r = 0.87, 0.91, respectively). A floor effect (lowest 10% of possible scores) was observed within the severe cohort (n = 32/35), whereas a ceiling effect (top 10%) was observed in the attenuated cohort (n = 13/17).This study characterized the spectrum of fine and visual motor function in the Aicardi-Goutières syndrome population, which correlated with overall neurologic dysfunction. The Peabody Developmental Motor Scales-2 grasping and visual-motor integration showed promise as potential assessment tools in moderate and attenuated Aicardi-Goutières syndrome cohorts. A better understanding of fine and visual motor function in this population will benefit clinical care and clinical trial design.

Nusinersen Treatment of Children with Later-Onset Spinal Muscular Atrophy and Scoliosis Is Associated with Improvements or Stabilization of Motor Function.

Nusinersen has been shown to improve or stabilize motor function in individuals with spinal muscular atrophy (SMA). We evaluated baseline scoliosis severity and motor function in nusinersen-treated non-ambulatory children with later-onset SMA. Post hoc analyses were conducted on 95 children initiating nusinersen treatment in the CHERISH study or SHINE long-term extension trial. Participants were categorized by baseline Cobb angle (first nusinersen dose): ≤10°, >10° to ≤20°, and >20° to <40° (no/mild/moderate scoliosis, respectively). Outcome measures included the Hammersmith Functional Motor Score-Expanded (HFMSE) and the Revised Upper Limb Module (RULM). Regression analysis determined the relationships between baseline scoliosis severity and later motor function. For children with no, mild, and moderate scoliosis, the mean increase in HFMSE from baseline to Day 930 was 6.0, 3.9, and 0.7 points, and in RULM was 6.1, 4.6, and 2.3 points. In the linear model, a 10° increase in baseline Cobb angle was significantly associated with a -1.4 (95% CI -2.6, -0.2) point decrease in HFMSE (p = 0.02) and a -1.2 (95% CI -2.1, -0.4) point decrease in RULM (p = 0.006) at Day 930. Treatment with nusinersen was associated with improvements/stabilization in motor function in all groups, with greater response in those with no/mild scoliosis at baseline.

Exploration of Gross Motor Function in Aicardi-Goutières Syndrome.

Background: Aicardi-Goutières syndrome (AGS) is a rare genetic disorder characterized by a spectrum of motor abilities. While the Aicardi-Goutières syndrome severity score favors severely impacted individuals, there is an unmet need to define tools measuring function across the Aicardi-Goutières syndrome spectrum as potential outcome assessments for future clinical trials. Methods: Gross Motor Function Measure-88 (GMFM-88) and AGS Severity Scale were administered in individuals affected by Aicardi-Goutières syndrome (n = 71). We characterized the performance variability by genotype. Derived versions of the GMFM-88, including the GMFM-66, GMFM-66 item set (GMFM-66IS), and GMFM-66 Basal&Ceiling (GMFM-66BC) were calculated. The Aicardi-Goutières syndrome cohort was divided into severe (AGS Severity Scale score <4) or attenuated (≥4). Performance on the AGS Severity Scale highly correlated with total GMFM-88 scores (Spearman Correlation: R = 0.91). To assess variability of the GMFM-88 within genotypic subcohorts, interquartile ranges (IQRs) were compared. Results: GMFM-88 performance in the TREX1 cohort had least variability while the SAMHD1 cohort had the largest IQR (4.23 vs 81.8). Floor effect was prominent, with most evaluations scoring below 20% (n = 46, 64.79%), particularly in TREX1- and RNASEH2-cohorts. Performance by the GMFM-66, GMFM-66IS, and GMFM-66BC highly correlated with the full GMFM-88. The Aicardi-Goutières syndrome population represents a broad range of gross motor skills. Conclusions: This work identified the GMFM-88 as a potential clinical outcome assessment in subsets of the Aicardi-Goutières syndrome population but underscores the need for additional validation of outcome measures reflective of the diverse gross motor function observed in this population, including low motor function. When time is limited by resources or patient endurance, shorter versions of the GMFM-88 may be a reasonable alternative.

2-Year Change in Revised Hammersmith Scale Scores in a Large Cohort of Untreated Paediatric Type 2 and 3 SMA Participants.

The Revised Hammersmith Scale (RHS) is a 36-item ordinal scale developed using clinical expertise and sound psychometrics to investigate motor function in participants with Spinal Muscular Atrophy (SMA). In this study, we investigate median change in the RHS score up to two years in paediatric SMA 2 and 3 participants and contextualise it to the Hammersmith Functional Motor Scale-Expanded (HFMSE). These change scores were considered by SMA type, motor function, and baseline RHS score. We consider a new transitional group, spanning crawlers, standers, and walkers-with-assistance, and analyse that alongside non-sitters, sitters, and walkers. The transitional group exhibit the most definitive change score trend, with an average 1-year decline of 3 points. In the weakest patients, we are most able to detect positive change in the RHS in the under-5 age group, whereas in the stronger patients, we are most able to detect decline in the RHS in the 8-13 age group. The RHS has a reduced floor effect compared to the HFMSE, although we show that the RHS should be used in conjunction with the RULM for participants scoring less than 20 points on the RHS. The timed items in the RHS have high between-participant variability, so participants with the same RHS total can be differentiated by their timed test items.

Psychometric evaluation of modified spinal muscular atrophy functional rating scale (SMAFRS) in adult patients using Rasch analysis.

INTRODUCTION/AIMS: The Spinal Muscular Atrophy Functional Rating Scale (SMAFRS) was first developed as a secondary functional outcome measure to detect changes over time in patients with spinal muscular atrophy (SMA) in clinical trials. Its modified version evaluates 10 activities of daily living. The aim of the study was to analyze modified SMAFRS data using item response theory psychometric models. METHODS: A total of 253 responses from 41 adult patients with ambulatory and non-ambulatory SMA types 2, 3, and 4 were analyzed. Rasch analysis was used to explore item-person targeting, fit statistics, category response functioning, dimensionality, and differential item functioning. RESULTS: Most items had good fitting with the exception of "toileting" and "respiratory." There were no major floor or ceiling effects, and most items covered a good range of disability with only a negligible breech of uni-dimensionality from eating, dressing, and respiratory items. Differential item function highlighted differences in toileting, turning, transferring, walking, and respiratory items between ambulatory and non-ambulatory populations. DISCUSSION: Despite subtle misfitting of certain items, mainly related to respiratory and bulbar function, overall modified SMAFRS remained a psychometrically stable and unidimensional outcome measure. There were some differences in measuring properties of certain functional items between ambulatory and non-ambulatory items that need to be taken into consideration in clinical trial design. Overall, the modified SMAFRS is a psychometrically reliable tool in assessment of adult patients with SMA.

Revised upper limb module in type II and III spinal muscular atrophy: 24-month changes.

The aim of the study was to establish 24-month changes in a large cohort of type II and III spinal muscular atrophy (SMA) patients assessed with the Revised Upper Limb Module (RULM), a tool specifically developed to assess upper limb function in SMA. We included 107 patients (54 type II and 53 type III) with at least 24-months follow up. The overall RULM 24-month changes showed a mean decline of -0.79 points. The difference between baseline and 24 months was significant in type II but not in type III patients. There was also a difference among functional subgroups but not in relation to age. Most patients had 24-month mean changes within 2 points, with 23% decreasing more than 2 points and 7% improving by >2 points. Our results suggest an overall progressive decline in upper limb function over 24 months. The negative changes were most notable in type II, in non-ambulant type III and with a different pattern of progression, also in non-sitter type II. In contrast, ambulant type III showed relative stability within the 24-month follow up. These findings will help in the interpretation of the real world data collected following the availability of new therapeutic approaches.

Reliability of the Telemedicine Application of the Gross Motor Function Measure-88 in Patients With Leukodystrophy.

BACKGROUND: Leukodystrophies are a rare class of disorders characterized by severe neuromotor disability. There is a strong need for research regarding the functional status of people with leukodystrophy which is limited by the need for in-person assessments of mobility. The purpose of this study is to assess the reliability of the Gross Motor Function Measure-88 (GMFM-88) using telemedicine compared with standard in-person assessments in patients with leukodystrophy. METHODS: A total of 21 subjects with a diagnosis of leukodystrophy (age range = 1.79-52.82 years) were evaluated by in-person and by telemedicine evaluations with the GMFM-88 by physical therapists. Inter-rater reliability was assessed through evaluation of the same subject by two independent raters within a three-week period (n = 10 encounters), and intrarater reliability was assessed through blinded rescoring of video-recorded assessments after a one-week time interval (n = 6 encounters). RESULTS: Remote assessments were performed by caregivers in all 21 subjects using resources found in the home with remote guidance. There was agreement between all paired in-person and remote measurements (Lin's concordance correlation ≥0.995). The Bland-Altman analysis indicated that the paired differences were within ±5%. Intrarater and inter-rater reliability demonstrated an intraclass correlation coefficient of >0.90. CONCLUSIONS: These results support that remote application of the GMFM-88 is a feasible and reliable approach to assess individuals with leukodystrophy. Telemedicine application of outcome measures may be of particular value in rare diseases and those with severe neurologic disability that impacts the ability to travel.

MLIP causes recessive myopathy with rhabdomyolysis, myalgia and baseline elevated serum creatine kinase.

Striated muscle needs to maintain cellular homeostasis in adaptation to increases in physiological and metabolic demands. Failure to do so can result in rhabdomyolysis. The identification of novel genetic conditions associated with rhabdomyolysis helps to shed light on hitherto unrecognized homeostatic mechanisms. Here we report seven individuals in six families from different ethnic backgrounds with biallelic variants in MLIP, which encodes the muscular lamin A/C-interacting protein, MLIP. Patients presented with a consistent phenotype characterized by mild muscle weakness, exercise-induced muscle pain, variable susceptibility to episodes of rhabdomyolysis, and persistent basal elevated serum creatine kinase levels. The biallelic truncating variants were predicted to result in disruption of the nuclear localizing signal of MLIP. Additionally, reduced overall RNA expression levels of the predominant MLIP isoform were observed in patients' skeletal muscle. Collectively, our data increase the understanding of the genetic landscape of rhabdomyolysis to now include MLIP as a novel disease gene in humans and solidifies MLIP's role in normal and diseased skeletal muscle homeostasis.

Nusinersen Treatment in Adults With Spinal Muscular Atrophy.

OBJECTIVE: To determine changes in motor and respiratory function after treatment with nusinersen in adults with spinal muscular atrophy (SMA) during the first two years of commercial availability in the USA. METHODS: Data were collected prospectively on adult (age >17 years at treatment initiation) SMA participants in the Pediatric Neuromuscular Clinical Research (PNCR) Network. Baseline assessments of SMA outcomes including the Expanded Hammersmith Functional Rating Scale (HFMSE), Revised Upper Limb Module (RULM), and 6-Minute Walk Test (6MWT) occurred <5 months before treatment, and post-treatment assessments were made up to 24 months after nusinersen initation. Patient-reported experiences, safety laboratory tests and adverse events were monitored. The mean annual rate of change over time was determined for outcome measures using linear mixed effects models. RESULTS: Forty-two adult SMA participants (mean age: 34 years, range 17-66) receiving nusinersen for a mean of 12.5 months (range 3-24 months) were assessed. Several motor and respiratory measures showed improvement distinct from the progressive decline typically seen in untreated adults. Participants also reported qualitative improvements including muscle strength, stamina, breathing and bulbar related outcomes. All participants tolerated nusinersen with normal surveillance labs and no significant adverse events. CONCLUSIONS: Trends of improvement emerged in functional motor, patient-reported, and respiratory measures, suggesting nusinersen may be efficacious in adults with SMA. Larger well-controlled studies and additional outcome measures are needed to firmly establish the efficacy of nusinersen in adults with SMA. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence regarding nusinersen tolerability and efficacy based on reported side effects and pulmonary and physical therapy assessments in an adult SMA cohort.

Psychometric properties of the PEDI-CAT for children and youth with spinal muscular atrophy.

PURPOSE: The purpose of this study was to examine the psychometric properties of the Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT) in children and youth with Spinal Muscular Atrophy (SMA). METHODS: In this prospective cross-sectional study, caregivers of children and youth with SMA completed the PEDI-CAT Daily Activities and Mobility domains. A subset of caregivers completed a questionnaire about the measure. RESULTS: Mean ranks of scaled scores for Daily Activities (n = 96) and Mobility (n = 95) domains were significantly different across the three SMA types and across the three motor classifications. Normative scores indicated that 85 participants (89.5%) had limitations in Mobility and 51 in Daily Activities (53.1%). Floor effects were observed in≤10.4% of the sample for Daily Activities and Mobility. On average, caregivers completed the Mobility domain in 5.4 minutes and the Daily Activities domain in 3.3 minutes. Most caregivers reported that they provided meaningful information (92.1%), were willing to use the PEDI-CAT format again (79%), and suggested adding content including power wheelchair mobility items. CONCLUSION: Convergent validity was demonstrated for the Daily Activities and Mobility domains. Normative scores detected limitations in Mobility and Daily Activity performance for most participants with SMA. The PEDI-CATwas feasible to administer and caregivers expressed willingness to complete the PEDI-CAT in the future.

Different trajectories in upper limb and gross motor function in spinal muscular atrophy.

INTRODUCTION: The Hammersmith Functional Motor Scale Expanded (HFMSE) and the Revised Upper Limb Module (RULM) have been widely used in natural history studies and clinical trials. Our aim was to establish how the scales relate to each other at different age points in spinal muscular atrophy (SMA) type 2 and 3, and to describe their coherence over 12 mo. METHODS: The study was performed by cross-sectional and longitudinal reanalysis of previously published natural history data. The longitudinal analysis of the 12-mo changes also included the analysis of concordance between scales with changes grouped as stable (±2 points), improved (>+2) or declined (>-2). RESULTS: Three hundred sixty-four patients were included in the cross-sectional analysis, showing different trends in score and point of slope change for the two scales. For type 2, the point of slope change was 4.1 y for the HFMSE and 5.8 for the RULM, while for type 3, it was 6 y for the HFMSE and 7.3 for the RULM. One-hundred-twenty-one patients had at least two assessments at 12 mo. Full concordance was found in 57.3% of the assessments, and in 40.4% one scale remained stable and the other changed. Each scale appeared to be more sensitive to specific age or functional subgroups. DISCUSSION: The two scales, when used in combination, may increase the sensitivity to detect clinically meaningful changes in motor function in patients with SMA types 2 and 3.

Nusinersen in pediatric and adult patients with type III spinal muscular atrophy.

OBJECTIVE: We report longitudinal data from 144 type III SMA pediatric and adult patients treated with nusinersen as part of an international effort. METHODS: Patients were assessed using Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM), and 6-Minute Walk Test (6MWT) with a mean follow-up of 1.83 years after nusinersen treatment. RESULTS: Over 75% of the 144 patients had a 12-month follow-up. There was an increase in the mean scores from baseline to 12 months on both HFMSE (1.18 points, p = 0.004) and RULM scores (0.58 points, p = 0.014) but not on the 6MWT (mean difference = 6.65 m, p = 0.33). When the 12-month HFMSE changes in the treated cohort were compared to an external cohort of untreated patients, in all untreated patients older than 7 years, the mean changes were always negative, while always positive in the treated ones. To reduce a selection bias, we also used a multivariable analysis. On the HFMSE scale, age, gender, baseline value, and functional status contributed significantly to the changes, while the number of SMN2 copies did not contribute. The effect of these variables was less obvious on the RULM and 6MWT. INTERPRETATION: Our results expand the available data on the effect of Nusinersen on type III patients, so far mostly limited to data from adult type III patients.

Age related treatment effect in type II Spinal Muscular Atrophy pediatric patients treated with nusinersen.

Previous natural history studies suggest that type II SMA patients remain stable over one year but show some progression over two years. Since nusinersen approval, there has been increasing attention to identify more specific age-related changes. The aim of the study was to establish 12-month changes in a cohort of pediatric type II SMA treated with nusinersen and to establish possible patterns of treatment effect in relation to different variables such as age, baseline value and SMN2 copy number. The Hammersmith Functional Motor Scale Expanded and the Revised Upper Limb Module were performed at T0 and 12 months after treatment (T12). Data in treated patients were compared to available data in untreated patients collected by the same evaluators.Seventy-seven patients of age between 2.64 and 17.88 years (mean:7.47, SD:3.79) were included. On t-test there was an improvement, with increased mean scores between T0 and T12 on both scales (p < 0.001). Using multivariate linear regression analysis, age and baseline scores were predictive of changes on both scales (p < 0.05) while SMN2 copy number was not. Differences were also found between study cohort and untreated data on both scales (p < 0.001). At 12 months, an increase in scores was observed in all the age subgroups at variance with natural history data. Our real-world data confirm the treatment effect of nusinersen in pediatric type II SMA patients and that the data interpretation should take into account different variables. These data confirm and expand the ones already reported in the Cherish study.

Development of a Mitochondrial Myopathy-Composite Assessment Tool.

BACKGROUND: 'Mitochondrial Myopathy' (MM) refers to genetically-confirmed Primary Mitochondrial Disease (PMD) that predominantly impairs skeletal muscle function. Validated outcome measures encompassing core MM domains of muscle weakness, muscle fatigue, imbalance, impaired dexterity, and exercise intolerance do not exist. The goal of this study was to validate clinically-meaningful, quantitative outcome measures specific to MM. METHODS: This was a single centre study. Objective measures evaluated included hand-held dynamometry, balance assessments, Nine Hole Peg Test (9HPT), Functional Dexterity Test (FDT), 30 second Sit to Stand (30s STS), and 6-minute walk test (6MWT). Results were assessed as z-scores, with < -2 standard deviations considered abnormal. Performance relative to the North Star Ambulatory Assessment (NSAA) of functional mobility was assessed by Pearson's correlation. RESULTS: In genetically-confirmed MM participants [n = 59, mean age 21.6 ± 13.9 (range 7 - 64.6 years), 44.1% male], with nuclear gene aetiologies, n = 18/59, or mitochondrial (mtDNA) aetiologies, n = 41/59, dynamometry measurements demonstrated both proximal [dominant elbow flexion (-2.6 ± 2.1, mean z-score ± standard deviation, SD), hip flexion (-2.5 ± 2.3), and knee flexion (-2.8 ± 1.3)] and distal muscle weakness [wrist extension (-3.4 ± 1.7), palmar pinch (-2.5 ± 2.8), and ankle dorsiflexion (-2.4 ± 2.5)]. Balance [Tandem Stance (TS) Eyes Open (-3.2 ± 8.8, n = 53) and TS Eyes Closed (-2.6 ± 2.7, n = 52)] and dexterity [FDT (-5.9 ± 6.0, n = 44) and 9HPT (-8.3 ± 11.2, n = 53)] assessments also revealed impairment. Exercise intolerance was confirmed by strength-based 30s STS test (-2.0 ± 0.8, n = 38) and mobility-based 6MWT mean z-score (-2.9 ± 1.3, n = 46) with significant decline in minute distances (slope -0.9, p = 0.03, n = 46). Muscle fatigue was quantified by dynamometry repetitions with strength decrement noted between first and sixth repetitions at dominant elbow flexors (-14.7 ± 2.2%, mean ± standard error, SEM, n = 21). All assessments were incorporated in the MM-Composite Assessment Tool (MM-COAST). MM-COAST composite score for MM participants was 1.3± 0.1(n = 53) with a higher score indicating greater MM disease severity, and correlated to NSAA (r = 0.64, p < 0.0001, n = 52) to indicate clinical meaning. Test-retest reliability of MM-COAST assessments in an MM subset (n = 14) revealed an intraclass correlation coefficient (ICC) of 0.81 (95% confidence interval: 0.59-0.92) indicating good reliability. CONCLUSIONS: We have developed and successfully validated a MM-specific Composite Assessment Tool to quantify the key domains of MM, shown to be abnormal in a Definite MM cohort. MM-COAST may hold particular utility as a meaningful outcome measure in future MM intervention trials.

Clinical Variability in Spinal Muscular Atrophy Type III.

OBJECTIVE: We report natural history data in a large cohort of 199 patients with spinal muscular atrophy (SMA) type III assessed using the Hammersmith Functional Motor Scale Expanded (HFMSE). The aim of the study was to establish the annual rate and possible patterns of progression according to a number of variables, such as age of onset, age at assessment, SMN2 copy number, and functional status. METHODS: HFMSE longitudinal changes were assessed using piecewise linear mixed-effects models. The dependency in the data due to repeated measures was accounted for by a random intercept per individual and an unstructured covariance R matrix was used as correlation structure. An additional descriptive analysis was performed for 123 patients, for a total of 375 12-month assessments. RESULTS: A break point at age 7 years was set for the whole cohort and for SMA IIIA and IIIB. Age, SMA type, and ambulatory status were significantly associated with changes in mean HFMSE score, whereas gender and SMN2 copy number were not. The increase in response before the break point of age 7 years is significant only for SMA IIIA (ß = 1.79, p < 0.0001). After the break point, the change in the rate of HFMSE score significantly decrease for both SMA IIIA (ß = -1.15, p < 0.0001) and IIIB (ß = -0.69, p = 0.002). INTERPRETATION: Our findings contribute to the understanding of the natural history of SMA type III and will be helpful in the interpretation of the real-world data of patients treated with commercially available drugs. ANN NEUROL 2020;88:1109-1117.