Reliability of the Hammersmith functional motor scale for spinal muscular atrophy in a multicentric study

Determining minimal clinically important differences in the Hammersmith Functional Motor Scale Expanded for untreated spinal muscular atrophy patients: An international study

BACKGROUND AND PURPOSE

Spinal muscular atrophy (SMA) is a rare and progressive neuromuscular disorder with varying severity levels. The aim of the study was to calculate minimal clinically important difference (MCID), minimal detectable change (MDC), and values for the Hammersmith Functional Motor Scale Expanded (HFMSE) in an untreated international SMA cohort.

METHODS

The study employed two distinct methods. MDC was calculated using distribution-based approaches to consider standard error of measurement and effect size change in a population of 321 patients (176 SMA II and 145 SMA III), allowing for stratification based on age and function. MCID was assessed using anchor-based methods (receiver operating characteristic [ROC] curve analysis and standard error) on 76 patients (52 SMA II and 24 SMA III) for whom the 12-month HFMSE could be anchored to a caregiver-reported clinical perception questionnaire.

RESULTS

With both approaches, SMA type II and type III patients had different profiles. The MCID, using ROC analysis, identified optimal cutoff points of -2 for type II and -4 for type III patients, whereas using the standard error we found the optimal cutoff points to be 1.5 for improvement and -3.2 for deterioration. Furthermore, distribution-based methods uncovered varying values across age and functional status subgroups within each SMA type.

CONCLUSIONS

These results emphasize that the interpretation of a single MCID or MDC value obtained in large cohorts with different functional status needs to be made with caution, especially when these may be used to assess possible responses to new therapies.

An interpretable data-driven prediction model to anticipate scoliosis in spinal muscular atrophy in the era of (gene-) therapies

5q-spinal muscular atrophy (SMA) is a neuromuscular disorder (NMD) that has become one of the first 5% treatable rare diseases. The efficacy of new SMA therapies is creating a dynamic SMA patient landscape, where disease progression and scoliosis development play a central role, however, remain difficult to anticipate. New approaches to anticipate disease progression and associated sequelae will be needed to continuously provide these patients the best standard of care. Here we developed an interpretable machine learning (ML) model that can function as an assistive tool in the anticipation of SMA-associated scoliosis based on disease progression markers. We collected longitudinal data from 86 genetically confirmed SMA patients. We selected six features routinely assessed over time to train a random forest classifier. The model achieved a mean accuracy of 0.77 (SD 0.2) and an average ROC AUC of 0.85 (SD 0.17). For class 1 'scoliosis' the average precision was 0.84 (SD 0.11), recall 0.89 (SD 0.22), F1-score of 0.85 (SD 0.17), respectively. Our trained model could predict scoliosis using selected disease progression markers and was consistent with the radiological measurements. During post validation, the model could predict scoliosis in patients who were unseen during training. We also demonstrate that rare disease data sets can be wrangled to build predictive ML models. Interpretable ML models can function as assistive tools in a changing disease landscape and have the potential to democratize expertise that is otherwise clustered at specialized centers.

Assessing the Assisted Six-Minute Cycling Test as a Measure of Endurance in Non-Ambulatory Patients with Spinal Muscular Atrophy (SMA)

Assessing endurance in non-ambulatory individuals with Spinal Muscular Atrophy (SMA) has been challenging due to limited evaluation tools. The Assisted 6-Minute Cycling Test (A6MCT) is an upper limb ergometer assessment used in other neurologic disorders to measure endurance. To study the performance of the A6MCT in the non-ambulatory SMA population, prospective data was collected on 38 individuals with SMA (13 sitters; 25 non-sitters), aged 5 to 74 years (mean = 30.3; SD = 14.1). The clinical measures used were A6MCT, Revised Upper Limb Module (RULM), Adapted Test of Neuromuscular Disorders (ATEND), and Egen Klassifikation Scale 2 (EK2). Perceived fatigue was assessed using the Fatigue Severity Scale (FSS), and effort was assessed using the Rate of Perceived Exertion (RPE). Data were analyzed for: (1) Feasibility, (2) Clinical discrimination, and (3) Associations between A6MCT with clinical characteristics and outcomes. Results showed the A6MCT was feasible for 95% of the tested subjects, discriminated between functional groups (p = 0.0086), and was significantly associated with results obtained from RULM, ATEND, EK2, and Brooke (p < 0.0001; p = 0.029; p < 0.001; p = 0.005). These findings indicate the A6MCT's potential to evaluate muscular endurance in non-ambulatory SMA individuals, complementing clinician-rated assessments. Nevertheless, further validation with a larger dataset is needed for broader application.

Caregivers' Expectations on Possible Functional Changes following Disease-Modifying Treatment in Type II and III Spinal Muscular Atrophy: A Comparative Study

Background: The primary aim of this study was to explore current caregivers' expectations on possible functional changes following treatment in comparison to data obtained in the pre-pharmacological era. Methods: A questionnaire, previously used in 2016, was administered to caregivers of type II and III SMA patients of age between 3 and 71 years, and to patients over the age of 13 years. The questionnaire focuses on (1) caregivers and patients expectations, (2) meaningfulness of the changes observed on the functional motor scales, and (3) their willingness to be enrolled in a clinical trial. A comparative study was performed with data obtained using the same questionnaire soon before the advent of disease-modifying therapies. Results: We administered the questionnaire to 150 caregivers. When comparing current caregiver data to those obtained in 2016, the most obvious differences were related to disease perception over the last year (stability: 16.5% in 2016 vs. 43.6% in 2022; deterioration 70.5% vs. 12.8%, and improvement: 12.9% vs. 43.6%) and expectations from clinical trials with higher expectations in 2022 compared to 2016 (p < 0.001). Forty-five of the 150 in the current study were caregivers of patients above the age of 13. In these 45 the questionnaire was also administered to the patient. No difference was found in responses between patients and their caregivers. Conclusions: Both carers and patients reported that even small changes on functional scales, similar to those reported by clinical studies and real-world data, are perceived as meaningful. Comparing the recent responses to those obtained in 2016, before pharmacological treatment was available, we found significant changes in caregivers' perception with increased expectations. These findings will provide a better understanding of the patients' expectations and facilitate discussion with regulators.

Real-Life Outcome After Gene Replacement Therapy for Spinal Muscular Atrophy: A Multicenter Experience

BACKGROUND

Onasemnogene abeparvovec-xioi (OA) has been available since 2019 as a gene replacement therapy for individuals with spinal muscular atrophy (SMA) under age two years. We aim to expand upon the sparse knowledge about its safety and clinical efficacy.

METHODS

The clinical outcome data of all the individuals with SMA who were treated with gene therapy in four tertiary hospitals in Israel were retrieved and analyzed.

RESULTS

The study participants included 25 individuals who received the gene therapy between age 11 days and 23 months and whose median follow-up duration was 18.0 (interquartile range [IQR], 12.4 to 18.3) months. Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores increased by a median (IQR) of 13 (8 to 20) points at the last follow-up compared with baseline. None of the patients experienced regression in motor abilities after gene therapy, which was generally well tolerated. There was gradual improvement in motor function, especially among presymptomatic patients (P ≤ 0.001) whose disease duration was shorter (≤8 months) before receiving gene therapy (P ≤ 0.001) and who did not experience recurrent infections and illnesses in the months following treatment (P ≤ 0.001).

CONCLUSIONS

OA was well tolerated and led to favorable functional motor outcomes at six to 24 months after treatment initiation. Better progress in motor function was observed in individuals who received OA earlier and who were presymptomatic, irrespective of the SMN2 copy number or type. Our results further strengthen the clinical efficacy of OA and reinforce the importance of early recognition of SMA via newborn screening programs.

Examination of Upper Limb Function and the Relationship with Gross Motor Functional and Structural Parameters in Patients with Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by the deletion or/and mutation in the survival motor neuron 1 (SMN1) gene on chromosome 5. Until now, only a few articles investigating the relationship between upper limb function and the gross motor function in untreated SMA patients have been published. However, there is still a lack of publications including the relationship between structural changes such as cervical rotation, trunk rotation and side trunk shortening, and upper limb function. The aim of the study was to examine the upper limb function in patients with spinal muscular atrophy and the relationship between the upper limb function, gross motor function, and structural parameters. We present an analysis of 25 SMA patients, divided into sitter and walker groups, undergoing pharmacological treatment (nusinersen or risdiplam), examined twice between the initial examination and evaluation after a 12-month period. The participants were tested using validated scales such as the Revised Upper Limb Module (RULM), the Hammersmith Functional Motor Scale-Extended (HFMSE), and the structural parameters. Our results showed that patients demonstrated greater improvement on the RULM scale than on the HFMSE scale. Moreover, persistent structural changes negatively affected both the upper limb function and gross motor skills.

Neurocognitive profile of a cohort of SMA type 1 pediatric patients and emotional aspects, resilience and coping strategies of their caregivers

Spinal muscular atrophy (SMA) type 1 represents the most severe condition of the spectrum of SMA 5q. In the absence of therapeutic interventions, patients do not achieve any motor milestone and their life expectancy does not exceed two years of age. To date, three disease-modifying drugs have been approved for SMA type I. These treatments have radically changed the natural history of the disease, improving motor, respiratory and bulbar functions. In recent years huge amount of data have been collected worldwide related to motor, respiratory and swallowing function outcome in treated patients, whereas the neurocognitive profile of treated patients has been poorly explored. Here we report the neurocognitive development profile of a cohort of SMA type I children treated with a disease modifying therapy. We also describe the burden and resilience as well as the coping strategies of their caregivers. Our finding show a global developmental delay in most patients and defects in gross motor functions contribute most to lower the general development quotient of Griffiths III, whereas the scores obtained on evaluating learning and language abilities scales suggest a positive trend in the developmental trajectory of general neurocognitive abilities. Some parents reported anxiety and stress but overall they were resilient (and had good coping strategies towards the burden of care for their child. These results reinforce the importance of routinely assessing the neurocognitive aspects in SMA type I patients and to offer an early intervention to favor the psychosocial development of these children.

Hybrid reflected-ultrasound computed tomography versus B-mode-ultrasound for muscle scoring in spinal muscular atrophy

BACKGROUND AND PURPOSE

Novel light- and sound-based technologies like multispectral optoacoustic tomography (MSOT) with co-registered reflected-ultrasound computed tomography (RUCT) could add additional value to conventional ultrasound (US) for disease phenotyping in pediatric spinal muscular atrophy (SMA). The aim of this study was to investigate the quality of RUCT compared to US for qualitative and quantitative assessment of imaging neuromuscular disorders.

METHODS

Subanalyzing the MSOT SMA study, 288 RUCT and 276 US images from 10 SMA patients (mean age 9.0 ± 3.7) and 10 gender- and age-matched healthy volunteers (HV; mean age 8.7 ± 4.3) were analyzed for quantitative (grayscale levels [GSLs]) and qualitative (echogenicity, distribution pattern, Heckmatt scale, and muscle texture) muscle changes. RUCT and US measures were further correlated with clinical standard motor outcomes.

RESULTS

Quantitative agreement using GSLs revealed significantly higher GSLs in muscles of SMA patients compared to healthy muscles in both techniques (US mean GSL [SD] SMA vs. HV: 110.70 [27.8] vs. 68.85 [19.2], p < .0001; RUCT mean GSL [SD] SMA vs. HV: 91.81 [21.8] vs. 59.86 [8.2], p < .0001) with good correlation with motor outcome tests, respectively. Qualitative agreement between methods for muscle composition was excellent for differentiation of pathological versus healthy muscles, echogenicity, and distribution pattern, moderate for Heckmatt scale, and poor for muscle texture.

CONCLUSIONS

The data suggest that RUCT may allow the assessment of basic qualitative and quantitative measures for muscular diseases with comparable results to conventional US.

Health-Related Quality of Life in Spinal Muscular Atrophy Patients and Their Caregivers-A Prospective, Cross-Sectional, Multi-Center Analysis

Spinal muscular atrophy (SMA) is a disabling disease that affects not only the patient’s health-related quality of life (HRQoL), but also causes a high caregiver burden (CGB). The aim of this study was to evaluate HRQoL, CGB, and their predictors in SMA. In two prospective, cross-sectional, and multi-center studies, SMA patients (n = 39) and SMA patient/caregiver couples (n = 49) filled in the EuroQoL Five Dimension Five Level Scale (EQ-5D-5L) and the Short Form Health Survey 36 (SF-36). Caregivers (CGs) additionally answered the Zarit Burden Interview (ZBI) and the Hospital Anxiety and Depression Scale (HADS). Patients were clustered into two groups with either low or high HRQoL (EQ-5D-5L index value <0.259 or >0.679). The latter group was mostly composed of ambulatory type III patients with higher motor/functional scores. More severely affected patients reported low physical functioning but good mental health and vitality. The CGB (mean ZBI = 22/88) correlated negatively with patients’ motor/functional scores and age. Higher CGB was associated with a lower HRQoL, higher depression and anxiety, and more health impairments of the CGs. We conclude that patient and CG well-being levels interact closely, which highlights the need to consider the health of both parties while evaluating novel treatments.

Revised Hammersmith Scale for spinal muscular atrophy: Inter and intra-rater reliability and agreement

The Revised Hammersmith Scale (RHS) for Spinal Muscular Atrophy (SMA) was designed as a psychometrically robust clinical outcome assessment to assess physical abilities of patients with type 2 and 3 SMA. The reliability properties of the RHS have not yet been reported. A prospective RHS reliability study was undertaken in a UK cohort of experienced neuromuscular paediatric Physiotherapists. Reliability testing was conducted via a virtual survey platform two weeks apart. Through the virtual platform participants scored videos of two RHS assessments, one of a child with SMA 2 and one of a child with SMA 3. Inter and intra-rater reliability was analysed using a type 3 Intraclass Correlation Coefficient (ICC). Intra-rater agreement was further analysed using Bland Altman (BA) Limits of Agreement (LOA) and plots. The acceptable inter and intra-rater variability was set as a change of ± 2 by the international team of expert physiotherapists who developed the RHS. Inter-rater agreement, n = 22 raters, type 3 ICC was 0.989 (95% CI 0.944 to 1.00), 97.7% of scores were within the acceptable limits of ± 2 points. Intra-rater agreement, n = 21 raters, type 3 ICC ranged from 0.922 to 1.0, with 97.6% of scores within the acceptable limits of ± 2 points. The mean SMA 2 intra-rater difference was -0.10 (-0.6 to 0.4), with lower LOA -2.24 and upper LOA +2.04. Intra-rater difference between tests for SMA 3 intra-rater difference was -0.05 (-0.6 to 0.5), with lower LOA -2.48 and upper LOA +2.38. Intra-rater scoring precision fell within BA agreement limits of ±2 points. The results demonstrate that the RHS is highly reliable when used by experienced UK physiotherapists, and variability of test scores regarding inter and intra-rater reliability was confirmed to lie within ±2 points.

Systematic Review of Motor Function Scales and Patient-Reported Outcomes in Spinal Muscular Atrophy

ABSTRACT

Spinal muscular atrophy is a heterogeneous disease that results in loss of motor function. In an evolving treatment landscape, establishing the suitability and limitations of existing motor function scales and patient-reported outcomes used to monitor patients with this disease is important. A systematic review was conducted to examine utility of motor function scales and patient-reported outcomes in evaluating patients with spinal muscular atrophy. Published literature was reviewed up to June 2021 with no start date restriction. Of the reports screened, 122 were deemed appropriate for inclusion and are discussed in this review (including 24 validation studies for motor function scales or patient-reported outcomes). Fifteen motor function scales and patient-reported outcomes were identified to be commonly used (≥5 studies), of which 11 had available validation assessments. Each instrument has its strengths and limitations. It is imperative that the patient population (e.g., age, mobility), goals of treatment, and outcomes or endpoints of interest be considered when selecting the appropriate motor function scales and patient-reported outcomes for clinical studies.

Clinical outcome assessments in Duchenne muscular dystrophy and spinal muscular atrophy: past, present and future

Scores and scales used in pediatric motor development for neuromuscular disorders have evolved greatly since the beginning of their development. In this review we provide a brief history of scales used in pediatric patients with neuromuscular disorders and an update regarding the advancement of the scales commonly used in patients with spinal muscular atrophy and Duchenne muscular dystrophy. We focus on the collaborative effort that has led to the development of outcomes and speak to the possible future of Clinical Outcome Assessments.

Neck and Trunk Muscle Strength in Children With Spinal Muscular Atrophy Is Lower Than in Healthy Controls and Depends on Disease Type

Background: Neck and trunk muscle strength and relationship with motor function in individuals with spinal muscular atrophy (SMA) is not investigated well. Information on maximum muscle strength that children with SMA may develop considerably expands the possibilities of assessing the effectiveness of pharmacological treatment methods and therapeutic procedures. This study sought to assess neck and trunk muscle strength in patients with SMA and to compare it with values noted in healthy children.

Methods: The study involved 56 individuals with SMA aged 5–16 not treated pharmacologically, including 9 patients with SMA type 1 (SMA1), 27 with SMA type 2 (SMA2), and 20 with SMA type 3 (SMA3). The control group included 111 healthy individuals aged 5–16. Neck and trunk muscle strength was assessed by means of a maximum voluntary isometric contraction method with the use of a handheld digital muscle tester MICROFET2. Moreover, relative strength was also calculated by standardising the maximum voluntary isometric contraction according to body mass. The Kruskal–Wallis test, Mann–Whitney U-test, and Spearman's rank correlation were used for statistical analysis.

Results: The reliability of the neck and trunk muscle strength measurements with the handheld digital muscle tester was excellent with ICC > 0.9. The values of muscle strength in SMA groups were significantly lower than in the control group. The values of relative torque of the neck muscles expressed in percentage values calculated with regard to the control group were at the level of 47.6–51.6% in SMA1 group, 54.8–58.1% in SMA2 group and 80.6–90.3% in SMA3 group. The percentage values for upper and lower trunk muscle strength were at the level of 42.6–68.4% in SMA1 group, 56.9–75.4% in SMA2 group and 76.7–94.8% in SMA3 group.

Conclusion: Handheld dynamometry provides reliable measures of neck and trunk muscle strength in SMA children. Neck and trunk muscle strength in children with SMA is lower than in healthy controls and depends on disease type, which confirms the theory based on clinical observations. Further, study is needed to investigate the effect of pharmacological treatment on the strength of the neck/trunk muscles, and relationship between neck and trunk muscle strength and motor capabilities.

Quantification of disease progression in spinal muscular atrophy with muscle MRI-a pilot study

OBJECTIVES

Quantitative MRI (qMRI) of muscles is a promising tool to measure disease progression or to assess therapeutic effects in neuromuscular diseases. Longitudinal imaging studies are needed to show sensitivity of qMRI in detecting disease progression in spinal muscular atrophy (SMA). In this pilot study we therefore studied one-year changes in quantitative MR parameters in relation to clinical scores.

METHODS

We repeated quantitative 3 T MR analysis of thigh muscles and clinical testing one year after baseline in 10 treatment-naïve patients with SMA, 5 with Type 2 (21.6 ± 7.0 years) and 5 with Type 3 (33.4 ± 11.9 years). MR protocol consisted of Dixon, T₂ mapping and diffusion tensor imaging (DTI). The temporal relation of parameters was examined with a mixed model.

RESULTS

We detected a significant increase in fat fraction (baseline, 38.2% SE 0.6; follow-up, 39.5% SE 0.6; +1.3%, p = 0.001) in all muscles. Muscles with moderate to high fat infiltration at baseline show a larger increase over time (+1.6%, p < 0.001). We did not find any changes in DTI parameters except for low fat-infiltration muscles (m. adductor longus and m. biceps femoris (short head)). The T₂ of muscles decreased from 28.2 ms to 28.0 ms (p = 0.07). Muscle strength and motor function scores were not significantly different between follow-up and baseline.

CONCLUSION

Longitudinal imaging data show slow disease progression in skeletal muscle of the thigh of (young-) adult patients with SMA despite stable strength and motor function scores. Quantitative muscle imaging demonstrates potential as a biomarker for disease activity and monitoring of therapy response.

The altered expression of neurofilament in mouse models and patients with spinal muscular atrophy

Objectives

To investigate the levels of neurofilaments (NFs) in transgenic mice and patients with spinal muscular atrophy (SMA), and to evaluate their efficacy as a biomarker in SMA.

Methods

The levels of NF mRNA transcripts were measured by quantitative real‐time PCR in spinal cord from SMA mice. Blood levels of NF heavy chain (NfH) from mice and patients were measured by an in‐house ELISA method. The response of NFs to therapeutic intervention was analysed in severe SMA mice treated with morpholino antisense oligonucleotides.

Results

Significant changes in NF transcript and protein in spinal cord and protein levels in blood were detected in SMA mice with severe or mild phenotypes, at different time points. A decrease in blood levels of NfH after antisense oligonucleotide treatment was only transient in the mice, despite the persistent benefit on the disease phenotype. A drastic reduction of over 90% in blood levels of NfF was observed in both control and SMA mice during early postnatal development. In contrast, blood levels of NfH were found to be decreased in older SMA children with chronic disease progression.

Interpretation

Our results show that blood NfH levels are informative in indicating disease onset and response to antisense oligonucleotides treatment in SMA mice, and indicate their potential as a peripheral marker reflecting the pathological status in central nervous system. In older patients with chronic SMA, however, the lower NfH levels may limit their application as biomarker, highlighting the need to continue to pursue additional biomarkers for this group of patients.

Sometimes they come back: New and old spinal muscular atrophy adults in the era of nusinersen

BACKGROUND AND PURPOSE

Following the commercial availability of nusinersen, there have been a number of new referrals of adults with spinal muscular atrophy (SMA) not regularly followed in tertiary-care centers or enrolled in any disease registry.

METHODS

We compared demographics and disease characteristics, including assessment of motor and respiratory function, in regularly followed patients and newcomers subdivided according to the SMA type.

RESULTS

The cohort included 166 adult patients (mean age: 37.09 years): one type I, 65 type II, 99 type III, and one type IV. Of these 166, there were 67 newcomers. There was no significant difference between newcomers and regularly followed patients in relation to age and disease duration. The Hammersmith Functional Motor Scale Expanded and Revised Upper Limb Module scores were higher in the regularly followed patients compared to newcomers in the whole cohort and in both SMA II and II. A difference was also found on ventilatory status (p = 0.013) and Cobb's angle >50° (p = 0.039) between the two subgroups. No difference was found in scoliosis surgery prevalence (p > 0.05).

CONCLUSIONS

Our results showed differences between the two subgroups, even if less marked in the type III patients. In the type II patients, there was a higher proportion of newcomers who were in the severe end of the spectrum. Of the newcomers, only approximately a third initiated treatment, as opposed to the 51% in the regularly followed patients. The identification of patients who were not part of the registries will help to redefine the overall prevalence of SMA and the occurrence of different phenotypes.

Salbutamol tolerability and efficacy in patients with spinal muscular atrophy type II

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by homozygous deletions or loss-of-function mutations in SMN1, which result in a degeneration of motor neurons in the spinal cord and brain stem. Even without a randomized placebo-controlled trial, salbutamol has been offered to patients with SMA in the neuromuscular clinics of most of hospitals for many years. We describe the response to salbutamol in 48 patients with SMA type II who were not taking any other medication. We investigate the changes over an eighteen-month period in motor functional scales and we analyze side effects and subjective response to treatment. Our results suggest that oral administration of salbutamol might be helpful in the maintenance of motor function in patients with SMA type II. An apparent beneficial effect was observed in functional scales of children under the age of 6, especially during the first 6 months of therapy. The majority of patients of all ages referred some kind of subjective positive effect associated with therapy intake. Salbutamol seemed safe and was well tolerated without serious side effects.

Reliability of four tests to assess body posture and the range of selected movements in individuals with spinal muscular atrophy

Background

The majority of individuals with spinal muscular atrophy (SMA) experience progressive skeletal deformities which may affect the quality of life and mobility. To date, no studies have evaluated the reliability of tests assessing body posture and joint mobility in SMA patients. The purpose of this study was to assess the reliability of Cervical Rotation test (CR), Supine Angle of Trunk Rotation test (SATR), Hip Extension test (HE) and Pelvic Obliquity test (PO) developed to evaluate the musculoskeletal system in SMA individuals.

Methods

Thirty individuals (12 girls and 18 boys) aged 4–15 with SMA type II (n = 24) and III (n = 6) confirmed by genetic examinations were qualified for the study. The participants were examined twice by three physiotherapists on the same day. The examination included four tests, i.e. CR, SATR, HE and PO tests aimed at assessing ranges of rotation in the cervical spine, chest deformities, ranges of hip extension and pelvis position while sitting. Statistical calculations were made with the use of statistical software IBM SPSS Statistics version 20. Reliability was assessed using the Intraclass Correlation Coefficient (ICC).

Results

Intraobserver reliability was excellent for CR (ICC range 0.839–0.911), SATR (ICC range 0.918–0.939 - the upper part of the sternum; ICC range 0.951–0.975 - the lower part of the sternum), HE (ICC range 0.988–0,991) and PO (ICC range 0.896–0.935) tests.

The interobserver ICC reached the excellent values in CR (ICC range 0.912–0.920), SATR (ICC = 0.888 - the upper part of the sternum, ICC = 0.951 - the lower part of the sternum), HE (ICC range 0.922–0.923) and PO (ICC = 0.928) tests.

Conclusions

CR, SATR, HE and PO tests are reliable and may be used for examining individuals with SMA. The application of these tests provides a possibility to detect early changes in the musculoskeletal system in children and adolescents and to assess the effectiveness of the implemented pharmacotherapy and rehabilitation.

Vibration-Assisted Home Training Program for Children With Spinal Muscular Atrophy

The aim of this study was to determine the effect of a new method of vibration-assisted neuromuscular rehabilitation in patients with spinal muscular atrophy types II and III. In this retrospective observational study, 38 children (mean age: 4.64 ± 1.95 years) were analyzed. The physiotherapy program, Auf die Beine, combines 6 months of home-based side-alternating whole-body vibration with interval blocks of intensive, goal-directed rehabilitation: 13 days at the start and 6 days after 3 months. Assessments were applied at the beginning (M0), after 6 months of home-based training (M6), and after 6 months of follow-up (M12). Motor abilities were assessed by the Gross Motor Function Measure 66 and Hammersmith Functional Mobility Scale. The Gross Motor Function Measure showed an increase of 1.69 (3.73) points (P = .124) and the Hammersmith Functional Mobility Scale a significant increase of 2.73 ± 1.79 points (P = .007) after 12 months; however, whether this leads to a long-term clinical benefit requires further investigation.

Motor Function Test Reliability During the NeuroNEXT Spinal Muscular Atrophy Infant Biomarker Study

BACKGROUND

The NeuroNEXT SMA Infant Biomarker Study, a two year, longitudinal, multi-center study of infants with SMA type 1 and healthy infants, presented a unique opportunity to assess multi-site rater reliability on three infant motor function tests (MFTs) commonly used to assess infants with SMA type 1.

OBJECTIVE

To determine the effect of prospective MFT rater training and the effect of rater experience on inter-rater and intra-rater reliability for the Test of Infant Motor Performance Screening Items (TIMPSI), the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) and the Alberta Infant Motor Scale (AIMS).

METHODS

Training was conducted utilizing a novel set of motor function test (MFT) videos to optimize accurate MFT administration and reliability for the study duration. Inter- and intra-rater reliability of scoring for the TIMPSI and inter-rater reliability of scoring for the CHOP INTEND and the AIMS was assessed using intraclass correlation coefficients (ICC). Effect of rater experience on reliability was examined using ICC. Agreement with 'expert' consensus scores was examined using Pearson's correlation coefficients.

RESULTS

Inter-rater reliability on all MFTs was good to excellent. Intra-rater reliability for the primary MFT, the TIMPSI, was excellent for the study duration. Agreement with 'expert' consensus was within predetermined limits (≥85%) after training. Evaluator experience with SMA and MFTs did not affect reliability.

CONCLUSIONS

Reliability of scores across evaluators was demonstrated for all three study MFTs and scores were reproducible on repeated administration. Evaluator experience had no effect on reliability.

Content validity and clinical meaningfulness of the HFMSE in spinal muscular atrophy

BACKGROUND

Reports on the clinical meaningfulness of outcome measures in spinal muscular atrophy (SMA) are rare. In this two-part study, our aim was to explore patients' and caregivers' views on the clinical relevance of the Hammersmith Functional Motor Scale Expanded- (HFMSE).

METHODS

First, we used focus groups including SMA patients and caregivers to explore their views on the clinical relevance of the individual activities included in the HFMSE. Then we asked caregivers to comment on the clinical relevance of possible changes of HFMSE scores over time. As functional data of individual patients were available, some of the questions were tailored according to their functional level on the HFMSE.

RESULTS

Part 1: Sixty-three individuals participated in the focus groups. This included 30 caregivers, 25 patients and 8 professionals who facilitated the discussion. The caregivers provided a comparison to activities of daily living for each of the HFMSE items. Part 2: One hundred and forty-nine caregivers agreed to complete the questionnaire: in response to a general question, 72% of the caregivers would consider taking part in a clinical trial if the treatment was expected to slow down deterioration, 88% if it would stop deterioration and 97% if the treatment was expected to produce an improvement. Caregivers were informed of the first three items that their child could not achieve on the HFMSE. In response 75% indicated a willingness to take part in a clinical trial if they could achieve at least one of these abilities, 89% if they could achieve two, and 100% if they could achieve more than 2.

CONCLUSIONS

Our findings support the use of the HFMSE as a key outcome measure in SMA clinical trials because the individual items and the detected changes have clear content validity and clinical meaningfulness for patients and their caregivers.

Patterns of disease progression in type 2 and 3 SMA: Implications for clinical trials

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The paper reports for the first time patterns of progression in type 2 and 3 SMA.

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Different trajectories can be identified in ambulant and non-ambulant patients.

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Age appears to be an important factor in determining trajectories of progression.

The aim of the study was to establish 12-month changes in the Hammersmith Functional motor scale in a large cohort of SMA patients, to identify patterns of disease progression and the effect of different variables. 268 patients were included in this multicentric study. Their age ranged between 2.5 and 55.5 years at baseline, 68 were ambulant and 200 non-ambulant. The baseline scores ranged between 0 and 66 (mean 23.91, SD 20.09). The 12-month change was between −14 and +9 (mean −0.56, SD 2.72). Of the 268 patients, 206 (76.86%) had changes between −2 and +2 points. Ambulant and non-ambulant subjects had a different relationship between baseline values and age (p for age X ambulation interaction = 0.007). There was no association with age in ambulant subjects, while there was a significant heterogeneity at different age for non-ambulant patients (p < 0.001). The 12-month change (adjusted for baseline) was not associated with age in ambulant patients (p = 0.34), but it was significantly different among various age groups in non-ambulant patients. Our results suggest that there are different profiles of progression in ambulant and non-ambulant patients, and that age may play an important role in the progression of non-ambulant patients.

Measuring disease progression in giant axonal neuropathy: implications for clinical trial design

As part of a natural history study of giant axonal neuropathy, we hypothesized that the Friedreich Ataxia Rating Scale and the Gross Motor Function Measure would show a significant change over 6 months, reflecting subjects' decline in motor function. The Friedreich Ataxia Rating Scale was performed on 11 subjects and the Gross Motor Function Measure was performed on 10 subjects twice with a six-month interval. A paired two-tailed t-test was used to assess the difference in each subject's score. Significant changes were found over six months of 11.7 ± 11.0 (P = 0.006) for the Friedreich Ataxia Rating Scale and -10.0 ± 13.5 (P = 0.043) for the Gross Motor Function Measure, reflecting subjects' decline in motor function on examination and by report. These standardized assessments of clinical function are the first to be validated in giant axonal neuropathy and will be used in an upcoming gene therapy clinical trial.

Upper limb evaluation and one-year follow up of non-ambulant patients with spinal muscular atrophy: an observational multicenter trial

Assessment of the upper limb strength in non-ambulant neuromuscular patients remains challenging. Although potential outcome measures have been reported, longitudinal data demonstrating sensitivity to clinical evolution in spinal muscular atrophy patients are critically lacking. Our study recruited 23 non-ambulant patients, 16 patients (males/females = 6/10; median age 15.4 years with a range from 10.7 to 31.1 years) with spinal muscular atrophy type II and 7 patients (males/females = 2/5; median age 19.9 years with a range from 8.3 to 29.9 years) with type III. The Brooke functional score was on median 3 with a range from 2 to 6. The average total vital capacity was 46%, and seven patients required non-invasive ventilation at night. Patients were assessed at baseline, 6 months, and 1 year using the Motor Function Measure and innovative devices MyoGrip, MyoPinch, and MoviPlate, which assess handgrip strength, key pinch strength, and hand/finger extension-flexion function, respectively. The study demonstrated the feasibility and reliability of these measures for all patients, and sensitivity to negative changes after the age of 14 years. The younger patients showed an increase of the distal force in the follow-up period. The distal force measurements and function were correlated to different functional scales. These data represent an important step in the process of validating these devices as potential outcome measures for future clinical trials.

Development and Reliability of the Functional Evaluation Scale for Duchenne Muscular Dystrophy, Gait Domain: A Pilot Study

BACKGROUND AND PURPOSE

The progression of Duchenne muscular dystrophy (DMD) results in the emergence of multiple and varied synergies to compensate muscle weakness and to deal with the demands of the functional tasks (e.g. gait). No functional evaluation instrument for individuals with DMD allows the detailed description (subjective qualitative evaluation) and compensatory movement scoring (objective quantitative evaluation) exclusively of gait. For this reason, clinicians and therapists face difficulties in assessment and decision-making of this functional activity. This study aimed to elaborate the gait domain of the Functional Evaluation Scale for DMD (FES-DMD-GD) and test its intra-rater and inter-rater reliabilities and its relationship with age and timed motor performance.

METHOD

We listed all the compensatory movements observed in 102 10-m gait videos of 51 children with DMD. Based on this report, the FES-DMD-GD was created and submitted to the review of 10 experts. After incorporating the experts suggestions, three examiners scored the videos using the FES-DMD-GD. The intra-rater and inter-rater reliabilities was calculated. Spearman correlation tests investigated the relationships between FES-DMD-GD and age and timed motor performance (p < 0.05).

RESULTS

The FES-DMD-GD was composed of three phases and had 14 items to quantify compensatory movements on gait. Intra-class correlation coefficients ranged from acceptable (0.74) to excellent (0.99). FES-DMD-GD correlated to age and timed motor performance.

CONCLUSION

This pilot version of FES-DMD-GD showed reliability and correlated to age and timed motor performance.

Rasch analysis of clinical outcome measures in spinal muscular atrophy

INTRODUCTION

Trial design for SMA depends on meaningful rating scales to assess outcomes. In this study Rasch methodology was applied to 9 motor scales in spinal muscular atrophy (SMA).

METHODS

Data from all 3 SMA types were provided by research groups for 9 commonly used scales. Rasch methodology assessed the ordering of response option thresholds, tests of fit, spread of item locations, residual correlations, and person separation index.

RESULTS

Each scale had good reliability. However, several issues impacting scale validity were identified, including the extent that items defined clinically meaningful constructs and how well each scale measured performance across the SMA spectrum.

CONCLUSIONS

The sensitivity and potential utility of each SMA scale as outcome measures for trials could be improved by establishing clear definitions of what is measured, reconsidering items that misfit and items whose response categories have reversed thresholds, and adding new items at the extremes of scale ranges.

Hammersmith Functional Motor Scale and Motor Function Measure-20 in non ambulant SMA patients

The aim of this prospective longitudinal multi centric study was to evaluate the correlation between the Hammersmith Functional Motor Scale and the 20 item version of the Motor Function Measure in non ambulant SMA children and adults at baseline and over a 12 month period. Seventy-four non-ambulant patients performed both measures at baseline and 49 also had an assessment 12 month later. At baseline the scores ranged between 0 and 40 on the Hammersmith Motor function Scale and between 3 and 45 on the Motor Function Measure 20. The correlation between the two scales was 0.733. The 12 month changes ranged between -11 and 4 for the Hammersmith and between -11 and 7 for the Motor Function Measure 20. The correlation between changes was 0.48. Our results suggest that both scales provide useful information although they appeared to work differently at the two extremes of the spectrum of abilities. The Hammersmith Motor Function Scale appeared to be more suitable in strong non ambulant patients, while the Motor Function Measures appeared to be more sensitive to capture activities and possible changes in the very weak patients, including more items capturing axial and upper limb activities. The choice of these measures in clinical trials should therefore depend on inclusion criteria and magnitude of expected changes.

Somatropin treatment of spinal muscular atrophy: a placebo-controlled, double-blind crossover pilot study

In preclinical studies growth hormone and its primary mediator IGF-1 have shown potential to increase muscle mass and strength. A single patient with spinal muscular atrophy reported benefit after compassionate use of growth hormone. Therefore we evaluated the efficacy and safety of growth hormone treatment for spinal muscular atrophy in a multicenter, randomised, double-blind, placebo-controlled, crossover pilot trial. Patients (n = 19) with type II/III spinal muscular atrophy were randomised to receive either somatropin (0.03 mg/kg/day) or placebo subcutaneously for 3 months, followed by a 2-month wash-out phase before 3 months of treatment with the contrary remedy. Changes in upper limb muscle strength (megascore for elbow flexion and hand-grip in Newton) were assessed by hand-held myometry as the primary measure of outcome. Secondary outcome measures included lower limb muscle strength, motor function using the Hammersmith Functional Motor Scale and other functional tests for motor function and pulmonary function. Somatropin treatment did not significantly affect upper limb muscle strength (point estimate mean: 0.08 N, 95% confidence interval (CI:-3.79;3.95, p = 0.965), lower limb muscle strength (point estimate mean: 2.23 N, CI:-2.19;6.63, p = 0.302) or muscle and pulmonary function. Side effects occurring during somatropin treatment corresponded with well-known side effects of growth hormone substitution in patients with growth hormone deficiency. In this pilot study, growth hormone treatment did not improve muscle strength or function in patients with spinal muscular atrophy type II/III.

Correlation between motor performance scales, body composition, and anthropometry in patients with Duchenne muscular dystrophy

The aim of this study is to investigate the relationship between body composition, anthropometry, and motor scales in patients with Duchenne muscular dystrophy (DMD). Twenty six patients with DMD were evaluated by Expanded Hammersmith Functional Motor Scale (HFMSE), gross motor function classification system (GMFCS), multifrequency bioelectrical impedance analysis, and anthropometric measurements. Seventeen healthy children served as control group. There were 26 patients with a mean age of 9.5 ± 4.8 years. Ages and anthropometric measurements did not differ between groups. Of the 26 patients, nine were level I, seven were level II, two were level III, seven were level IV, and one was level V, according to the GMFCS. Despite the similar percentage of total body water, extracellular water/intracellular water ratio was significantly elevated in DMD patients (p = 0.001). Increased values of fat percentage and body fat mass index (BFMI) correlated positively with elevated GMFCS levels (r = 0.785 and 0.719 respectively). Increased fat-free mass index (FFMI) correlated negatively with elevated GMFCS levels (r = -0.401). Increased fat percentage and BFMI correlated negatively with HFMSE scores (r = -0.779 and -0.698, respectively). Increased values of FFMI correlated positively with HFMSE scores. There was also a negative correlation between increased skin fold measurements from triceps and scapula and HFMSE scores (r = -0.618 and -0.683, respectively). Increased skin fold values from the same regions correlated positively with elevated GMFCS levels (r = 0.643 and 0.712, respectively). Significant body composition changes occur in patients with DMD. Anthropometric and multifrequency bioelectrical impedance analyses measurements show good correlation between motor function scales. These results may also be helpful to evaluate the effects of new treatment strategies.

Motor and cognitive assessment of infants and young boys with Duchenne Muscular Dystrophy: results from the Muscular Dystrophy Association DMD Clinical Research Network

Therapeutic trials in Duchenne Muscular Dystrophy (DMD) exclude young boys because traditional outcome measures rely on cooperation. The Bayley III Scales of Infant and Toddler Development (Bayley III) have been validated in developing children and those with developmental disorders but have not been studied in DMD. Expanded Hammersmith Functional Motor Scale (HFMSE) and North Star Ambulatory Assessment (NSAA) may also be useful in this young DMD population. Clinical evaluators from the MDA-DMD Clinical Research Network were trained in these assessment tools. Infants and boys with DMD (n = 24; 1.9 ± 0.7 years) were assessed. The mean Bayley III motor composite score was low (82.8 ± 8; p ≤ .0001) (normal = 100 ± 15). Mean gross motor and fine motor function scaled scores were low (both p ≤ .0001). The mean cognitive comprehensive (p=.0002), receptive language (p ≤ .0001), and expressive language (p = .0001) were also low compared to normal children. Age was negatively associated with Bayley III gross motor (r = -0.44; p = .02) but not with fine motor, cognitive, or language scores. HFMSE (n=23) showed a mean score of 31 ± 13. NSAA (n = 18 boys; 2.2 ± 0.4 years) showed a mean score of 12 ± 5. Outcome assessments of young boys with DMD are feasible and in this multicenter study were best demonstrated using the Bayley III.

Childhood spinal muscular atrophy: controversies and challenges

Spinal muscular atrophy is an autosomal recessive disorder characterised by degeneration of motor neurons in the spinal cord and is caused by mutations of the survival of motor neuron 1 gene SMN1. The severity of spinal muscular atrophy is highly variable and no cure is available at present. Consensus has been reached on several aspects of care, the availability of which can have a substantial effect on prognosis, but controversies remain. The development of standards of care for children with the disorder and the identification of promising treatment strategies have changed the natural history of spinal muscular atrophy, and the prospects are good for further improvements in function, quality of life, and survival. A long-term benefit for patients will be the development of effective interventions (such as antisense oligonucleotides), some of which are in clinical trials. The need to be prepared for clinical trials has been the impetus for a remarkable and unprecedented cooperation between clinicians, scientists, industry, government, and volunteer organisations on an international scale.

Thigh muscle volume measured by magnetic resonance imaging is stable over a 6-month interval in spinal muscular atrophy

Changes in thigh muscle volume over 6 months were assessed using magnetic resonance imaging in 11 subjects aged 6 to 47 years with spinal muscular atrophy (4 type 2 and 7 type 3; 4 ambulatory and 3 nonambulatory). Muscle volume with normal and abnormal signal was measured using blinded, semiautomated analysis of reconstructed data. Volumes at baseline and 6 months were correlated with clinical function at each epoch. There was minimal increase in normal (0.3 ± 1.4 mL/cm) and total (0.1 ± 1.3 mL/cm) muscle. Muscle volume correlated closely with clinical function. Minimal interval change in muscle volume is consistent with the established clinical history of minimal disease progression over intervals shorter than 1 year. Relative constancy of muscle volume estimation and correlation with established functional measures suggest a role for segmental magnetic resonance imaging as a biomarker of treatment effect in future therapeutic trials.

Reliability of the Modified Hammersmith Functional Motor Scale in young children with spinal muscular atrophy

INTRODUCTION

The test-retest reliability of the Modified Hammersmith Functional Motor Scale (MHFMS) in children with spinal muscular atrophy (SMA) ≤30 months of age was assessed. The age at which typically developing children (TD) achieve maximum MHFMS scores was also studied.

METHODS

Twenty-two children with SMA type II [mean age (SD) = 20 (5) months, range 9-30 months) were tested twice using the MHFMS. Twenty-five TD children [mean age (SD) = 18 (7) months, range 9-30 months) were tested once.

RESULTS

The average difference between MHFMS scores for SMA children was 0.18 [first assessment: mean (SD) = 12.8 (9.8); second assessment: mean (SD) = 13.0 (8.8)]. Reliability was excellent (ICC(1,3) = 0.96, SEM 1.86). TD participants had MHFMS scores ranging from 36 to 40 [mean (SD) = 39.2 (1.2)] and achieved maximum test scores at 12 months of age.

DISCUSSION

MHFMS scores in young children with SMA type II showed excellent test-retest stability. This suggests that the MHFMS can be used reliably in this younger population for clinical trials and follow-up.

Muscle volume estimation by magnetic resonance imaging in spinal muscular atrophy

Thigh muscle volume was assessed using magnetic resonance imaging in 16 subjects with spinal muscular atrophy. Scans were successful for 14 of 16 subjects (1 type 1, 6 type 2, and 7 type 3) as young as 5.7 years. Muscle volume with normal and abnormal signal was measured using blinded, semiautomated analysis of reconstructed data. Results were compared with segmental lean mass estimated by dual-energy X-ray absorptiometry and correlated with clinical and electrophysiological measures of disease severity. Muscle volume was reduced with abnormal signal quality. Test-retest reliability (r = .99) and correlation with dual-energy X-ray absorptiometry (r = .91) were excellent. Type 2 subjects had lower volume (3.5 ± 1.6 vs 6.3 ± 2.8 mL/cm height; P = .06) and higher percentage of muscle with abnormal signal (68% ± 20% vs 47% ± 27%; P = .14) than type 3. Reproducibility, tolerability, and strong correlation with clinical measures make magnetic resonance imaging a candidate biomarker for clinical research.

Drug discovery and development for spinal muscular atrophy: lessons from screening approaches and future challenges for clinical development

Spinal muscular atrophy (SMA) is a progressive pediatric neuromuscular disease. Because disease severity is related to survival motor neuron (SMN) protein levels, increasing SMN production from the SMN2 gene has been a major SMA drug-discovery strategy. Cell-based assays using neuronal cell lines and cells from SMA patients have identified compounds that can increase SMN protein expression. Our experience of using such an assay signaled potential risks to be avoided through the use of appropriate secondary assays. In addition to the ‘SMN2’ approach, compensating for decreased SMN protein or neuroprotection are also potential SMA drug-discovery strategies. SMA clinical trials are now a reality; however, trial design in a slowly progressing rare disease such as SMA will present an interesting future challenge.

Adiposity is increased among high-functioning, non-ambulatory patients with spinal muscular atrophy

The relationship between body composition and function in spinal muscular atrophy (SMA) is poorly understood. 53 subjects with SMA were stratified by type and Hammersmith functional motor scale, expanded score into three cohorts: low-functioning non-ambulatory (type 2 with Hammersmith score < 12, n=19), high-functioning non-ambulatory (type 2 with Hammersmith score > or = 12 or non-ambulatory type 3, n=17), and Ambulatory (n=17). Lean and fat mass was estimated using dual-energy X-ray absorptiometry. Anthropometric data was incorporated to measure fat-free (lean mass in kg/stature in m(2)) and fat (fat mass in kg/stature in m(2)) mass indices, the latter compared to published age and sex norms. Feeding dysfunction among type 2 subjects was assessed by questionnaire. Fat mass index was increased in the high-functioning non-ambulatory cohort (10.4+/-4.5) compared with both the ambulatory (7.2+/-2.1, P=0.013) and low-functioning non-ambulatory (7.6+/-3.1, P=0.040) cohorts. 12 of 17 subjects (71%) in the high-functioning non-ambulatory cohort had fat mass index > 85th percentile for age and gender (connoting "at risk of overweight") versus 9 of 19 subjects (47%) in the low-functioning non-ambulatory cohort and 8 of 17 ambulatory subjects (47%). Despite differences in clinical function, a similar proportion of low functioning (7/18, 39%) and high functioning (2/7, 29%) type 2 subjects reported swallowing or feeding dysfunction. Non-ambulatory patients with relatively high clinical function may be at particular risk of excess adiposity, perhaps reflecting access to excess calories despite relative immobility, emphasizing the importance of individualized nutritional management in SMA.

Treatment strategies for spinal muscular atrophy

Progress in understanding the genetic basis and pathophysiology of spinal muscular atrophy (SMA), along with continuous efforts in finding a way to increase survival motor neuron (SMN) protein levels have resulted in several strategies that have been proposed as potential directions for efficient drug development. Here we provide an overview on the current status of the following approaches: 1) activation of SMN2 gene and increasing full length SMN2 transcript level, 2) modulating SMN2 splicing, 3) stabilizing SMN mRNA and SMN protein, 4) development of neurotrophic, neuroprotective and anabolic compounds and 5) stem cell and gene therapy. The new preclinical advances warrant a cautious optimism for emergence of an effective treatment in the very near future.

Clinical outcome measures in spinal muscular atrophy

Spinal muscular atrophy is one of the most devastating neurological diseases of childhood. Affected infants and children suffer from often severe muscle weakness caused by degeneration of lower motor neurons in the spinal cord and brainstem. Identification of the causative genetic mutation in most cases has resulted in development of potential treatment strategies. To test these new drugs, clinically feasible outcomes are needed. Several different assessments, validated in spinal muscular atrophy or similar disorders, are being used by national and international research groups; however, their sensitivity to detect change is unknown. Acceptance of a few standardized, easily administered, and functionally meaningful outcomes, applicable to the phenotypic spectrum of spinal muscular atrophy, is needed. Consensus is imperative to facilitate collaboration and explore the ability of these measures to identify the therapeutic effect of disease-modifying agents. Following is an evidence-based review of available clinical outcome measures in spinal muscular atrophy.

Phase II open label study of valproic acid in spinal muscular atrophy

Preliminary in vitro and in vivo studies with valproic acid (VPA) in cell lines and patients with spinal muscular atrophy (SMA) demonstrate increased expression of SMN, supporting the possibility of therapeutic benefit. We performed an open label trial of VPA in 42 subjects with SMA to assess safety and explore potential outcome measures to help guide design of future controlled clinical trials. Subjects included 2 SMA type I ages 2-3 years, 29 SMA type II ages 2-14 years and 11 type III ages 2-31 years, recruited from a natural history study. VPA was well-tolerated and without evident hepatotoxicity. Carnitine depletion was frequent and temporally associated with increased weakness in two subjects. Exploratory outcome measures included assessment of gross motor function via the modified Hammersmith Functional Motor Scale (MHFMS), electrophysiologic measures of innervation including maximum ulnar compound muscle action potential (CMAP) amplitudes and motor unit number estimation (MUNE), body composition and bone density via dual-energy X-ray absorptiometry (DEXA), and quantitative blood SMN mRNA levels. Clear decline in motor function occurred in several subjects in association with weight gain; mean fat mass increased without a corresponding increase in lean mass. We observed an increased mean score on the MHFMS scale in 27 subjects with SMA type II (p

CONCLUSIONS

While VPA appears safe and well-tolerated in this initial pilot trial, these data suggest that weight gain and carnitine depletion are likely to be significant confounding factors in clinical trials. This study highlights potential strengths and limitations of various candidate outcome measures and underscores the need for additional controlled clinical trials with VPA targeting more restricted cohorts of subjects.

TRIAL REGISTRATION

ClinicalTrials.gov.

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Key Words Collapse

MESH Headings

• Absorptiometry, Photon
• Adolescent
• Adult
• Analysis of Variance
• Body Composition/drug effects
• Bone Density/drug effects
• Child
• Child, Preschool
• Electrophysiology
• Enzyme Inhibitors/administration & dosage
• Enzyme Inhibitors/adverse effects
• Enzyme Inhibitors/pharmacology
• Enzyme Inhibitors/therapeutic use
• Humans
• Muscular Atrophy, Spinal/drug therapy
• Muscular Atrophy, Spinal/genetics
• Muscular Atrophy, Spinal/pathology
• Neurologic Examination
• Respiratory Function Tests
• Survival of Motor Neuron 2 Protein/genetics
• Treatment Outcome
• Valproic Acid/administration & dosage
• Valproic Acid/adverse effects
• Valproic Acid/pharmacology
• Valproic Acid/therapeutic use
• Young Adult

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Grants

• R01 HD054599-05 NICHD NIH HHS
• R01 HD054599 NICHD NIH HHS
• C06 RR011234 NCRR NIH HHS
• UL1-RR025764 NCRR NIH HHS
• UL1 RR025764 NCRR NIH HHS

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Affiliation(s)

Kathryn J. Swoboda Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Charles B. Scott CBS Squared, Inc, Fort Washington, Pennsylvania, United States of America
Sandra P. Reyna Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Thomas W. Prior Departments of Molecular Pathology and Neurology, Ohio State University Medical Center, Columbus, Ohio, United States of America
Bernard LaSalle Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Susan L. Sorenson Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Janine Wood Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Gyula Acsadi Departments of Neurology and Pediatrics, Wayne State University School of Medicine, Detroit, Michigan, United States of America
Thomas O. Crawford Departments of Neurology and Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
John T. Kissel Departments of Molecular Pathology and Neurology, Ohio State University Medical Center, Columbus, Ohio, United States of America
Kristin J. Krosschell Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
Guy D'Anjou Division of Pediatric Neurology, Hôpital Sainte-Justine Montréal, Montréal, Québec, Canada
Mark B. Bromberg Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Mary K. Schroth Department of Pediatrics, University of Wisconsin School of Medicine, Madison, Wisconsin, United States of America
Gary M. Chan Departments of Neurology, Pediatrics, Neonatology and General Clinical Research Center, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
Bakri Elsheikh Departments of Molecular Pathology and Neurology, Ohio State University Medical Center, Columbus, Ohio, United States of America
Louise R. Simard Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba, Canada

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Spinal muscular atrophy

Spinal muscular atrophy (SMA) is a potentially devastating and lethal neuromuscular disease frequently manifesting in infancy and childhood. The discovery of the underlying mutation in the survival of motor neurons 1 (SMN1) gene has accelerated preclinical research, leading to treatment targets and transgenic mouse models, but there is still no effective treatment. The clinical severity is inversely related to the copy number of SMN2, a modifying gene producing some full-length SMN transcript. Drugs shown to increase SMN2 function in vitro, therefore, have the potential to benefit patients with SMA. Because several drugs are now on the horizon of clinical investigation, we review recent clinical trials for SMA and discuss the challenges and opportunities associated with SMA drug development. Although an orphan disease, SMA is well-positioned for successful trials given that it has a common genetic etiology in most cases, that it can be readily diagnosed, that preclinical research in vitro and in transgenic animals has identified candidate compounds, and that trial networks have been established.

Diagnosis and clinical management of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of lower motor neurons, with resulting progressive muscle weakness. The clinical phenotype and disease severity can be varied and occupy a wide spectrum. Although many advances have been made regarding our understanding of SMA, no cure is yet available. The care of patients who have SMA can often be complex, with many medical issues to consider. When possible, a multidisciplinary team approach is effective. The current understanding of SMA, and the clinical management and rehabilitative care of patients who have SMA, are discussed in this article.