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

Rehabilitation improves the effectiveness of nusinersen in children with type 2 spinal muscular atrophy: pNF-H and muscle MRI as potential biomarkers

Introduction

Rehabilitation therapy is an important approach for spinal muscular atrophy (SMA) management. Currently, rare articles introduce that the combination of nusinersen and rehabilitation yields better results in SMA patients compared to using nusinersen alone. The present study examined whether rehabilitation therapy can improve the effectiveness of nusinersen and phosphorylated neurofilament heavy chain (pNF-H) and muscle magnetic resonance imaging (MRI) can serve as potential biomarkers for evaluating the therapeutic effects in type-2 SMA patients.

Methods

This observational study enrolled 22 pediatric patients with type-2 SMA. Enrolled patients were divided into two groups based on the rehabilitation treatment. Motor function and swallowing function were analyzed at baseline, 6, 10, and 14 months. The level of pNF-H and MRI of the thigh skeletal muscles were analyzed at baseline and 14 months.

Results

Greater improvement in motor function was observed in the rehabilitation group compared with the non-rehabilitation group. The levels of pNF-H in the serum and cerebrospinal fluid significantly decreased at 14 months. One patient from the rehabilitation treatment group showed mild improvement in the degree of fatty infiltration in the quadriceps muscles after 14 months.

Conclusion

This study suggests that rehabilitation therapy improves the effectiveness of nusinersen on type-2 SMA patients, and the levels of pNF-H and skeletal muscle MRI can serve as potential biomarkers for evaluating the effectiveness of SMA treatment.

Systematic literature review of the impact of spinal muscular atrophy therapies on bulbar function

BACKGROUND

Improvement and maintenance of bulbar function are important goals of disease-modifying treatments (DMTs) for spinal muscular atrophy (SMA), but standardized and validated measures for assessing bulbar function do not exist, nor does a widely accepted definition of bulbar function in SMA. As such, the impact of DMTs on bulbar function has not yet been comprehensively evaluated.

OBJECTIVE

We conducted a systematic literature review (SLR) to identify evidence about the impact of DMTs for SMA on bulbar function.

METHODS

We used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines to conduct this review. Embase® and MEDLINE® databases were searched through August 10, 2023. Eligible studies included patients with SMA who were treated with any DMT and reported bulbar function outcomes. Non-English studies were excluded.

RESULTS

We identified 51 studies (across 83 publications) that evaluated SMA DMTs and bulbar function for more than 1600 patients. The ability to feed orally, the ability to tolerate liquids, and the need for nutrition support were commonly reported. Most infants treated with any DMT before SMA symptom onset preserved bulbar function. Infants, children, and adults treated after SMA symptom onset experienced variable results in terms of bulbar function outcomes.

CONCLUSIONS

The definition and assessment of bulbar function are not standardized. Therefore, the tools, scales, methods, and timing used for bulbar function assessments varied among studies. Larger prospective studies using standardized and age-based assessments with longer follow-up periods are needed to assess the clinical stability of bulbar function for patients with SMA who receive DMTs.

An exploratory qualitative assessment of patient and clinician perspectives on patient-reported outcome measures and disease-modifying therapies in adults with spinal muscular atrophy

OBJECTIVE

To understand patient, caregiver, and clinician perspectives on patient-reported outcome measures, critical functional domains, and disease-modifying therapies in adult spinal muscular atrophy.

DESIGN

An exploratory qualitative single-site study.

PATIENTS

Ten adults with spinal muscular atrophy and two clinicians participated in semi-structured interviews.

METHODS

Semi-structured interviews were conducted virtually or in person with participants after they completed outcome measures at a routine clinic visit. Two researchers analysed transcripts concurrently using a thematic approach to determine themes.

RESULTS

Ten themes were identified among partici-pants. Patient-reported outcome measure preference varied between functional groups and was under-responsive, although it captured meaningful data. Motor stability was most frequently expected with disease-modifying therapy, but participants also reported improved fatigue and respiratory status.

CONCLUSION

After considering patient goals, functional status, and preferences, patient-reported outcome measures represent a valuable adjunct to standard clinical and research tools. Optimal selection of patient-reported outcome measures requires careful consideration of multiple patient factors. Collaborative development of modified patient-reported outcome measures may yield a responsive, meaningful, and acceptable tool that can be used across a broad functional spectrum.

Development of the SMA EFFORT: A new approach to characterize perceived physical fatigability in spinal muscular atrophy

BACKGROUND

Fatigue and fatigability are commonly reported in spinal muscular atrophy (SMA). Physical fatigability, proposed to be the most relevant to SMA pathophysiology, encompasses performance-based and perceived physical fatigability (PPF) assessments. While performance-based measures have highlighted physical fatigability as an SMA hallmark, PPF is not well characterized due to the lack of disease- and construct-specific scales.

OBJECTIVE

Our aim was to create a patient-reported outcome measure tailored for SMA, named the SMA EFFORT, to improve PPF assessment. Here, we describe the scale development process, assess scale properties, and discuss future research and application.

METHODS

SMA and scale development experts organized a comprehensive physical activity item bank, relevant across the SMA phenotypic spectrum. Activities were systematically categorized by varying intensities and durations. The SMA EFFORT was completed by an international cohort of individuals with all types of SMA. To compare PPF across demographic and clinical variables, SMA EFFORT PPF percent (PPF%) composite scoring was established.

RESULTS

One hundred eighteen participants completed the SMA EFFORT. Total PPF% scores were broadly distributed within functional groups, with differences between non-sitters (35.1 ± 21.0) and sitters (24.9 ± 15.1) (p = 0.006), and those with (34.4 ± 18.1) and without respiratory support (26.4 ± 17.8) (p = 0.02). Participants treated with disease modifying therapy (DMT) showed similar scores to those without treatment (p = 0.70). Further, no differences in scores were observed in participants with scoliosis surgery and those without (p = 0.71). Subscale analyses revealed differences in mean PPF% subscale scores by functional group.

CONCLUSIONS

The novel SMA EFFORT standardizes PPF ratings by anchoring activity to intensity and duration. Item and scale data insights will inform the next iteration, which will undergo additional investigation. The SMA EFFORT aims to improve upon current measures to better assess treatment impact on physical well-being across the SMA spectrum.

Methodological quality of 100 recent systematic reviews of health-related outcome measurement instruments: an overview of reviews

PURPOSE

Systematic reviews evaluating and comparing the measurement properties of outcome measurement instruments (OMIs) play an important role in OMI selection. Earlier overviews of review quality (2007, 2014) evidenced substantial concerns with regards to alignment to scientific standards. This overview aimed to investigate whether the quality of recent systematic reviews of OMIs lives up to the current scientific standards.

METHODS

One hundred systematic reviews of OMIs published from June 1, 2021 onwards were randomly selected through a systematic literature search performed on March 17, 2022 in MEDLINE and EMBASE. The quality of systematic reviews was appraised by two independent reviewers. An updated data extraction form was informed by the earlier studies, and results were compared to these earlier studies' findings.

RESULTS

A quarter of the reviews had an unclear research question or aim, and in 22% of the reviews the search strategy did not match the aim. Half of the reviews had an incomprehensive search strategy, because relevant search terms were not included. In 63% of the reviews (compared to 41% in 2014 and 30% in 2007) a risk of bias assessment was conducted. In 73% of the reviews (some) measurement properties were evaluated (58% in 2014 and 55% in 2007). In 60% of the reviews the data were (partly) synthesized (42% in 2014 and 7% in 2007); evaluation of measurement properties and data syntheses was not conducted separately for subscales in the majority. Certainty assessments of the quality of the total body of evidence were conducted in only 33% of reviews (not assessed in 2014 and 2007). The majority (58%) did not make any recommendations on which OMI (not) to use.

CONCLUSION

Despite clear improvements in risk of bias assessments, measurement property evaluation and data synthesis, specifying the research question, conducting the search strategy and performing a certainty assessment remain poor. To ensure that systematic reviews of OMIs meet current scientific standards, more consistent conduct and reporting of systematic reviews of OMIs is needed.

Taldefgrobep Alfa and the Phase 3 RESILIENT Trial in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, genetic neurodegenerative disorder caused by insufficient production of survival motor neuron (SMN) protein. Diminished SMN protein levels lead to motor neuron loss, causing muscle atrophy and weakness that impairs daily functioning and reduces quality of life. SMN upregulators offer clinical improvements and increased survival in SMA patients, although significant unmet needs remain. Myostatin, a TGF-β superfamily signaling molecule that binds to the activin II receptor, negatively regulates muscle growth; myostatin inhibition is a promising therapeutic strategy for enhancing muscle. Combining myostatin inhibition with SMN upregulation, a comprehensive therapeutic strategy targeting the whole motor unit, offers promise in SMA. Taldefgrobep alfa is a novel, fully human recombinant protein that selectively binds to myostatin and competitively inhibits other ligands that signal through the activin II receptor. Given a robust scientific and clinical rationale and the favorable safety profile of taldefgrobep in patients with neuromuscular disease, the RESILIENT phase 3, randomized, placebo-controlled trial is investigating taldefgrobep as an adjunct to SMN upregulators in SMA (NCT05337553). This manuscript reviews the role of myostatin in muscle, explores the preclinical and clinical development of taldefgrobep and introduces the phase 3 RESILIENT trial of taldefgrobep in SMA.

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.

Pharmacological Doses of Thiamine Benefit Patients with the Charcot-Marie-Tooth Neuropathy by Changing Thiamine Diphosphate Levels and Affecting Regulation of Thiamine-Dependent Enzymes

Charcot-Marie-Tooth (CMT) neuropathy is a polygenic disorder of peripheral nerves with no effective cure. Thiamine (vitamin B1) is a neurotropic compound that improves neuropathies. Our pilot study characterizes therapeutic potential of daily oral administration of thiamine (100 mg) in CMT neuropathy and its molecular mechanisms. The patient hand grip strength was determined before and after thiamine administration along with the blood levels of the thiamine coenzyme form (thiamine diphosphate, ThDP), activities of endogenous holo-transketolase (without ThDP in the assay medium) and total transketolase (with ThDP in the assay medium), and transketolase activation by ThDP [1 - (holo-transketolase/total transketolase),%], corresponding to the fraction of ThDP-free apo-transketolase. Single cases of administration of sulbutiamine (200 mg) or benfotiamine (150 mg) reveal their effects on the assayed parameters within those of thiamine. Administration of thiamine or its pharmacological forms increased the hand grip strength in the CMT patients. Comparison of the thiamin status in patients with different forms of CMT disease to that of control subjects without diagnosed pathologies revealed no significant differences in the average levels of ThDP, holo-transketolase, or relative content of holo and apo forms of transketolase. However, the regulation of transketolase by thiamine/ThDP differed in the control and CMT groups: in the assay, ThDP activated transketolase from the control individuals, but not from CMT patients. Thiamine administration paradoxically decreased endogenous holo-transketolase in CMT patients; this effect was not observed in the control group. Correlation analysis revealed sex-specific differences in the relationship between the parameters of thiamine status in both the control subjects and patients with the CMT disease. Thus, our findings link physiological benefits of thiamine administration in CMT patients to changes in their thiamine status, in particular, the blood levels of ThDP and transketolase regulation.

Non-Invasive Spinal Cord Stimulation for Motor Rehabilitation of Patients with Spinal Muscular Atrophy Treated with Orphan Drugs

Spinal muscular atrophy (SMA) is an orphan disease characterized by the progressive degeneration of spinal alpha motor neurons. In recent years, nusinersen and several other drugs have been approved for the treatment of this disease. Transcutaneous spinal cord stimulation (tSCS) modulates spinal neuronal networks, resulting in changes in locomotion and posture in patients with severe spinal cord injury and stroke. We hypothesize that tSCS can activate motor neurons that are intact and restored by medication, slow the decline in motor activity, and contribute to the development of motor skills in SMA patients. Thirty-seven children and adults with SMA types 2 and 3 participated in this study. The median duration of drug treatment was over 20 months. The application of tSCS was performed during physical therapy for 20-40 min per day for ~12 days. Outcome measures were specific SMA motor scales, goniometry of contractured joints, and forced vital capacity. Significant increases in motor function, improved respiratory function, and decreased contracture were observed in both type 2 and 3 SMA participants. The magnitude of functional changes was not associated with participant age. Further studies are needed to elucidate the reasons for the beneficial effects of spinal cord electrical stimulation on SMA.

Enhancing public health in developing nations through smartphone-based motor assessment

Several protocols for motor assessment have been validated for use on smartphones and could be employed by public healthcare systems to monitor motor functional losses in populations, particularly those with lower income levels. In addition to being cost-effective and widely distributed across populations of varying income levels, the use of smartphones in motor assessment offers a range of advantages that could be leveraged by governments, especially in developing and poorer countries. Some topics related to potential interventions should be considered by healthcare managers before initiating the implementation of such a digital intervention.

Differential impact on motor unit characteristics across severities of adult spinal muscular atrophy

OBJECTIVE

To test the hypotheses that decomposition electromyography (dEMG) motor unit action potential (MUAP) amplitude and firing rate are altered in SMA; dEMG parameters are associated with strength and function; dEMG parameters are correlated with traditional electrophysiological assessments.

METHODS

Ambulatory and non-ambulatory adults with SMA on nusinersen and healthy controls were enrolled. MUAPs were decomposed from multielectrode surface recordings during 30-s maximum contraction of the abductor digiti minimi (ADM). Isometric strength, upper limb function, patient-reported function, and standard electrophysiologic measures of the ADM (compound muscle action potential [CMAP], single motor unit potential [SMUP], motor unit number estimation [MUNE]) were collected.

RESULTS

dEMG MUAP amplitudes were higher in ambulatory versus control and non-ambulatory groups and were higher in controls versus non-ambulatory SMA. In contrast, dEMG firing rates were higher in ambulatory versus non-ambulatory and control groups but similar between non-ambulatory and control. dEMG parameters showed moderate to strong positive correlation with strength and function whereas CMAP and MUNE better correlated with function than strength. SMUP did not correlate with strength, function, or dEMG MUAP amplitude. dEMG parameters show overall good test-retest reliability.

INTERPRETATION

dEMG provided reliable, noninvasive measure of MUAP amplitude size and firing rate and revealed divergent patterns across disease severity in adults with SMA. Firing rate enhancement, as seen in milder SMA, may provide a therapeutic avenue for improving function in more severe SMA, where firing rates appear preserved. MUAP amplitude size and firing rate, quantified with dEMG, may be promising monitoring biomarker candidates for noninvasive assessment of SMA.

First Use of Non-Invasive Spinal Cord Stimulation in Motor Rehabilitation of Children with Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is characterized by the degeneration of spinal alpha motorneurons. Nusinersen demonstrated good efficacy in the early disease phases. The feasibility of transcutaneous spinal cord stimulation (tSCS) in motor rehabilitation of patients with spinal cord injury has been demonstrated. We hypothesize that tSCS may activate intact and restored by nusinersen motorneurons and slow down the decline in motor activity, and may contribute to the development of motor skills in children with SMA. A case series is presented. Five children (6-13 years old) with SMA type II or III participated in the study. They were treated with nusinersen for ~2 years. Application of tSCS was carried out during physical therapy for 30-40 min per day in the course of 10-14 days. Outcome measures were goniometry of joints with contracture, forced vital capacity (FVC), RULM and HFMSE scales. The participants tolerated the stimulation well. The reduction of the contracture was ≥5 deg. RULM and HFMSE increased by ~1-2 points. Predicted FVC increased by 1-7% in three participants. Each participant expanded their range of active movements and/or learned new motor skills. Spinal cord stimulation may be an effective rehabilitation method in patients treated with nusinersen. More research is needed.

Caracterización clínica y funcional de pacientes con atrofia muscular espinal en el centro-occidente colombiano

Introducción.

La atrofia muscular espinal es una enfermedad neurodegenerativa huérfana de origen genético que afecta las neuronas motoras del asta anterior de la médula espinal, y produce atrofia y debilidad muscular. En Colombia, son pocos los estudios publicados sobre la enfermedad y no hay ninguno con análisis funcional.

Objetivo.

Caracterizar clínica y funcionalmente una serie de casos de atrofia muscular espinal del centro-occidente colombiano.

Materiales y métodos.

Se hizo un estudio descriptivo transversal, entre el 2007 y el 2020, de pacientes con diagnóstico clínico y molecular de atrofia muscular espinal que consultaron en el centro de atención. La evaluación funcional se realizó con las escalas Hammersmith y Chop Intend. En la sistematización de los datos, se empleó el programa Epi-Info, versión 7.0.

Resultados.

Se analizaron 14 pacientes: 8 mujeres y 6 hombres. La atrofia muscular espinal más prevalente fue la de tipo II, la cual se presentó en 10 casos. Se encontró variabilidad fenotípica en términos de funcionalidad en algunos pacientes con atrofia muscular espinal de tipo II, cinco de los cuales lograron alcanzar la marcha. La estimación de la supervivencia fue de 28,6 años.

Conclusiones.

Los hallazgos en el grupo de pacientes analizados evidenciaron que los puntajes de la escala de Hammersmith revisada y expandida, concordaron con la gravedad de la enfermedad.