Spinal muscular atrophy: a clinical and research update

Scoliosis Development in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-Modifying Treatments

BACKGROUND

Spinal muscular atrophy (SMA) is caused by abnormalities of the survival motor neuron (SMN) 1 gene, leading to deficiency in SMN protein and loss of spinal cord alpha motor neurons. Newer disease-modifying agents (DMA) targeting the involved genes, including nusinersen and gene replacement therapies, have improved gross motor and respiratory function, but their impact on scoliosis development has not been established. This study aimed to determine risk factors for scoliosis development in SMA, specifically genetic severity and DMA use.

METHODS

In this retrospective cohort study, children with SMA and minimum 2-year follow-up were included. The primary outcome was the prevalence of clinically relevant scoliosis. Secondary outcomes included SMA type, SMN2 copy number, Hammersmith Functional Motor Scale (HFMS), ambulatory status [functional mobility scale at 50m (FMS 50 )], DMA use, and hip displacement as risk factors. Univariate/multivariate logistic regression analyses were performed to identify dependent/independent risk factors.

RESULTS

One hundred sixty-five patients (51% female) with SMA types I-III met the inclusion criteria, with total follow-up of 9.8 years. The prevalence of scoliosis was 79%; age of onset 7.9 years. The major curve angle for the entire cohort at first assessment and final follow-up was 37 degrees (SD: 27 degrees) and 62 degrees (SD: 31 degrees) ( P <0.0001), respectively. Significant risk factors for scoliosis by univariate analysis were SMA type (I/II, P =0.02), HFMS (>23, P <0.001), nonambulatory status (FMS 50 =1, P <0.0001), DMA treatment ( P =0.02), and hip displacement ( P <0.0001). Multivariate analysis revealed that HFMS >23 ( P =0.02) and DMA ( P =0.05) treatment were independent (protective) risk factors.

CONCLUSIONS

The development of scoliosis in SMA is high, with risk factors associated with proxy measures of disease severity, including SMA type, nonambulatory status, hip displacement, and most notably, gross motor function (by HFMS). DMA use and HFMS >23 were associated with a decreased risk of scoliosis development. Identified risk factors can be used in the development of surveillance programs for early detection of scoliosis in SMA.

LEVEL OF EVIDENCE

Level III.

Spinal muscular atrophy in an upper-middle-income nation before the advent of reimbursed disease-modifying therapies

OBJECTIVE

To elucidate the clinical characteristics and standard of care (SoC) of spinal muscular atrophy (SMA) patients in Thailand, focusing on primary endpoints: age at death and a composite of death or tracheostomy need.

DESIGN

Retrospective observational study.

SETTING

Seven tertiary centres across Thailand.

PATIENTS

Records of 110 patients with genetically confirmed SMA, spanning 2012-2021.

INTERVENTIONS

Historical data review; no active interventions.

MAIN OUTCOME MEASURES

Age at death and a composite measure of death or tracheostomy necessity.

RESULTS

The cohort included 1 SMA0, 50 SMA1, 40 SMA2 and 19 SMA3 cases. Median ages at the onset and diagnosis of SMA1 were 3 and 6.2 months. Of SMA1 patients, 63% required ventilators, and eight received dimethyltryptamines (DMTs) at a median of 15 months (range 6.4-24.5 months). The median time from onset to DMT was 11 months (range 4.2-20.5 months). Among SMA1 patients, 73% died by the study's end. SMA2 and SMA3 patients' median onset ages were 11 and 24 months, respectively, with diagnosis at 24.8 and 68.7 months. Half of all types received physical therapy.

CONCLUSIONS

Significant delays in diagnosis and SoC access, including DMTs, were observed, underscoring urgent needs for improved diagnostic and care strategies to enhance SMA patient outcomes in Thailand.

Survival analysis and life expectancy of pediatric patients with spinal muscular atrophy in Thailand

Background

Survival data for Thai patients with 5q spinal muscular atrophy (SMA), the leading cause of infant mortality worldwide, are lacking.

Objective

This study aimed to determine the survival rates and life expectancies of pediatric patients with SMA types 1, 2, and 3.

Methods

We conducted a retrospective cohort analysis of genetically confirmed 5q SMA patients aged 0-18 years who were treated between 1999 and 2021 at the pediatric neuromuscular clinic of Siriraj Hospital, Bangkok, Thailand. Mortality data were sourced from the Civil Registration Office.

Results

The study included 113 patients: 37 with SMA type 1, 53 with type 2, and 23 with type 3. Life expectancy varied significantly by SMA type: 2.2 years for type 1, 11 years for type 2, and 16.5 years for type 3. The median survival times for SMA type 1 and 2 were 1.9 and 19 years, respectively. In SMA type 2, early onset (<1 year) correlated with a shorter median survival than later onset (≥1 year) (log-rank test P = 0.009). Early onset SMA type 2 had a median survival time of 15.9 years, while 75 % of those with later onset SMA type 2 survived until the age of 19 years. Cox proportional hazards analysis revealed that each month's delay in disease onset reduced the annual mortality risk by 17 % for type 1 patients and by 20 % for type 2 patients. Compared with female patients, male patients with type 2 disease had a 12-fold increased mortality risk.

Conclusions

Age at onset is a significant predictor of survival and life expectancy in patients with SMA types 1 and 2. These insights are crucial for genetic counseling and prognostic discussions in clinical settings.

Spinal Muscular Atrophy Scoliosis in the Era of Background Therapies-A Review of the Literature

Spinal deformities are considered an important complication of neuromuscular disorders such as spinal muscular atrophy (SMA). SMA patients typically develop progressive early-onset scoliosis, which is associated with increased functional decline, discomfort, and respiratory dysfunction. Over the second decade of the twenty-first century, a lot has changed in terms of the therapeutic options available to people with SMA. Specifically, the use of pharmaceutical agents such as nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma), and risdiplam (Evrysdi) has dramatically changed the landscape for SMA patients. These medications significantly alter motor- and respiratory functioning, as well as the natural progression of spinal deformities. When evaluating these agents and their impact on the development of scoliosis and motor functioning, it is important to consider the timing of treatment initiation. In patients treated after they had already developed symptoms, a shift of phenotype to a less severe subtype has been observed. This results in a delay in the onset of scoliosis for the less severe SMA types and an increase in early-onset scoliosis for the severe types in patients who would typically not live to develop scoliosis. Patients who receive treatment before they develop symptoms achieve almost normal motor functioning and will likely have a significant decrease in scoliosis prevalence or at least delay its onset.

Real-world safety and effectiveness of nusinersen, a treatment for spinal muscular atrophy, in 401 Japanese patients: results from an interim analysis of post-marketing surveillance

Purpose: Nusinersen is an antisense oligonucleotide for the treatment of spinal muscular atrophy (SMA). A post-marketing surveillance (PMS) has been ongoing (August 2017-August 2025) in all patients in Japan who received intrathecal nusinersen in real-world clinical settings. We report the interim analysis results of safety and effectiveness.Methods: This interim analysis was conducted using data collected from 401 patients whose case report forms were obtained at least once by 30 May 2020. Collected data included patient demographics and adverse events (AEs) for safety, and motor function assessments and Clinical Global Impressions of Improvement (CGI-I) for effectiveness.Results: All 401 patients were diagnosed with SMA and were included in the safety and effectiveness analysis (infantile-onset SMA [n = 126, 31.4%], later-onset SMA [n = 275, 68.6%]). The median duration of treatment was 330 days (range 1-823 days). The incidence proportion of AEs was 31.7% (37.3% in infantile-onset SMA and 29.1% in later-onset SMA). The most common AEs were headache (4.5%), pyrexia (4.2%), and pneumonia (3.7%). The incidence proportion of serious AEs was 11.5%. Nusinersen improved motor function scores and was assessed as 'effective' based on CGI-I in 99.7-100% of patients.Conclusions: This interim analysis of the PMS in Japanese patients treated with nusinersen found no new safety concerns, with the type of AEs consistent with the expected safety profile. The benefit-risk balance of nusinersen treatment remains favorable.

Diagnosis of Challenging Spinal Muscular Atrophy Cases with Long-Read Sequencing

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder primarily caused by the deletion or mutation of the survival motor neuron 1 (SMN1) gene. This study assesses the diagnostic potential of long-read sequencing (LRS) in three patients with SMA. For Patient 1, who has a heterozygous SMN1 deletion, LRS unveiled a missense mutation in SMN1 exon 5. In Patient 2, an Alu/Alu-mediated rearrangement covering the SMN1 promoter and exon 1 was identified through a blend of multiplex ligation-dependent probe amplification, LRS, and PCR across the breakpoint. The third patient, born to a consanguineous family, bore four copies of hybrid SMN genes. LRS determined the genomic structures, indicating two distinct hybrids of SMN2 exon 7 and SMN1 exon 8. However, a discrepancy was found between the SMN1/SMN2 ratio interpretations by LRS (0:2) and multiplex ligation-dependent probe amplification (0:4), which suggested a limitation of LRS in SMA diagnosis. In conclusion, this newly adapted long PCR-based third-generation sequencing introduces an additional avenue for SMA diagnosis.

Hip Displacement in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-modifying Treatments

PURPOSE

Hip displacement (HD) is common in spinal muscular atrophy (SMA), but neither genetic severity nor gross motor function level have been investigated as risk factors. Although disease-modifying agents (DMA) have improved function and overall health, their effects on the prevention of HD are unknown. The purpose of this study was to determine risk factors for HD development in SMA.

METHODS

Retrospective cohort. Children with SMA presenting between January 2005 and August 2021, at least 1 hip radiograph, and a minimum 2-year follow-up were included. The primary outcome measure was the prevalence of HD (migration percentage ≥40%). Secondary outcomes included SMA type (I/II/III), survival motor neuron 2 copy number, Hammersmith Functional Motor Scale (HFMS, out of 66), ambulatory status (Functional Mobility Scale at 50 m), clinically relevant scoliosis (>40 degrees and/or surgery), and DMA treatment (>1-year duration, nusinersen/risdiplam/onasemnogene abeparvovec) as risk factors. Univariate and multivariate logistic regression analyses were performed.

RESULTS

Eighty-two patients (52% female) with SMA type I (n=32, 39%), II (n=36, 44%), and III (n=14, 17%) met the inclusion criteria, with a final follow-up of 4.5 (SD: 2.7) years. Age at first hip radiograph was 3.4 (SD: 2.9) years. The prevalence of HD was 75.6%, with a mean age of onset of 4.6 (SD: 2.7) years. When stratified by SMA type, the prevalence/age of onset (mean, years) was 84%/3.1 (SD: 1.7), 80%/5.8 (SD: 2.3), and 36%/9.0 (SD: 4.3), respectively. HFMS score >23 was protective against HD by receiver operating characteristic analysis ( P =0.008). Significant risk factors by univariate analysis were SMA type I ( P =0.002) and II ( P =0.002), HFMS ≤23 ( P =0.01), nonambulatory status (Functional Mobility Scale at 50 m = 1, P =0.001), clinically relevant scoliosis ( P =0.01), and DMA treatment ( P =0.01). By multivariate analysis, only SMA type II ( P =0.04) and scoliosis ( P =0.04) were independent risk factors.

CONCLUSIONS

The prevalence of HD in SMA is highly linked to disease severity. Identified risk factors can be used in the development of surveillance programs for early detection of HD in SMA, allowing for timely management.

LEVEL OF EVIDENCE

Level III.

Establishment of a Pilot Newborn Screening Program for Spinal Muscular Atrophy in Saint Petersburg

Spinal muscular atrophy 5q (SMA) is one of the most common neuromuscular inherited diseases and is the most common genetic cause of infant mortality. SMA is associated with homozygous deletion of exon 7 in the SMN1 gene. Recently developed drugs can improve the motor functions of infants with SMA when they are treated in the pre-symptomatic stage. With aim of providing an early diagnosis, newborn screening (NBS) for SMA using a real-time PCR assay with dried blood spots (DBS) was performed from January 2022 through November 2022 in Saint Petersburg, which is a representative Russian megapolis. Here, 36,140 newborns were screened by the GenomeX real-time PCR-based screening test, and three genotypes were identified: homozygous deletion carriers (4 newborns), heterozygous carriers (772 newborns), and wild-type individuals (35,364 newborns). The disease status of all four newborns that screened positive for the homozygous SMN1 deletion was confirmed by alternate methods. Two of the newborns had two copies of SMN2, and two of the newborns had three copies. We determined the incidence of spinal muscular atrophy in Saint Petersburg to be 1 in 9035 and the SMA carrier frequency to be 1 in 47. In conclusion, providing timely information regarding SMN1, confirmation of disease status, and SMN2 copy number as part of the SMA newborn-screening algorithm can significantly improve clinical follow-up, testing of family members, and treatment of patients with SMA.

Spinal Muscular Atrophy Treatment: The MTOR Regulatory Intervention

Spinal muscular atrophy (SMA) is a hereditary disorder affecting neurons and muscles, resulting in muscle weakness and atrophy. Most SMA cases are diagnosed during infancy or early childhood, the most common inherited cause of infant mortality without treatment. Still, SMA might appear at older ages with milder symptoms. SMA patients demonstrate progressive muscle waste, movement problems, tremors, dysphagia, bone and joint deformations, and breathing difficulties. The mammalian target of rapamycin (mTOR), the mechanistic target of rapamycin, is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases encoded by the mTOR gene in humans. The mTOR phosphorylation, deregulation, and autophagy have shown dissimilarity amongst SMA cell types. Therefore, exploring the underlying molecular process in SMA therapy could provide novel insights and pave the way for finding new treatment options. This paper provides new insight into the possible modulatory effect of mTOR/ autophagy in SMA management.

Efficacy of risdiplam in spinal muscular atrophy: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to assess the efficacy and safety of risdiplam on motor and respiratory function in spinal muscular atrophy (SMA). We systematically searched Medline, Scopus, Web of Science, and the Cochrane Library from inception to March 2023. We included pre-post studies that determined the effect of risdiplam on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), the 32-item Motor Function Measure (MFM32), the Revised Upper Limb Module (RULM), the Hammersmith Functional Motor Scale - Expanded (HFMSE), respiratory function, and the proportion of risdiplam-related adverse events in a population with SMA (phenotypes 1 and 2/3). Meta-analyses were also performed where possible. Eleven studies were included. After 12 months of treatment, 57% of participants with SMA1 achieved a CHOP-INTEND score ≥ 40 points, and more than half were able to feed orally and had head control. In SMA2/3, MFM32, RULM, and HFMSE increased by 2.09 (1.17, 3.01), 1.73 (1.25, 2.20), and 1.00 (0.40, 1.59) points, respectively. Efficacy on respiratory function in SMA2/3 was inconsistent. Finally, 16% of participants experienced adverse events, but serious adverse events could not be quantified due to a lack of cases. The limited available evidence suggests that risdiplam is an effective and safe drug for the treatment of SMA. In addition, long-term clinical benefit may be partly determined by the stage of disease at which treatment is initiated.

Sleep disordered breathing in infants identified through newborn screening with spinal muscular atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic disorder that may result in neuromuscular weakness and respiratory insufficiency. Gene replacement therapy has changed the trajectory of this condition, but long-term outcomes related to sleep disordered breathing are not known.

METHODS

This was a retrospective review of infants with SMA identified via newborn screening who subsequently received onasemnogene abeparvovec at the Hospital for Sick Children (Ontario, Canada). Polysomnograms were conducted at the time of confirmed diagnosis as well as regularly thereafter.

RESULTS

Eleven children (4 female) were identified via newborn screen (7 with 2 copies of the SMN2 gene and 4 with 3 copies of the SMN2 gene) and received onasemnogene abeparvovec at a median age of 3.6 weeks. All eleven infants met criteria for sleep disordered breathing based on their first completed polysomnograms but improved over time. Three infants required respiratory technology, including a premature infant who was prescribed nocturnal supplemental oxygen therapy for central sleep apnea and two symptomatic infants with neuromuscular weakness who required nocturnal noninvasive ventilation. We did not find a correlation between motor scores and polysomnogram parameters.

CONCLUSION

Children treated with onasemnogene abeparvovec have reduced sleep disordered breathing over time. Polysomnograms revealed abnormal parameters in all children, but the clinical significance of these findings was unclear for children who were asymptomatic for sleep disordered breathing or neuromuscular weakness. These results highlight the need to evaluate both motor scores and respiratory symptoms to ensure a holistic evaluation of clinical status.

Nifedipine Ameliorates Cellular Differentiation Defects of Smn-Deficient Motor Neurons and Enhances Neuromuscular Transmission in SMA Mice

In spinal muscular atrophy (SMA), mutations in or loss of the Survival Motor Neuron 1 (SMN1) gene reduce full-length SMN protein levels, which leads to the degeneration of a percentage of motor neurons. In mouse models of SMA, the development and maintenance of spinal motor neurons and the neuromuscular junction (NMJ) function are altered. Since nifedipine is known to be neuroprotective and increases neurotransmission in nerve terminals, we investigated its effects on cultured spinal cord motor neurons and motor nerve terminals of control and SMA mice. We found that application of nifedipine increased the frequency of spontaneous Ca²⁺ transients, growth cone size, cluster-like formations of Cav2.2 channels, and it normalized axon extension in SMA neurons in culture. At the NMJ, nifedipine significantly increased evoked and spontaneous release at low-frequency stimulation in both genotypes. High-strength stimulation revealed that nifedipine increased the size of the readily releasable pool (RRP) of vesicles in control but not SMA mice. These findings provide experimental evidence about the ability of nifedipine to prevent the appearance of developmental defects in SMA embryonic motor neurons in culture and reveal to which extent nifedipine could still increase neurotransmission at the NMJ in SMA mice under different functional demands.

Novel Alu-mediated deletions of the SMN1 gene were identified by ultra-long read sequencing technology in patients with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by biallelic variants of the survival motor neuron 1 (SMN1) gene. In this study, our aim was to make a molecular diagnosis in two patients with SMA carrying only one SMN1 copy number. Using ultra-long read sequencing (Ultra-LRS), 1415 bp deletion and 3348 bp deletion of the SMN1 gene were identified in patient 1 and the father of patient 2, respectively. Ultra-LRS revealed two novel deletions, starting from the SMN1 promoter to intron 1. It also accurately provided the location of the deletion breakpoints in the SMN1 gene: chr5 g.70,924,798-70,926,212 for a 1415 bp deletion; chr5 g.70,922,695-70,926,042 for a 3348 bp deletion. By analyzing the breakpoint junctions, we identified that these genomic sequences were composed of Alu sequences, including AluJb, AluYm1, AluSq, and AluYm1, indicating that Alu-mediated rearrangements are a mechanism of SMN1 deletion events. In addition, full-length SMN1 transcripts and SMN protein in patient 1 were significantly decreased (p < 0.01), suggesting that a 1415 bp deletion that included the transcription and translation initiation sites of the SMN1 gene had severe consequences for SMN expression. Ultra-LRS can easily distinguish highly homozygous genes compared to other detection technologies, which is useful for detecting SMN1 intragenic mutations, to quickly discover structural rearrangements and to precisely present the breakpoint positions.

Onasemnogene Abeparvovec in Type 1 Spinal Muscular Atrophy: A Systematic Review and Meta-Analysis

One of the latest approved therapies for spinal muscular atrophy (SMA) is onasemnogene abeparvovec, which transduces motor neurons with the survival of motor neuron gene. The aim of this meta-analysis was to estimate the effect of onasemnogene abeparvovec on motor function in participants with type 1 SMA. Medline, Web of Science, Scopus, and Cochrane Library were searched for studies published from inception to August 2022. Pre-post clinical trials and observational studies determining the effect of onasemnogene abeparvovec on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) score or motor milestones (i.e., head control, sit unassisted, feed orally, not use permanent ventilatory support, crawl, stand alone, and walk alone) in participants with type 1 SMA were included. Continuous outcomes (i.e., CHOP-INTEND score) were expressed as pre-post mean difference and 95% confidence interval (CI), while the proportion of participants who achieved >40, >50, and >58/60 points on the CHOP-INTEND and the achievement of the motor milestones were expressed as proportions and 95% CI. A random effects meta-analysis was conducted on each outcome, and the baseline CHOP-INTEND score was considered a covariate. Eleven studies were included in the systematic review, and four were included in the meta-analyses. Onasemnogene abeparvovec improved CHOP-INTEND scores by 11.06 (9.47 to 12.65) and 14.14 (12.42 to 15.86) points at 3 and 6 months postinfusion, respectively. Moreover, 87%, 51%, and 12% achieved CHOP-INTEND scores of >40, >50, and >58/60 points, respectively. However, this proportion increased to 100% in presymptomatic participants with greater baseline CHOP-INTEND. Motor milestones were also improved, especially in presymptomatic participants. Our systematic review not only showed a marked improvement in motor function in type 1 SMA but also showed that treatment in the presymptomatic stage improves the development of these children toward an evolution close to normal for their age.

The Japan Registry for Adult Subjects of Spinal Muscular Atrophy (jREACT-SMA): Protocol for a Longitudinal Observational Study

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive genetic neuromuscular disorder with progressive muscle weakness and atrophy, mainly caused by lower motor neuron degeneration resulting from decreased levels of the survival motor neuron protein. Recently, 3 disease-modifying therapies for SMA (nusinersen, onasemnogene abeparvovec, and risdiplam) were approved in Japan that are expected to improve the prognosis of patients with SMA. Long-term clinical follow-up of adult patients treated with disease-modifying therapies and the natural history of SMA are essential to assess the real-world effectiveness of available treatments. Until recently, nusinersen was the only treatment option for patients with SMA in Japan; however, because Japanese approval of nusinersen was based on global clinical trials in infants and children aged 0-15 years with SMA, the effectiveness of nusinersen in adult patients has not been fully assessed in Japan. In addition, longitudinal clinical data of adult patients have not been systematically collected in Japan.

OBJECTIVE

This longitudinal observational study of adult patients with SMA who have been diagnosed with 5q-SMA in Japan aims to gain a better understanding of the natural history of SMA, as well as the long-term effectiveness of disease-modifying therapies. Here, we describe the protocol for the study.

METHODS

The Japan Registry for Adult Subjects of Spinal Muscular Atrophy (jREACT-SMA) study is a longitudinal (prospective and retrospective) observational study with a 60-month prospective follow-up being conducted at 19 investigational sites using the newly established jREACT-SMA registry. Patients aged ≥18 years with genetically confirmed 5q-SMA were planned to be enrolled in the registry from December 2020 to May 2022. The planned enrollment was 100 patients. The protocol was approved on September 28, 2020 (approval 2020-0289) by the ethical review committee of Nagoya University. Registration, demographics, genetic diagnosis, motor functions, patient-reported outcomes/quality-of-life outcomes, and other clinical data have been or will be collected.

RESULTS

As of May 2022, 113 patients had been enrolled, and the completion of patient registration has been extended from May 2022 to December 2022. Data at registration and during the follow-up period were and will be prospectively collected at least once a year until November 2025 (maximum 60 months). Data analyses will be conducted when all data have been collected. Results are expected to be available in 2026 and the study is expected to be completed by March 2027.

CONCLUSIONS

This jREACT-SMA study will provide longitudinal prospective follow-up data in adult patients with SMA in Japan, including data on the natural history of the disease and data on the long-term effectiveness of disease-modifying therapies.

TRIAL REGISTRATION

University Hospital Medical Information Network Center Clinical Trials Registry UMIN000042015; https://rctportal.niph.go.jp/en/detail?trial_id=UMIN000042015.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/38878.

MLPA analysis for molecular diagnosis of spinal muscular atrophy and correlation of 5q13.2 genes with disease phenotype in Egyptian patients

Background

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease representing the most prevalent monogenic cause of infant mortality. It results from the loss of SMN1 gene, but retention of its paralog SMN2 whose copy number can modulate the disease severity and guide the therapeutic regimen.

Methods

For SMA molecular analysis, 236 unrelated Egyptian patients were enrolled at our institution. The Multiplex ligation-dependent probe amplification analysis (MLPA) was applied to investigate the main genetic defect in the enrolled patients (SMN1 loss) and to determine a possible genotype–phenotype correlation between the copy number of other genes in the SMN locus (5q13.2) and disease severity in Egyptian patients with SMA. A small cohort of healthy subjects (n = 57) was also included to investigate the possible differences in the distributions of SMN2 and NAIP genes between patients and healthy individuals.

Results

Disease diagnosis was confirmed in only 148 patients (62.7%) highlighting the clinical overlapping of the disease and emphasizing the importance of molecular diagnosis. In patients with homozygous SMN1 loss, the disease was mediated by gene deletion and conversion in 135 (91.2%) and 13 (8.8%) patients, respectively. In the study cohort, SMN2 and NAIP copy numbers were inversely correlated with disease severity. However, no significant association was detected between GTF2H2A and SERF1B copy numbers and patient phenotype. Significant differences were demonstrated in the copy numbers of SMN2 and NAIP between SMA patients and healthy subjects.

Conclusion

Molecular analysis of SMA is essential for disease diagnosis. Consistent with previous studies on other populations, there is a close relationship between SMN2 and NAIP copy numbers and clinical phenotype. Additionally, potential differences in these two genes distributions are existing between patients and healthy subjects. National program for carrier screening should be established as a preventive disease strategy. On the other hand, neonatal testing would provide accurate estimation for disease incidence.

Experience and Perspectives in the US on the Evolving Treatment Landscape in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disorder that, until recently, was the most common inherited cause of infant mortality. Since 2016, three disease-modifying therapies have emerged, nusinersen, onasemnogene abeparvovec-xioi, and risdiplam, leading to a transformation in the SMA treatment landscape, changes in disease trajectories, and a profound impact on clinical care. This environment poses a challenge to making informed treatment decisions, including initial treatment choice, treatment changes, and potential use of combination therapies as new data emerge. To better understand factors that influence physician-patient decision-making, a roundtable discussion was convened by Biogen (sponsor) with a panel of four US SMA experts. This report shares the panel’s opinions and clinical experiences, with the goals of helping clinicians and people with SMA and their families to better understand the factors influencing real-world treatment decisions and stimulating a broader discussion in the SMA community. The panelists highlighted that patients are often heavily involved in treatment decisions, and physicians must be aware of current data to guide patients in making the best decisions. Thus, in the absence of data from head-to-head treatment comparisons, physicians’ roles include reviewing treatment options and describing what is known of the benefits, challenges, and potential side effects of each therapy with patients and families. For infants and young children, the panelists expressed a sense of urgency for early intervention to minimize motor function loss, whereas the goal for adults is long-term disease stabilization. In the panelists’ experience, factors that influence patients’ decisions to change to an alternative therapy include convenience, administration route, novelty of therapy, and hope for improved function, while reasons for returning to a previous therapy include a perception of decreased efficacy and side effects. Ongoing clinical trials and analyses of real-world experiences should further inform treatment decisions and optimize patient outcomes.

R-loop Mediated DNA Damage and Impaired DNA Repair in Spinal Muscular Atrophy

Defects in DNA repair pathways are a major cause of DNA damage accumulation leading to genomic instability and neurodegeneration. Efficient DNA damage repair is critical to maintain genomicstability and support cell function and viability. DNA damage results in the activation of cell death pathways, causing neuronal death in an expanding spectrum of neurological disorders, such as amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), Alzheimer’s disease (AD), and spinal muscular atrophy (SMA). SMA is a neurodegenerative disorder caused by mutations in the Survival Motor Neuron 1 (SMN1) gene. SMA is characterized by the degeneration of spinal cord motor neurons due to low levels of the SMN protein. The molecular mechanism of selective motor neuron degeneration in SMA was unclear for about 20 years. However, several studies have identified biochemical and molecular mechanisms that may contribute to the predominant degeneration of motor neurons in SMA, including the RhoA/ROCK, the c-Jun NH₂-terminal kinase (JNK), and p53-mediated pathways, which are involved in mediating DNA damage-dependent cell death. Recent studies provided insight into selective degeneration of motor neurons, which might be caused by accumulation of R-loop-mediated DNA damage and impaired non-homologous end joining (NHEJ) DNA repair pathway leading to genomic instability. Here, we review the latest findings involving R-loop-mediated DNA damage and defects in neuron-specific DNA repair mechanisms in SMA and discuss these findings in the context of other neurodegenerative disorders linked to DNA damage.

Comparative All-Cause Mortality Among a Large Population of Patients with Spinal Muscular Atrophy Versus Matched Controls

INTRODUCTION

There is little information about survival of spinal muscular atrophy (SMA) patients into adulthood, in particular from population-based samples. We estimated and compared age-specific, all-cause mortality rates in patients with SMA and matched controls in a large, retrospective cohort study using electronic health records (EHRs) from the pre-treatment era.

METHODS

The US Optum® de-identified EHR database contains EHRs for ~ 104 million persons (study period: January 1, 2007-December 22, 2016). SMA cases were identified by one or more International Classification of Diseases, Ninth/Tenth Edition codes for SMA. Controls with no SMA diagnosis code were matched 10:1 to SMA cases based on birth year, gender, and first diagnostic code date. For both groups, ≥ 1 month of observation and (if deceased) a valid date of death were required for inclusion. Age-specific mortality rates per person-year (PY) and hazard ratios were calculated.

RESULTS

Five thousand one hundred seventy-nine SMA cases and 51,152 controls were analyzed. The overall hazard ratio comparing cases with controls was 1.76 (95% CI 1.63-1.90). In patients with SMA type III diagnostic codes only, the all-age mortality rate was 1059/100,000 PYs in cases and 603/100,000 PYs in controls. In older age groups (13-20, 21-30, 31-40, 41-50, 51-60, and > 60 years), age-specific mortality rates for cases consistently exceeded those of controls. Limitations of this study included the inability to confirm the SMA diagnosis or SMA type by genetic or clinical confirmation.

CONCLUSION

Patients with SMA of all ages, including adults and type III patients, had a higher all-cause mortality rate as compared to age-matched controls during the pre-treatment era.

A possible case of paralysis in early modern Vilnius and the implications for social care

OBJECTIVE

To present a case of possible paralysis from early modern Vilnius and to discuss the potential level of care that was provided in the society of that time.

MATERIALS

A partially disturbed skeleton of a young female from a 16th-17th century Orthodox Christian cemetery.

METHODS

Macroscopic, osteometric and X-ray examinations coupled with a literature review aimed at providing a differential diagnosis.

RESULTS

The skeletal remains showed signs of disuse atrophy most probably due to a neurological disorder acquired in the woman's late teens. Differentials suggest that the observed limb atrophy was most likely a consequence of poliomyelitis.

CONCLUSIONS

The case of a young female with paralysis presented in this paper could serve as an example of care provided by her household.

SIGNIFICANCE

This study substantially contributes to further understanding of the nature and quality of care provided to disabled individuals in their households even in the absence of written sources.

LIMITATIONS

There is a degree of diagnostic ambiguity due to the application of routine clinical criteria to paleopathological cases.

SUGGESTIONS FOR FURTHER RESEARCH

The article makes several recommendations for future research, e.g., systematic investigation of possible cases of bone atrophy in a broader sociocultural context, as well as searching for evidence of gastrointestinal infections, especially poliomyelitis, supplemented by the application of biomolecular technologies.

Nusinersen in Adults with 5q Spinal Muscular Atrophy: a Systematic Review and Meta-analysis

Evidence for nusinersen administration in adult 5q spinal muscular atrophy (5q-SMA) patients is scarce and based on real-world observational data. The present systematic review and meta-analysis aimed to explore the efficacy and safety of nusinersen in patients older than 12 years of age with 5q-SMA. We searched MEDLINE, EMBASE, the Cochrane Library, and grey literature through April 2021. Cross-sectional studies, case reports, review articles, and studies with follow-up less than 6 months were excluded. We included 12 records (seven case-series, five cohorts) representing 11 population cohorts and enrolling 428 SMA patients. We observed statistically significant improvements on motor function Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM) scores at the longest follow-up assessments [SMD = 0.17(95% CI 0.01-0.33), SMD = 0.22(95% CI 0.06-0.38), respectively]. HFMSE and RULM significant improvements were also detected at the subgroup analysis during 10 and 14 months. HFMSE and RULM amelioration occurred earlier in patients with SMA type 3 or 4 during short-term analysis (≤ 6 months). 6-min walk tests (6MWT) and pulmonary function tests did not change. Minimal clinically important differences in HFMSE and RULM were observed in 43.3% (95% CI 34.5-52.3) and 38.9% (95% CI 27.7-50.7), respectively. Severe adverse events were reported in 2% (95% CI 0-5.8). Treatment withdrawal rate was 3% (95% CI 0.5-6.6). Despite the low quality of evidence and the unmet need for randomized data to establish the safety and efficacy of nusinersen in adults, our meta-analysis confirms that nusinersen is a valuable treatment option for older patients with longer-disease duration.Trial registration: PROSPERO database CRD42020223109.

Development of the SMA independence scale-upper limb module (SMAIS-ULM): A novel scale for individuals with Type 2 and non-ambulant Type 3 SMA

BACKGROUND

The amount of assistance required to perform daily activities for individuals with Type 2 and non-ambulant Type 3 spinal muscular atrophy (SMA) is often cited as meaningful for quality of life, and important to routinely assess.

METHODS

The SMA Independence Scale (SMAIS), a patient-reported outcome measure for individuals with SMA aged ≥12 years, and an observer-reported outcome measure for caregivers of individuals aged ≥2 years, was developed and evaluated in two phases. In Phase 1, 30 draft items were developed following review of the literature. Semi-structured interviews were then conducted with individuals with SMA and caregivers to establish content validity, resulting in a 29-item measure. In Phase 2, classical test theory and Rasch measurement theory methods were used to examine the cross-sectional and longitudinal measurement performance of the SMAIS in two independent datasets.

RESULTS

Phase 1 qualitative findings supported the relevance, acceptability, and comprehensibility of 29 items. In Phase 2, psychometric analyses indicated that the five response options were poorly discriminated and were thus collapsed to three options for subsequent analyses. Items showed statistical misfit, implying that the SMAIS was not assessing a single underlying construct. Based on conceptual evaluation of the items, and assessment of item performance, a more targeted 22-item upper limb score was derived. Reliability and validity analyses confirmed acceptable measurement properties of this score.

CONCLUSIONS

Qualitative and quantitative analyses support the use of the 22-item SMAIS-Upper Limb Module in individuals with Type 2 and non-ambulant Type 3 SMA, aged ≥2 years.

Bone mineral density and its influencing factors in Chinese children with spinal muscular atrophy types 2 and 3

Background

Patients with spinal muscular atrophy (SMA) are at risk of decreased bone mineral density (BMD). The bone health status of Chinese patients with SMA has been poorly studied. We aimed to evaluate the BMD of children with SMA types 2 and 3 in mainland China and investigate its influencing factors.

Methods

Forty patients with a mean age of 5.5 years affected by SMA types 2 and 3 (n = 22 and n = 18, respectively) were enrolled between September 2017 and May 2019. Total body less head (TBLH) BMD, lumbar spine (LS) BMD, and body composition were measured using dual-energy X-ray absorptiometry (DXA). Serum bone metabolism markers and complete spinal radiographs were assessed. We utilized a linear regression model to explore the correlations between BMD and its related factors.

Results

A total of 67.5% (27/40) of patients were diagnosed with low BMD and 2.5% (1/40) were diagnosed with osteoporosis. The TBLH BMD and LS BMD Z-scores in children with SMA type 2 were significantly lower than those with SMA type 3. Both TBLH and LS BMD Z-scores tended to increase with the change of SMA subtypes from 2a-3b. Vitamin D insufficiency and deficiency were found in 37.5% (15/40) of the patients. Serum Ca, phosphorus (P), alkaline phosphatase (ALP) and parathormone (PTH) levels were normal. There were no significant differences among the four subtypes in terms of all the serum bone metabolism markers. Phenotype was significantly associated with TBLH BMD and LS BMD Z-scores, and serum PTH levels were significantly associated with TBLH BMD Z-scores.

Conclusions

Low BMD and osteoporosis were highly prevalent in mainland Chinese children with SMA types 2 and 3. Phenotype and serum PTH level might be the influencing factors of BMD. Regular monitoring of BMD by DXA scan and taking active interventions aim to SMA children with different types are important.

Phenotypes of SMA patients retaining SMN1 with intragenic mutation

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous deletion or intragenic mutation of the SMN1 gene. It is well-known that high copy number of its homologous gene, SMN2, modifies the phenotype of SMN1-deleted patients. However, in the patients with intragenic SMN1 mutation, the relationship between phenotype and SMN2 copy number remains unclear.

METHODS

We have analyzed a total of 515 Japanese patients with SMA-like symptoms (delayed developmental milestones, respiratory failures, muscle weakness etc.) from 1996 to 2019. SMN1 and SMN2 copy numbers were determined by quantitative polymerase chain reaction (PCR) method and/or multiplex ligation-dependent probe amplification (MLPA) method. Intragenic SMN1 mutations were identified through DNA and RNA analysis of the fresh blood samples.

RESULTS

A total of 241 patients were diagnosed as having SMA. The majority of SMA patients showed complete loss of SMN1 (n = 228, 95%), but some patients retained SMN1 and carried an intragenic mutation in the retaining SMN1 (n = 13, 5%). Ten different mutations were identified in these 13 patients, consisting of missense, nonsense, frameshift and splicing defect-causing mutations. The ten mutations were c.275G > C (p.Trp92Ser), c.819_820insT (p.Thr274Tyrfs*32), c.830A > G (p.Tyr277Cys), c.5C > T (p.Ala2Val), c.826 T > C (p.Tyr276His), c.79C > T (p.Gln27*), c.188C > A (p.Ser63*), c.422 T > C (p.Leu141Pro), c.835-2A > G (exon 7 skipping) and c.835-3C > A (exon 7 skipping). It should be noted here that some patients with milder phenotype carried only a single SMN2 copy (n = 3), while other patients with severe phenotype carried 3 SMN2 copies (n = 4).

CONCLUSION

Intragenic mutations in SMN1 may contribute more significantly to clinical severity than SMN2 copy numbers.

Systematically Studying the Effect of Small Molecules Interacting with RNA in Cellular and Preclinical Models

The interrogation and manipulation of biological systems by small molecules is a powerful approach in chemical biology. Ideal compounds selectively engage a target and mediate a downstream phenotypic response. Although historically small molecule drug discovery has focused on proteins and enzymes, targeting RNA is an attractive therapeutic alternative, as many disease-causing or -associated RNAs have been identified through genome-wide association studies. As the field of RNA chemical biology emerges, the systematic evaluation of target validation and modulation of target-associated pathways is of paramount importance. In this Review, through an examination of case studies, we outline the experimental characterization, including methods and tools, to evaluate comprehensively the impact of small molecules that target RNA on cellular phenotype.

Newborn Screening for Spinal Muscular Atrophy: Ontario Testing and Follow-up Recommendations

BACKGROUND

Spinal muscular atrophy (SMA) is characterized by the progressive loss of motor neurons causing muscle atrophy and weakness. Nusinersen, the first effective SMA therapy was approved by Health Canada in June 2017 and has been added to the provincial formulary of all but one Canadian province. Access to this effective therapy has triggered the inclusion of SMA in an increasing number of Newborn Screening (NBS) programs. However, the range of disease-modifying SMN2 gene copy numbers encountered in survival motor neuron 1 (SMN1)-null individuals means that neither screen-positive definition nor resulting treatment decisions can be determined by SMN1 genotype alone. We outline an approach to this challenge, one that specifically addresses the case of SMA newborns with four copies of SMN2.

OBJECTIVES

To develop a standardized post-referral evaluation pathway for babies with a positive SMA NBS screen result.

METHODS

An SMA NBS pilot trial in Ontario using first-tier MassARRAY and second-tier multi-ligand probe amplification (MLPA) was launched in January 2020. Prior to this, Ontario pediatric neuromuscular disease and NBS experts met to review the evidence regarding the diagnosis and treatment of children with SMA as it pertained to NBS. A post-referral evaluation algorithm was developed, outlining timelines for patient retrieval and management.

CONCLUSIONS

Ontario's pilot NBS program has created a standardized path to facilitate early diagnosis of SMA and initiation of treatment. The goal is to provide timely access to those SMA infants in need of therapy to optimize motor function and prolong survival.

An open-label phase 1 clinical trial of the allogeneic side population adipose-derived mesenchymal stem cells in SMA type 1 patients

INTRODUCTION

Spinal muscular atrophy (SMA), an autosomal recessive neurodegenerative disorder of alpha motor neurons of spinal cord associated with progressive muscle weakness and hypotonia, is the most common genetic cause of infant mortality. Although there is few promising treatment for SMA, but the field of translational research is active in it, and stem cell-based therapy clinical trials or case studies are ongoing. Combination of different therapeutic approaches for noncurative treatments may increase their effectiveness and compliance of patients. We present a phase 1 clinical trial in patients with SMA1 who received side population adipose-derived mesenchymal stem cells (SPADMSCs).

METHODS

The intervention group received three intrathecal administrations of escalating doses of SPADMSCs and followed until 24 months or the survival time. The safety analysis was assessed by controlling the side effects and efficacy evaluations performed by the Hammersmith Infant Neurological Examination (HINE), Ballard score, and electrodiagnostic (EDX) evaluation. These evaluations were performed before intervention and at the end of the follow-up.

RESULTS

The treatment was safe and well tolerated, without any adverse event related to the stem cell administration. One of the patients in the intervention group was alive after 24 months of study follow-up. He is a non-sitter 62-month-old boy with appropriate weight gain and need for noninvasive ventilation (NIV) for about 8 h per day. Clinical scores, need for supportive ventilation, and number of hospitalizations were not meaningful parameters in the response of patients in the intervention and control groups. All five patients in the intervention group showed significant improvement in the motor amplitude response of the tibial nerve (0.56mV; p: 0.029).

CONCLUSION

This study showed that SPADMSCs therapy is tolerable and safe with promising efficacy in SMA I. Probably same as other treatment strategies, early intervention will increase its efficacy and prepare time for more injections. We suggest EDX evaluation for the follow-up of treatment efficacy.

Dysphagia Phenotypes in Spinal Muscular Atrophy: The Past, Present, and Promise for the Future

Purpose The aim of this study was to provide clinicians with an overview of literature relating to dysphagia in spinal muscular atrophy (SMA) to guide assessment and treatment. Method In this clinical focus article, we review literature published in Scopus and PubMed between 1990 and 2020 pertaining to dysphagia in SMA across the life span. Original research articles that were published in English were included. Searches were conducted within four themes of inquiry: (a) etiology and phenotypes, (b) respiratory systemic deficits and management, (c) characteristics of natural history dysphagia and its treatment, and (d) dysphagia outcomes with disease-modifying therapies. Articles for the first two themes were selected by content experts who identified the most salient articles that would provide clinicians foundational background knowledge about SMA. Articles for the third theme were identified using search terms, including spinal muscular atrophy, swallow, dysphagia, bulbar, nutrition, g-tube, alternative nutrition, jaw, mouth, palate, OR mandible. Search terms for the fourth theme included spinal muscular atrophy AND nusinersen OR AVXS-101/onasemnogene abeparvovec-xioi. Review of Pertinent Literature Twenty-nine articles were identified. Findings across identified articles support the fact that patients with SMA who do not receive disease-modifying therapy exhibit clinically significant deficits in oropharyngeal swallow function. Few investigations provided systematic information regarding the underlying physiological deficits responsible for this loss in function, the timing of the degradation, or how disease-modifying therapies change these outcomes. Conclusion Future research outlining the physiological and functional oropharyngeal swallowing deficits among patients with SMA who receive disease-modifying therapy is critical in developing standards of dysphagia care to guide clinicians.

The incidence of hydrocephalus among patients with and without spinal muscular atrophy (SMA): Results from a US electronic health records study

Background

The incidence of hydrocephalus in the spinal muscular atrophy (SMA) population relative to the general population is currently unknown. Since the approval of nusinersen, an intrathecally administered drug for SMA, a small number of hydrocephalus cases among nusinersen users have been reported. Currently, the incidence of hydrocephalus in untreated SMA patients is not available, thereby making it difficult to determine if hydrocephalus is a side effect of nusinersen or part of SMA’s natural history. This retrospective, matched cohort study used electronic health records (EHRs) to estimate and compare the incidence of hydrocephalus in both SMA patients and matched non-SMA controls in the time period prior to the approval of nusinersen.

Methods

The U.S. Optum® de-identified EHR database contains records for approximately 100 million persons. The current study period spanned January 1, 2007–December 22, 2016. Patients with SMA were identified by one or more International Classification of Diseases (ICD)-9 and/or ICD-10 codes for SMA appearing as primary, admission, or discharge diagnoses, without a pregnancy diagnostic code in the 1-year time before and after the first occurrence of SMA. The first occurrence of SMA defined the index date and non-SMA controls were matched to cases. Incident cases of hydrocephalus were identified with one or more ICD-9 and/or ICD-10 code for any type of hydrocephalus following the index date. Hydrocephalus incidence rates per person-months and the incidence rate ratio comparing SMA cases with non-SMA controls were calculated.

Results

There were 5354 SMA cases and an equal number of matched non-SMA controls. Incident hydrocephalus events were identified in 42 SMA cases and 9 non-SMA controls. Hydrocephalus incidence rates per 100,000 person-months were 15.5 (95% CI: 11.2–20.9) among SMA cases and 3.3 (95% CI: 1.5–6.3) among non-SMA controls. The incidence rate ratio was 4.7 (95% CI: 2.4–10.2).

Conclusions

Based on this retrospective analysis utilizing US EHR data, SMA patients had an approximately fourfold increased risk of hydrocephalus compared with non-SMA controls in the era preceding nusinersen treatment. This study may assist in properly evaluating adverse events in nusinersen-treated SMA patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01822-4.

Prognostic Factors and Treatment-Effect Modifiers in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disease characterized by loss of motor neurons and muscle atrophy. Untreated infants with type 1 SMA do not achieve major motor milestones, and death from respiratory failure typically occurs before 2 years of age. Individuals with types 2 and 3 SMA exhibit milder phenotypes and have better functional and survival outcomes. Herein, a systematic literature review was conducted to identify factors that influence the prognosis of types 1, 2, and 3 SMA. In untreated infants with type 1 SMA, absence of symptoms at birth, a later symptom onset, and a higher survival of motor neuron 2 (SMN2) copy number are all associated with increased survival. Disease duration, age at treatment initiation, and, to a lesser extent, baseline function were identified as potential treatment‐modifying factors for survival, emphasizing that early treatment with disease‐modifying therapies (DMT) is essential in type 1 SMA. In patients with types 2 and 3 SMA, factors considered prognostic of changes in motor function were SMN2 copy number, age, and ambulatory status. Individuals aged 6–15 years were particularly vulnerable to developing complications (scoliosis and progressive joint contractures) which negatively influence functional outcomes and may also affect the therapeutic response in patients. Age at the time of treatment initiation emerged as a treatment‐effect modifier on the outcome of DMTs. Factors identified in this review should be considered prior to designing or analyzing studies in an SMA population, conducting population matching, or summarizing results from different studies on the treatments for SMA.

Evolving Surgical Management for Early-Onset Scoliosis in Spinal Muscular Atrophy Type 1 Given Improvements in Survival

CASE

We present a case of an 18-month-old child with early-onset scoliosis in the setting of spinal muscular atrophy (SMA) type 1 whose rapidly progressive scoliosis is successfully managed with magnetic growing rods, the youngest age of implantation in a patient with SMA we are currently aware of. Technical challenges, complications, and outcome are described in this case presentation.

CONCLUSION

Patients with SMA type 1 and early-onset scoliosis can be managed with growing-rod constructs given dramatic improvements in medical care that have expanded life expectancy.

Safety and efficacy of nusinersen in spinal muscular atrophy: The EMBRACE study

Introduction

The EMBRACE study (Clinical Trials No. NCT02462759) evaluated nusinersen in infants/children with infantile‐ or later‐onset spinal muscular atrophy (SMA) who were ineligible for the ENDEAR and CHERISH studies.

Methods

Participants were randomized to intrathecal nusinersen (12‐mg scaled equivalent dose; n = 14) or sham procedure (n = 7) in part 1 (~14 months) and subsequently received open‐label nusinersen for ~24 months in part 2 of the study.

Results

Part 1 was stopped early after the demonstration of motor function benefit with nusinersen in ENDEAR. There were no nusinersen‐related adverse events (AEs) and no study discontinuations due to nusinersen‐related AEs. The most common AEs included pyrexia, cough, pneumonia, and upper respiratory tract infections. Motor milestone responder rates were higher in those receiving nusinersen at last available assessment (93%) than in those receiving sham procedure in part 1 (29%) or transitioned from sham to nusinersen in part 2 (83%). This functional improvement was observed despite the small sample size and shortened part 1 trial duration that undermined the power of the study to demonstrate such treatment effects at a significant level.

Discussion

Nusinersen demonstrated a favorable long‐term benefit‐risk profile in this broad population of individuals with infantile‐ or later‐onset SMA.

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.

Natural history in spinal muscular atrophy Type I in Taiwanese population: A longitudinal study

INTRODUCTION

Spinal muscular atrophy (SMA) is caused by a defect in the survival motor neuron 1 (SMN1) gene. The Cooperative Study of the natural history of SMA Type I in Taiwan is a retrospective, longitudinal, observational study that helps in further understanding SMA disease progression in patients who have not received disease-modifying therapeutic interventions.

METHODS

Case report forms were used to collect demographics; genetic confirmation; SMN2 copy number; treatment patterns; and clinical outcomes including ventilator use, endotracheal tube intubation, tracheostomy, gastrostomy, complications, and survival.

RESULTS

A total of 111 patients with SMA Type I were identified over the study period (1979-2015). Mean (median) age of onset and age at confirmed diagnosis were 1.3 (0.8) and 4.9 (4.4) months, respectively. SMN1 deletion/mutation was documented in 70 patients and SMN2 copy number in 32 (2 copies, n = 20; 3 copies, n = 12). At 240 months, survival probability for patients born during 1995-2015 versus 1979-1994 was significantly longer (p = 0.0057). Patients with 3 SMN2 copies showed substantially longer 240-month survival versus patients with 2 SMN2 copies. Over the 36-year period, mean (median) age at death was 31.9 (8.8) months. As of December 2015, 95 patients had died, 13 were alive, and 3 were lost to follow-up. The use of supportive measures (tracheostomy and gastrostomy) was associated with improved survival.

CONCLUSIONS

These data describe the short survival of patients with SMA Type I in Taiwan in the pretreatment era, emphasizing the positive impact of supportive measures on survival.

Nusinersen safety and effects on motor function in adult spinal muscular atrophy type 2 and 3

OBJECTIVE

To retrospectively investigate safety and efficacy of nusinersen in a large cohort of adult Italian patients with spinal muscular atrophy (SMA).

METHODS

Inclusion criteria were: (1) clinical and molecular diagnosis of SMA2 or SMA3; (2) nusinersen treatment started in adult age (>18 years); (3) clinical data available at least at baseline (T0-beginning of treatment) and 6 months (T6).

RESULTS

We included 116 patients (13 SMA2 and 103 SMA3) with median age at first administration of 34 years (range 18-72). The Hammersmith Functional Rating Scale Expanded (HFMSE) in patients with SMA3 increased significantly from baseline to T6 (median change +1 point, p<0.0001), T10 (+2, p<0.0001) and T14 (+3, p<0.0001). HFMSE changes were independently significant in SMA3 sitter and walker subgroups. The Revised Upper Limb Module (RULM) in SMA3 significantly improved between T0 and T14 (median +0.5, p=0.012), with most of the benefit observed in sitters (+2, p=0.018). Conversely, patients with SMA2 had no significant changes of median HFMSE and RULM between T0 and the following time points, although a trend for improvement of RULM was observed in those with some residual baseline function. The rate of patients showing clinically meaningful improvements (as defined during clinical trials) increased from 53% to 69% from T6 to T14.

CONCLUSIONS

Our data provide further evidence of nusinersen safety and efficacy in adult SMA2 and SMA3, with the latter appearing to be cumulative over time. In patients with extremely advanced disease, effects on residual motor function are less clear.

Identification of two novel SMN1 point mutations associated with a very severe SMA-I phenotype

Spinal muscular atrophy (SMA) is a common autosomal recessive genetic disorder characterized by degeneration of motor neurons and weakness and muscle atrophy. Approximately 95% of SMA patients are caused by homozygous deletions of the SMN1 gene, whereas the remaining 5% of patients harbor compound heterozygous mutations such as an SMN1 deletion allele and an intragenic mutation (insertions, deletions, or point mutations) in the other SMN1 allele. Although analysis for the SMN1/SMN2 copy number is relatively easy, molecular genetic testing for patients with subtle mutations is still compromised due to the presence of a highly homologous SMN2 gene. Herein, we analyzed the SMN1/SMN2 copy number by multiplex ligation-dependent probe amplification (MLPA) and subtle mutations by long-range PCR (LR-PCR) for two "nondeletion" SMA patients. We identified a missense mutation (c.280G > T, p. (Val94Phe)) and a splicing mutation c.*3+3A > T in SMN1 gene not previously described in the scientific literature. Giving the severe phenotype of the two patients, we speculated that these two point mutations could significantly affect the function of SMN proteins. Our results provide important information for genetic counseling and prenatal diagnosis in these families and enrich the SMN1 mutation database.

Ultrasound assessment of diaphragmatic function in type 1 spinal muscular atrophy

OBJECTIVE

To investigate ultrasound features of diaphragm motion and function in type 1 spinal muscular atrophy (SMA-1) patients.

DESIGN

Prospective study.

PATIENTS

The study cohort included SMA-1 children younger than 18-year-old. Control subjects included type 2 and type 3 SMA and other neuromuscular disorders younger than 18-year-old.

METHODOLOGY

Diaphragm ultrasound evaluating diaphragmatic excursion, speed of diaphragmatic contraction, duration of the respiratory cycle, inspiratory/expiratory relationship, end-inspiratory and -expiratory thickness, thickening fraction, and pattern of contractility. The interrater reliability for each variable was established by calculation of Cohen's k coefficient.

RESULTS

Twenty-three SMA-1 patients and 12 controls were evaluated. Diaphragm ultrasound values were within normal ranges in all study cohort patients and no difference was found with controls. There was a gradient of diaphragm function with SMA 1.9 subgroup having the best and SMA 1.1 having the worst parameters, particularly in end-inspiratory thickness and diaphragmatic excursion (P = .031 and P = .041, respectively). Seventy-four percent of SMA-1 patients had a dysmotility pattern of diaphragm contraction, mostly represented in SMA 1.9 subgroup (P = .001). This pattern was observed in 92.8% of children on noninvasive ventilation (NIV) for less than 16 hours/d of and in 20% patients with invasive ventilation or NIV for more than 16 hours/d (P = .027). The dysmotility pattern was never observed in the control group. The levels of interobserver agreement were high for "diaphragm irregularities," "inspiratory/expiratory relationship," and "diaphragm thickness," and good for the other variables.

CONCLUSIONS

Ultrasound can be used to evaluate diaphragm function and contractility in SMA-1 children, providing additional information to the clinical examination and functional respiratory tests, describing a characteristic contractility pattern in these patients. Longitudinal studies are needed to understand the impact of diaphragm dysmotility and other parameters on long-term outcome in SMA-1 patients.

Spinal Muscular Atrophy in Blonde D'Aquitaine Calves Is Not Associated With FVT1 Gene Mutation

Spinal muscular atrophy (SMA) is a motor neuron disease (MND) in humans and diverse animal species: canid, felid, and bovid. To date, bovine SMA has been reported in Brown Swiss, Holstein, Friesian, and Red Danish breed; it has been associated with a genetic mutation of the FVT1 gene, also known as 3-ketodihydrosphingosine reductase (KDSR). The aim of the present case series was to describe clinical presentation, pathological findings, and genetic analysis of five Blond d'Aquitaine calves diagnosed with SMA and to determine whether the mutation was associated with the disease. Five Blonde d'Aquitaine calves (three females and two males) from the same cow-calf operation farm were presented between June 2018 and February 2019 because unable to stand or walk unassisted since birth. Neurological examination aroused suspicion of a diffuse lesion affecting the peripheral nervous system in all calves. Findings from electromyographic investigations and muscle and nerve biopsies were consistent with a non-regenerative, chronic, active axonal neuropathy and marked neurogenic muscular atrophy and assumed to be associated with a neurodegenerative process. Histopathological examination of tissue samples from two animals revealed neuronal loss and several degenerated, shrunken, and hypereosinophilic neurons at the level of the ventral horn of the cervico-thoracic and the lumbo-sacral intumescence, diffuse loss of myelinated axons at the level of the ventral funiculi of all segments of the spinal cord, and moderate diffuse astrocytic reaction. These findings confirmed the diagnosis of SMA. No mutation of the FVT1 gene was found on genetic analysis. Further study into the causative gene mutation of SMA in Blonde D'Aquitaine calves is under way. Identification of a novel genetic mutation could improve our understanding of the disease in human medicine.

Health, wellbeing and lived experiences of adults with SMA: a scoping systematic review

BACKGROUND

Spinal muscular atrophy (SMA) is a neurodegenerative disease that has a substantial and multifaceted burden on affected adults. While advances in supportive care and therapies are rapidly reshaping the therapeutic environment, these efforts have largely centered on pediatric populations. Understanding the natural history, care pathways, and patient-reported outcomes associated with SMA in adulthood is critical to advancing health policy, practice and research across the disease spectrum. The aim of this study was to systematically review research investigating the healthcare, well-being and lived experiences of adults with SMA.

METHODS

In accordance with the Preferred Reported Items for Systematic Reviews and Meta-Analysis guidelines, seven electronic databases were systematically searched until January 2020 for studies examining clinical (physical health, natural history, treatment) and patient-reported (symptoms, physical function, mental health, quality of life, lived experiences) outcomes in adults with SMA. Study risk of bias and the level of evidence were assessed using validated tools.

RESULTS

Ninety-five articles met eligibility criteria with clinical and methodological diversity observed across studies. A heterogeneous clinical spectrum with variability in natural history was evident in adults, yet slow declines in motor function were reported when observational periods extended beyond 2 years. There remains no high quality evidence of an efficacious drug treatment for adults. Limitations in mobility and daily activities associated with deteriorating physical health were commonly reported, alongside emotional difficulties, fatigue and a perceived lack of societal support, however there was no evidence regarding effective interventions.

CONCLUSIONS

This systematic review identifies the many uncertainties regarding best clinical practice, treatment response, and long-term outcomes for adults with SMA. This comprehensive identification of the current gaps in knowledge is essential to guide future clinical research, best practice care, and advance health policy with the ultimate aim of reducing the burden associated with adult SMA.

Spinal Muscular Atrophy in the Black South African Population: A Matter of Rearrangement?

Spinal muscular atrophy (SMA) is a neuromuscular disorder, characterized by muscle atrophy and impaired mobility. A homozygous deletion of survival motor neuron 1 (SMN1), exon 7 is the main cause of SMA in ~94% of patients worldwide, but only accounts for 51% of South African (SA) black patients. SMN1 and its highly homologous centromeric copy, survival motor neuron 2 (SMN2), are located in a complex duplicated region. Unusual copy number variations (CNVs) have been reported in black patients, suggesting the presence of complex pathogenic rearrangements. The aim of this study was to further investigate the genetic cause of SMA in the black SA population. Multiplex ligation-dependent probe amplification (MLPA) testing was performed on 197 unrelated black patients referred for SMA testing (75 with a homozygous deletion of SMN1, exon 7; 50 with a homozygous deletion of SMN2, exon 7; and 72 clinically suggestive patients with no homozygous deletions). Furthermore, 122 black negative controls were tested. For comparison, 68 white individuals (30 with a homozygous deletion of SMN1, exon 7; 8 with a homozygous deletion of SMN2, exon 7 and 30 negative controls) were tested. Multiple copies (>2) of SMN1, exon 7 were observed in 50.8% (62/122) of black negative controls which could mask heterozygous SMN1 deletions and potential pathogenic CNVs. MLPA is not a reliable technique for detecting carriers in the black SA population. Large deletions extending into the rest of SMN1 and neighboring genes were more frequently observed in black patients with homozygous SMN1, exon 7 deletions when compared to white patients. Homozygous SMN2, exon 7 deletions were commonly observed in black individuals. No clear pathogenic CNVs were identified in black patients but discordant copy numbers of exons suggest complex rearrangements, which may potentially interrupt the SMN1 gene. Only 8.3% (6/72) of clinically suggestive patients had heterozygous deletions of SMN1, exon 7 (1:0) which is lower than previous SA reports of 69.5%. This study emphasizes the lack of understanding of the architecture of the SMN region as well as the cause of SMA in the black SA population. These factors need to be taken into account when counseling and performing diagnostic testing in black populations.

Economic burden of spinal muscular atrophy in the United States: a contemporary assessment

Aims: To estimate healthcare resource utilization (HRU) and costs among patients with spinal muscular atrophy (SMA) type 1 (SMA1) in real-world practice, overall and among patients treated with nusinersen. As a secondary objective, HRU and costs were estimated among patients with other SMA types (i.e. 2, 3, or 4 combined), overall and among patients treated with nusinersen.Materials and methods: Patients with SMA were identified from the Symphony Health's Integrated Dataverse (IDV) open claims database (September 1, 2016-August 31, 2018) and were classified into four cohorts based on SMA type and nusinersen treatment (i.e. SMA1, SMA1 nusinersen, other SMA, and other SMA nusinersen cohorts). The index date was the date of the first SMA diagnosis after December 23, 2016 or, for nusinersen cohorts, the date of nusinersen initiation. The study period spanned from the index date to the earlier among the end of clinical activity or data availability.Results: Patients in the SMA1 (n = 349) and SMA1 nusinersen (n = 45) cohorts experienced an average of 59.4 and 56.6 days with medical visits per-patient-per-year (PPPY), respectively, including 14.1 and 4.6 inpatient days. Excluding nusinersen-related costs, total mean healthcare costs were $137,627 and $92,618 PPPY in the SMA1 and SMA1 nusinersen cohorts, respectively. Mean nusinersen-related costs were $191,909 per-patient-per-month (PPPM) for the first 3 months post-initiation (i.e. loading phase) and $36,882 PPPM thereafter (i.e. maintenance phase). HRU and costs were also substantial among patients in the other SMA (n = 5,728) and other SMA nusinersen (n = 404) cohorts, with an average of 44.5 and 63.7 days with medical visits PPPY and total mean healthcare costs (excluding nusinersen-related costs) of $49,175 and $76,371 PPPY, respectively.Limitations: The database may contain inaccuracies or omissions in diagnoses, procedures, or costs, and does not capture medical services outside of the IDV network.Conclusions: HRU and healthcare costs were substantial in patients with SMA, including in nusinersen-treated patients.

Identification of novel SMN1 subtle mutations using an allelic-specific RT-PCR

Spinal muscular atrophy (SMA) is caused by homozygous deletions of the SMN1 gene in approximately 95% of patients. The remaining 5% of patients with SMA retain at least one copy of the SMN1 gene carrying insertions, deletions, or point mutations. Although molecular genetic testing for most SMA patients is quite easy, diagnosing "nondeletion" SMA patients is still compromised by the presence of a highly homologous SMN2 gene. In this study, we analyzed the SMN1/SMN2 copy number by quantitative PCR and multiplex ligation-dependent probe amplification (MLPA). Further, common primers for both SMN1 and SMN2 sequences were used to screen DNA intragenic mutations. To confirm whether the identified mutations occurred in SMN1 or SMN2, we improved the traditional RT-PCR method by only amplifying SMN1 transcripts using an allelic-specific PCR (AS-RT-PCR) strategy. We identified six SMN1 point mutations and small indels in 8 families, which included c.683T>A, c.22dupA, c.815A>G, c.19delG, c.551_552insA and c.401_402delAG. To the best of our knowledge, the latter three have never been previously reported. The most common mutation in Chinese patients is c.22dupA, which was identified in three families. In this work, we demonstrated AS-RT-PCR to be reliable for identifying SMN1 subtle mutations, especially the prevalent mutation c.22dupA in Chinese SMA patients. By reviewing published papers and summarizing reported SMN1 mutations, a distinct ethnic specificity was found in SMA patients from China. Our research extends the SMN1 mutation spectrum.

Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: Interim efficacy and safety results from the Phase 2 NURTURE study

Spinal muscular atrophy (SMA) is a neurodegenerative disease associated with severe muscle atrophy and weakness in the limbs and trunk. We report interim efficacy and safety outcomes as of March 29, 2019 in 25 children with genetically diagnosed SMA who first received nusinersen in infancy while presymptomatic in the ongoing Phase 2, multisite, open-label, single-arm NURTURE trial. Fifteen children have two SMN2 copies and 10 have three SMN2 copies. At last visit, children were median (range) 34.8 [25.7-45.4] months of age and past the expected age of symptom onset for SMA Types I or II; all were alive and none required tracheostomy or permanent ventilation. Four (16%) participants with two SMN2 copies utilized respiratory support for ≥6 h/day for ≥7 consecutive days that was initiated during acute, reversible illnesses. All 25 participants achieved the ability to sit without support, 23/25 (92%) achieved walking with assistance, and 22/25 (88%) achieved walking independently. Eight infants had adverse events considered possibly related to nusinersen by the study investigators. These results, representing a median 2.9 years of follow up, emphasize the importance of proactive treatment with nusinersen immediately after establishing the genetic diagnosis of SMA in presymptomatic infants and emerging newborn screening efforts.

Neurofilament Heavy Chain and Tau Protein Are Not Elevated in Cerebrospinal Fluid of Adult Patients with Spinal Muscular Atrophy during Loading with Nusinersen

Nusinersen is the first approved drug for the treatment of spinal muscular atrophy (SMA). Treatment of SMA with nusinersen is based on a fixed dosing regimen. For other motoneuron diseases, such as amyotrophic lateral sclerosis (ALS), biomarkers are available for clinical diagnostics; however, no such biomarkers have yet been found for SMA. Serum and cerebrospinal fluid (CSF) samples of 11 patients with adult SMA type 3 were prospectively collected and analyzed during loading with nusinersen. Neurofilament heavy chain, tau protein, S100B protein, and neuron-specific enolase were investigated as potential biomarkers of motor neuron destruction. No significant pathological alterations in levels of neurofilament heavy chain, tau protein, or S100B protein were detected in the CSF or blood samples under baseline conditions or during loading with nusinersen. Neuron-specific enolase was marginally elevated in CSF and blood samples without significant alteration during treatment. In a mixed cohort of adult patients with SMA type 3, neurofilament heavy chain, tau protein, S100B protein, and neuron-specific enolase do not serve as potential biomarkers during the loading phase of nusinersen. The slow progression rate of SMA type 3 may not lead to detectable elevation of levels of these common markers of axonal degradation.

Therapeutic perspectives for structural and functional abnormalities of cilia

Ciliopathies are a group of hereditary disorders that result from structural or functional abnormalities of cilia. Recent intense research efforts have uncovered the genetic bases of ciliopathies, and our understanding of the assembly and functions of cilia has been improved significantly. Although mechanism-specific therapies for ciliopathies have not yet received regulatory approval, the use of innovative therapeutic modalities such as oligonucleotide therapy, gene replacement therapy, and gene editing in addition to symptomatic treatments are expected to provide valid treatment options in the near future. Moreover, candidate chemical compounds for developing small molecule drugs to treat ciliopathies have been identified. This review introduces the key features of cilia and ciliopathies, and summarizes the advances as well as the challenges that remain with the development of therapies for treating ciliopathies.

ZPR1-Dependent Neurodegeneration Is Mediated by the JNK Signaling Pathway

The zinc finger protein ZPR1 deficiency causes neurodegeneration and results in a mild spinal muscular atrophy (SMA)-like disease in mice with reduced Zpr1 gene dosage. Mutation of the survival motor neuron 1 (SMN1) gene causes SMA. Spinal muscular atrophy is characterized by the degeneration of the spinal cord motor neurons caused by chronic low levels of SMN protein. ZPR1 interacts with SMN and is required for nuclear accumulation of SMN. Patients with SMA express reduced levels of ZPR1. Reduced Zpr1 gene dosage increases neurodegeneration and severity of SMA disease in mice. Mechanisms underlying ZPR1-dependent neurodegeneration are largely unknown. We report that neurodegeneration caused by ZPR1 deficiency is mediated by the c-Jun NH₂-terminal kinase (JNK) group of mitogen-activated protein kinases (MAPK). ZPR1-dependent neuron degeneration is mediated by central nervous system (CNS)-specific isoform JNK3. ZPR1 deficiency activates the MAPK signaling cascade, MLK3 → MKK7 → JNK3, which phosphorylates c-Jun and activates caspase-mediated neuron degeneration. Neurons from Jnk3-null mice show resistance to ZPR1-dependent neurodegeneration. Pharmacologic inhibition of JNK reduces degeneration of ZPR1-deficient neurons. These data show that ZPR1-dependent neurodegeneration is mediated by the JNK signaling pathway and suggest that ZPR1 downregulation in SMA may contribute to JNK-mediated neurodegeneration associated with SMA pathogenesis.