A Review on Spinal Muscular Atrophy: Awareness, Knowledge, and Attitudes

Spinal muscular atrophy carrier screening program: awareness and attitude of healthcare professionals in Turkey

Spinal Muscular Atrophy (SMA) is an autosomal recessive disease caused by variants in the SMN1 gene, leading to progressive muscle weakness. The carrier frequency of SMN1 gene variants, including variant and copy number variations, is estimated to be around 1 in 50 people, while the global prevalence of SMA is 1-3 per 10,000 live births. In response to the increasing carrier proportion, especially due to consanguineous marriages, Turkey launched the SMA Carrier Screening Program in 2021. Notably, recent SMA cases have been observed in the children of healthcare workers who did not undergo carrier screening, prompting us to evaluate their awareness of this program. After receiving ethics approval, 1,322 healthcare professionals completed a 15-item survey based on the SMA Carrier Screening Guidelines. Of these, 5.8% were unaware of SMA, and 26% lacked information about the national screening program. Awareness of the screening program was significantly lower among secondary and tertiary healthcare professionals compared to primary healthcare professionals (p < 0.0001) and among non-physician healthcare professionals compared to physicians (p < 0.0001). Additionally, a serious lack of knowledge was observed concerning the parts of the screening covering the pregnancy period. Although there is generally high awareness of the SMA Carrier Screening Program among healthcare professionals, significant knowledge gaps exist. These findings highlight the need for increased efforts to more effectively deliver screening programs and continue the education of healthcare professionals. Education and awareness campaigns can enhance program awareness and effectiveness, reach wider audiences, and contribute to preventive measures for the health of future generations.

Carrier Screening and Diagnosis for Spinal Muscular Atrophy Using Droplet Digital PCR Versus MLPA: Analytical Validation and Early Test Outcome

Background: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular life-threatening disorder. Owing to high carrier frequency, population-wide SMA screening to quantify the copy number of SMN gene is recommended by American College of Medical Genetics and Genomics. An accurate, reliable, short runaround time and cost-effective method may be helpful in mass population screening for SMA. Methods: Multiplex ligation-dependent probe amplification (MLPA) is a gold standard to estimate the copy number variation (CNV) for SMN1 and SMN2 genes. In this study, we validated droplet digital polymerase chain reaction (ddPCR) for the determination of CNV for both SMN1 and SMN2 exon 7 for a diagnostic purpose. In total, 66 clinical samples were tested using ddPCR, and results were compared with the MLPA as a reference test. Results: For all samples, CNV for SMN1 and SMN2 exon 7 was consentaneous between ddPCR and MLPA test results (κ = 1.000, p < 0.0001). In addition, ddPCR also showed a significant acceptable degree of test repeatability, coefficient of variation < 4%. Conclusion: ddPCR is expected to be utilitarian for CNV detection for carrier screening and diagnosis of SMA. ddPCR test results for CNV detection for SMN1/SMN2 exon 7 are concordant with the gold standard. ddPCR is a more cost-effective and time-saving diagnostic test for SMA than MLPA. Furthermore, it can be used for population-wide carrier screening for SMA.

Screening of Spinal Muscular Atrophy Carriers and Prenatal Diagnosis in Pregnant Women in Yancheng, China

Spinal muscular atrophy (SMA) is a neuromuscular disorder with an autosomal recessive inheritance pattern. Patients with severe symptoms may suffer respiratory failure, leading to death. The homozygous deletion of exon 7 in the SMN1 gene accounts for nearly 95% of all cases. Population carrier screening for SMA and prenatal diagnosis by amniocentesis for high-risk couples can assist in identifying the risk of fetal disease. We provided the SMA carrier screening process to 55,447 pregnant women in Yancheng from October 2020 to December 2022. Among them, 8185 participated in this process, with a participation rate of around 14.76% (95% CI 14.47-15.06%). Quantitative real-time polymerase chain reaction (qPCR) was used to detect deletions of SMN1 exons 7 and 8 (E7, E8) in screened pregnant women. 127 were identified as carriers (111 cases of E7 and E8 heterozygous deletions, 15 cases of E7 heterozygous deletions, and 1 case of E7 heterozygous deletions and E8 homozygous deletions), resulting in a carrying rate of around 1.55% (95% CI 1.30-1.84%). After genetic counseling, 114 spouses of pregnant women who tested positive underwent SMA carrier screening; three of them were screened as SMA carriers. Multiplexed ligation-dependent probe amplification (MLPA) was used for the prenatal diagnosis of the fetuses of high-risk couples. Two of them exhibited two copies of SMN1 exon 7 (normal), and the pregnancy was continued; one exhibited no copies of SMN1 exon 7 and exon 8 (SMA patient), and the pregnancy was terminated. Analyzing SMN1 mutations in Yancheng and provide clinical evidence for SMA genetic counseling and birth defect prevention. Interventional prenatal diagnosis for high-risk families can promote informed reproductive selection and prepare for the fetus's early treatment.

Safety and Efficacy of Nusinersen and Risdiplam for Spinal Muscular Atrophy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

We performed a systematic review and meta-analysis of the efficacy and safety of nusinersen and risdiplam in the treatment of spinal muscular disease (SMA).

METHODS

We screened the literature published in Pubmed, Web of Science, Embase, and Cochrane before July 2023 to conduct randomized controlled trials to test the treatment of SMA patients with nusinersen and risdiplam. The data were analyzed using Review Manager 5.4 software and Stata version 15.0 software.

RESULTS

A total of six randomized controlled trials were included, involving 728 SMA patients, to synthesize evidence. It is reported that nusinersen treatment was beneficial for increasing the score of the Hammersmith Functional Motor Scale-Expanded (HFMSE) (WMD: 4.90; 95% CI: 3.17, 6.63; p < 0.00001), Revised Upper Limb Module (RULM) (WMD: 3.70; 95% CI: 3.30, 4.10; p < 0.00001), and Hammersmith Infant Neurological Evaluation Section 2 (HINE-2) (WMD: 5.21; 95% CI: 4.83, 5.60; p < 0.00001). In addition, the risdiplam treatment group also showed statistically significant improvements in the HFMSE score (WMD:0.87; 95% CI: 0.05, 1.68; p = 0.04), the 32-item Motor Function Measure (MFM32) (WMD:1.48; 95% CI: 0.58, 2.38; p = 0.001), and (WMD: 1.29; 95% CI: 0.57, 2.01; p = 0.0005). Nusinersen and risdiplam did not cause a statistically significant increase in the RULM score for adverse events (OR: 0.93; 95% CI: 0.51, 1.7; p = 0.82) and for severe adverse events (OR: 0.77; 95% CI: 0.47, 1.27; p = 0.31).

CONCLUSION

Our analysis found that nusinersen and risdiplam treatment showed clinically meaningful improvement in motor function and a similar incidence rate of adverse events compared with the placebo. Further research should be carried out to provide a direct comparison between the two drugs in terms of safety and efficacy.

Longitudinal developmental profile of newborns and toddlers treated for spinal muscular atrophy

Background

Spinal muscular atrophy (SMA) results from a loss-of-function mutation in the SMN1 gene. SMA patients suffer progressive motor disability, although no intellectual impairments have been described. Three drugs have been recently approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). These drugs result in longer life expectancy for SMA type 1 (SMA1) patients.

Objective

The objective of the study was to assess longitudinally the psychomotor development of patients with SMA1 treated after the symptom onset and of patients treated presymptomatically.

Design

Longitudinal, monocentric, noninterventional, prospective study.

Methods

Our study included 11 SMA1 patients and seven presymptomatic SMA patients. The SMA1 patients were treated with an approved drug beginning after onset of symptoms; treatment for the presymptomatic patients was begun before symptom onset. They were longitudinally evaluated between September 2018 and January 2022 using the Bayley Scales of Infant and Toddler Development™ - Third Edition.

Results

At each time point, all patients treated presymptomatically scored above those treated postsymptomatically on the motor scale. The cognitive scores of six of the seven patients treated presymptomatically were average; one patient was in the low average range. In the 11 postsymptomatically treated patients, four scored either in the low average or the abnormal range on the cognitive scale, but a positive trend was observed during the follow-up.

Conclusion

A significant proportion of patients treated postsymptomatically scored below average on cognitive and communicative scales, with most significant concerns raised about the age of 1 year. Our study indicates that intellectual development should be considered as an important outcome in treated SMA1 patients. Cognitive and communicative evaluations should be performed as part of standard of care, and guidance should be provided to parents for optimal stimulation.

Severe Combined Immunodeficiency: Knowledge and Information Needs Among Healthcare Providers

BACKGROUND

Severe combined immunodeficiency (SCID) is a group of life-threatening genetic disorders responsible for severe dysfunctions of the immune system. Despite the expansion of newborn screening in the U.S., there are gaps in healthcare providers' knowledge of SCID.

METHODS

We recruited 277 U.S. healthcare providers for an online survey. The survey assessed providers' experience with SCID patients, knowledge about SCID, and needs and preferred formats for SCID-related informational resources. We examined differences between providers who have seen 2 or more patients with SCID (SCID provider group) and those who have seen 0-1 SCID patients (non-SCID provider group).

RESULTS

Overall, 210 (75.8%) providers were included in the non-SCID provider group, and 121 (57.6%) of these providers were pediatricians. Compared to the SCID provider group, non-SCID provider group reported lower mean rating of SCID knowledge (x̄ = 4.8 vs. x̄ = 8.6, p < 0.0001) and higher informational needs. The largest informational needs identified by the non-SCID provider group were "understanding specific type of SCID" and "understanding what to expect across the lifespan." In the SCID provider group, the highest rated informational need was "family support referrals." Participants in the non-SCID provider group identified scientific publications and websites as preferred formats, with some variation between medical specialties.

CONCLUSION

Based on their experience with treating SCID patients, providers have varying levels of SCID knowledge and different informational needs. For providers who have encountered few SCID patients, informational needs start early, usually immediately after receiving a positive newborn screening result. These findings provide useful direction for the development and preferred outlets for receiving SCID-related information, with some variations between different types of providers. Results from this study will serve as a guide for creating relevant and accessible SCID resources for providers who can utilize them to improve care for SCID patients.

Modulating the endoplasmic reticulum stress response attenuates neurodegeneration in a Caenorhabditis elegans model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating autosomal recessive neuromuscular disease resulting in muscle atrophy and neurodegeneration, and is the leading genetic cause of infant death. SMA arises when there are homozygous deletion mutations in the human SMN1 gene, leading to a decrease in corresponding SMN1 protein. Although SMN1 is expressed across multiple tissue types, much of the previous research into SMA focused on the neuronal aspect of the disease, overlooking many of the potential non-neuronal aspects of the disease. Therefore, we sought to address this gap in knowledge by modeling SMA in the nematode Caenorhabditis elegans. We mutated a previously uncharacterized allele, which resulted in the onset of mild SMA-like phenotypes, allowing us to monitor the onset of phenotypes at different stages. We observed that these mutant animals recapitulated many key features of the human disease, and most importantly, we observed that muscle dysfunction preceded neurodegeneration. Furthermore, we tested the therapeutic efficacy of targeting endoplasmic reticulum (ER) stress in non-neuronal cells and found it to be more effective than targeting ER stress in neuronal cells. We also found that the most potent therapeutic potential came from a combination of ER- and neuromuscular junction-targeted drugs. Together, our results suggest an important non-neuronal component of SMA pathology and highlight new considerations for therapeutic intervention.

Summary: A new non-larval-lethal C. elegans model of spinal muscular atrophy shows mild phenotypes, such as muscle cell and neuronal degeneration, and is therefore useful for testing potential drug treatments.

Quantitative description of upper extremity function and activity of people with spinal muscular atrophy

BACKGROUND

Therapeutic management of the upper extremity (UE) function of people with spinal muscular atrophy (SMA) requires sensitive and objective assessment. Therefore, we aimed to measure physiologic UE function of SMA patients with different functional abilities and evaluate the relation between these physiologic measures and functional UE scales.

METHODS

12 male and 5 female SMA patients (mean age 42 years; range 6-62 years) participated in this explorative study. Concerning the physiologic level, the maximal muscle torque, the maximal and normalized surface electromyography (sEMG) amplitudes, and the maximal passive and active joint angles were measured. Concerning the activity level, the Performance of the Upper Limb (PUL) scale was used, and hand function was examined using the Nine-Hole Peg Test and the Timed Test of In-Hand Manipulation (TIHM).

RESULTS

Outcome measures that significantly related to the functional ability were: the PUL score (all dimensions); the finger to palm task of the Timed TIHM; biceps, triceps, and forearm extensor strength; and the active range of motion of shoulder abduction, shoulder flexion, and wrist extension. In addition, the following physiologic variables were related to the activity level (PUL score): hand function (the Nine-Hole Peg Test; Rs = - 0.61), the Timed TIHM (Rs = - 0.53), the maximal muscle torque (Rs = 0.74), the maximal sEMG amplitude (Rs = 0.79), and the maximal active joint angle (Rs = 0.88).

CONCLUSIONS

Muscle functions in SMA patients are already affected before activity limitations are noticeable. Consequently, monitoring the maximal muscle strength and the normalized muscle activity during task performance could play a role in the early detection of UE limitations. The mechanism behind the loss of arm activities due to SMA is primarily caused by decreasing muscle capacity, which influences the ability to move an arm actively. In clinical practices, these dimensions should be considered separately when monitoring disease progression in order to better evaluate the need for interventions.

Motor neuron diseases caused by a novel VRK1 variant - A genotype/phenotype study

Background

Motor neuron disorders involving upper and lower neurons are a genetically and clinically heterogenous group of rare neuromuscular disorders with overlap among spinal muscular atrophies (SMAs) and amyotrophic lateral sclerosis (ALS). Classical SMA caused by recessive mutations in SMN1 is one of the most common genetic causes of mortality in infants. It is characterized by degeneration of anterior horn cells in the spinal cord, leading to progressive muscle weakness and atrophy. Non‐SMN1‐related spinal muscular atrophies are caused by variants in a number of genes, including VRK1, encoding the vaccinia‐related kinase 1 (VRK1). VRK1 variants have been segregated with motor neuron diseases including SMA phenotypes or hereditary complex motor and sensory axonal neuropathy (HMSN), with or without pontocerebellar hypoplasia or microcephaly.

Results

Here, we report an association of a novel homozygous splice variant in VRK1 (c.1159 + 1G>A) with childhood‐onset SMA or juvenile lower motor disease with brisk tendon reflexes without pontocerebellar hypoplasia and normal intellectual ability in a family with five affected individuals. We show that the VRK1 splice variant in patients causes decreased splicing efficiency and a mRNA frameshift that escapes the nonsense‐mediated decay machinery and results in a premature termination codon.

Conclusions

Our findings unveil the impact of the variant on the VRK1 transcript and further support the implication of VRK1 in the pathogenesis of lower motor neuron diseases.

"I didn't take it too seriously because I'd just never heard of it": Experiential knowledge and genetic screening for thalassaemia in the UK

Members of the public face particular challenges when undergoing reproductive genetic screening. Lack of family history with genetic disease has been identified as a key barrier affecting screening uptake and responses to genetic risk. This study explores this obstacle using beta thalassaemia as a case study. Fifteen in-depth qualitative interviews were conducted exploring the reproductive views and decisions of people at risk of transmitting thalassaemia. Eleven participants had thalassaemia themselves and/or were members of an affected family. Four participants were identified as thalassaemia carriers through genetic screening programmes with no family history. Notable differences were observed between these two groups. For thalassaemic individuals and families, past experience clarified and facilitated their sense of reproductive responsibility, however carriers struggled to relate to, and incorporate the information into their lives. It was witnessing their child becoming symptomatic-rather than receiving a diagnosis or genetic risk information per se that had the most substantial influence on carriers' subsequent views and decisions. Educational resources used to support genetic screening programmes would benefit from an engagement with the experiential accounts of life with genetic disease in order to more effectively bridge the chasm in knowledge and understanding between affected families and the general public, towards whom expansive genetic screening is aimed.

Supraglottoplasty in neonates and infants: A radiofrequency ablation approach

BACKGROUND

Supraglottoplasty is the mainstay of surgical treatment for laryngomalacia. A novel supraglottoplasty surgical technique is needed to achieve better efficacy. The purpose of this study was to introduce modified microscopic radiofrequency ablation supraglottoplasty (MMRAS) for the treatment of congenital laryngomalacia and to evaluate the outcome and effectiveness of this novel approach.

METHODS

Seventeen children with severe laryngomalacia who underwent MMRAS were studied retrospectively. Supraglottoplasty of type III laryngomalacia was different from classical method. All the patients were kept intubated for 5 days after surgery to achieve a better epiglottal position and to avoid reconglutination of aryepiglottic folds. The patients' demographic information, symptoms, comorbidities, type of laryngomalacia, synchronous airway lesions and final outcomes were examined.

RESULTS

The median age at the time of surgery was 3.36 months (3 months 10 days). Operative indications included feeding difficulties, noisy breathing or respiratory distress (or both), and sleep-related symptoms. The MMRAS success rate was 82.4%. Most patients were extubated successfully on postoperative day 5. The major postoperative complication was pulmonary infection which occurred in 3 cases (17.6%) and required anti-infective therapy. No perioperative deaths and no long-term complications occurred. Failures were observed in 3 (17.6%) of 17 cases, 2 patients presented with a neurological disease and required tracheostomy, 1 patient relapsed because of postoperative adhesions and later underwent revision supraglottoplasty.

CONCLUSIONS

From these results, we conclude that MMRAS is an effective and safe treatment for symptomatic laryngomalacia and has the potential to provide better breathing, feeding, and sleeping outcomes in children with severe laryngomalacia. Postoperative intubation for 5 days may result in better therapeutic outcomes. Multicenter cooperative studies of comparison between MMRAS and conventional approaches would lend further evidence-based support for this surgical method.

The role of experiential knowledge within attitudes towards genetic carrier screening: A comparison of people with and without experience of spinal muscular atrophy

Purpose

Autosomal recessive conditions, while individually rare, are a significant health burden with limited treatment options. Population carrier screening has been suggested as a means of tackling them. Little is known, however, about the attitudes of the general public towards such carrier screening and still less about the views of people living with candidate genetic diseases. Here, we focus on the role that such experience has on screening attitudes by comparing views towards screening of people with and without prior experience of the monogenetic disorder, Spinal Muscular Atrophy.

Methods

An exploratory sequential mixed methods design was adopted. In‐depth qualitative interviews were used to develop two surveys. The surveys addressed attitudes towards carrier screening (pre‐conceptual and prenatal) for SMA.

Participants

337 participants with SMA experience completed the SMA Screening Survey (UK) and 336 participants with no prior experience of SMA completed the UK GenPop Survey, an amended version of the SMA Screening Survey (UK).

Results

The majority of both cohorts were in favour of pre‐conception and prenatal carrier screening, however people with experience of type II SMA were least likely to support either. Key differences emerged around perceptions of SMA, with those without SMA experience taking a dimmer view of the condition than those with.

Conclusion

This study underscores the significance of prior experience with the condition to screening attitudes. It highlights the need for accurate and high‐quality educational resources to support any future carrier screening programmes, that particularly in relation to rare genetic disorders like SMA that will fall outside the remit of everyday experience for the majority of the population.

Combination of valproic acid and morpholino splice-switching oligonucleotide produces improved outcomes in spinal muscular atrophy patient-derived fibroblasts

Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality worldwide, is characterised by the homozygous loss of the survival motor neuron 1 (SMN1) gene. The consequent degeneration of spinal motor neurons and progressive atrophy of voluntary muscle groups results in paralysis and eventually premature infantile death. Humans possess a second nearly identical copy of SMN1, known as SMN2. However, SMN2 produces only 10-20% functional SMN protein due to aberrant splicing of its pre-mRNA that leads to the exclusion of exon 7. This level of SMN is insufficient to rescue the phenotype. Recently developed splice-switching antisense oligonuclotides (SSO) have shown great promise in correcting the aberrant splicing of SMN2 towards producing functional SMN protein. Several FDA approved drugs are being repurposed for SMA treatment including valproic acid (VPA), a histone deacetylase inhibitor, which has been shown to increase overall SMN2 expression. In this study, we have characterised the effects of single and combined treatment of VPA and a SSO based on phosphorodiamidate morpholino oligomer (PMO) chemistry. We conjugated both VPA and PMO to a single cell-penetrating peptide (Apolipoprotein E (ApoE)) for their simultaneous intracellular delivery. Treatment of SMA Type I patient-derived fibroblasts with the conjugates showed no additive increase in the level of full-length SMN2 mRNA expression over both 4 and 16 h treatments indicating that conjugation of VPA to ApoE-PMO has limited benefit. However, treatment with a combination of VPA and ApoE-PMO induced more favourable splice switching activity than either agent alone, promoting exon 7 inclusion in SMN2 transcripts. Our results suggest that combination therapy of VPA and ApoE-PMO is superior in upregulating SMN2 production in vitro, as compared to singular treatment of each compound at both transcriptional and protein levels. This study provides the first indication of a novel dual therapy approach for the potential treatment of SMA.

Population Pharmacokinetics of Nusinersen in the Cerebral Spinal Fluid and Plasma of Pediatric Patients With Spinal Muscular Atrophy Following Intrathecal Administrations

Nusinersen is an antisense oligonucleotide intended for the treatment of spinal muscular atrophy. The pharmacokinetics of nusinersen, following intrathecal administrations, in the cerebrospinal fluid (CSF) and plasma of 72 pediatric patients (3 months to 17 years) with spinal muscular atrophy across 5 clinical trials was analyzed via population-based modeling. With sparse data in the CSF and profile data in the plasma, a linear 4-compartment model simultaneously described the time-concentration profiles in both matrices. The typical population parameters were: Q_p = 0.572 L/h, Q_CSF = 0.069 L/h, CL_p = 2.50 L/h, CL_CSF = 0.133 L/hr, V_CSF = 0.441 L, V_p = 32.0 L, V_{systemic_tissue} = 429 L, and V_{CNS_tissue} = 258 L. A full covariate modeling approach identified baseline body weight to be a statistically and clinically relevant covariate on V_CSF , V_p , and CL_p . The model predicted that the CSF volume of distribution increased steadily with age from 0 to 2 years but became relatively steady for children >2 years. Simulations from the final model showed that age-based dosing in children under 2 years ensured a more comparable exposure (peak concentration and area under the concentration-time curve) across subjects in the population relative to a fixed dosing scheme. However, because no dose-limiting toxicity has been reported in any of the trials, a fixed-dose scheme (12 mg across all age groups) was recommended. The median terminal half-life of nusinersen in the CSF was determined from the model to be 163 days, which supported infrequent dosing, once every 4 to 6 months in pediatric patients with spinal muscular atrophy.

Disease impact on general well-being and therapeutic expectations of European Type II and Type III spinal muscular atrophy patients

Spinal muscular atrophy (SMA) is a neurodegenerative disorder showing a broad clinical spectrum and no cure to date. To design and select evaluation criteria for the potential assessment of drugs currently being developed, the patient's perspective is critical. A survey, aiming to obtain a view on the current clinical state of European Type II and Type III SMA patients, the impact of this situation on their quality of life and their expectations regarding clinical development, was carried out by SMA-Europe member organizations in July 2015. A questionnaire was set up, translated into 8 European languages and sent out directly via electronic mailing to the targeted SMA patient population by the respective European patient organizations. We were able to collect 822 valid replies in less than two weeks. The questionnaire captured the current abilities of the respondents, their perception of the disease burden which appeared very similar across Europe despite some regional variations in care. According to the great majority of the respondents, stabilization of their current clinical state would represent a therapeutic progress for a compelling majority of the respondents to the questionnaire.