Spinal Muscular Atrophy Type 1: Prolongation of Survival by Noninvasive Respiratory Aids

Spinal Muscular Atrophy Mortality Despite Novel Medications: Case Reports

ABSTRACT

Despite new effective medications, patients with spinal muscular atrophy types 1-3 can continue to have inadequate cough flows to prevent episodes of acute respiratory failure. Ventilator unweanable intubated patients are thought to require tracheostomy tubes. As a result, potentially beneficial medications may be discontinued and patients die despite receiving these medications. Three cases are presented of medically treated, physically strengthening children, with spinal muscular atrophy type 1. All three subsequently died or underwent tracheotomy. However, there is no evidence of extubation attempts to noninvasive ventilatory support settings or optimal mechanical insufflation-exsufflation despite this option being described to be over 98% successful for extubating unweanable medically untreated children with spinal muscular atrophy 1.

Sleep and sleep-related breathing disorders in patients with spinal muscular atrophy: a changing perspective from novel treatments?

Spinal Muscular Atrophy (SMA) is an inherited neuromuscular disorder characterized by progressive muscle weakness and atrophy, resulting from the degeneration of motor neurons in the spinal cord. A critical aspect of SMA is its impact on respiratory function. As the disease progresses, respiratory muscles, in particular intercostal muscles, become increasingly affected, leading to breathing difficulties and respiratory failure. Without intervention, many children with SMA type 1 die from respiratory failure before their second year of life. While assisted ventilation has improved survival, it often results in ventilator dependence. The development of new SMN-augmenting therapies has renewed optimism, but their long-term impact on respiratory function is uncertain, and non-invasive respiratory support remains an important part of SMA management. Despite the importance of respiratory support in SMA, knowledge regarding sleep disorders in this population is limited. This review aims to synthesize existing literature on sleep and sleep-related breathing disorders in patients with SMA, with a focus on SMA type 1. We summarize evidence of sleep-disordered breathing and respiratory failure in SMA, as well as outcomes and survival benefits associated with non-invasive or invasive ventilation with or without pharmacological therapies. We also discuss current knowledge regarding the effects of novel disease-modifying therapies for SMA on respiratory function and sleep. In conclusion, optimal care for children with SMA requires a multidisciplinary approach that includes neurology and respiratory specialists. This review highlights the importance of monitoring sleep and respiratory function in SMA, as well as the potential benefits and challenges associated with assisted ventilation combined with new therapies.

Long-Term Comparative Efficacy and Safety of Risdiplam and Nusinersen in Children with Type 1 Spinal Muscular Atrophy

INTRODUCTION

Spinal muscular atrophy (SMA) is a severe genetic neuromuscular disease characterized by a loss of motor neurons and progressive muscle weakness. Children with untreated type 1 SMA never sit independently and require increasing levels of ventilatory support as the disease progresses. Without intervention, and lacking ventilatory support, death typically occurs before the age of 2 years. There are currently no head-to-head trials comparing available treatments in SMA. Indirect treatment comparisons are therefore needed to provide information on the relative efficacy and safety of SMA treatments for healthcare decision-making.

METHODS

The long-term efficacy and safety of risdiplam versus nusinersen in children with type 1 SMA was evaluated using indirect treatment comparison methodology to adjust for differences between population baseline characteristics, to reduce any potential bias in the comparative analysis. An unanchored matching-adjusted indirect comparison was conducted using risdiplam data from 58 children in FIREFISH (NCT02913482) and published aggregate nusinersen data from 81 children obtained from the ENDEAR (NCT02193074) and SHINE (NCT02594124) clinical trials with at least 36 months of follow-up.

RESULTS

Children with type 1 SMA treated with risdiplam had a 78% reduction in the rate of death, an 81% reduction in the rate of death or permanent ventilation, and a 57% reduction in the rate of serious adverse events compared with children treated with nusinersen. Children treated with risdiplam also had a 45% higher rate of achieving a Hammersmith Infant Neurological Examination, Module 2 motor milestone response and a 186% higher rate of achieving a ≥ 4-point improvement in Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders compared with children treated with nusinersen.

CONCLUSION

Long-term data supported risdiplam as a superior alternative to nusinersen in children with type 1 SMA. Video abstract available for this article. Video abstract (MP4 184542 KB).

Spinal Muscular Atrophy Type 1 Survival Without New Pharmacotherapies: Two Treatment Paradigms

OBJECTIVES

The aims of the study are to present noninvasive respiratory management outcomes using continuous noninvasive ventilatory support and mechanical in-exsufflation from infancy for spinal muscular atrophy type 1 and to consider bearing on new medical therapies.

DESIGN

Noninvasive ventilatory support was begun for consecutively referred symptomatic infants with spinal muscular atrophy type 1 from 1 to 10 mos of age. Intercurrent episodes of respiratory failure were managed by intubation then extubation to continuous noninvasive ventilatory support and mechanical in-exsufflation despite failing ventilator weaning and extubation attempts. Intubations, tracheotomies, and survival were monitored.

RESULTS

Of 153 patients with spinal muscular atrophy 1 consecutively referred since 1995, 37 became continuous noninvasive ventilatory support dependent, almost half before 10 yrs of age. Of the 37, 18 required continuous noninvasive ventilatory support for a mean 18.6 ± 3.3 yrs to a mean 25.3 (range, 18-30) yrs of age, dependent from as young as 4 mos of age with 0 to 40 ml of vital capacity. One of the 18 died from COVID-19 acute respiratory distress syndrome at age 24 after 23 yrs of continuous noninvasive ventilatory support. Extubation success rate of 85% per attempt (150/176) resulted in only one undergoing tracheotomy.

CONCLUSIONS

Medical treatments begun during the first 6 wks of age convert spinal muscular atrophy 1 into spinal muscular atrophy 2 or 3 but cough flows remain inadequate to avoid many pneumonias that, once resolved by a treatment paradigm of extubation to continuous noninvasive ventilatory support and mechanical in-exsufflation, eliminates need to resort to tracheotomies.

Amyotrophic Lateral Sclerosis and Noninvasive Positive Pressure Ventilatory Support: "Nasal Noninvasive Ventilation" or "Noninvasive Ventilatory Support"?

ABSTRACT

Many studies suggest a brief statistical benefit on survival and quality of life by using nasal noninvasive ventilation for patients with amyotrophic lateral sclerosis and other neuromuscular conditions. Indeed, nasal noninvasive ventilation has become synonymous with continuous positive airway pressure and lo-span bilevel positive airway pressure. Nasal noninvasive ventilation, however, may not normalize CO2 levels and continuous positive airway pressure and O2 exacerbate hypercapnia and often lead to CO2 narcosis, intubation, and ultimately tracheostomy or palliative care death. However, a third option can be to offer up to continuous noninvasive ventilatory support and extubation to it. Noninvasive ventilatory support can be effective for full, definitive ventilatory support, even for people with no measurable vital capacity, and has maintained classic amyotrophic lateral sclerosis patients for up to 12 yrs without resort to tracheotomies. Nineteen centers have reported 335 amyotrophic lateral sclerosis patients using continuous noninvasive ventilatory support instead of tracheostomy mechanical ventilation for an average of 14 mos (6 mos to 14 yrs). The noninvasive ventilatory support must also be used in conjunction with mechanical insufflation-exsufflation to clear airway debris and normalize or renormalize ambient air oxyhemoglobin saturation, both to avoid intubation and to facilitate extubation. People with amyotrophic lateral sclerosis satisfying specific criteria, even when continuously dependent on tracheostomy mechanical ventilation, can be decannulated and placed on continuous noninvasive ventilatory support with mechanical insufflation-exsufflation.

Real-world respiratory and bulbar comorbidities of SMA type 1 children treated with nusinersen: 2-Year single centre Australian experience

AIM

To describe the respiratory and nutritional supportive care and hospitalisations required in the real-world scenario in children with SMA type 1 treated with nusinersen.

METHODS

Single-centre observational cohort study of children with SMA1 commencing nusinersen from November 2016 to September 2018. Motor, respiratory and nutritional clinical characteristics and management are described from initiation of nusinersen for a minimum of two years.

RESULTS

Nine children (5 females, 4 males), median age 10.7 months (range 2.7-181.2) commenced treatment with nusinersen and outcomes were assessed over a total of 270.5 patient months and 209 hospital admissions. Supportive care in newly-diagnosed patients (n = 7) included gastrostomy insertion (n = 4) and commencement of noninvasive ventilation (n = 4) at an average of 8.3 and 4.5 months after diagnosis, respectively. The annualised hospitalisation rate was 9.3/patient/year, average length of stay (LOS) of 3.3 days (SD = 5.6). Children with two SMN2 copies required more gastrostomies (p < 0.05) and had more frequent admissions (p < 0.05). Number of total admissions halved from the first to the second year of treatment in all patients (p < 0.005).

INTERPRETATION

Children with treated SMA1 experienced considerable respiratory and bulbar comorbidities, necessitating substantial respiratory and nutritional supportive care. Proactive respiratory and nutritional surveillance and management is essential in SMA1 patients treated with nusinersen.

An updated cost-utility model for onasemnogene abeparvovec (Zolgensma®) in spinal muscular atrophy type 1 patients and comparison with evaluation by the Institute for Clinical and Effectiveness Review (ICER)

Background: Recent cost-utility analysis (CUA) models for onasemnogene abeparvovec (Zolgensma®, formerly AVXS-101) in spinal muscular atrophy type 1 (SMA1) differ on key assumptions and results. Objective: To compare the manufacturer's proprietary CUA model to the model published by the Institute for Clinical and Economic Review (ICER), and to update the manufacturer's model with long-term follow-up data and some key ICER assumptions. Study design: We updated a recent CUA evaluating value for money in cost per incremental Quality-adjusted Life Year (QALY) of onasemnogene abeparvovec versus nusinersen (Spinraza®) or best supportive care (BSC) in symptomatic SMA1 patients, and compared it to the ICER model. Setting/Perspective: USA/Commercial payer Participants: Children aged <2 years with SMA1. Interventions: Onasemnogene abeparvovec, a single-dose gene replacement therapy, versus nusinersen, an antisense oligonucleotide, versus BSC. Main outcome measure: Incremental-cost effectiveness ratio and value-based price using traditional thresholds for general medicines in the US. Results: Updated survival (undiscounted) predicted by the model was 37.60 years for onasemnogene abeparvovec compared to 12.10 years for nusinersen and 7.27 years for BSC. Updated quality-adjusted survival using ICER's utility scores and discounted at 3% were 13.33, 2.85, and 1.15 discounted QALYs for onasemnogene abeparvovec, nusinersen, and BSC, respectively. Using estimated net prices, the discounted lifetime cost/patient was $3.93 M for onasemnogene abeparvovec, $4.60 M for nusinersen, and $1.96 M for BSC. The incremental cost per QALY gained for onasemnogene abeparvovec was dominant against nusinersen and $161,648 against BSC. These results broadly align with the results of the ICER model, which predicted a cost per QALY gained of $139,000 compared with nusinersen, and $243,000 compared with BSC (assuming a placeholder price of $2 M for onasemnogene abeparvovec), differences in methodology notwithstanding. Exploratory analyses in presymptomatic patients were similar. Conclusion: This updated CUA model is similar to ICER analyses comparing onasemnogene abeparvovec with nusinersen in the symptomatic and presymptomatic SMA populations. At a list price of $2.125 M, onasemnogene abeparvovec is cost-effective compared to nusinersen for SMA1 patients treated before age 2 years. When compared to BSC, cost per QALY of onasemnogene abeparvovec is higher than commonly used thresholds for therapies in the USA ($150,000 per QALY).

Assessment of respiratory muscles and motor function in children with SMA treated by nusinersen

INTRODUCTION

Nusinersen is associated with an improvement in motor function in children with spinal muscular atrophy (SMA) but data on respiratory muscles strength are scarce. Respiratory muscles performance and lung function were evaluated in children with SMA 1c and 2 after six injections of nusinersen (M14). Results from patients with SMA2 were compared with data of age-matched historical controls. Motor function tests (MFM and HINE-2) were assessed at baseline and M14 in the treated patients.

RESULTS

Sixteen children (2 SMA Type 1c and 14 SMA Type 2), mean age 9.4 ± 2.3 years, were included. The data of 14 historical SMA 2 controls (mean age 9.3 ± 1.9 years) were gathered. The strength of the global inspiratory muscles of SMA 2 treated with nusinersen, assessed on maximal static inspiratory pressure, forced vital capacity, and esophageal pressure during a maximal sniff was significantly better compared with historical controls (p < .05). A significant improvement in MFM and HINE-2 was observed in the patients with 16 SMA treated with nusinersen after 14 months as compared with baseline.

CONCLUSION

In children with SMA Type 2, respiratory muscle performance was significantly better after six injections of nusinersen as compared with age-matched SMA Type 2 historical controls.

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.

The role of sleep diagnostics and non-invasive ventilation in children with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a degenerative motor neurone disorder causing progressive muscular weakness. Without assisted ventilation or novel therapies, most children with SMA type 1 die before the second year of life due to respiratory failure as the respiratory muscles and bulbar function are severely affected. Active respiratory treatment (mechanically assisted cough, invasive or non-invasive ventilation) has improved survival significantly in recent decades, but often at the cost of becoming ventilator dependent. The advent of a new oligonucleotide based therapy (Nusinersen) has created new optimism for improving motor function. However, the long-term effect on respiratory function is unclear and non-invasive respiratory support will remain an important part of medical management in patients with SMA. This review summarises the existing knowledge about sleep-disordered breathing and respiratory failure in patients with SMA, especially type 1, as well as the evidence of improved outcome and survival in patients treated with non-invasive or invasive ventilation. Practical considerations and ethical concerns are delineated with discussion on how these may be affected by the advent of new therapies such as Nusinersen.

Noninvasive Positive Pressure Ventilatory Support Begins During Sleep

The goal of sleep doctors has been to titrate away apneas and hypopneas using noninvasive ventilation, a term that has become synonymous with continuous positive airway pressure and bilevel positive airway pressure at the lowest effective bilevel settings. It is now time to appreciate noninvasive ventilatory support as an alternative to invasive mechanical ventilation. This article discusses mechanisms of action, two paradigms, and ancillary techniques for noninvasive ventilatory support.

Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy type 1 (SMA1) is a progressive, monogenic motor neuron disease with an onset during infancy that results in failure to achieve motor milestones and in death or the need for mechanical ventilation by 2 years of age. We studied functional replacement of the mutated gene encoding survival motor neuron 1 (SMN1) in this disease.

METHODS

Fifteen patients with SMA1 received a single dose of intravenous adeno-associated virus serotype 9 carrying SMN complementary DNA encoding the missing SMN protein. Three of the patients received a low dose (6.7×10¹³ vg per kilogram of body weight), and 12 received a high dose (2.0×10¹⁴ vg per kilogram). The primary outcome was safety. The secondary outcome was the time until death or the need for permanent ventilatory assistance. In exploratory analyses, we compared scores on the CHOP INTEND (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders) scale of motor function (ranging from 0 to 64, with higher scores indicating better function) in the two cohorts and motor milestones in the high-dose cohort with scores in studies of the natural history of the disease (historical cohorts).

RESULTS

As of the data cutoff on August 7, 2017, all 15 patients were alive and event-free at 20 months of age, as compared with a rate of survival of 8% in a historical cohort. In the high-dose cohort, a rapid increase from baseline in the score on the CHOP INTEND scale followed gene delivery, with an increase of 9.8 points at 1 month and 15.4 points at 3 months, as compared with a decline in this score in a historical cohort. Of the 12 patients who had received the high dose, 11 sat unassisted, 9 rolled over, 11 fed orally and could speak, and 2 walked independently. Elevated serum aminotransferase levels occurred in 4 patients and were attenuated by prednisolone.

CONCLUSIONS

In patients with SMA1, a single intravenous infusion of adeno-associated viral vector containing DNA coding for SMN resulted in longer survival, superior achievement of motor milestones, and better motor function than in historical cohorts. Further studies are necessary to confirm the safety and efficacy of this gene therapy. (Funded by AveXis and others; ClinicalTrials.gov number, NCT02122952 .).

Noninvasive Respiratory Management of Patients With Neuromuscular Disease

This review article describes definitive noninvasive respiratory management of respiratory muscle dysfunction to eliminate need to resort to tracheotomy. In 2010 clinicians from 22 centers in 18 countries reported 1,623 spinal muscular atrophy type 1 (SMA1), Duchenne muscular dystrophy (DMD), and amyotrophic lateral sclerosis users of noninvasive ventilatory support (NVS) of whom 760 required it continuously (CNVS). The CNVS sustained their lives by over 3,000 patient-years without resort to indwelling tracheostomy tubes. These centers have now extubated at least 74 consecutive ventilator unweanable patients with DMD, over 95% of CNVS-dependent patients with SMA1, and hundreds of others with advanced neuromuscular disorders (NMDs) without resort to tracheotomy. Two centers reported a 99% success rate at extubating 258 ventilator unweanable patients without resort to tracheotomy. Patients with myopathic or lower motor neuron disorders can be managed noninvasively by up to CNVS, indefinitely, despite having little or no measurable vital capacity, with the use of physical medicine respiratory muscle aids. Ventilator-dependent patients can be decannulated of their tracheostomy tubes.

Survival of patients with spinal muscular atrophy type 1

BACKGROUND

Spinal muscular atrophy type 1 (SMA1) is a progressive disease and is usually fatal in the first year of life.

METHODS

A retrospective chart review was performed of SMA1 patients and their outcomes according to the following choices: letting nature take its course (NT); tracheostomy and invasive mechanical ventilation (TV); continuous noninvasive respiratory muscle aid (NRA), including noninvasive ventilation; and mechanically assisted cough.

RESULTS

Of 194 consecutively referred patients enrolled in this study (103 males, 91 females), NT, TV, and NRA were chosen for 121 (62.3%), 42 (21.7%), and 31 (16%) patients, respectively. Survival at ages 24 and 48 months was higher in TV than NRA users: 95% (95% confidence interval: 81.8%-98.8%) and 67.7% (95% confidence interval: 46.7%-82%) at age 24 months (P < .001) and 89.43% and 45% at age 48 months in the TV and NRA groups, respectively (P < .001). The choice of TV decreased from 50% (1992-1998) to 12.7% (2005-2010) (P < .005) with a nonstatistically significant increase for NT from 50% to 65%. The choice of NRA increased from 8.1% (1999-2004) to 22.7% (2005-2010) (P < .001).

CONCLUSIONS

Long-term survival outcome is determined by the choice of the treatment. NRA and TV can prolong survival, with NRA showing a lower survival probability at ages 24 and 48 months.

Noninvasive respiratory management and diaphragm and electrophrenic pacing in neuromuscular disease and spinal cord injury

The purpose of this monograph is to describe noninvasive management of respiratory muscle weakness/paralysis for patients with neuromuscular disease (NMD) and spinal cord injury (SCI). Noninvasive ventilation (NIV) assists and supports inspiratory muscles, whereas mechanically assisted coughing (MAC) simulates an effective cough. Long-term outcomes will be reviewed as well as the use of NIV, MAC, and electrophrenic pacing (EPP) and diaphragm pacing (DP) to facilitate extubation and decannulation. Although EPP and DP can facilitate decannulation and maintain alveolar ventilation for high-level SCI patients when they cannot use NIV because of lack of access to oral interfaces, there is no evidence that they have any place in the management of NMD.

The natural course of infantile spinal muscular atrophy with respiratory distress type 1 (SMARD1)

BACKGROUND

Only scarce information is available on the long-term outcome and the natural course of children with infantile spinal muscular atrophy with respiratory distress type 1 (SMARD1) due to mutations in the IGHMBP2 gene.

OBJECTIVE

To describe the natural disease course, to systematically quantify the residual capacities of children with SMARD1 who survive on permanent mechanical respiration, and to identify markers predicting the disease outcome at the time of manifestation.

METHODS

We conducted a longitudinal study of 11 infantile SMARD1 patients over a mean observational period of 7.8 (SD 3.2) years. Disease-specific features were continuously assessed by using a semiquantitative scoring system. Additionally, we analyzed the residual enzymatic activity of 6 IGHMBP2 mutants in our patients.

RESULTS

After an initial rapid decline of the clinical score until the age of 2 years, residual capabilities reached a plateau or even improved. The overall clinical outcome was markedly heterogeneous, but clinical scores at the age of 3 months showed a positive linear correlation with the clinical outcome at 1 year and at 4 years of age. If expressed in an in vitro recombinant system, mutations of patients with more favorable outcomes retained residual enzymatic activity.

CONCLUSIONS

Despite their severe disabilities and symptoms, most SMARD1 patients are well integrated into their home environment and two thirds of them are able to attend kindergarten or school. This information will help to counsel parents at the time of disease manifestation.