Feeding and Swallowing Problems in Infants with Spinal Muscular Atrophy Type 1: an Observational Study

A Systematic Literature Review of the Natural History of Respiratory, Swallowing, Feeding, and Speech Functions in Spinal Muscular Atrophy (SMA)

Background

Respiratory and bulbar dysfunctions (including swallowing, feeding, and speech functions) are key symptoms of spinal muscular atrophy (SMA), especially in its most severe forms. Demonstrating the long-term efficacy of disease-modifying therapies (DMTs) necessitates an understanding of SMA natural history.

Objective

This study summarizes published natural history data on respiratory, swallowing, feeding, and speech functions in patients with SMA not receiving DMTs.

Methods

Electronic databases (Embase, MEDLINE, and Evidence-Based Medicine Reviews) were searched from database inception to June 27, 2022, for studies reporting data on respiratory and/or bulbar function outcomes in Types 1-3 SMA. Data were extracted into a predefined template and a descriptive summary of these data was provided.

Results

Ninety-one publications were included: 43 reported data on respiratory, swallowing, feeding, and/or speech function outcomes. Data highlighted early loss of respiratory function for patients with Type 1 SMA, with ventilatory support typically required by 12 months of age. Patients with Type 2 or 3 SMA were at risk of losing respiratory function over time, with ventilatory support initiated between the first and fifth decades of life. Swallowing and feeding difficulties, including choking, chewing problems, and aspiration, were reported in patients across the SMA spectrum. Swallowing and feeding difficulties, and a need for non-oral nutritional support, were reported before 1 year of age in Type 1 SMA, and before 10 years of age in Type 2 SMA. Limited data relating to other bulbar functions were collated.

Conclusions

Natural history data demonstrate that untreated patients with SMA experience respiratory and bulbar function deterioration, with a more rapid decline associated with greater disease severity. This study provides a comprehensive repository of natural history data on bulbar function in SMA, and it highlights that consistent assessment of outcomes in this area is necessary to benefit understanding and approval of new treatments.

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).

Longitudinal changes of swallowing safety and efficiency in infants with spinal muscular atrophy who received disease modifying therapies

BACKGROUND

Dysphagia is a common feature of the natural history of patients with spinal muscular atrophy (SMA). Literature regarding swallowing safety and efficiency is scarce in patients with SMA, particularly in the era of newborn screening programs and disease-modifying therapies.

OBJECTIVE

To describe the longitudinal changes of swallowing safety and efficiency in children with SMA who received one or more disease modifying therapies METHODS: Case series of patients with SMA followed at the University of Florida from 1 May 2019 to 31 December 2022 who had two or more videofluoroscopy swallowing studies (VFSS), with the first being within 30 days of their first treatment. Data extracted from the electronic health record included: neuromotor outcomes, VFSS penetration aspiration scores (PAS), presence of abrnormal oral or pharyngeal residue, clinical history, and timing of disease-modifying therapies administration.

RESULTS

Seven subjects were included (five male); three were diagnosed via newborn screen. Median age at diagnosis was 10 days (range: 4-250). Median age at initial VFSS was 29 days (range: 9-246), and age at the last VFSS was 26.1 months (range: 18.2-36.2). All subjects received onasemnogene-abeparvovec (OA); four received additional therapies. PAS at diagnosis was abnormal in four subjects. Six subjects required feeding modifications after VFSS results. Of these, three had silent aspiration (PAS 8) and three of them improved after treatment.

CONCLUSIONS

Swallowing safety and efficiency can be impaired in patients with SMA despite early treatment. Larger, prospective studies are needed to define optimal timiing of longitudinal instrumental evaluations.

Long-Term Follow-Up Cares and Check Initiative: A Program to Advance Long-Term Follow-Up in Newborns Identified with a Disease through Newborn Screening

In the United States and around the world, newborns are screened on a population basis for conditions benefiting from pre-symptomatic diagnosis and treatment. The number of screened conditions continues to expand as novel technologies for screening, diagnosing, treating, and managing disease are discovered. While screening all newborns facilitates early diagnosis and treatment, most screened conditions are treatable but not curable. Patients identified by newborn screening often require lifelong medical management and community support to achieve the best possible outcome. To advance the long-term follow-up of infants identified through newborn screening (NBS), the Long-Term Follow-up Cares and Check Initiative (LTFU-Cares and Check) designed, implemented, and evaluated a system of longitudinal data collection and annual reporting engaging parents, clinical providers, and state NBS programs. The LTFU-Cares and Check focused on newborns identified with spinal muscular atrophy (SMA) through NBS and the longitudinal health information prioritized by parents and families. Pediatric neurologists who care for newborns with SMA entered annual data, and data tracking and visualization tools were delivered to state NBS programs with a participating clinical center. In this publication, we report on the development, use of, and preliminary results from the LTFU-Cares and Check Initiative, which was designed as a comprehensive model of LTFU. We also propose next steps for achieving the goal of a national system of LTFU for individuals with identified conditions by meaningfully engaging public health agencies, clinicians, parents, families, and communities.

Assessing the Swallowing Function in Children with Spinal Muscular Atrophy: An Easily Accessible and Objective Multidimensional Approach

Background

Spinal muscular atrophy (SMA), a genetic neuromuscular disease caused by lack of survival of motor neuron (SMN) protein, is characterized by muscular atrophy and respiratory and bulbar dysfunction. While swallowing disorders are common, they remain poorly studied.

Objectives

Our study aimed to explore 1) intraoral pressure measurements with the Iowa Oral Performance Instrument system and the reliability of a Swallowing Function Assessment Questionnaire (SFAQ) in healthy controls, and 2) evaluate their use as swallowing function biomarkers and the evolution of swallowing function over time in children with SMA.

Methods

We recruited 53 healthy children and 27 SMA patients all treated with SMN gene modulator therapy. Participants completed the SFAQ and underwent at least one measurement of maximal oral pressures (lingual, labial, and masseter).

Results

Mean oral normalized pressure index were lower (all sites p < 0.001) and mean SFAQ scores were higher (p < 0.001) in patients compared with healthy controls. Pressure evolution over 1 year in SMA patients for all three oral sites did not show significant differences. SFAQ scores correlated negatively with oral pressures at all three sites in patients.

Conclusions

Both tools provided new insights on the oral and pharyngeal phase of swallowing in SMA patients. In SMA patients, muscle strength in certain crucial anatomical regions during swallowing is weaker than in healthy children.

DySMA - an Instrument to Monitor Swallowing Function in Children with Spinal Muscular Atrophy ages 0 to 24 Months: Development, Consensus, and Pilot Testing

Background

The manifestation of bulbar symptoms, especially swallowing, is important for evaluating disease-modifying therapies for spinal muscular atrophy (SMA). Due to the lack of instruments, the topic is still underrepresented in research.

Objective

This study aimed to develop a tool to monitor swallowing development in children aged 0 to 24 months with SMA.

Methods

The method was guided by the COSMIN guidelines and followed a multi-stage Delphi process. The first step was a rapid review of swallowing outcomes in children with SMA younger than 24 months. In the second step, online group interviews with experts (n = 7) on dysphagia in infants were conducted, followed by an anonymous online survey among experts in infants with SMA (n = 19). A predefined consensus threshold for nominal scaled voting was set at≥75 % and for 5-point Likert scale voting at 1.25 of the interquartile range. The third step was the pilot test of the instrument, performed with three groups (healthy controls n = 8; pre-symptomatic n = 6, symptomatic n = 6).

Results

Based on the multi-level interprofessional consensus, the DySMA comprises two parts (history and examination), ten categories, with 36 items. Implementation and scoring are clearly articulated and easy to implement. The pilot test showed that swallowing development could be recorded in all groups.

Conclusion

The DySMA is well suited for monitoring swallowing development in pre-symptomatic and symptomatic treated infants with SMA. It can be performed in a time-efficient and interprofessional manner. The resulting score is comparable to results from other instruments measuring other domains, e.g., motor function.

Feeding characteristics of healthy infants without reported feeding impairments throughout the first month of life

OBJECTIVE

Elucidate characteristics of feeding performance in healthy infants without reported feeding problems throughout the first month of life.

STUDY DESIGN

Feeding was monitored in 61 healthy infants by caregiver report for 48 h a week from birth to 4 weeks old. Outcomes included feeding modality, how much they consumed, how long the feed lasted, and how many coughing episodes the infant exhibited. Data were analyzed with descriptive and non-parametric statistics.

RESULT

The majority of infants (68%) exhibited at least one problematic feeding behavior. Infants consumed 68 ml/feed over 20 min, though the milk volumes and feed durations were highly variable. Coughing occurred an average of 2 feeds per day. No significant change in coughing was observed throughout the first month of life (p = 0.64). Infants coughed significantly less during breast feeds than bottle feeds (p = 0.02).

CONCLUSION

Healthy term infants exhibit what appear to be normal developmental imperfections in feeding performance throughout the first month of life.

Development of an International SMA Bulbar Assessment for Inter-professional Administration

BACKGROUND

Progressive weakness can affect bulbar muscles in individuals with moderate to severe forms of spinal muscular atrophy (SMA). The paucity of standardized, valid bulbar assessments capturing clinically significant deficits in SMA impedes the ability to monitor function, facilitate intervention, or detect treatment response.

OBJECTIVE

To fill this void, an international multidisciplinary team gathered to develop an agreed upon consensus-derived assessment of bulbar function in SMA for inter-professional administration to enhance our ability to monitor disease progression, support clinical management, and evaluate treatment effects.

METHODS

Fifty-six international clinicians experienced in SMA were invited and engaged using the Delphi method over multiple rounds of web-based surveys to establish consensus.

RESULTS

Serial virtual meetings occurred with 42 clinicians (21 speech and language therapists, 11 physical therapists, 5 neurologists, 4 occupational therapists, and 1 dentist). Seventy-two validated assessments of bulbar function were identified for potential relevance to individuals with SMA (32 accessible objective, 11 inaccessible objective, 29 patient-reported outcomes). Delphi survey rounds (n = 11, 15, 15) achieved consensus on individual items with relevance and wording discussed. Key aspects of bulbar function identified included: oral intake status, oral facial structure and motor strength, swallowing physiology, voice & speech, and fatigability.

CONCLUSIONS

Multidisciplinary clinicians with expertise in bulbar function and SMA used Delphi methodology to reach consensus on assessments/items considered relevant for SMA across all age groups. Future steps include piloting the new scale moving towards validation/reliability. This work supports the advancement of assessing bulbar function in children and adults with SMA by a variety of professionals.

Flexible endoscopic evaluation of swallowing in children with type 1 spinal muscular atrophy

PURPOSE

This study aimed to report on implementing flexible endoscopic evaluation of swallowing (FEES) in infants and toddlers with type 1 spinal muscular atrophy (SMA). In addition, a comparison of FEES results and clinical scores was carried out.

METHODS

A prospective pilot study was conducted including ten symptomatic children with SMA type 1 (two SMN2 copies). They started treatment with one of the three currently approved therapies for SMA at a median age of 3.8 months (range 0.7-8.9). FEES was performed according to a standard protocol using Penetration-Aspiration Scale (PAS) and Murray Secretion Scale as a primary outcome. The Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) for motor function, Neuromuscular Disease Swallowing Status Scale (NdSSS), Oral and Swallowing Abilities Tool (OrSAT), and single clinical swallowing-related parameters were also assessed.

RESULTS

Distinct swallowing disorders were already evident in eight children at inclusion. The most common findings from FEES were pharyngeal secretion pooling, penetration, and aspiration of saliva and food as well as delayed initiation of swallowing. Despite an average increase in motor function, no comparable improvement was found in swallowing function. None of the surveyed clinical scores showed a significant dependence on PAS in a mixed linear model.

CONCLUSIONS

Valuable information regarding the status of dysphagia can be gathered endoscopically, particularly concerning secretion management and when oral intake is limited. Currently available clinical tools for children with type 1 may represent a change in nutritional status but are not yet mature enough to conclude swallowing ability. Further development is still required.

Patients with Spinal Muscular Atrophy Type 1 Achieve and Maintain Bulbar Function Following Onasemnogene Abeparvovec Treatment

BACKGROUND

Improvement and maintenance of bulbar function are goals of disease-modifying treatments for spinal muscular atrophy (SMA). Lack of standardized measures and a widely accepted definition of bulbar function represents a gap in SMA care.

OBJECTIVE

A multidisciplinary team conducted post-hoc analyses of pooled data from one phase 1 (START) and two phase 3 (STR1VE-US, STR1VE-EU) studies to define and evaluate bulbar function of infants with SMA type 1 after receiving one-time gene replacement therapy, onasemnogene abeparvovec.

METHODS

We defined bulbar function as the ability to meet nutritional needs while maintaining airway protection and the ability to communicate verbally. Four endpoints represented adequate bulbar function: (1) absence of clinician-identified physiologic swallowing impairment, (2) receiving full oral nutrition, (3) absence of adverse events indicating pulmonary instability, and (4) the ability to vocalize at least two different, distinct vowel sounds. We descriptively assessed numbers/percentages of patients who achieved each endpoint and all four collectively. Patients were followed until 18 months old (STR1VE-US and STR1VE-EU) or 24 months (START) post-infusion.

RESULTS

Overall, 65 patients were analyzed for swallowing, nutrition intake, and adverse events, and 20 were analyzed for communication. At study end, 92% (60/65) of patients had a normal swallow, 75% (49/65) achieved full oral nutrition, 92% (60/65) had no evidence of pulmonary instability, 95% (19/20) met the communication endpoint, and 75% (15/20) achieved all four bulbar function components in the composite endpoint.

CONCLUSIONS

In these three clinical trials, patients with SMA type 1 who received onasemnogene abeparvovec achieved and maintained the bulbar function criteria utilized within this investigation.

Assessing Bulbar Function in Spinal Muscular Atrophy Using Patient-Reported Outcomes

BACKGROUND

Novel Spinal Muscular Atrophy (SMA) treatments have demonstrated improvements on motor measures that are clearly distinct from the natural history of progressive decline. Comparable measures are needed to monitor bulbar function, which is affected in severe SMA.

OBJECTIVE

To assess bulbar function with patient-reported outcome measures (PROs) and determine their relationships with clinical characteristics.

METHODS

We recruited 47 non-ambulatory participants (mean (SD) age = 29.8 (13.7) years, range = 10.3-73.2) with SMA. PROs including Voice Handicap Index (VHI) and Eating Assessment Tool-10 (EAT-10) were collected alongside clinical characteristics and standardized motor assessments. Associations were assessed using Spearman correlation coefficients and group comparisons were performed using Wilcoxon rank sum tests.

RESULTS

A majority of the 47 participants were SMA type 2 (70.2%), non-sitters (78.7%), 3 copies of SMN2 (77.5%), and using respiratory support (66.0%). A majority (94%) reported voice issues primarily in 8/30 VHI questions. Problems included: difficulty understanding me in a noisy room (87.2%); difficult for people to hear me (74.5%); and people ask me to repeat when speaking face-to-face (72.3%). A majority (85.1%) reported swallowing issues primarily in 3/10 EAT-10 questions: swallowing pills (68.1%); food sticks to my throat (66.0%); and swallowing solids (61.7%). The two PROs were moderately associated (rs = 0.66).

CONCLUSIONS

Weaker individuals with SMA experience bulbar problems including difficulties with voice and swallowing. Further refinement and assessment of functional bulbar scales will help determine their relevance and responsiveness to changes in SMA. Additional study is needed to quantify bulbar changes caused by SMA and their response to disease-modifying treatments.

Addressing the implementation gap in advanced therapeutics for spinal muscular atrophy in the era of newborn screening programs

Spinal muscular atrophy (SMA) is a rare genetic disease that results in progressive neuromuscular weakness. Without therapy, the most common form of the disease, type 1, typically results in death or chronic respiratory failure in the first 2 years of life. Thanks to the recent introduction of newborn screening programs and the discovery of three disease-modifying therapies in the last decade, the outcomes of children with SMA have dramatically improved. Patients are able to achieve many, if not all, of the typical neuromotor milestones, such as sitting, standing and walking, as well as safe oral intake. As the natural history of treated patients is continuously evolving, children with SMA continue to require complex and multidisciplinary care, posing implementation and sustainability challenges. Accordingly, there is a significant need for the application and evaluation of implementation science to address the steps involved in the diagnosis and treatment of patients with SMA, ensuring that all pertinent stakeholders and systems are working effectively to deliver timely and appropriate care. In this manuscript, we discuss the current challenges and gaps in the care for children with SMA, as well as how implementation science can advance this field. In addition, we provide an adapted implementation science framework that includes the main domains and subdomains involved in the care of patients with SMA.

Population-based assessment of nusinersen efficacy in children with spinal muscular atrophy: a 3-year follow-up study

Nusinersen (Spinraza®) improves survival of infants with hereditary proximal spinal muscular atrophy and motor function in children up to 12 years. Population-based assessments of treatment efficacy are limited and confined to select cohorts of patients. We performed a nationwide, population-based, single-centre cohort study in children with spinal muscular atrophy younger than 9.5 years at start of treatment in line with reimbursement criteria in the Netherlands. We assessed age-relevant motor function scores, the need for tube feeding, hours of ventilatory support and documented adverse events. We used linear mixed modelling to assess treatment effects. We compared motor function during treatment with natural history data and to individual trajectories of muscle strength and motor function before the start of treatment. We included 71 out of 72 Dutch children who were treated (median age 54 months; range 0–117) and followed them for a median of 38 months (range 5–52). We observed improvement of motor function in 72% and stabilization in another 18% of the symptomatic children, which differed from the natural disease course in a matched cohort of which we had previously collected natural history data. Longitudinal analysis showed that motor function improved up to a median of 24 months (range 12–30) of treatment after which it stabilized. Shorter disease duration at start of treatment resulted in better treatment efficacy (P < 0.01). Sixteen children (23%) achieved new motor milestones. Bulbar and respiratory function did not improve significantly during treatment. In 15 patients from whom treatment-naïve data were available, the pre-treatment trajectory of motor function decline changed to stabilization or improvement after the start of treatment. We documented 82 adverse events after 934 injections (9%) in 45 patients. None of the adverse events led to treatment discontinuation. Intrathecal nusinersen treatment is safe and improves or stabilizes motor function in 90% of young children with spinal muscular atrophy types 1c–3a. We did not observe improvement of respiratory and bulbar functions.

Congenital or Early Developing Neuromuscular Diseases Affecting Feeding, Swallowing and Speech – A Review of the Literature from January 1998 to August 2021

Background:

The knowledge about the impact of oral motor impairment in neuromuscular diseases (NMDs) is limited but increasing.

Objective:

The aim of this review was to collect and compile knowledge on how muscle weakness in congenital or early developing NMDs directly or indirectly affects feeding, swallowing, speech and saliva control.

Methods:

A literature search was performed in PubMed from January 1, 1998, to August 31, 2021. The keywords “feeding”, “dysphagia”, “swallowing”, “dysarthria”, “speech”, “drooling” and “sialorrhea” were used in combination with “paediatric neuromuscular disease” or specific diagnoses.

Results:

Sixty-five studies were selected for the review, 33 focused on feeding and swallowing, 11 on speech, four on a combination of feeding, swallowing, saliva control or speech and 17 general descriptions. Most of the studies reported on patients with a disorder affecting muscles. These studies show that muscle weakness and impaired motility affecting the muscles innervated by the cranial nerves may influence feeding, swallowing, and speech, and that respiratory function, general health and neurodevelopmental delay also influence these functions. Feeding impairment and breathing difficulties are common in NMDs. Lifesaving interventions such as tube feeding and ventilatory support are common in severe cases.

Conclusions:

Feeding impairment, dysphagia and dysarthria are prevalent in NMDs with congenital or early age of onset. Feeding and swallowing has been studied more than speech and saliva control. More children with NMD survive thanks to new treatment options and it is therefore urgent to follow up how these therapies may impact the development of feeding, swallowing, and speech.

Evolution of bulbar function in spinal muscular atrophy type 1 treated with nusinersen

AIM

To assess the evolution of bulbar function in nusinersen-treated spinal muscular atrophy type 1 (SMA1).

METHOD

This single-centre retrospective study identified 24 patients (14 females and 10 males) with SMA1, treated with nusinersen between 2017 and 2020. We adapted and validated the Paediatric Functional Oral Intake Scale (p-FOIS), which is an outcome measure to assess bulbar function. Analysis considered SMA1 subtype, nutritional support, and Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) and p-FOIS scores at initiation of nusinersen treatment (baseline) and at 6, 12, and 24 months after initiation.

RESULTS

The median age at baseline was 11 months (range 1 month-7 years 6 months). Median age at initiation of tube feeding was 8 months (range 0-2 years 2 months). Fourteen patients were tube fed at baseline. The median p-FOIS score was 3 at baseline and 2 at 12 and 24 months. Four patients, all with type 1c SMA, remained orally fed at 24 months. Median CHOP INTEND scores increased from 32 at baseline to 42 at 12 and 24 months.

INTERPRETATION

Impaired bulbar function persisted as a significant complication in most nusinersen-treated patients with SMA1, in contrast to the improvement in motor abilities demonstrated in the majority. p-FOIS allows for tracking of bulbar function progression and treatment response. Larger, prospective studies investigating the longer-term impacts of nusinersen on bulbar function are warranted.

Distribution of weight, stature, and growth status in children and adolescents with spinal muscular atrophy: An observational retrospective study in the United States

Introduction/Aims

Data regarding weight, height/length, and growth status of patients with spinal muscular atrophy (SMA) who have received only supportive care are limited. This cross‐sectional study describes these measurements in patients with Type 1 and Types 2/3 SMA and compares them with reference values from typically developing children.

Methods

Retrospective baseline data from three sites in the Pediatric Neuromuscular Clinical Research Network (Boston, New York, Philadelphia) were used. Descriptive statistics for weight, height/length, body mass index‐for‐age, as well as weight‐for‐length and absolute and relative deviations from reference values (ie, 50th percentile from World Health Organization/Centers for Disease Control growth charts) were calculated. Furthermore, growth status was reported.

Results

A total of 91 genetically confirmed patients with SMA receiving optimal supportive care and without any disease‐modifying treatment were stratified into Types 1 (n = 28) and 2/3 SMA (n = 63). Patients with Type 1 SMA weighed significantly less (median = −7.5%) compared with reference values and patients with Types 2/3 SMA were significantly shorter (mean = −3.0%) compared with reference values. The median weight was considerably below the 50th percentile in both groups of patients, even if they received a high standard of care and proactive feeding support.

Discussion

More research is needed to understand which factors influence growth longitudinally, and how to accurately capture growth in patients with SMA. Further research should investigate the best time to provide feeding support to avoid underweight, especially in patients with Type 1, and how to avoid the risk of overfeeding, especially in patients with Types 2/3 SMA.

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

ABSTRACT

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

Nonrespiratory complications of nusinersen-treated spinal muscular atrophy type 1 patients

BACKGROUND

Emergence of new treatments for spinal muscular atrophy type 1 (SMA1) has led to dramatic improvements in respiratory failure and survival. However, these "treated" patients sustain major problems in other organ systems, which may directly or indirectly affect their respiratory function. We observed three main nonrespiratory manifestations in these patients comprised of facial deformities, feeding problems, and spinal deformities.

OBJECTIVE

To investigate these three main sequelae in nusinersen-treated SMA1 patients.

METHODS

Data on nusinersen-treated SMA1 patients were prospectively collected throughout a 3-year period, with special focus upon nonrespiratory features of the disease.

RESULTS

Twenty nusinersen-treated SMA1 patients were included (eight males, median age 13.5 months, interquartile range: 4-56.2 months), among whom 17 survived after 3 years of follow-up. At follow-up, 15 (88%) patients were diagnosed with facial weakness, hypoplasia, or deformity. All but one patient (94%) were fed invasively by percutaneous endoscopic gastrostomy or nasogastric tube feeding. Four patients (25%) had maintained oral feeding in parallel to gastrostomy feeding and had clinical and radiologic evidence of aspirations. Fifteen (88%) patients were diagnosed with scoliosis, of whom seven had undergone or were scheduled to undergo corrective surgery.

CONCLUSIONS

Nusinersen-treated SMA1 patients may sustain facial deformities, feeding problems, and severe scoliosis, all of which affect their respiratory system. Strict surveillance of these complications is essential to avoid further respiratory morbidity.

Respiratory outcome of spinal muscular atrophy type 1 patients treated with nusinersen

BACKGROUND

Respiratory failure is the leading cause of mortality in spinal muscular atrophy type 1 (SMA1) children. The current study aims to evaluate the effect of nusinersen treatment on respiratory outcome of the patients with SMA1.

METHODS

In this retrospective, single-center study, 52 SMA1 patients treated with nusinersen were included in the analysis. Patients were divided into two groups based on their age at the time of their first nusinersen treatment (Group 1: ≤6 months, Group 2: >6 months). Respiratory outcome on the 180th day of treatment is defined as the type of ventilation support (spontaneous breathing, noninvasive ventilation (NIV), and tracheostomized or intubated on invasive mechanical ventilation). Demographic data, respiratory outcome, and Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores were obtained from medical records.

RESULTS

On the 180th day of treatment, 46 of the 52 (88.4%) children were alive. Prevalence of the mortality was similar in both groups (P = 0.65). The comparison of respiratory outcome in patients between group 1 and group 2 was as follows: spontaneous breathing, 7 (43.7%) versus 4 (13.3%) (P = 0.03); NIV <16 h/day, 3 (18.7%) versus 4 (13.3%) (P = 0.68); invasive mechanical ventilation, 6 (37.5%) versus 22 (73.3%) (P = 0.01). There were no patients using NIV ≥16 h/day. There were significant improvements in Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores of the patients at day 180 in comparison with the baseline (P < 0.001).

CONCLUSIONS

Early initiation of nusinersen treatment in SMA1 patients may alter the disease's natural course.

Recombinant Adeno-Associated Virus Serotype 9 Gene Therapy in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by deletion or mutation of the SMN1 gene. It is characterized by a progressive loss of motor neurons resulting in muscle weakness. The disease affects 1 in 11,000 live births and before the era of treatment SMA was a leading genetic cause of mortality in infants. Recently, disease modifying therapies have been introduced in clinical practice. They include intrathecal and oral antisense oligonucleotides binding to pre-mRNA of SMN2 gene and increasing the translation of fully functional SMN protein as well as SMN1 gene replacement therapy. Onasemnogene abeparvovec uses the adeno-associated virus 9 (AAV9) vector to deliver the SMN1 gene. Phase 1 and phase 3 clinical trials showed that a single administration of onasemnogene abeparvovec resulted in improvement of motor functions in the majority of infants with SMA. Currently, phase 3 trials in SMA1 and SMA2 patients, as well as presymptomatic infants diagnosed with SMA, are ongoing. The drug was approved for medical use in the US in 2019, and in Japan and the European Union in 2020. Thus, first real-world data on efficacy and safety of onasemnogene abeparvovec in SMA patients are available.

Matching-adjusted indirect treatment comparison of onasemnogene abeparvovec and nusinersen for the treatment of symptomatic patients with spinal muscular atrophy type 1

OBJECTIVE

Onasemnogene abeparvovec, a one-time intravenous gene replacement therapy, and nusinersen, an antisense oligonucleotide that requires ongoing intrathecal administration, have been evaluated as treatments for spinal muscular atrophy (SMA) type 1 in separate Phase III trials, but no head-to-head comparison studies have been conducted. Onasemnogene abeparvovec was compared with nusinersen using a matching-adjusted indirect comparison (MAIC) to estimate the treatment effect of onasemnogene abeparvovec relative to nusinersen for the treatment of symptomatic patients with SMA type 1 for up to 24 months of follow-up.

METHODS

In the absence of studies for both onasemnogene abeparvovec and nusinersen with a common comparator, a Bayesian naïve indirect treatment comparison (ITC) and MAIC between onasemnogene abeparvovec and nusinersen were conducted to compare efficacy and safety of onasemnogene abeparvovec with nusinersen. Outcomes of interest were event-free survival (EFS), overall survival (OS), and motor milestone achievements (independent sitting and independent walking). Relative treatment effects were expressed as relative risk (RR) and risk difference.

RESULTS

Pooled and weighted patient-level data illustrated a favorable effect toward onasemnogene abeparvovec, suggesting longer EFS for patients compared with nusinersen (HR of onasemnogene abeparvovec vs. nusinersen: 0.19 [95% CI: 0.07-0.54; 99% CI: 0.05-0.74]). At 24 months of follow-up, patients receiving onasemnogene abeparvovec were statistically significantly more likely to achieve the motor milestone of sitting independently compared with patients treated with nusinersen. Although statistically significant differences were not observed at 6 to 18 months between treatment options, the likelihood of sitting independently at 12 and 18 months numerically favored onasemnogene abeparvovec. A numerically greater likelihood of walking by 18 and 24 months was also observed for patients treated with onasemnogene abeparvovec compared with nusinersen. Onasemnogene abeparvovec therapy was also associated with a favorable (but statistically nonsignificant) outcome for OS and may be associated with prolonged survival compared with nusinersen (HR of onasemnogene abeparvovec vs. nusinersen: 0.35 [95% CI: 0.09-1.32; 99% CI: 0.06-2.01]). Bayesian naïve ITC results were similar to the MAIC analysis for EFS, OS, and motor milestone achievements. Small sample size limited covariate matching to baseline CHOP INTEND and nutritional support requirement, leading to wider CIs and statistically inconclusive outcomes for some of the results.

CONCLUSIONS

Despite limitations of the current MAIC analysis (mainly a small sample size for statistical testing, even for the pooled onasemnogene abeparvovec trials, and potential differences in prognostic and predictive factors between studies), the relative treatment effects in EFS, OS, and motor milestone achievement indicate that onasemnogene abeparvovec may offer continued benefit compared with nusinersen through 24 months of follow-up.

Oral and Swallowing Abilities Tool (OrSAT) for Type 1 SMA Patients: Development of a New Module

We describe the development of a new tool specifically designed to record oral abilities, swallowing and, more generally, feeding in young type 1 SMA patients, to be used during the first 24 months of life.The tool is composed by a checklist and a separate section summarizing the functional abilities into levels of feeding/swallowing impairment. The checklist includes 12 questions assessing aspects thought to be clinically meaningful for a type 1 SMA population and developmentally appropriate for infants during the first months of life. Each item is graded with a score of 0 or 1, depending on the child's ability to perform the activity. As some items are age-dependent, the number of items to be used, and therefore the maximum score, changes with increasing age. The levels of feeding/swallowing impairment include four levels that can be identified using easily identifiable clinical criteria.In an attempt to validate the tool in an untreated population we applied it to 24 type 1 SMA patients (age range: 2.3-24.1 months, mean: 10.8) in whom the same information collected by the new tool had been previously recorded using a less-structured format.When patients were classified in three groups according to the Dubowitz decimal classification, there was a significant difference both at baseline and at follow-up (p < 0.001). The items assessing fatigue during the nursing sessions were the most frequently impaired even in infants who did not have any other obvious clinical sign of swallowing difficulties.

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 relationship between pulmonary and swallowing functions in patients with neuromuscular diseases followed up by a tertiary referral center: a cross-sectional study

INTRODUCTION

Respiratory muscle weakness is common in patients with neuromuscular diseases (NMD). This puts them at risk for dysphagia and other pulmonary complications.

OBJECTIVES

To investigate the relationship between pulmonary function and swallowing in NMD.

MATERIALS AND METHODS

In this cross-sectional study, medical records of patients undergoing treatment at the Tertiary Referral Center for Neuromuscular Diseases of Hospital de Apoio de Brasília, Brazil, were reviewed. Respiratory function was assessed through spirometry (FVC and FEV1 measured) and swallowing assessed by the Dysphagia Risk Evaluation Protocol and the Functional Oral Intake Scale.

RESULTS

Two hundred and twenty-two patients were included. Dysphagia was present in 46.8% of patients and impairment of pulmonary function in 64.0%. The mean FVC observed was 66.9% and FEV1 was 66.0%, indicating restrictive lung disease. A correlation between the decline of pulmonary and swallowing functions was observed in patients with NMDs (FVC vs. DREP, R = 0.46; FVC vs. FOIS, R = 0.42; FEV1 vs. DREP, R = 0.42; FEV1 vs. FOIS, R = 0.40, p<.01). FVC and FEV1 values tend to be lower in patients with dysphagia in the context of NMD.

CONCLUSIONS

A positive correlation between pulmonary function and swallowing outcomes was observed in patients with NMD. Despite respiratory and swallowing impairment being widely present in the population with NMD, they require different treatments according to the disease's pathophysiology. Future studies should be conducted to explore the disease-specific relationship between pulmonary function and swallowing in patients with NMD.