Pulmonary manifestations of neuromuscular disease with special reference to Duchenne muscular dystrophy and spinal muscular atrophy

Chest and spinal disease in patients with progressive neuromuscular disease

The chest and spine deformity in neuromuscular disease (NMDz) can impact respiratory mechanics and pulmonary function by changing the orientation of the muscles and joints of the respiratory system and placing them in a mechanically unfavorable position. This increases mechanical load on weak respiratory muscles and eventually can cause respiratory failure. Therefore, chest and spine deformity in NMDz will both lead to increased respiratory "load" and decreased respiratory muscle "pump", an exceptionally bad combination. While the current pharmacotherapies used for progressive neuromuscular disease focus on slowing progression, a similar approach has been used for decades in managing chest and spine deformity in patients with NMDz. There are, however, variable approaches to doing so and a recognition that not all "neuromuscular scoliosis" is the same and that each patient type (i.e. hypotonic vs. hypertonic) requires a different approach. Figuring out what approach to use requires both an understanding of the underlying pathophysiology of a particular neuromuscular condition and considering available options for and timing of surgical interventions. The remaining discussion will focus on hypotonic neuromuscular scoliosis.

Respiratory comorbidities and treatments in Duchenne muscular dystrophy: impact on life expectancy and causes of death

BACKGROUND

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder with progressive decline of pulmonary function increasing the risk of early mortality. The aim of this study was to explore the respiratory-related comorbidities, and the effect of these comorbidities and treatments on life expectancy and causes of death.

METHODS

All male patients living in Sweden with DMD, born and deceased 1970-2019, were included. Data regarding causes of death were collected from the Cause of Death Registry and cross-checked with the medical records along with diagnostics and relevant clinical features.

RESULTS

Hundred and twenty nine patients were included with a median lifespan of 24.3 years. Acute respiratory failure accounted for 63.3% of respiratory-related causes of death. 70.1% suffered at least one pneumonia, with first episode at a median age of 17.8 years. Hypoventilation was found in 73.0% with onset at 18.1 years. 60.5% had their first pneumonia before established hypoventilation. Age at onset of hypoventilation showed a strong correlation with age at first pneumonia. First pneumonia and scoliosis non-treated with scoliosis surgery increased the risk of dying of respiratory-related causes. In 10% of the patients, first pneumonia resulted in acute tracheostomy or early death. Patients treated with assisted ventilation had higher life expectancy compared to untreated patients.

CONCLUSIONS

Our results highlight the importance of identifying subclinical hypoventilation in a timely manner and the importance of an active treatment regime upon clinical signs of pneumonia.

Paediatric sleep diagnostics in the 21st century: the era of "sleep-omics"?

Paediatric sleep diagnostics is performed using complex multichannel tests in specialised centres, limiting access and availability and resulting in delayed diagnosis and management. Such investigations are often challenging due to patient size (prematurity), tolerability, and compliance with "gold standard" equipment. Children with sensory/behavioural issues, at increased risk of sleep disordered breathing (SDB), often find standard diagnostic equipment difficult.SDB can have implications for a child both in terms of physical health and neurocognitive development. Potential sequelae of untreated SDB includes failure to thrive, cardiopulmonary disease, impaired learning and behavioural issues. Prompt and accurate diagnosis of SDB is important to facilitate early intervention and improve outcomes.The current gold-standard diagnostic test for SDB is polysomnography (PSG), which is expensive, requiring the interpretation of a highly specialised physiologist. PSG is not feasible in low-income countries or outwith specialist sleep centres. During the coronavirus disease 2019 pandemic, efforts were made to improve remote monitoring and diagnostics in paediatric sleep medicine, resulting in a paradigm shift in SDB technology with a focus on automated diagnosis harnessing artificial intelligence (AI). AI enables interrogation of large datasets, setting the scene for an era of "sleep-omics", characterising the endotypic and phenotypic bedrock of SDB by drawing on genetic, lifestyle and demographic information. The National Institute for Health and Care Excellence recently announced a programme for the development of automated home-testing devices for SDB. Scorer-independent scalable diagnostic approaches for paediatric SDB have potential to improve diagnostic accuracy, accessibility and patient tolerability; reduce health inequalities; and yield downstream economic and environmental benefits.

Biomarkers in 5q-associated spinal muscular atrophy-a narrative review

5q-associated spinal muscular atrophy (SMA) is a rare genetic disease caused by mutations in the SMN1 gene, resulting in a loss of functional SMN protein and consecutive degeneration of motor neurons in the ventral horn. The disease is clinically characterized by proximal paralysis and secondary skeletal muscle atrophy. New disease-modifying drugs driving SMN gene expression have been developed in the past decade and have revolutionized SMA treatment. The rise of treatment options led to a concomitant need of biomarkers for therapeutic guidance and an improved disease monitoring. Intensive efforts have been undertaken to develop suitable markers, and numerous candidate biomarkers for diagnostic, prognostic, and predictive values have been identified. The most promising markers include appliance-based measures such as electrophysiological and imaging-based indices as well as molecular markers including SMN-related proteins and markers of neurodegeneration and skeletal muscle integrity. However, none of the proposed biomarkers have been validated for the clinical routine yet. In this narrative review, we discuss the most promising candidate biomarkers for SMA and expand the discussion by addressing the largely unfolded potential of muscle integrity markers, especially in the context of upcoming muscle-targeting therapies. While the discussed candidate biomarkers hold potential as either diagnostic (e.g., SMN-related biomarkers), prognostic (e.g., markers of neurodegeneration, imaging-based markers), predictive (e.g., electrophysiological markers) or response markers (e.g., muscle integrity markers), no single measure seems to be suitable to cover all biomarker categories. Hence, a combination of different biomarkers and clinical assessments appears to be the most expedient solution at the time.

Risk of Obstructive Sleep Apnea in Saudi Male Boys with Duchenne Muscular Dystrophy (DMD)

Background

Duchenne muscular dystrophy (DMD) patients are at a high risk of developing sleep-related breathing disorders (SRBD) such as obstructive sleep apnea (OSA). This study aimed to determine the risk of developing OSA among DMD patients.

Methods

This cross-sectional study was conducted from February 2022 to July 2022 in a tertiary healthcare facility. As a screening tool for OSA, we used the Pediatric Sleep Questionnaire (PSQ).

Results

Subjects included 60 boys with DMD, mean age 10.15 ± 3.54 years. The mean BMI for all subjects was 18.9 ± 4.08 kg/m2. Of these, 22 (36.7%) children were at high risk of OSA. Children who were overweight, and on steroids tended to be at higher risk of developing OSA (P < 0.043) and (P < 0.029) respectively.

Conclusion

Our study shows a significant risk of OSA in DMD patients. Therefore, Sleep studies should be part of the standard of care for DMD patients.

A Virtual Reality Exergame: Clinician-Guided Breathing and Relaxation for Children with Muscular Dystrophy

This study introduces a VR-based breathing and relaxation exergame tailored for individuals with Duchenne muscular dystrophy (DMD). DMD is a rare neuromuscular disease that leads to respiratory muscle dysfunction with anxiety being a common comorbidity. Clinical management requires frequent visits to rare disease specialists to manage symptom progression. Limited availability and/or proximity of rare disease experts present challenges to care and can lead to missed care opportunities and reduced quality of life. We propose a breathing and relaxation exergame with remote telehealth applicability that incorporates shared patient-clinician VR interaction, and physiological sensors that provide both real-time feedback to the patient and health analytics for the clinician. The game focuses on two key aspects of DMD clinical care that can be mediated through control of breathing: relaxation/mindfulness training and respiratory muscle exercise. The system was evaluated among 13 individuals, including 4 participants with DMD. Feedback surveys, interviews, and focus group discussions with participants, accompanying family members, and clinicians demonstrated the feasibility of this VR tool for telehealth or as part of a home exercise program.

Rapidly and slowly progressive neuromuscular disease: differences in pulmonary function, respiratory tract infections and response to lung volume recruitment therapy (LVR)

INTRODUCTION

Reduced lung volumes are a hallmark of respiratory muscle weakness in neuromuscular disease (NMD). Low respiratory system compliance (C_rs) may contribute to restriction and be amenable to lung volume recruitment (LVR) therapy. This study evaluated respiratory function and the immediate impact of LVR in rapidly progressive compared to slowly progressive NMD.

METHODS

We compared vital capacity (VC), static lung volumes, maximal inspiratory and expiratory pressures (MIP, MEP), C_rs and peak cough flow (PCF) in 80 adult participants with motor neuron disease ('MND'=27) and more slowly progressive NMDs ('other NMD'=53), pre and post a single session of LVR. Relationships between respiratory markers and a history of respiratory tract infections (RTI) were examined.

RESULTS

Participants with other NMD had lower lung volumes and C_rs but similar reduction in respiratory muscle strength compared with participants with MND (VC=1.30±0.77 vs 2.12±0.75 L, p<0.001; C_rs=0.0331±0.0245 vs 0.0473±0.0241 L/cmH₂O, p=0.024; MIP=39.8±21.3 vs 37.8±19.5 cmH₂O). More participants with other NMD reported an RTI in the previous year (53% vs 22%, p=0.01). The likelihood of having a prior RTI was associated with baseline VC (%predicted) (OR=1.03 (95% CI 1.00 to 1.06), p=0.029). Published thresholds (VC<1.1 L or PCF<270 L/min) were, however, not associated with prior RTI.A single session of LVR improved C_rs (mean (95% CI) increase = 0.0038 (0.0001 to 0.0075) L/cmH₂O, p=0.047) but not VC.

CONCLUSION

These findings corroborate the hypothesis that ventilatory restriction in NMD is related to weakness initially with respiratory system stiffness potentiating lung volume loss in slowly progressive disease. A single session of LVR can improve C_rs. A randomised controlled trial of regular LVR is needed to assess longer-term effects.

Budget Impact of the Vest™ High Frequency Chest Wall Oscillation System for Managing Airway Clearance in Patients with Complex Neurological Disorders: A US Healthcare Payers' Perspective Analysis

OBJECTIVE

As a recognized therapy to improve airway clearance, high-frequency chest wall oscillation (HFCWO) is used to manage reduced vital capacity in patients with complex neuromuscular disorders (cNMD). This study aimed to investigate the budget impact of HFCWO versus chest wall physical therapy (CWPT) from a US-commercial payer perspective.

METHODS

In combination with a previously developed cost-effectiveness model, a budget impact model was developed to evaluate the incremental budgetary impact associated with introducing a HFCWO device over a 5-year time horizon. The model compared the cost implications associated with the commonly used CWPT procedure, as the current scenario, with a new scenario consisting of 80% of market share for HFCWO. The resource use and costs included in the analyses were costs associated with the HFCWO device (Vest™ System) and its consumables, patient training, and medical services such as hospitalization, medications, emergency room, and outpatient visits. The primary outcome measures included total and incremental budgetary impact per member per year (PMPY).

RESULTS

In a hypothetical plan of 1,000,000 members (men: 49.2%), 2099 patients with cNMD were estimated to be eligible to receive airway clearance services over 5 years. The new scenario (HFCWO and CWPT [US$24 PMPY]) was cost-saving compared with the current scenario (CWPT only [$34 PMPY]) with a cost reduction of US$9.46 PMPY. The model estimated a net cost-saving of US$1,594,131 and US$9,591,343 over 1 and 5 years, respectively.

CONCLUSION

This study suggests the HFCWO technique to manage the reduction in vital capacity in patients with cNMD would lead to favorable budget impact results.

Characterization of sleep-disordered breathing in children with Duchenne muscular dystrophy by the American Academy of Sleep Medicine criteria vs disease-specific criteria: what are the differences?

STUDY OBJECTIVES

Individuals with Duchenne muscular dystrophy (DMD) frequently develop sleep-disordered breathing. Noninvasive ventilation is often prescribed for sleep-disordered breathing treatment based on the American Academy of Sleep Medicine (AASM) criteria. In 2018, DMD disease-specific criteria for sleep-disordered breathing were established. Our study aimed to examine the clinical interpretation differences using these different criteria.

METHODS

We performed a multicenter, retrospective chart review of children with DMD followed at The Hospital for Sick Children, Toronto, Canada, and Rady Children's Hospital, San Diego, California, who underwent polysomnography from August 1, 2012, to February 29, 2020. Baseline characteristics and polysomnography data were summarized using descriptive statistics. Agreement for the diagnosis of sleep-disordered breathing evaluated by kappa statistics and sensitivity/specificity analysis was assessed.

RESULTS

One hundred five male children with DMD (mean ± SD age: 12.1 ± 3.8 years; body mass index z score: 0.2 ± 2.3) were included. The proportions of children with DMD that met at least 1 AASM criterion and at least 1 DMD criterion were 45.7% and 67.6%, respectively. We found that 32.4% of children met neither AASM nor DMD criteria. Overall agreement between AASM and DMD criteria was moderate (k = 0.57). There was almost perfect agreement in sleep apnea diagnosis (k = 0.90); however, there was only slight agreement in hypoventilation diagnosis (k = 0.12) between AASM and DMD criteria.

CONCLUSIONS

There were more children with DMD diagnosed with nocturnal hypoventilation and prescribed noninvasive ventilation using DMD criteria compared with AASM criteria. Future studies should address whether the prescription of noninvasive ventilation for children with DMD based on both criteria is associated with different clinical outcomes.

CITATION

Hurvitz MS, Sunkonkit K, Massicotte C, Li R, Bhattacharjee R, Amin R. Characterization of sleep-disordered breathing in children with Duchenne muscular dystrophy by the American Academy of Sleep Medicine criteria vs disease-specific criteria: what are the differences? J Clin Sleep Med. 2022;18(2):609-615.

One in five patients with Duchenne muscular dystrophy dies from other causes than cardiac or respiratory failure

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder with increasing life expectancy from late teens to over 30 years of age. The aim of this nationwide study was to explore the prevalence, life expectancy and leading causes of death in patients with DMD in Sweden. Patients with DMD were identified through the National Quality Registry for Neuromuscular Diseases in Sweden, the Swedish Registry of Respiratory Failure, pathology laboratories, neurology and respiratory clinics, and the national network for neuromuscular diseases. Age and cause of death were retrieved from the Cause of Death Registry and cross-checked with medical records. 373 DMD patients born 1970–2019 were identified, of whom 129 patients deceased during the study period. Point prevalence of adult patients with DMD on December 31st 2019 was 3.2 per 100,000 adult males. Birth prevalence was 19.2 per 100,000 male births. Median survival was 29.9 years, the leading cause of death being cardiopulmonary in 79.9% of patients. Non-cardiopulmonary causes of death (20.1% of patients) mainly pertained to injury-related pulmonary embolism (1.3 per 1000 person-years), gastrointestinal complications (1.0 per 1000 person-years), stroke (0.6 per 1000 person-years) and unnatural deaths (1.6 per 1000 person-years). Death from non-cardiopulmonary causes occurred at younger ages (mean 21.0 years, SD 8.2; p = 0.004). Age at loss of independent ambulation did not have significant impact on overall survival (p = 0.26). We found that non-cardiopulmonary causes contribute to higher mortality among younger patients with DMD. We present novel epidemiological data on the increasing population of adult patients with DMD.

Inspiratory muscle training in children and adolescents living with neuromuscular diseases: A pre-experimental study

Background

Children with neuromuscular diseases (NMD) are at risk of morbidity and mortality because of progressive respiratory muscle weakness and ineffective cough. Inspiratory muscle training (IMT) aims to preserve or improve respiratory muscle strength, thereby reducing morbidity and improving health-related quality of life (HRQoL).

Objectives

To describe the safety and feasibility of a 6-week IMT programme using an electronic threshold device (Powerbreathe®). Any adverse events and changes in functional ability, spirometry, peak expiratory cough flow (PECF), inspiratory muscle strength and HRQoL (Pediatric Quality of Life [PedsQL]) were recorded.

Methods

A convenience sample of eight participants (n = 4 boys; median [interquartile range {IQR}] age: 12.21 [9.63–16.05] years) with various NMD were included in a pre-experimental, observational pre-test post-test feasibility study. Training consisted of 30 breaths, twice daily, 5 days a week, for 6 weeks.

Results

There were significant pre- to post-intervention improvements in upper limb function and coordination (p = 0.03) and inspiratory muscle strength: maximum inspiratory mouth pressure (Pimax) (p = 0.01); strength-index (p = 0.02); peak inspiratory flow (PIF) (p = 0.02), with no evidence of change in spirometry, PECF or HRQoL. No adverse events occurred and participant satisfaction and adherence levels were high.

Conclusion

Inspiratory muscle training (at an intensity of 30% Pimax) appears safe, feasible and acceptable, in a small sample of children and adolescents with NMD and was associated with improved inspiratory muscle strength, PIF and upper limb function and coordination.

Clinical implications

Larger, longer-term randomised controlled trials are warranted to confirm the safety and efficacy of IMT as an adjunct respiratory management strategy in children with NMD.

Lower Extremity Muscle Involvement in the Intermediate and Bethlem Myopathy Forms of COL6-Related Dystrophy and Duchenne Muscular Dystrophy: A Cross-Sectional Study

Collagen VI-related dystrophies (COL6-RDs) and Duchenne muscular dystrophy (DMD) cause progressive muscle weakness and disability. COL6-RDs are caused by mutations in the COL6 genes (COL6A1, COL6A2 and COL6A3) encoding the extracellular matrix protein collagen VI, and DMD is caused by mutations in the DMD gene encoding the cytoplasmic protein dystrophin. Both COL6-RDs and DMD are characterized by infiltration of the muscles by fatty and fibrotic tissue. This study examined the effect of disease pathology on skeletal muscles in lower extremity muscles of COL6-RDs using timed functional tests, strength measures and qualitative/ quantitative magnetic resonance imaging/spectroscopy measures (MRI/MRS) in comparison to unaffected (control) individuals. Patients with COL6-RD were also compared to age and gender matched patients with DMD.Patients with COL6-RD presented with a typical pattern of fatty infiltration of the muscle giving rise to an apparent halo effect around the muscle, while patients with DMD had evidence of fatty infiltration throughout the muscle areas imaged. Quantitatively, fat fraction, and transverse relaxation time (T2) were elevated in both COL6-RD and DMD patients compared to unaffected (control) individuals. Patients with COL6-RD had widespread muscle atrophy, likely contributing to weakness. In contrast, patients with DMD revealed force deficits even in muscle groups with increased contractile areas.

Cough augmentation techniques for people with chronic neuromuscular disorders

BACKGROUND

People with neuromuscular disorders may have a weak, ineffective cough predisposing them to respiratory complications. Cough augmentation techniques aim to improve cough effectiveness and mucous clearance, reduce the frequency and duration of respiratory infections requiring hospital admission, and improve quality of life.

OBJECTIVES

To determine the efficacy and safety of cough augmentation techniques in adults and children with chronic neuromuscular disorders.

SEARCH METHODS

On 13 April 2020, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL, and ClinicalTrials.gov for randomised controlled trials (RCTs), quasi-RCTs, and randomised cross-over trials.

SELECTION CRITERIA

We included trials of cough augmentation techniques compared to no treatment, alternative techniques, or combinations thereof, in adults and children with chronic neuromuscular disorders.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, extracted data, and assessed risk of bias. The primary outcomes were the number and duration of unscheduled hospitalisations for acute respiratory exacerbations. We assessed the certainty of evidence using GRADE.

MAIN RESULTS

The review included 11 studies involving 287 adults and children, aged three to 73 years. Inadequately reported cross-over studies and the limited additional information provided by authors severely restricted the number of analyses that could be performed. Studies compared manually assisted cough, mechanical insufflation, manual and mechanical breathstacking, mechanical insufflation-exsufflation, glossopharyngeal breathing, and combination techniques to unassisted cough and alternative or sham interventions. None of the included studies reported on the primary outcomes of this review (number and duration of unscheduled hospital admissions) or listed 'adverse events' as primary or secondary outcome measures. The evidence suggests that a range of cough augmentation techniques may increase peak cough flow compared to unassisted cough (199 participants, 8 RCTs), but the evidence is very uncertain. There may be little to no difference in peak cough flow outcomes between alternative cough augmentation techniques (216 participants, 9 RCTs). There was insufficient evidence to determine the effect of interventions on measures of gaseous exchange, pulmonary function, quality of life, general function, or participant preference and satisfaction.

AUTHORS' CONCLUSIONS

We are very uncertain about the safety and efficacy of cough augmentation techniques in adults and children with chronic neuromuscular disorders and further studies are needed.

Volume-assured pressure support mode for noninvasive ventilation: can it improve overnight adherence in children with neuromuscular disease?

Purpose

Volume-assured pressure support in noninvasive ventilation (VAPS-NIV) is a newer mode providing automatic pressure support adjustment to ensure a constant alveolar ventilation. Previous studies have shown that NIV effectiveness depends on patient adherence and tolerance. The aim of this study was to determine the adherence and efficacy of VAPS-NIV compared to spontaneous-time (S/T) mode in pediatric patients with neuromuscular disease (NMD).

Methods

This was a prospective observational study. Children with NMD who utilized NIV at home for ≥ 3 months were recruited from the Long-term ventilation clinic at The Hospital for Sick Children, Toronto, Canada, from July 1, 2015, to July 1, 2019. Baseline characteristics, date of initiation of NIV, and pulmonary function tests were recorded. Polysomnogram (PSG) data and adherence were recorded and analyzed comparing VAPS and S/T modes.

Results

Twenty children with NMD (17 male, 85%) were enrolled. The mean (SD) age at initiation of NIV was 11.6 ± 4.6 years. The median (IQR) duration of ventilation was 1.36 (0.80–2.98) years. The mean average daily usage and the median daily usage for VAPS mode and S/T mode were 8.4 ± 1.6 versus 7.2 ± 2.5 h (p = 0.012) and 8.6 ± 1.4 versus 7.8 ± 2.1 h (p = 0.022), respectively. There was no difference in sleep architecture, gas exchange, or parent proxy report of NIV tolerance between S/T and VAPS modes.

Conclusion

VAPS was associated with an improvement in adherence to therapy in children with NMD compared to S/T mode. Longitudinal studies are required to evaluate long-term clinical outcomes using VAPS mode in children with NMD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-021-02288-1.

RESPIRATORY MUSCLE IMPAIRMENT EVALUATED WITH MEP/MIP RATIO IN CHILDREN AND ADOLESCENTS WITH CHRONIC RESPIRATORY DISEASE

OBJECTIVE

To evaluate the strength of respiratory muscles and to compare maximum inspiratory (MIP) and expiratory (MEP) pressure and MEP/MIP ratio between patients with chronic respiratory diseases and healthy individuals.

METHODS

Case-control study. Individuals with neuromuscular disease and post-infectious bronchiolitis obliterans were considered. In addition, they were also matched according to anthropometric and demographic characteristics with healthy children and adolescents. MIP, MEP in the three groups, and pulmonary function only in patients with chronic respiratory diseases were recorded.

RESULTS

A total of 52 subjects with CRD (25 with neuromuscular disease, and 27 with post-infectious bronchiolitis obliterans) and 85 healthy individuals were included, with an average age of 11.3±2.1 years. Patients with neuromuscular disease and post-infectious bronchiolitis obliterans presented lower MIP and MEP when compared with healthy individuals, although MEP/MIP ratio was lower in patients with neuromuscular disease (0.87±0.3) and higher in patients with post-infectious bronchiolitis obliterans (1.1±0.3) compared to the healthy group (0.97±0.2). Only in patients with neuromuscular disease a negative correlation was observed between MEP/MIP ratio and age (r=-0.50; p=0.01).

CONCLUSIONS

Differences in the pattern of muscular weakness between patients with chronic respiratory diseases were observed. In patients with neuromuscular disease, a decrease in the MEP/MIP ratio depending on MIP was verified; and in those patients with post-infectious bronchiolitis obliterans, an increase in the MEP/MIP ratio depending on MIP was also observed.

Expiratory dysfunction in young dogs with golden retriever muscular dystrophy

Respiratory disease is a leading cause of morbidity in people with Duchenne muscular dystrophy and also occurs in the golden retriever muscular dystrophy (GRMD) model. We have previously shown that adult GRMD dogs have elevated expiratory flow as measured non-invasively during tidal breathing. This abnormality likely results from increased chest and diaphragmatic recoil associated with fibrosis and remodeling. Treatments must reverse pathologic effects on the diaphragm and other respiratory muscles to maximally reduce disease morbidity and mortality. Here, we extended our work in adults to younger GRMD dogs to define parameters that would be helpful in preclinical trials. Tidal breathing spirometry and respiratory inductance plethysmography were performed in GRMD dogs at approximately 3 and 6 months of age, corresponding to approximately 5-10 years in DMD, when clinical trials are often conducted. Expiratory flows were markedly elevated in GRMD versus normal dogs at 6 months. Values increased in GRMD dogs between 3 and 6 months, providing a 3-month window to assess treatment efficacy. These changes in breathing mechanics have not been previously identified at such an early age. Expiratory flow measured during tidal breathing of unsedated young GRMD dogs could be a valuable marker of respiratory mechanics during preclinical trials.

Skip constructs in spinal muscular atrophy: outcomes of a novel approach for posterior spinal instrumentation and fusion

PURPOSE

Many children with spinal muscular atrophy (SMA) develop progressive spinal deformity, worsening already compromised pulmonary function and global spinal balance. Early results demonstrate that intrathecal administration of nusinersen, a recent FDA-approved drug, improves motor function and ventilator-free survival, necessitating preservation of intrathecal access when considering PSIF. The purpose of this study is to assess medium-term outcomes of a specialized approach for posterior spinal instrumentation and fusion (PSIF) to preserve intrathecal access in patients with SMA.

METHODS

A retrospective review of patients with SMA undergoing PSIF at a single tertiary academic medical center during a 3-year period was completed. To facilitate intrathecal drug administration, the traditional approach to PSIF was modified to "skip" one or more intervertebral levels at the thoracolumbar junction. Clinical notes and radiographs were reviewed for postoperative outcomes including major coronal curve correction and complications, including loss of correction, hardware failure and surgical revision.

RESULTS

Eight patients were identified, with a mean age of 12.7 ± 1.6 years and follow-up of 4 years. These patients had a mean preoperative major coronal curve of 56.4°, with mean curve correction of 35.2°. At follow-up, no patients experienced rod breakage, loss of correction, or postoperative chronic pain. Only one patient required revision surgery due to bony overgrowth at the skipped level after three and a half years.

CONCLUSION

Implementing the skip construct approach for PSIF in patients with SMA allows for scoliosis correction without compromising intrathecal drug delivery. Follow-up at 4 years reveals no adverse clinical events, hardware failure or loss of correction.

LEVEL OF EVIDENCE

IV.

A Wearable Device for Breathing Frequency Monitoring: A Pilot Study on Patients with Muscular Dystrophy

Patients at risk of developing respiratory dysfunctions, such as patients with severe forms of muscular dystrophy, need a careful respiratory assessment, and periodic follow-up visits to monitor the progression of the disease. In these patients, at-home continuous monitoring of respiratory activity patterns could provide additional understanding about disease progression, allowing prompt clinical intervention. The core aim of the present study is thus to investigate the feasibility of using an innovative wearable device for respiratory monitoring, particularly breathing frequency variation assessment, in patients with muscular dystrophy. A comparison of measurements of breathing frequency with gold standard methods showed that the device based on the inertial measurement units (IMU-based device) provided optimal results in terms of accuracy errors, correlation, and agreement. Participants positively evaluated the device for ease of use, comfort, usability, and wearability. Moreover, preliminary results confirmed that breathing frequency is a valuable breathing parameter to monitor, at the clinic and at home, because it strongly correlates with the main indexes of respiratory function.

The Effect of Inspiratory Muscle Training on Duchenne Muscular Dystrophy: A Meta-analysis

PURPOSE

This study reports the respiratory muscle training effect on strength and endurance in individuals with Duchenne muscular dystrophy.

METHODS

Articles published from 1984 to 2017 were reviewed. Six articles met the inclusion criteria that included within-subject control or between-subject control group, participants with a diagnosis of only Duchenne muscular dystrophy, participation in respiratory muscle training intervention, and outcome measures of endurance and strength. Effect sizes were calculated for each study and overall, weighted mean effect sizes for strength and endurance outcome measures.

RESULTS

There was a large effect for improving respiratory endurance and a moderate effect for muscle strength. However, these effects were not significant.

CONCLUSION

Findings justify further exploration of the potential benefits of respiratory muscle training for individuals with Duchenne muscular dystrophy.

Investigating the clinical use of structured light plethysmography to assess lung function in children with neuromuscular disorders

BACKGROUND

Children and young people with neuromuscular disorders (NMD), such as Duchenne Muscular Dystrophy (DMD), develop progressive respiratory muscles weakness and pulmonary restriction. Pulmonary function monitoring of the decline in lung function allows for timely intervention with cough assist techniques and nocturnal non-invasive ventilation (NIV). NMD may find the measurement of lung function difficult using current techniques. Structured Light Plethysmography (SLP) has been proposed as a novel, non-contact, self-calibrating, non-invasive method of assessing lung function. The overarching aim of this study was to investigate the use of SLP as a novel method for monitoring respiratory function in children with neuromuscular disease.

METHODS

SLP thoraco-abdominal (TA) displacement was correlated with forced vital capacity measurements recorded by spirometry and the repeatability of the measurements with both methods examined. SLP tidal breathing parameters were investigated to assess the range and repeatability of regional right and left side TA displacement and rib cage and abdominal wall displacement.

RESULTS

The comparison of the FVC measured with SLP and with spirometry, while having good correlation (R = 0.78) had poor measurement agreement (95% limits of agreement: -1.2 to 1.2L) The mean relative contribution of right and left TA displacement in healthy controls was 50:50 with a narrow range. Repeatability of this measure with SLP was found to be good in healthy controls and moderate in NMD children with/without scoliosis but with a wider range. The majority of the control group displayed a predominant rib cage displacement during tidal breathing and those who displayed predominant abdominal wall displacement showed displacement of both regions close to 50:50 with similar results for the rib cage and abdomen. In comparison, children with NMD have a more variable contribution for all of these parameters. In addition, SLP was able to detect a reduction in abdominal contribution to TA displacement with age in the DMD group and detect paradoxical breathing in children with NMD. Using SLP tracings during tidal breathing we were able to identify three specific patterns of breathing amongst healthy individuals and in children with NMD.

CONCLUSIONS

SLP is a novel method for measuring lung function that requires limited patient cooperation and may be especially useful in children with neuromuscular disorders. Measuring the relative contributions of the right and left chest wall and chest versus abdominal movements allows a more detailed assessment.

The utility of using peak expiratory flow and forced vital capacity to predict poor expiratory cough flow in children with neuromuscular disorders

Background

Approximately one in every 1200 South Africans is affected by a neuromuscular disease (NMD). Weak respiratory muscles and ineffective cough contribute to the development of respiratory morbidity and mortality. Early identification of individuals at risk of respiratory complications, through peak expiratory cough flow (PCF) measurement, may improve patient outcomes through timely initiation of cough augmentation therapy.

Objectives

The aim of this study was to investigate the relationship between peak expiratory flow (PEF), forced vital capacity (FVC) and PCF in South African children with neuromuscular disorders.

Methods

A retrospective descriptive study of routinely collected data was conducted.

Results

Forty-one participants (aged 11.5 ± 3.6 years; 75.6% male) were included. There was a strong linear correlation between PCF and PEF (R = 0.78; p = 0.0001) and between PCF and FVC (R = 0.61; p = 0.0001). There was good agreement between PCF and PEF, with intraclass correlation coefficient of 0.8 (95% confidence interval, 0.7–0.9; p < 0.0001). Peak expiratory flow < 160 L.min⁻¹ and FVC < 1.2 L were significantly predictive of PCF < 160 L.min⁻¹ (suggestive of cough ineffectiveness), whilst PEF < 250 L.min⁻¹ was predictive of PCF < 270 L.min⁻¹, the level at which cough assistance is usually implemented.

Conclusion

PEF and FVC may be surrogate measures of cough effectiveness in children with neuromuscular disorders.

Clinical implications

PEF and FVC may be considered for clinical use as screening tools to identify patients at risk for pulmonary morbidity related to ineffective cough.

Inspiratory muscle training in severe spinal muscular atrophy: a case report

Background/Aims

Inspiratory muscle training aims to preserve or improve respiratory muscle strength in children with neuromuscular diseases in order to prevent or minimise pulmonary morbidity. The aim of this study was to determine the effect of inspiratory muscle training on clinical outcomes and health-related quality of life in a child with advanced neuromuscular disease and severe pulmonary restriction.

Methods

A one patient pre-test post-test study design was implemented. General function, spirometry, peak expiratory cough flow and health-related quality of life were measured at baseline and after a 6-week inspiratory muscle training programme. Inspiratory muscle strength (maximal inspiratory mouth pressure and sniff nasal inspiratory pressure) was measured every 2 weeks. The patient used a tapered flow threshold inspiratory training device (POWERbreathe K3) at an intensity of ± 30% of maximal inspiratory mouth pressure twice a day, 5 days per week.

Findings

The non-ambulatory 10-year-old girl with type 2 spinal muscular atrophy initially had a forced vital capacity of 18% predicted and peak expiratory cough flow of 60 litres/minute. A substantial improvement was seen in inspiratory muscle strength between baseline and 4 weeks. Patient health-related quality of life improved and patient satisfaction was high, with a score of 9/10. The patient developed a lower respiratory tract infection towards the end of the inspiratory muscle training period. No other adverse events occurred.

Conclusions

Improved inspiratory muscle strength and health-related quality of life was associated with inspiratory muscle training in a child with advanced spinal muscular atrophy. Controlled clinical trials are recommended to determine the safety and efficacy of inspiratory muscle training in children with advanced spinal muscular atrophy and severe respiratory muscle weakness to inform clinical practice.

Disorders of the Diaphragm

Pathologic processes that involve the central nervous system, phrenic nerve, neuromuscular junction, and skeletal muscle can impair diaphragm function. When these processes are of sufficient severity to cause diaphragm dysfunction, respiratory failure may be a consequence. This article reviews basic diaphragm anatomy and physiology and then discusses diagnostic and therapeutic approaches to disorders that result in unilateral or bilateral diaphragm dysfunction. This discussion provides a context in which disorders of the diaphragm and their implications on respiratory function can be better appreciated.

Screening and evaluation tools of dysphagia in adults with neuromuscular diseases: a systematic review

Background:

The purpose of this systematic review was to summarize the different dysphagia screening and evaluation tools, and to identify their measurement properties in adults with neuromuscular diseases (NMDs).

Methods:

A systematic review was performed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search strategy was conducted across three databases (PubMed, CINAHL and ScienceDirect). Measurement properties of each tools and the Quality Index, developed by Downs and Black, were considered for the different investigated studies.

Results:

The search strategy produced 2221 articles. After removal of duplicates and full-text analysis, 19 studies were included. Most of the publications focused on amyotrophic lateral sclerosis (ALS; n = 10) and Duchenne muscular dystrophy (DMD; n = 4). A total of 12 tools, listed as instrumental and noninstrumental examinations, were retrieved. A total of five of them used videofluoroscopic swallow study (VFSS). Measurement properties of the tools are not completely described in detail in many studies. The neuromuscular disease swallowing status scale, a noninstrumental tool, is the only one that assessed all measurement properties in ALS patients. The median score reported for the Quality Index was 16.

Conclusions:

This systematic review identified 12 different tools for the screening and evaluation of dysphagia in adults with NMD. Majority of the studies presented VFSS as a valid and reliable examination to assess dysphagia in ALS and DMD. Other tools were mainly evaluated in ALS patients, but further studies are needed to complete their measurement properties. In other NMDs, no firm conclusion can be made because of insufficient data and heterogeneity of NMDs.

Intensive Care Management of the Neuromuscular Patient

Neuromuscular emergencies are a distinct group of acute neurological diseases with distinct characteristic presentations. Patients who suffer from this group of diseases are at immediate risk of losing protection of their native airway as well as aspirating orogastric contents. This is secondary to weakness of the muscles of the oropharynx and respiratory muscles. Although some neuromuscular emergencies such as myasthenia gravis or Guillain-Barré syndrome are well understood, others such as critical illness myopathy and neuropathy are less well characterized. In this chapter, we have discussed the pathophysiology, diagnostic evaluation, and management options in patients who are admitted to the intensive care unit. We have also emphasized the importance of a thorough understanding of the use of pharmacological anesthetic agents in this patient population.

Pico de fluxo de tosse em crianças e jovens com atrofia muscular espinhal tipo II e tipo III

RESUMO A atrofia muscular espinhal é uma doença neurodegenerativa, que pode cursar com insuficiência respiratória progressiva. O objetivo deste trabalho é descrever o pico de fluxo de tosse de crianças e jovens com atrofia muscular espinhal dos tipos II e III. Trata-se de um estudo transversal descritivo realizado em ambulatório de neuropediatria entre março de 2011 e maio de 2012, com pacientes com atrofia muscular e espinhal dos tipos II e III com mais de 5 anos de idade. Dos 53 pacientes elegíveis, 21 participaram da pesquisa. A medição do pico de fluxo de tosse foi realizada através do peak flow meter com os pacientes sentados e deitados. Após registradas três medidas, foi selecionada a maior entre elas. Os indivíduos do tipo III alcançaram valores de pico de fluxo de tosse superiores aos dos indivíduos do tipo II. As medidas tomadas em posição sentada (AME tipo II 159,4 l/min; AME tipo III 287,9 l/min) foram superiores às medidas em posição deitada (AME tipo II 146,9 l/min; AME tipo III 257,5 l/min), com diferença significativa (p-valor=0,008 posição sentada e p=0,033 posição deitada). Concluiu-se que indivíduos com AME tipo III apresentam maior PFT, principalmente quando sentados, em comparação com o tipo II.

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.

Anisomycin Activates Utrophin Upregulation Through a p38 Signaling Pathway

Duchenne muscular dystrophy is a recessive X‐linked disease characterized by progressive muscle wasting; cardiac or respiratory failure causes death in most patients by the third decade.  The disease is caused by mutations in the dystrophin gene that lead to a loss of functional dystrophin protein. Although there are currently few treatments for Duchenne muscular dystrophy, previous reports have shown that upregulating the dystrophin paralog utrophin in Duchenne muscular dystrophy mouse models is a promising therapeutic strategy. We conducted in silico mining of the Connectivity Map database for utrophin‐inducing agents, identifying the p38‐activating antibiotic anisomycin. Treatments of C2C12, undifferentiated murine myoblasts, and mdx primary myoblasts with anisomycin conferred increases in utrophin protein levels through p38 pathway activation.  Anisomycin also induced utrophin protein levels in the diaphragm of mdx mice.  Our study shows that repositioning small molecules such as anisomycin may prove to have Duchenne muscular dystrophy clinical utility.

Efficacy of Idebenone to Preserve Respiratory Function above Clinically Meaningful Thresholds for Forced Vital Capacity (FVC) in Patients with Duchenne Muscular Dystrophy

BACKGROUND

Patients with DMD experience progressive restrictive respiratory disease and eventual respiratory failure. Standard of care guidelines command changes in disease management when forced vital capacity percent of predicted (FVC% p) falls below clinically relevant thresholds. The Phase 3 DELOS trial in patients with DMD demonstrated that idebenone reduces the loss of peak expiratory flow and FVC compared to placebo (Buyse GM, et al.; Lancet 2015; 385 : 1748-57).

OBJECTIVE

Post-hoc analyses were conducted to assess whether treatment with idebenone could reduce the risk of patients dropping below clinically meaningful thresholds of FVC% p.

METHODS

The DELOS trial enrolled DMD patients 10-18 years of age not using glucocorticoids to receive idebenone (N = 31) or placebo (N = 33) for 12 months. Change from baseline in FVC and FVC% p was assessed by hospital spirometry and analyzed by mixed model of repeated measures and slope analysis and proportions of patients falling below clinically meaningful thresholds of FVC% p were compared.

RESULTS

The change over 1 year in FVC and FVC% p showed a consistent pattern in favor of idebenone treatment across multiple analysis methods and fewer patients in the idebenone group declined by a margin of 10% or more in FVC and FVC% p compared to placebo. There were also fewer patients in the idebenone group (15%) with a decline below FVC% p of 50% compared to the placebo group (25%) and fewer patients in the idebenone group (28%) showed a decline below FVC% p of 50% or 40% or 30% compared to the placebo group (43%).

CONCLUSIONS

These data added to the consistency and clinical meaningfulness of findings from the DELOS trial showing that idebenone can slow the loss of pulmonary function in patients with DMD.

Anisotropic mechanosensitive pathways in the diaphragm and their implications in muscular dystrophies

The diaphragm is the "respiratory pump;" the muscle that generates pressure to allow ventilation. Diaphragm muscles play a vital function and thus are subjected to continuous mechanical loading. One of its peculiarities is the ability to generate distinct mechanical and biochemical responses depending on the direction through which the mechanical forces applied to it. Contractile forces originated from its contractile components are transmitted to other structural components of its muscle fibers and the surrounding connective tissue. The anisotropic mechanical properties of the diaphragm are translated into biochemical signals that are directionally mechanosensitive by mechanisms that appear to be unique to this muscle. Here, we reviewed the current state of knowledge on the biochemical pathways regulated by mechanical signals emphasizing their anisotropic behavior in the normal diaphragm and analyzed how they are affected in muscular dystrophies.

Sleep Disordered Breathing in Duchenne Muscular Dystrophy

This review aims to explain the inevitable imbalance between respiratory load, drive, and muscular force that occurs in the natural aging of Duchenne muscular dystrophy and that predisposes these patients to sleep disordered breathing (SDB). In DMD, SDB is characterized by oxygen desaturation, apneas, hypercapnia, and hypoventilation during sleep and ultimately develops into respiratory failure during wakefulness. It can be present in all age groups. Young patients risk obstructive apneas because of weight gain, secondary to progressive physical inactivity and prolonged corticosteroid therapy; older patients hypoventilate and desaturate because of respiratory muscle weakness, in particular the diaphragm. These conditions are further exacerbated during REM sleep, the phase of maximal muscle hypotonia during which the diaphragm has to provide most of the ventilation. Evidence is given to the daytime predictors of early symptoms of SDB, important indicators for the proper time to initiate mechanical ventilation.

Dystrophin-Deficient Cardiomyopathy

Dystrophinopathies are a group of distinct neuromuscular diseases that result from mutations in the structural cytoskeletal Dystrophin gene. Dystrophinopathies include Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), X-linked dilated cardiomyopathy, as well as DMD and BMD female carriers. The primary presenting symptom in most dystrophinopathies is skeletal muscle weakness. However, cardiac muscle is also a subtype of striated muscle and is similarly affected in many of the muscular dystrophies. Cardiomyopathies associated with dystrophinopathies are an increasingly recognized manifestation of these neuromuscular disorders and contribute significantly to their morbidity and mortality. Recent studies suggest that these patient populations would benefit from cardiovascular therapies, annual cardiovascular imaging studies, and close follow-up with cardiovascular specialists. Moreover, patients with DMD and BMD who develop end-stage heart failure may benefit from the use of advanced therapies. This review focuses on the pathophysiology, cardiac involvement, and treatment of cardiomyopathy in the dystrophic patient.

Screening and evaluation tools of dysphagia in children with neuromuscular diseases: a systematic review

AIM

Dysphagia is frequent in paediatric patients with neuromuscular diseases (pNMD). Its detection is important for initiating early diagnosis and treatment as well as for minimizing related complications. The aim of this study was to review the literature on dysphagia screening and evaluation tools in pNMD.

METHOD

A systematic review was performed on the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three databases (PubMed, CINAHL, and ScienceDirect) were searched. Measurement properties of tools and the quality index developed by Downs and Black were considered.

RESULTS

Our search yielded four studies and four different tools for paediatric patients with Duchenne muscular dystrophy (DMD). The Sydney Swallow Questionnaire, surface electromyography, Neuromuscular Disease Swallowing Status Scale, and videofluoroscopic swallow study showed interesting properties for DMD. No data were available for other NMD and children under 9 years. The mean total score for the quality index was 17.5.

INTERPRETATION

We did not identify any superior validated tools, either for screening or for evaluation of dysphagia, and no widely accepted protocol. Further studies are needed to identify the simplest assessment with the best psychometric properties for pNMD. We recommend establishing a specific tool for pNMD.

Characterization of pulmonary function in 10-18 year old patients with Duchenne muscular dystrophy

Pulmonary function loss in patients with Duchenne muscular dystrophy (DMD) is progressive and leads to pulmonary insufficiency. The purpose of this study in 10-18 year old patients with DMD is the assessment of the inter-correlation between pulmonary function tests (PFTs), their reliability and the association with the general disease stage measured by the Brooke score. Dynamic PFTs (peak expiratory flow [PEF], forced vital capacity [FVC], forced expiratory volume in one second [FEV1]) and maximum static airway pressures (MIP, MEP) were prospectively collected from 64 DMD patients enrolled in the DELOS trial (ClinicalTrials.gov, number NCT01027884). Baseline PEF percent predicted (PEF%p) was <80% and patients had stopped taking glucocorticoids at least 12 months prior to study start. At baseline PEF%p, FVC%p and FEV1%p correlated well with each other (Spearman's rho: PEF%p-FVC%p: 0.54; PEF%p-FEV1%p: 0.72; FVC%p-FEV1%p: 0.91). MIP%p and MEP%p correlated well with one another (MIP%p-MEP%p: 0.71) but less well with PEF%p (MIP%p-PEF%p: 0.40; MEP%p-PEF%p: 0.41) and slightly better with FVC%p (MIP%p-FVC%p: 0.59; MEP%p-FVC%p: 0.74). The within-subject coefficients of variation (CV) for successive measures were 6.97% for PEF%p, 6.69% for FVC%p and 11.11% for FEV1%p, indicating that these parameters could be more reliably assessed compared to maximum static airway pressures (CV for MIP%p: 18.00%; MEP%p: 15.73%). Yearly rates of PFT decline (placebo group) were larger in dynamic parameters (PEF%p: -8.9% [SD 2.0]; FVC%p: -8.7% [SD 1.1]; FEV1%p: -10.2% [SD 2.0]) than static airway pressures (MIP%p: -4.5 [SD 1.3]; MEP%p: -2.8 [SD 1.1]). A considerable drop in dynamic pulmonary function parameters was associated with loss of upper limb function (transition from Brooke score category 4 to category 5). In conclusion, these findings expand the understanding of the reliability, correlation and evolution of different pulmonary function measures in DMD patients who are in the pulmonary function decline phase.

Idebenone reduces respiratory complications in patients with Duchenne muscular dystrophy

In Duchenne muscular dystrophy (DMD), progressive loss of respiratory function leads to restrictive pulmonary disease and places patients at significant risk for severe respiratory complications. Of particular concern are ineffective cough, secretion retention and recurrent respiratory tract infections. In a Phase 3 randomized controlled study (DMD Long-term Idebenone Study, DELOS) in DMD patients 10-18 years of age and not taking concomitant glucocorticoid steroids, idebenone (900 mg/day) reduced significantly the loss of respiratory function over a 1-year study period. In a post-hoc analysis of DELOS we found that more patients in the placebo group compared to the idebenone group experienced bronchopulmonary adverse events (BAEs): placebo: 17 of 33 patients, 28 events; idebenone: 6 of 31 patients, 7 events. The hazard ratios (HR) calculated "by patient" (HR 0.33, p = 0.0187) and for "all BAEs" (HR 0.28, p = 0.0026) indicated a clear idebenone treatment effect. The overall duration of BAEs was 222 days (placebo) vs. 82 days (idebenone). In addition, there was also a difference in the use of systemic antibiotics utilized for the treatment of BAEs. In the placebo group, 13 patients (39.4%) reported 17 episodes of antibiotic use compared to 7 patients (22.6%) reporting 8 episodes of antibiotic use in the idebenone group. Furthermore, patients in the placebo group used systemic antibiotics for longer (105 days) compared to patients in the idebenone group (65 days). This post-hoc analysis of DELOS indicates that the protective effect of idebenone on respiratory function is associated with a reduced risk of bronchopulmonary complications and a reduced need for systemic antibiotics.

Diaphragm: A vital respiratory muscle in mammals

The diaphragm is a respiratory muscle that is primarily responsible for the respiratory function in normal individuals. In mammals, the diaphragm muscle has been studied from the early days of zoology, comparative and experimental anatomy, physiology, medicine, physics, and philosophy. However, even with these early advances in knowledge pertaining to the diaphragm, comprehensive morphological data on the diaphragm are still incomplete. In this review, we summarize the beginnings of the morphological description of the diaphragm, and we describe the current status of the known morphological and embryological features. In addition, we correlate how the impairment of the diaphragm muscle in Duchenne muscular dystrophy (DMD) can lead to patient deaths. DMD is the most common X-linked muscle degenerative disease and is caused by a lack of dystrophin protein. Dystrophin is an important muscle protein that links the cellular cytoskeleton with the extracellular matrix. In the absence of dystrophin, the muscle becomes susceptible to damage during muscle contraction. This review allows researchers to obtain an overview of the diaphragm, transcending the morphological data from animals described in conventional literature.

Long-term Follow-up of Pulmonary Function and Scoliosis in Patients With Duchenne's Muscular Dystrophy and Spinal Muscular Atrophy

BACKGROUND

Spine surgery for neuromuscular scoliosis in patients with Duchenne's Muscular Dystrophy (DMD) and Spinal Muscular Atrophy (SMA) remained controversial. This study aimed to review the long-term results of spine surgery and its effect on pulmonary function in these patients.

METHODS

A retrospective review was conducted for the above patients who had undergone surgery from 1990 to 2006 in a tertiary hospital. Their yearly lung function tests, clinical records, and x-ray films before and after surgery were reviewed. All patients had at least 2 lung function tests performed before surgery and at least 3 lung function tests performed after surgery. Records of perioperative pulmonary infections that resulted in hospital admissions were also retrieved from the hospital computer system.

RESULTS

Forty patients were reviewed: 29 with DMD, 11 with SMA. The mean follow-up period was 11.6 years. For patients with DMD, the mean correction of Cobb's angle from surgery was 34.1 degrees. The rate of decline of the predicted forced vital capacity preoperatively was 7.80% per year, and was reduced to 4.26% per year postoperatively (P<0.001). For patients with SMA, the mean correction of Cobb's angle from surgery was 44.1 degrees. The rate of decline of the predicted forced vital capacity preoperatively was 5.31% per year, and was reduced to 1.77% per year postoperatively (P<0.001). For both DMD and SMA patients, the difference between the rate of preoperative and postoperative pulmonary infections that resulted in hospital admission were, however, not significant (P=0.433 and 0.452, respectively).

CONCLUSIONS

Scoliosis surgery in patients with DMD and SMA results in a long-term decreased rate of decline in pulmonary function over a follow-up period of more than 10 years. The level of the apical vertebrae of the scoliosis did not demonstrate a significant trend on the pulmonary function. The frequency of chest infections did not improve by scoliosis surgery.

LEVEL OF SIGNIFICANCE

Level III—Retrospective study.

Arquitetura comparativa dos pulmões de camundongos normais e afetados pela Distrofia Muscular de Duchenne

Resumo: A Distrofia Muscular de Duchenne (DMD) é uma doença genética de caráter recessivo que caracterizada por fraqueza muscular progressiva de cintura pélvica e escapular evoluindo para insuficiência respiratória e, ou cardíaca. O camundongo mdx é um modelo amplamente utilizado para estudos da DMD. Apesar do fenótipo destes animais serem mais suave, estes apresentam o principal músculo respiratório, o diafragma com morfologia e bioquímica semelhante à DMD humana, fato este que pode comprometer a função respiratória e consequentemente os pulmões. Foi realizado um estudo anatômico descritivo do parênquima pulmonar dos pulmões de 5 animais modelo mdx comparando estes com os pulmões de 5 camundongos BALB/C57 (Mus musculus). Os pulmões foram analisados macroscopicamente e através de microscopia de luz e eletrônica de varredura. Os achados sugerem que o modelo mdx apresenta morfologia pulmonar semelhante aos camundongos BALB/C57 e que seu uso deve ser cauteloso e criterioso em ensaios clínicos que aborde este órgão.