Respiratory problems in spinal muscular atrophies

Bioinformatic analysis of SMN1-ACE/ACE2 interactions hinted at a potential protective effect of spinal muscular atrophy against COVID-19-induced lung injury

Patients with spinal muscular atrophy (SMA) are susceptible to the respiratory infections and might be at a heightened risk of poor clinical outcomes upon contracting coronavirus disease 2019 (COVID-19). In the face of the COVID-19 pandemic, the potential associations of SMA with the susceptibility to and prognostication of COVID-19 need to be clarified. We documented an SMA case who contracted COVID-19 but only developed mild-to-moderate clinical and radiological manifestations of pneumonia, which were relieved by a combined antiviral and supportive treatment. We then reviewed a cohort of patients with SMA who had been living in the Hubei province since November 2019, among which the only 1 out of 56 was diagnosed with COVID-19 (1.79%, 1/56). Bioinformatic analysis was carried out to delineate the potential genetic crosstalk between SMN1 (mutation of which leads to SMA) and COVID-19/lung injury-associated pathways. Protein-protein interaction analysis by STRING suggested that loss-of-function of SMN1 might modulate COVID-19 pathogenesis through CFTR, CXCL8, TNF and ACE. Expression quantitative trait loci analysis also revealed a link between SMN1 and ACE2, despite low-confidence protein-protein interactions as suggested by STRING. This bioinformatic analysis could give hint on why SMA might not necessarily lead to poor outcomes in patients with COVID-19.

[Effect of thoracic bracing on lung function in children with neuromuscular disease]

Respiratory muscle weakness associated with scoliosis in neuromuscular disease leads to respiratory impairment. Children with scoliosis are usually treated with spinal bracing to delay the progress of disease. We studied the impact of spinal bracing on lung function in these children.

METHODS

Retrospective study of patient data from January 1997 to January 2003. Spirometry and measurement of lung volume involved 32 observations, corresponding to 17 children with neuromuscular disease, including 14 with spinal muscular atrophy. Data for children with and without a brace were studied.

RESULTS

A total of 72% of the children had severe scoliosis (Cobb score>30 degrees ); 40% wore a Garchois brace. Children without a brace showed a mean vital capacity of 65% of predicted value, with a restrictive syndrome in 44% of observations. Children with a brace showed significantly reduced vital capacity (-4.6%; P<0.001) and forced expiratory volume in 1 s (-4.6%; P=0.002). The reduced vital capacity was lower in children with the Garchois brace: -1% (P=0.02). Severity of scoliosis and measured volumes were not related.

CONCLUSION

Spinal bracing in children with neuromusclar disease leads to significant respiratory impairment. Assessment of pulmonary function is necessary when a brace is indicated. The Garchois brace might lead to less impairment of respiratory function.

Atrofia muscular espinhal – Apoio ventilatório não invasivo em pediatria

The deterioration of the respiratory function in children suffering from degenerative neuromuscular disease is the main cause of the high mortality rate associated with these diseases. Noninvasive ventilation (NIV) has reduced the morbidity and mortality due to respiratory insufficiency in these children. However, the use of support ventilation in some cases of spinal muscular atrophy (SMA) is still controversial. A retrospective study of 22 patients suffering from SMA who were followed up in the Paediatric Hospital of Coimbra is presented: 7 of type I, 11 of type II, and 4 of type III. In 17 of these cases, non-invasive ventilation by mask was begun, and in 3 of them NIV was applied for prophylactic purposes. The 7 children with SMA type I began NIV when they were 13 months of age on average (3 months-3 years); 5 of them died, between 1 and 15 months after the beginning of the ventilation. Of the 11 children with SMA type II, 8 were submitted to NIV and one died 22 months later. Three of the children in this group began NIV in a prophylactic way, and in all of them a decrease in the thoracic deformity was observed. Of the 4 patients of type III, 2 of them were submitted to non-invasive ventilation. In all of the symptomatic cases, a decrease in the frequency and severity of respiratory infections was observed, after ventilation was started. The respiratory support with NIV may improve the quality of life of children suffering from SMA as well as prolong their life expectancies. In SMA type I, whose clinical manifestations are precocious and whose prognostic is very serious, the application of this support has been debated.

Respiratory capacity course in patients with infantile spinal muscular atrophy

STUDY OBJECTIVES

To describe the clinical and respiratory course in infantile spinal muscular atrophy (SMA) type I, type II, and type III, and to evaluate the respiratory needs for these patients, using noninvasive or tracheostomy ventilation.

DESIGN

Retrospective cohort study.

METHODS

We report 33 patients with SMA true type I (onset before age 3 months), 35 patients with SMA intermediate type I (onset between 3 months and 6 months), 100 patients with SMA type II (onset between 6 months and 18 months), 12 patients with SMA type III (onset after age 18 months). We report the clinical symptoms, respiratory course, and respiratory management: respiratory physiotherapy, periodic hyperinsufflation, nasal nocturnal ventilation (NNV), and tracheostomy. Also, we measured the FVC over several years during childhood and adolescence.

RESULTS

In patients with SMA true type I, 82% of patients died, one third of whom underwent tracheostomy. In patients with SMA intermediate type I, 43% needed NNV, 57% underwent tracheostomy, and 26% died. In patients with SMA type II, 38% needed NNV, 15% underwent tracheostomy, and 4% died. In patients with SMA type III, respiratory impairment was moderate and began during the second decade of life.

CONCLUSION

This data shows the progressively worsening course of restrictive respiratory insufficiency in patients with SMA, and the importance of early respiratory management to limit pulmonary complications and improve the quality of life for these patients.

Genetics and early disturbances of breathing control

Early disturbances in breathing control, including apneas of prematurity and apparently life-threatening events, account for some cases of sudden infant death syndrome and for a rare disorder called congenital central hypoventilation syndrome (CCHS). Data suggesting a genetic basis for CCHS have been obtained. Recently, we found heterozygous de novo mutations of the PHOX2B gene in 18 of 29 individuals with CCHS. Most mutations consisted of five to nine alanine expansions within a 20-residue polyalanine tract, probably resulting from nonhomologous recombination. Other mutations, generally inherited from one of the parents, in the coding regions of genes involved in the endothelin and RET signaling pathways and in the brain-derived-neurotrophic factor (BDNF) gene have been found in a few CCHS patients. Interestingly, all these genes are involved in the development of neural crest cells. Targeted disruption of these genes in mice has provided information on the pathophysiological mechanisms underlying CCHS. Despite the identification of these genes involved in breathing control, none of the genetically engineered mice developed to date replicate the full human CCHS respiratory phenotype. Recent insights into the genetic basis for CCHS may shed light on the genetics of other early disturbances in breathing control, such as apnea of prematurity and sudden infant death syndrome.

Pulmonary function and scoliosis in children with spinal muscular atrophy types II and III

AIMS

The objectives were to evaluate the clinical course of spinal muscular atrophy (SMA) types II and III patients necessitating scoliosis surgery at the National University Hospital, Singapore.

METHODS

A retrospective review of SMA types II and III patients, born over a 10-year period between 1983 and 1992, was conducted.

RESULTS

There were eight patients: four with SMA type II and four with SMA type III. The mean age at scoliosis surgery was 9 years 7 months (range 7 years 6 months-12 years 4 months). The mean preoperative Cobb angle was 65.4 degrees (range 43-90 degrees ) and the mean postoperative Cobb angle was 22.6 degrees (range 12-45 degrees ), with a mean correction of 64.8% (range 47.7-77.8%). The decline in percentage predicted forced vital capacity (FVC) was 7.7% (95% CI: 12.4% to 3.0%) per year preoperatively and this was reduced to 3.8% (95% CI: 5.8% to 1.9%) per year postoperatively. The mean length of preoperative and postoperative lung function follow-up was 6.3 months (range 0.03-31 months) and 44 months (range 0-110 months), respectively.

CONCLUSIONS

This study suggests that pulmonary function in SMA types II and III continues to decline after scoliosis surgery, though the rate of decline is less marked. Overall, the combined results from this study and all other previously published studies are conflicting in regard to the effect of scoliosis surgery on pulmonary function in SMA types II and III, though half of the studies (3 of 6) did demonstrate a continued decline in lung function postoperatively. This decline in pulmonary function despite spinal stabilization is likely secondary to the progressive neuromuscular weakness of the disease.

Initiation of home mechanical ventilation in children with neuromuscular diseases

OBJECTIVE

To determine how often home mechanical ventilation (HMV) is instituted electively in children with respiratory failure from neuromuscular diseases and whether there were opportunities to discuss therapeutic options with patients/families before respiratory failure.

METHODS

Patients with neuromuscular disease (n = 73) requiring HMV (age, 2 months to 24 years) were studied. Whether HMV was initiated nonelectively because of acute respiratory failure or electively before acute respiratory failure, and opportunities for health care providers to discuss therapeutic options with patients/families before acute respiratory failure (hospitalization with pneumonia, clinic visits for preoperative evaluation, pulmonary function testing [PFT] and/or polysomnography [PSG]) were recorded.

RESULTS

HMV was initiated electively in 21% of patients with neuromuscular disease; 69% of the nonelective HMV group had HMV initiated after respiratory failure caused by pneumonia. In the nonelective group, opportunities for discussion of therapeutic options with the patients and families could have occurred before respiratory failure during 111 hospitalizations for pneumonia, 13 preoperative evaluations, 43 abnormal PFTs, and 24 abnormal PSGs.

CONCLUSIONS

Most patients with neuromuscular disease had HMV initiated nonelectively after acute respiratory failure caused by pneumonia. Opportunities for discussing the therapeutic options with patients and families before respiratory failure were missed or ineffective.

Resolution of obstructive sleep apnea syndrome after adenoidectomy in congenital central hypoventilation syndrome

We report on a 2 1/2-year-old boy who is currently ventilated at home by positive pressure ventilation through a nasal mask during the night because of congenital central hypoventilation syndrome (CCHS). Up to age 2 he had developed normally. A reevaluation was performed because of symptoms suggestive of obstructive sleep apnea syndrome (OSAS), including snoring, nocturnal sweating, frequent nighttime awakenings, speech impairment, daytime fatigue, and failure to thrive. A sleep study indicated obstructive apnea episodes lasting up to 40 s and arterial desaturations below 50% during spontaneous sleep. During mechanical ventilation snoring persisted, and capillary PCO2 rose to 60 mm Hg. Partial upper airway obstruction, leaking around the mask, and arousal movements developed on passive flexion of the neck to 20 degrees. After adenoidectomy, symptoms of OSAS resolved. There were no more obstructive apneas during spontaneous sleep, but obstructive apneas could be provoked by neck flexion to 20 degrees. During ventilation, neck flexion of 20 degrees was tolerated, but a 40 degrees flexion led to partial obstruction. In CCHS patients, the problem of upper airway obstruction is rarely noted because most patients are ventilated through a permanent tracheostomy. Today, noninvasive ventilation strategies are becoming more common. Reduced activity of upper airway muscles and impaired reflex mechanisms could lead to upper airway obstruction during face mask positive pressure ventilation in children with CCHS. Enlarged adenoids worsened this problem in our patient, leading to insufficient ventilation and OSAS. Adenoidectomy resolved symptoms of OSAS and enabled successful nasal mask ventilation. Close follow-up of the patient avoided hypoxia and sequelae from OSAS such as pulmonary hypertension.

Congenital central hypoventilation syndrome: an update

Awareness of the existence of CCHS has led to increasingly frequent reports of such patients from all over the world. However, the exact pathophysiologic mechanisms underlying the clinical manifestations of this congenital disease entity remain unknown. For the respiratory physiologist, CCHS can be viewed as an experiment of nature that provides an important and unique window into central cardiorespiratory regulation. For the pediatrician, CCHS children represent an unique clinical challenge in coordinating the diagnostic and therapeutic procedures required to enhance the patients' quality of life.