Congenital central hypoventilation syndrome in children

Home continuous positive airway pressure therapy in infants: a single-center experience

STUDY OBJECTIVES

There are limited data on indications and outcomes of home continuous positive airway pressure (CPAP) therapy in the first year of life. We aimed to analyze the clinical, demographic, and polysomnographic characteristics of a cohort of children initiated on home CPAP for treatment of sleep-disordered breathing and as respiratory support in the first year of life.

METHODS

Children started on CPAP in the first year of life at the Queensland Children's Hospital were retrospectively evaluated for clinical and demographic parameters, underlying diagnoses, respiratory support, airway surgical intervention, and polysomnography results at baseline and on CPAP.

RESULTS

Twenty-nine infants (median age [interquartile range] at CPAP initiation, 182 days [126-265.5 days]) were included. The underlying etiology included Trisomy 21 (n = 6), craniofacial syndromes (n = 5), hypotonia (n = 8; 5 with noncraniofacial syndrome), airway malacia (n = 5), skeletal dysplasia (n = 2), nonsyndromic upper airway obstruction (n = 2), and chronic neonatal lung disease (n = 1). The median (interquartile range) obstructive apnea-hypopnea index was 14 events/h (6.2-31 events/h) at CPAP initiation, which improved on CPAP to 3.4 events/h (1.4-6.4 events/h). The median (interquartile range) transcutaneous CO2 max remained unchanged on CPAP (56.6 mm Hg [49-66.5 mm Hg] pre-CPAP vs 54.9 mm Hg [47-62 mm Hg] on CPAP). Fifteen children needed surgical airway intervention (11 pre-CPAP and 4 post-CPAP). CPAP therapy could be successfully stopped in 9 children, 2 children needed tracheostomy, and 1 child died during the follow-up period.

CONCLUSIONS

Home CPAP as respiratory support is an effective long-term therapy in infancy, and these patients can be weaned from CPAP therapy even if it was initiated early. Prospective studies with predefined criteria for CPAP initiation and cessation would help ascertain long-term outcomes in this poorly researched group.

CITATION

Joshi SS, Sivapalan D, Leclerc M-J, Kapur N. Home continuous positive airway pressure therapy in infants: a single-center experience. J Clin Sleep Med. 2023;19(3):473-477.

Dyspnea

The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.

THE ESTIMATION OF RESPIRATION RATE BASED ON THE AMPLIFICATION OF RESPIRATION MOTION IN VIDEO

Standard instrument for the clinical diagnosis of sleep apnea is large and based on invasive method, which is not comfortable and not suitable for daily inspection. A video-based measurement method for the respiration rate (RR) is therefore proposed, which is meaningful to the home diagnosis of sleep apnea. We proposed a novel method for the visualization and calculation of RR from a video containing a sleeping person. The video was decomposed by spatio-temporal Laplacian pyramid method into multiresolution image sequences, which were filtered by an infinite-impulse-response bandpass filter to extract the respiration movement in the video. The respiration movement was amplified, and fused into the original video. On the other hand, the signal intensity of the filtering results was compared between layers of Laplacian pyramid to identify the layer with the strongest movement caused by respiration. A morphological calculation was conducted on the image reshaped from the filtered results in this layer, to find the region of interest (ROI) with most significant movement of respiration. The image intensity in the ROI was spatially averaged into a one-dimensional signal, of which the frequency domain was analyzed to obtain RR. The ROI and the calculation results for RR were visualized on the video with enhanced respiration movement. Ten videos lasting 30–60[Formula: see text]s were recorded by a general webcam. The respiration movement of the subject was successfully extracted and amplified, no matter the posture was supine or side lying. The thoracic and abdominal parts were generally identified as ROI in all postures. RR was calculated by the frequency domain analysis for the averaged image intensity in ROI with the error no more than 1 time per minute, and further, as well as ROI, was fused into the amplified video. The region of respiration movement and RR is calculated by the noncontact method, and well visualized in a video. The method provides a novel screening tool for the population suspected of sleep apnea, and is meaningful to the home diagnosis of sleep illness.

Congenital central hypoventilation syndrome in neonates: report of fourteen new cases and a review of the literature

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is a rare autosomal dominant disorder caused by pathogenic variants in paired-like homeobox 2B (PHOX2B) gene. Characteristics of neonatal-onset CCHS cases have not been well assessed. The aim of this study is to expand current knowledge of clinical and genetic features of neonates with CCHS and provide data on the genotype-phenotype correlation.

METHODS

We made a retrospective analysis of 14 neonates carrying PHOX2B pathogenic variants from 2014 to 2019 and we reviewed previously published neonatal-onset cases. Clinical and genetic data were analyzed. Moreover, genotype-phenotype correlation analysis was performed.

RESULTS

We identified a total of 60 neonatal-onset CCHS cases (35 males and 25 females) including 14 novel cases from our local cohort. Nearly 20% (18.2%) of the patients were born prematurely. Nearly half (46.2%) of the patients had abnormal family history. Polyhydramnios was observed in 21.3% (10/47) of the patients. About 90% of the patients manifested symptoms of hypoventilation in the first week of life. Fourteen patients (23.3%) were classified as mild-CCHS and the rest were severe-CCHS. Gastrointestinal manifestations were observed in 71.7% of the patients. Approximately twofold more males than females were affected by Hirschprung disease (HSCR)/variant HSCR (75.8% vs. 35%, P=0.003). Neural crest tumor occurred in 9.1% (4/44) patients. Half patients had polyalanine repeat expansion mutations (PARMs) in PHOX2B (seven with 25 PARM, nine with 26 PARM, twelve with 27 PARM, one with 28 PARM and one with 31 PARM) and the other half patients had 23 distinct non-polyalanine repeat expansion mutations (NPARMs) with one novel pathogenic variant (c.684dup). The prevalence of HSCR and mild-CCHS among patients with NPARMs was significantly greater than that of the patients with PARMs.

CONCLUSIONS

This report provides a large cohort of neonatal-onset CCHS cases. The results indicate that severe hypoventilation and HSCR are frequently observed in this group. NPARMs accounted for half of the cohort with some genotypes tend to be associated with mild phenotype. Molecular testing in neonates with suspicion of CCHS and genetic counseling for CCHS families are highly recommended.

Sleep-disordered breathing and nocturnal hypoventilation in children with the MECP2 duplication syndrome: A case series and review of the literature

There is limited knowledge on the occurrence of respiratory manifestations and sleep-disordered breathing in particular in children with the MECP2 duplication syndrome. Although sleep-disordered breathing and nocturnal hypoventilation are currently not cited as an important symptom in these children, we present three cases who all had an abnormal breathing during sleep. In view of the consequences associated with sleep apnea and hypoventilation, we advise to perform a polysomnography in children with MECP2 duplication. Different treatment modalities (ENT surgery, CPAP, and non-invasive ventilation) can be applied to successfully treat these conditions.

Noninvasive ventilation in a young infant with congenital central hypoventilation and 7-year follow-up

INTRODUCTION

Congenital central hypoventilation syndrome (CCHS) is a rare disorder characterized by alveolar hypoventilation and autonomic system dysregulation secondary to mutations of the PHOX2B gene. Treatment consists of assisted ventilation using positive-pressure ventilators via tracheostomy, bi-level positive airway pressure (BPAP) via a noninvasive interface, negative-pressure ventilators, or diaphragm pacing. The long-term use of BPAP in younger children at home has been less frequently reported.

CASE PRESENTATION

We present a case of a 2-month-old infant with CCHS who was successfully managed by BPAP without the need for tracheostomy and followed up for 7 years.

CONCLUSION

CCHS is a rare disease that manifests as nocturnal desaturation and carbon dioxide retention in early life. Noninvasive ventilation can be successfully used in young infants via an appropriate mask.

Congenital central hypoventilation syndrome and Hirschsprung disease: A retrospective review of the French National Registry Center on 33 cases

AIM OF THE STUDY

Congenital Central Hypoventilation Syndrome (CCHS) is a rare affection associated to Hirschsprung disease (HD) in 20% of the cases. Using the French CCHS registry, we described the population of patients suffering from both CCHS and HD reporting the outcome on these patients.

METHODS

Medical records were reviewed. Epidemiological, clinical, histological and genetic data were analyzed and extracted from the national French registry data.

RESULTS

33 patients had CCHS and HD. Thirty percent had a severe form of CCHS (Death owing to CCHS or 24/24 ventilation beyond 1 year old). Fifty four percent required tracheotomy. HD's pathologic segment was classic (Rectosigmoid and left colic form) in 20% and long (Above the splenic flexure) in 80%. Twenty four percent were treated with daily irrigation, 21% had colostomy without undergoing pullthrough, and 55% underwent optimal treatment (pull through). We failed to demonstrate a correlation between severity of CCHS and HD's length. The rate of mortality was 57% and was higher in the long HD group (p = 0.0005). Fourteen patients were still alive, aged 1 to 31 years old. Ninety two percent were weaned off the 24/24 ventilation. Regarding the intestinal function, 38% presented with soiling and 30% with chronic diarrhea. Hundred percent had CCHS follow-up while only 35% had no surgical follow-up in regard to the HD.

CONCLUSIONS

This is the largest study regarding the CCHS / HD association and its long-term followup. Mortality is high demonstrating that a multidisciplinary follow-up on respiratory and intestinal function is necessary to improve outcome. Level III study.

Síndrome de Ondina (hipoventilación central congénita), una amenaza contra la vida al dormir

El síndrome de Ondina, o síndrome de hipoventilación central congénita, es una enfermedad neurológica rara, donde hay fracaso en el control de la ventilación en el sistema nervioso central, llevando a la hipoxia e hipercapnia que pueden generar problemas del neurodesarrollo y, finalmente, ocasionar la muerte. Puede representar una situación muy dolorosa para los familiares de los pacientes que la padecen, despertando sentimientos difíciles de enfrentar, es por esto que es importante tener conocimiento acerca de esta condición para así impactar en la disminución de su incidencia.

Congenital Central Hypoventilation Syndrome: A Case-Based Learning Opportunity for Neonatal Clinicians

Congenital central hypoventilation syndrome (CCHS) is a rare and sporadic neurocristopathy characterized by alveolar hypoventilation and autonomic nervous system dysfunction. CCHS manifests quickly after birth, initially as respiratory distress. Mortality risk is estimated at 38 percent, with a median age of death of three months of age. A timely and accurate diagnosis is critical. Genetic testing for PHOX2B gene mutations is necessary to confirm the diagnosis; however, laboratory turnaround time often imposes an additional 7-14-day waiting period on an often anxious family. Neonatal clinicians should recognize that families require disease-specific education, emotional support, and time to rehearse daily caregiving in preparation for discharge. Therefore, this article presents the key clinical, pathophysiologic, and diagnostic factors, as well as a discussion of discharge needs. A case report of an infant, born to parents with no known history of CCHS, is included as a case-based learning opportunity for readers.

Inhalational Anesthetics Induce Neuronal Protein Aggregation and Affect ER Trafficking

Anesthetic agents have been implicated in the causation of neurological and cognitive deficits after surgery, the exacerbation of chronic neurodegenerative disease, and were recently reported to promote the onset of the neurologic respiratory disease Congenital Central Hypoventilation Syndrome (CCHS), related to misfolding of the transcription factor Phox2B. To study how anesthetic agents could affect neuronal function through alterations to protein folding, we created neuronal cell models emulating the graded disease severity of CCHS. We found that the gas anesthetic isoflurane and the opiate morphine potentiated aggregation and mislocalization of Phox2B variants, similar to that seen in CCHS, and observed transcript and protein level changes consistent with activation of the endoplasmic reticulum (ER) unfolded protein response. Attenuation of ER stress pathways did not result in a correction of Phox2B misfolding, indicating a primary effect of isoflurane on protein structure. We also observed that isoflurane hindered the folding and activity of proteins that rely heavily on ER function, like the CFTR channel. Our results show how anesthetic drugs can alter protein folding and induce ER stress, indicating a mechanism by which these agents may affect neuronal function after surgery.

Current Perspectives for the use of Gonane Progesteronergic Drugs in the Treatment of Central Hypoventilation Syndromes

BACKGROUND

Central alveolar hypoventilation syndromes (CHS) encompass neurorespiratory diseases resulting from congenital or acquired neurological disorders. Hypercapnia, acidosis, and hypoxemia resulting from CHS negatively affect physiological functions and can be lifethreatening. To date, the absence of pharmacological treatment implies that the patients must receive assisted ventilation throughout their lives.

OBJECTIVE

To highlight the relevance of determining conditions in which using gonane synthetic progestins could be of potential clinical interest for the treatment of CHS.

METHODS

The mechanisms by which gonanes modulate the respiratory drive were put into the context of those established for natural progesterone and other synthetic progestins.

RESULTS

The clinical benefits of synthetic progestins to treat respiratory diseases are mixed with either positive outcomes or no improvement. A benefit for CHS patients has only recently been proposed. We incidentally observed restoration of CO2 chemosensitivity, the functional deficit of this disease, in two adult CHS women by desogestrel, a gonane progestin, used for contraception. This effect was not observed by another group, studying a single patient. These contradictory findings are probably due to the complex nature of the action of desogestrel on breathing and led us to carry out mechanistic studies in rodents. Our results show that desogestrel influences the respiratory command by modulating the GABAA and NMDA signaling in the respiratory network, medullary serotoninergic systems, and supramedullary areas.

CONCLUSION

Gonanes show promise for improving ventilation of CHS patients, although the conditions of their use need to be better understood.

[Non-invasive and invasive out of hospital ventilation in chronic respiratory failure : Consensus report of the working group on ventilation and intensive care medicine of the Austrian Society of Pneumology]

The current consensus report was compiled under the patronage of the Austrian Society of Pneumology (Österreichischen Gesellschaft für Pneumologie, ÖGP) with the intention of providing practical guidelines for out-of-hospital ventilation that are in accordance with specific Austrian framework parameters and legal foundations. The guidelines are oriented toward a 2004 consensus ÖGP recommendation concerning the setup of long-term ventilated patients and the 2010 German Respiratory Society S2 guidelines on noninvasive and invasive ventilation of chronic respiratory insufficiency, adapted to national experiences and updated according to recent literature. In 11 chapters, the initiation, adjustment, and monitoring of out-of-hospital ventilation is described, as is the technical equipment and airway access. Additionally, the different indications-such as chronic obstructive pulmonary diseases, thoracic restrictive and neuromuscular diseases, obesity hypoventilation syndrome, and pediatric diseases-are discussed. Furthermore, the respiratory physiotherapy of adults and children on invasive and noninvasive long-term ventilation is addressed in detail.

Perspectives on neonatal and infant tracheostomy

Neonates and infants may need a tracheostomy for many different reasons, ranging from airway obstruction to a requirement for long term mechanical ventilator support. Here, we present the pathophysiology of the many congenital and acquired conditions that might be managed with a tracheostomy. Decisions about tracheostomy demand consideration of not only the benefits, but also the potential side-effects, which may differ in the short and long term and may be attributable to underlying conditions as well as the tracheostomy. Evaluation of potential advantages of tracheostomy will influence decisions about optimal timing. In many cases, an infant may 'graduate' from dependence on a tracheostomy and resume a natural airway, although some will require reconstructive airway surgery.

Sleep disordered breathing at the extremes of age: infancy

EDUCATIONAL AIMS

The reader will be able to: Understand normal sleep patterns in infancyAppreciate disorders of breathing in infancyAppreciate disorders of respiratory control. Normal sleep in infancy is a time of change with alterations in sleep architecture, sleep duration, sleep patterns and respiratory control as an infant grows older. Interactions between sleep and respiration are key to the mechanisms by which infants are vulnerable to sleep disordered breathing. This review discusses normal sleep in infancy, as well as normal sleep breathing in infancy. Sleep disordered breathing (obstructive and central) as well as disorders of ventilatory control and infant causes of hypoventilation are all reviewed in detail.

Home Mechanical Ventilation in Children

The number of children dependent on home mechanical ventilation has been reported to be increasing in many countries around the world. Home mechanical ventilation has been well accepted as a standard treatment of children with chronic respiratory failure. Some children may need mechanical ventilation as a lifelong therapy. To send mechanically ventilated children back home may be more difficult than adults. However, relatively better outcomes have been demonstrated in children. Children could be safely ventilated at home if they are selected and managed properly. Conditions requiring home ventilation include increased respiratory load from airway or lung pathologies, ventilatory muscle weakness and failure of neurologic control of ventilation. Home mechanical ventilation should be considered when the patient develops progressive respiratory failure or intractable failure to wean mechanical ventilation. Polysomnography or overnight pulse oximetry plus capnometry are used to detect nocturnal hypoventilation in early stage of respiratory failure. Ventilator strategy including non-invasive and invasive approach should be individualized for each patient. The author strongly believes that parents and family members are able to take care of their child at home if they are trained and educated effectively. A good team work with dedicated members is the key factor of success.

[Congenital central alveolar hypoventilation syndrome]

BACKGROUND

Congenital central alveolar hypoventilation syndrome (CCAHS) is a rare sleep-related breathing disorder. Although increasingly frequently diagnosed in sleep clinics and pediatric pulmonology services, its epidemiology is not known. There are about 300 reported cases reported in the literature with an incidence of 1 case per 200,000 live births. CCAHS is characterized by alveolar hypoventilation that occurs or worsens during sleep and is secondary to a reduction/absence of the ventilatory response to hypercapnia and/or hypoxemia. In 90% of the cases it is due to a PARM-type mutation of the PHOX2B gene. Treatment includes mechanical ventilation and diaphragmatic pacemaker. If therapy is not initiated promptly the patient can evolve to chronic respiratory failure, pulmonary hypertension, cor pulmonale and death.

CASE REPORTS

In this paper we present three cases of CCAHS diagnosed, treated and followed up at the Sleep Disorders Clinic of the National Institute of Respiratory Diseases in Mexico.

CONCLUSIONS

Early diagnosis is important to initiate ventilatory support so as to prevent any complications and to reduce mortality.

Congenital hypoventilation syndrome and Hirschsprung's disease - Haddad syndrome: A neonatal case presentation

Congenital central hypoventilation syndrome (CCHS) is an uncommon cause of apnea in the newborn characterized by the occurrence of apnea predominantly during sleep. Haddad syndrome is CCHS with Hirschsprung's disease. We report a newborn with Haddad syndrome that had a family history of spinal muscular atrophy and discuss aspects of CCHS and important considerations in the evaluation of apnea in the term newborn.

Proceedings of the fourth international conference on central hypoventilation

Central hypoventilation syndromes (CHS) are rare diseases of central autonomic respiratory control associated with autonomous nervous dysfunction. Severe central hypoventilation is the hallmark and the most life-threatening feature. CHS is a group of not-fully defined disorders. Congenital CHS (CCHS) (ORPHA661) is clinically and genetically well-characterized, with the disease-causing gene identified in 2003. CCHS presents at birth in most cases, and associated with Hirschsprung's disease (ORPHA99803) and neural crest tumours in 20% and 5% of cases, respectively. The incidence of CCHS is estimated to be 1 of 200,000 live births in France, yet remains unknown for the rest of the world. In contrast, late-onset CHS includes a group of not yet fully delineated diseases. Overlap with CCHS is likely, as a subset of patients harbours PHOX2B mutations. Another subset of patients present with associated hypothalamic dysfunction. The number of these patients is unknown (less than 60 cases reported worldwide). Treatment of CHS is palliative using advanced techniques of ventilation support during lifetime. Research is ongoing to better understand physiopathological mechanisms and identify potential treatment pathways.The Fourth International Conference on Central Hypoventilation was organised in Warsaw, Poland, April 13-15, 2012, under the patronage of the European Agency for Health and Consumers and Public Health European Agency of European Community. The conference provided a state-of-the-art update of knowledge on all the genetic, molecular, cellular, and clinical aspects of these rare diseases.

An assistive device for congenital central hypoventilation syndrome outpatients during sleep

Congenital Central Hypoventilation Syndrome is a genetic disease characterized by alveolar hypoventilation and autonomic dysregulation. Patients have hypoventilations, especially during sleep, conditioning hypercapnia which can lead to neurological damage and death. They therefore need mechanical ventilators, that provide sufficient gas exchange, and pulse-oximeters that monitor oxy-hemoglobin blood concentration. Due to the restrictions regarding domiciliary assistive devices, the presence of a caregiver is required all night long. Currently, the only alarm systems available are the ones integrated in the ventilators and monitoring systems. During the night, multiple false alarms may occur, interrupting the sleep and causing anxiety. In this work we describe an assistive device that acquires real-time data from a pulse-oximeter, provides a multisensory stimulation if oxygen saturation falls under a certain threshold, and wakes up the patient if the hypoxia is severe. Tests on healthy subjects have shown that the device guarantees rapid awakenings, with a stimulator-dependent efficacy, and that it does not affect sleep efficiency. The purpose of the device is to determine a gentle awakening if mild hypoxia conditions persist, and to assure rapid awakening when a severe hypoxia occurs, reducing false alarms, improving the quality of sleep and increasing the self-sufficiency of the patients.

Congenital central hypoventilation syndrome; safety of early transition to non-invasive ventilation

Congenital central hypoventilation syndrome (CCHS) is a rare disorder of autonomic dysregulation, characterized by alveolar hypoventilation especially during sleep. As a result, lifelong ventilatory assistance is necessary in these patients. Many infants and children initially require positive pressure ventilation via tracheostomy for support. Associated complications and psychosocial pressure may prompt early transition to non-invasive ventilation. We present the details of a patient with CCHS who successfully transitioned from tracheostomy to bilevel positive airway pressure ventilation at an early age of 3 years.

Genetic diseases: congenital central hypoventilation, Rett, and Prader-Willi syndromes

The present review summarizes current knowledge on three rare genetic disorders of respiratory control, congenital central hypoventilation syndrome (CCHS), Rett syndrome (RTT), and Prader-Willi syndrome (PWS). CCHS is characterized by lack of ventilatory chemosensitivity caused by PHOX2B gene abnormalities consisting mainly of alanine expansions. RTT is associated with episodes of tachypneic and irregular breathing intermixed with breathholds and apneas and is caused by mutations in the X-linked MECP2 gene encoding methyl-CpG-binding protein. PWS manifests as sleep-disordered breathing with apneas and episodes of hypoventilation and is caused by the loss of a group of paternally inherited genes on chromosome 15. CCHS is the most specific disorder of respiratory control, whereas the breathing disorders in RTT and PWS are components of a more general developmental disorder. The main clinical features of these three disorders are reviewed with special emphasis on the associated brain abnormalities. In all three syndromes, disease-causing genetic defects have been identified, allowing the development of genetically engineered mouse models. New directions for future therapies based on these models or, in some cases, on clinical experience are delineated. Studies of CCHS, RTT, and PWS extend our knowledge of the molecular and cellular aspects of respiratory rhythm generation and suggest possible pharmacological approaches to respiratory control disorders. This knowledge is relevant for the clinical management of many respiratory disorders that are far more prevalent than the rare diseases discussed here.

Genetic and immunologic aspects of sleep and sleep disorders

The study of genetics is providing new and exciting insights into the pathogenesis, diagnosis, and treatment of disease. Both normal sleep and several types of sleep disturbances have been found to have significant genetic influences, as have traits of normal sleep, such as those evident in EEG patterns and the circadian sleep-wake cycle. The circadian sleep-wake cycle is based on a complex feedback loop of genetic transcription over a 24-h cycle. Restless legs syndrome (RLS) and periodic limb movements in sleep (PLMS) have familial aggregation, and several genes have a strong association with them. Recent genome-wide association studies have identified single nucleotide polymorphisms linked to RLS/PLMS, although none has a definite functional correlation. Narcolepsy/cataplexy are associated with HLA DQB1*0602 and a T-cell receptor α locus, although functional correlations have not been evident. Obstructive sleep apnea is a complex disorder involving multiple traits, such as anatomy of the oropharynx, ventilatory control, and traits associated with obesity. Although there is clear evidence of familial aggregation in the obstructive sleep apnea syndrome, no specific gene or locus has been identified for it. Angiotensin-converting enzyme has been proposed as a risk variant, but evidence is weak. Fatal familial insomnia and advanced sleep phase syndrome are sleep disorders with a definite genetic basis.

Sleep-disordered breathing

PURPOSE OF REVIEW

This article introduces readers to the clinical presentation, diagnosis, and treatment of sleep-disordered breathing and reviews the associated risk factors and health consequences.

RECENT FINDINGS

Sleep-disordered breathing is associated with significant impairments in daytime alertness and cognitive function as well as adverse health outcomes. The initial treatment of choice is positive airway pressure. Improvements in technology and mask delivery systems have helped to make this treatment more comfortable and convenient for many patients.

SUMMARY

Sleep-disordered breathing, particularly in the form of obstructive sleep apnea, is highly prevalent in the general population and has important implications for neurology patients. Sleep-disordered breathing is characterized by repetitive periods of cessation in breathing, termed apneas, or reductions in the amplitude of a breath, known as hypopneas, that occur during sleep. These events are frequently associated with fragmentation of sleep, declines in oxygen saturation, and sympathetic nervous system activation with heart rate and blood pressure elevation. Obstructive sleep apnea, which represents cessation of airflow, develops because of factors such as anatomic obstruction of the upper airway related to obesity, excess tissue bulk in the pharynx, and changes in muscle tone and nerve activity during sleep. Central sleep apnea represents cessation of airflow along with absence or significant reduction in respiratory effort during sleep and is more commonly found in the setting of congestive heart failure, neurologic disorders, or cardiopulmonary disease.

Brain-derived neurotrophic factor interacts with astrocytes and neurons to control respiration

Respiratory rhythm is generated and modulated in the brainstem. Neuronal involvement in respiratory control and rhythmogenesis is now clearly established. However, glial cells have also been shown to modulate the activity of brainstem respiratory groups. Although the potential involvement of other glial cell type(s) cannot be excluded, astrocytes are clearly involved in this modulation. In parallel, brain-derived neurotrophic factor (BDNF) also modulates respiratory rhythm. The currently available data on the respective roles of astrocytes and BDNF in respiratory control and rhythmogenesis lead us to hypothesize that there is BDNF-mediated control of the communication between neurons and astrocytes in the maintenance of a proper neuronal network capable of generating a stable respiratory rhythm. According to this hypothesis, progression of Rett syndrome, an autism spectrum disease with disordered breathing, can be stabilized in mouse models by re-expressing the normal gene pattern in astrocytes or microglia, as well as by stimulating the BDNF signaling pathway. These results illustrate how the signaling mechanisms by which glia exerts its effects in brainstem respiratory groups is of great interest for pathologies associated with neurological respiratory disorders.

Congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is characterized by hypoventilation during sleep and impaired ventilatory responses to hypercapnia and hypoxemia. Most cases are sporadic and caused by de novo PHOX2B gene mutations, which are usually polyalanine repeat expansions. Physiological and neuroanatomical studies of genetically engineered mice and analyses of cellular responses to mutated Phox2b have shed light on the pathophysiological mechanisms of CCHS. Findings in Phox2b(27Ala/+) knock-in mice consisted of unstable breathing with apneas, absence of the ventilatory response to hypercapnia, death within a few hours after birth, and absence of the retrotrapezoid nucleus (RTN). Conditional mouse mutants in which Phox2b(27Ala) was targeted to the RTN also lacked the ventilatory response to hypercapnia at birth but survived to adulthood and developed a partial hypercapnia response. The therapeutic effects of desogestrel are being evaluated in clinical trials, and recent analyses of cellular responses to polyAla Phox2b aggregates have suggested new pharmacological approaches designed to counteract the toxic effects of mutated Phox2b.