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

Obstructive Apneas in a Mouse Model of Congenital Central Hypoventilation Syndrome

Rationale: Congenital central hypoventilation syndrome (CCHS) is characterized by life-threatening sleep hypoventilation and is caused by PHOX2B gene mutations, most frequently the PHOX2B^27Ala/+ mutation, with patients requiring lifelong ventilatory support. It is unclear whether obstructive apneas are part of the syndrome. Objectives: To determine if Phox2b^27Ala/+ mice, which present the main symptoms of CCHS and die within hours after birth, also express obstructive apneas, and to investigate potential underlying mechanisms. Methods: Apneas were classified as central, obstructive, or mixed by using a novel system combining pneumotachography and laser detection of abdominal movement immediately after birth. Several respiratory nuclei involved in airway patency were examined by immunohistochemistry and electrophysiology in brainstem-spinal cord preparations. Measurements and Main Results: The median (interquartile range) of obstructive apnea frequency was 2.3 (1.5-3.3)/min in Phox2b^27Ala/+ pups versus 0.6 (0.4-1.0)/min in wild types (P < 0.0001). Obstructive apnea duration was 2.7 seconds (2.3-3.9) in Phox2b^27Ala/+ pups versus 1.7 seconds (1.1-1.9) in wild types (P < 0.0001). Central and mixed apneas presented similar significant differences. In Phox2b^27Ala/+ preparations, the hypoglossal nucleus had fewer (P < 0.05) and smaller (P < 0.01) neurons, compared with wild-type preparations. Importantly, coordination of phrenic and hypoglossal motor activities was disrupted, as evidenced by the longer and variable delay of hypoglossal activity with respect to phrenic activity onset (P < 0.001). Conclusions: The Phox2b^27Ala/+ mutation predisposed pups not only to hypoventilation and central apneas, but also to obstructive and mixed apneas, likely because of hypoglossal dysgenesis. These results thus demand attention toward obstructive events in infants with CCHS.

Airway obstruction in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is the failure of the autonomic system to control adequate ventilation while asleep with preserved ventilatory response while awake. We report a case of a patient with CCHS who presented with intrathoracic and extrathoracic airway obstruction after tracheostomy tube decannulation and phrenic nerve pacer placement. Nocturnal polysomnography (NPSG) revealed hypoxia, hypercapnia and obstructive sleep apnoea, which required bilevel positive airway pressure titration. Airway endoscopy demonstrated tracheomalacia and paretic true vocal cords in the paramedian position during diaphragmatic pacing. Laryngeal electromyography demonstrated muscular electrical impulses that correlated with diaphragmatic pacer settings. Thus, we surmise that the patient's upper and lower airway obstruction was secondary to diaphragmatic pacer activity. Thorough airway evaluation, including NPSG and endoscopy, may help identify the side effects of diaphragmatic pacing, such as airway obstruction, in patients with CCHS.

OSAS in children

BACKGROUND

Major risk factors for obstructive sleep apnea syndrome (OSAS) in children include adenotonsillar hypertrophy, neuromuscular disease and syndromes such as Down's or Pierre-Robin's syndrome; there is currently no consensus concerning diagnosis and therapy.

METHODS

The study analyses 40 children, aged 2 through 14 years, with macroscopic tonsillar hypertrophy (without recurrent tonsillitis but with OSAS) underwent adenotonsillectomy. Parents were invited to indicate the intensity of their children's symptomatology using a subjective evaluation scale, each patient underwent cephalometric analysis and polysomnography (PSG) before and after surgery.

RESULTS

The subjective scale of symptoms passed from 3.01 before treatment to 0.42 after treatment, rhinomanometry, passed from 3.456 to 0.896 p after 1 month the surgical operation (P<0.05). The polysomnography showed a resolution of the number of obstructive events in 37 patients and a reduction in 3 patients and RDI index fell from a mean of 26.9-2.6 after therapy. The average of oxygen saturation changed from 79% before treatment to 95% after therapy.

CONCLUSIONS

Adenotonsillectomy plays a major role in the treatment of OSAS.

Novel insights into congenital hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is a rare and unique condition that may prompt unparalleled approaches to the discovery of genes involved in development of cardiorespiratory control and gas exchange homeostasis. Its higher risk of recurrence in families and its association with Hirschsprung's disease suggest that an underlying genetic mechanism is involved. However, screening for mutations of the receptor tyrosine kinase RET and endothelin 3 has revealed only occasional patients affected by these mutations, therefore suggesting that CCHS may result from disruption of more than a single gene. In recent years, three principal issues have become apparent: 1) the autonomic nervous system is involved universally in CCHS cases, albeit to a varying extent; 2) the use of novel functional imaging approaches incorporating refined stimulus paradigms may provide essential research and clinical insights into localization and assessment of neural sites underlying the phenotypic expression of this syndrome; and 3) efforts to transition patients' nocturnal respiratory support to a noninvasive ventilatory modality should be critically evaluated and pursued, when appropriate, to improve the quality of life for patients and families.