Central hypoventilation syndrome (CHS) is a rare disorder, which can be both congenital and acquired. Congenital central hypoventilation syndrome (CCHS) is caused by chromosomal mutations in the PHOX2B gene on chromosome 4p12. The non-congenital or acquired form of CHS may be due to brain stem tumour, infarct, or edema. As the acquired form of this disease is quite rare the main focus of this article will be the congenital form of central hypoventilation syndrome.
The main characteristic of CCHS disease is small tidal volumes and monotonous respiratory rates while awake and asleep with more profound alveolar hypoventilation during sleep. Due to hypoventilation these patients develop hypercapnia and hypoxemia but lack the normal ventilatory responses to overcome these conditions while asleep. However, while awake they do have the ability to consciously alter the rate and depth of breathing. While sleeping, these children will have shallow respirations interspersed with periods of apnoea most commonly during non-REM sleep.
CCHS is a lifelong condition and will require some form of ventilatory support throughout life either positive pressure ventilation via tracheostomy or nasal mask. Other forms of long-term management include negative pressure ventilation and diaphragmatic pacing. CCHS usually manifests itself in the new born period with episodes of cyanosis and apnea, and most infants will require mechanical ventilation immediately after birth. CCHS can also present in later infancy, childhood, and even adulthood is termed as Late Onset CCHS (LO-CCHS).
The diagnosis of LO-CCHS should be considered if there is hypoventilation, cyanosis or seizures after administration of CNS depressants or anaesthetics, pulmonary infection and treatment of obstructive sleep apnoea. LO-CCHS reflects the variable penetrance of the PHOX2B mutations. As the PHOX2B gene plays a role in neural crest cell migration this disease is also linked with other neurocristopathies such as Hirschsprung disease caused by an absence of segmental colonic ganglia. Presence of Hirschsprung disease occurs in 20% of patients with CCHS and has been termed as Haddad syndrome. In addition CCHS may also be associated with tumours of the neural crest and a number of symptoms due to autonomic nervous system dysfunction (ANSD). These include heart rate variability and transient abrupt asystoles, decreased pupillary light response, esophageal dysmotility, breath holding spells, reduced body temperature, sporadic profuse sweating and lack of physiological responses to the challenges of exercise and environmental stressors.