Congenital Central Hypoventilation Syndrome (CCHS)

I. Introduction & Definition

• Synonym: "Ondine’s Curse."
• Definition: A rare, life-threatening disorder of the autonomic nervous system characterized by alveolar hypoventilation resulting from a failure of autonomic respiratory control.
• Key Feature: Hypoventilation is most severe during non-REM sleep, though severe cases affect awake breathing.
• Incidence: Rare (1 in 200,000 live births).

II. Etiopathogenesis (Genetics)

• Gene: PHOX2B gene on Chromosome 4p12.
• Mutation:
  • Polyalanine Repeat Expansion Mutation (PARM): 90% of cases. The number of repeats (20/24 to 20/33) correlates with disease severity.
  • Non-PARM: Missense/nonsense mutations (associated with more severe autonomic dysfunction and tumors).
• Inheritance: Autosomal Dominant (mostly de novo mutations).

III. Clinical Features

1. Respiratory:
   • Presentation in Newborns: Recurrent apnea, cyanosis, or respiratory failure immediately after birth, especially during sleep.
   • Breathing Pattern: Shallow breathing (low tidal volume) + monotonous rate.
   • Awake State: Usually normal ventilation (in milder cases) but blunted response to hypercapnia ($C{O}_2$) and hypoxia.
2. Autonomic Dysregulation (ANS Dysfunction):
   • Temperature instability, profuse sweating, arrhythmias (sinus pauses), reduced pupillary light response.
3. Associations:
   • Haddad Syndrome: CCHS + Hirschsprung Disease (15–20% of cases).
   • Neural Crest Tumors: Neuroblastoma or Ganglioneuroma (requires surveillance).

IV. Diagnosis

Diagnosis is one of exclusion followed by genetic confirmation.

1. Clinical Criteria: Persistent hypoventilation ($PaC{O}_2$ >60 mmHg) during sleep without primary lung, cardiac, or neuromuscular disease.
2. Polysomnography (Sleep Study): Shows severe hypoventilation/apnea with absence of arousal despite hypercapnia.
3. Genetic Testing (Gold Standard): Detection of PHOX2B mutation confirms diagnosis.

V. Management

There is no cure; management is supportive and lifelong.

1. Ventilatory Support (Crucial):
   • Tracheostomy + Positive Pressure Ventilation: Gold standard for infants/young children to ensure safety during sleep.
   • Non-Invasive Ventilation (BiPAP): May be attempted in older, stable children (usually >6-7 years).
2. Diaphragm Pacing:
   • Phrenic nerve pacing allows for increased mobility and "liberation" from mechanical ventilators during the day (implanted in older children).
3. Monitoring:
   • Continuous pulse oximetry and capnography ($EtC{O}_2$) during sleep.
   • Annual screening for Neuroblastoma and Holter monitoring (cardiac pauses).

VI. Prognosis

• Lifelong dependence on ventilation during sleep.
• Neurocognitive outcome depends on the prevention of hypoxic insults.