Ondine's curse
Synonyms and keywords: Central Hypoventilaion Syndrome, primary alveolar hypoventilation, Haddad syndrome, Ondine-Hirschsprung disease, failure of autonomic control

# Overview
Ondine's Curse is a failure of the involuntary nervous system to trigger breathing while the patient is asleep, and as a result, the patient stops breathing during sleep (respiratory arrest) which is usually fatal.

# Pathophysiology
This very rare and serious form of central sleep apnea involves an inborn failure of autonomic control of breathing.
Various sources mistakenly publish that Ondine's curse is synonymous with Congenital Central Hypoventilation Syndrome.  Indeed, Ondine's curse can be either congenital or acquired depending on whether it was present at birth.
Ondine's curse is exhibited typically as a congenital disorder, but in rare circumstances, can also result from severe brain or spinal trauma (such as after an automobile accident, stroke, or an error made during neurosurgery).
Medical investigation of patients with this syndrome has led to a deeper understanding of how the body and brain regulate breathing on a molecular level. PHOX2B can be associated with this condition. This homeobox gene is important for the normal development of the autonomic nervous system.
The disease used to be classified as a "neurocristopathy", or disease of the neural crest because part of the autonomic nervous system (such as sympathetic ganglia) derives from the neural crest. However, this denomination should be dropped because essential neurons of the autonomic nervous system, including those that underlie the defining symptom of the disease (respiratory arrests), are derived from the neural tube (the medulla), not from the neural crest.

# Demographics and Epidemiolgoy
About 1 in 200,000 live born children have the condition.  In 2006, there were only about 200 known cases worldwide.

# Diagnosis

## Symptoms
As in many disorders that are very rare, an infant with this unusual form of sleep apnea suffers from the probability that their physician has most likely never seen another case and will not recognize the diagnosis. In some locations, such as France, optimal management of patients, once identified, has been aided by the creation of a national registry and the formation of a network of centers.
Ondine's curse is associated with respiratory arrests during sleep and, with incomplete penetrance, neuroblastoma (tumors of the sympathetic ganglia), Hirschprung disease (partial agenesis of the enteric nervous system), dysphagia (difficulty swallowing), anomalies of the pupilla, etc. In all cases, episodes of apnea occur in sleep, but in a few patients, at the most severe end of the spectrum, apnea also occurs while awake.
Children with Congenital Central Hypoventilaion Syndrome develop life-threatening episodes of apnea with cyanosis, usually in the first months of life. Medical evaluation excludes lesions of the brain, heart, and lungs but demonstrate impaired responses to build-up of carbon dioxide (hypercapnia)  and decreases of oxygen in the circulation (hypoxia), the two strongest stimuli to increase breathing rate.

## Laboratory Findings

### Polysomnography
Polysomnography shows that hypoventilation is most marked during slow-wave sleep. In the most severe cases, hypoventilation is present during other nonrapid eye movement sleep stages and even wakefulness. A subset of CCHS patients are at very high risk for developing malignant neural crest derived tumors, such as neuroblastoma.

### Genetic Testing
The sequence of PHOX2B reveals mutations in 91% of the cases.

# Treatment and prognosis
Patients generally require tracheotomies and lifetime mechanical ventilation on a respirator in order to survive. However, it is now been shown that Biphasic Cuirass Ventilation can effectively be used without the need of a tracheotomy.
Most people with congenital Ondine's curse do not survive infancy, unless they receive ventilatory assistance during sleep. An alternative to a mechanical ventilator is Phrenic Nerve Pacing/diaphragm pacing.
Although rare, cases of long-term untreated CCHS have been reported.

# History and etymology
It was first described in 1962 by Severinghaus and Mitchell in three patients following surgery to the upper cervical spinal cord and brainstem.
Its name is a reference to the myth of Ondine, a water nymph who had an unfaithful mortal lover. He swore to her that his "every waking breath would be a testimony of  love", and upon witnessing his adultery, she cursed that if he should fall asleep, he would forget to breathe. Eventually, he fell asleep from sheer exhaustion, and his breathing stopped.

# Cultural references
- Ondine's curse was mentioned in the 1987 film Black Widow starring Debra Winger, Theresa Russell, Terry O'Quinn and D. W. Moffett. Ondine's Curse was given as a reason for the death of a mafia connected man who suddenly died in his sleep for no reason.
- Ondine's curse was also mentioned in the book It's Kind of A Funny Story (Ned Vizzini).  The main character describes the phenomenon after having read it in DSM (the Diagnostic and Statistical Manual), a psychiatric textbook.