SciTech

Health Talk: Congenital central hypoventilation syndrome

Ondine, who fell in love with a mortal, cursed him upon learning that he was unfaithful. He would stop breathing if he slept. This has basis in real life and is known as congenital central hypoventilation syndrome, which affects patients’ involuntary breathing. (credit: Courtesy of Wikimedia Commons) Ondine, who fell in love with a mortal, cursed him upon learning that he was unfaithful. He would stop breathing if he slept. This has basis in real life and is known as congenital central hypoventilation syndrome, which affects patients’ involuntary breathing. (credit: Courtesy of Wikimedia Commons)

Of the many stories of love and punishment, one of the most popular is that of Ondine. According to German folklore, Ondine was a nymph who fell in love with a mortal. On learning that Ondine’s lover was unfaithful, the angered king of nymphs cursed the mortal. The mortal would now have to remember to deliberately perform functions such as breathing, which are normally involuntary. The mortal lived throughout the day, but when he fell asleep, he forgot to breathe and died.

The story, as told in an article on www.emedicine.net, is not as fanciful as it seems. Congenital central hypoventilation syndrome (CCHS), also known as Ondine’s curse, affects involuntary breathing in patients. During the day when the patients are awake, they can make conscious, voluntary efforts to breathe regularly and manage to function normally. However, when they sleep, they cannot make such voluntary efforts to breathe. Thus, the patients tend to have slow and shallow breathing at night, a condition termed hypoventilation.

CCHS is caused by a malfunction of the autonomic nervous system (ANS), which is the part of the nervous system responsible for controlling the involuntary functions of the body. Malformation of the ANS during early development is the main cause of CCHS. In congruence with the theory that the ANS of such patients is severely affected, many other functions that are controlled by the ANS are also affected. Thus, these patients have a hard time regulating body temperature and heart rate. Also, their eyes are not adequately responsive to light, and their blood pressure varies to a great extent.

Although the congenital form of the disease is caused by an ANS defect, damage to certain areas of the brain, such as the brain stem, that are responsible for controlling involuntary functions like breathing can also lead to similar symptoms. Since the majority of the cases of CCHS are caused by developmental defects, they can be traced back to a mutation in a gene needed for proper development. The GeneReviews section of the website of the National Center for Biotechnology Information (NCBI) states that CCHS is linked to a mutation in the PHOX2B gene. Nearly 92 percent of the patients with CCHS have a mutation in PHOX2B gene. Analysis has also shown that the mutation is a dominant trait, which means that having one defective copy of the gene is enough to cause the disease.

Considering the fatal nature of the disease, many researchers have tried to develop successful treatments for the condition. Simply providing extra oxygen to such patients is not useful. Furthermore, medicines for stimul ating the respiratory system have not shown much effectiveness when treating such patients. As of now, the most successful method of managing the condition is to provide mechanical ventilation to the patients when they sleep at night. Infants may require 24-hour ventilation, and in severe cases, a tracheostomy — where an incision is made in the windpipe — may be needed to provide adequate oxygen.

Another possible method of dealing with the condition involves stimulating the phrenic nerve. The role of the phrenic nerve is to control the diaphragm, which controls the expansion of the lungs. By stimulating this nerve, the proper movements of the diaphragm could be restored.

Although management of the condition is difficult, it is not impossible. The GeneReviews page for the disease on the NCBI website states that many of the patients who were ventilated and given proper management and care are now around 20 years of age. Therefore, with proper management, children suffering from CCHS can lead a relatively normal and long life.