Newborn babies with extreme jaundice are at risk of developing a type of brain damage called kernicterus. The condition is rare in developed countries, as it can be prevented through close monitoring of infants who are at risk. Brain damage in children with kernicterus is caused by the build-up of bilirubin, a yellow-colored pigment which circulates in red blood cells.
Excess levels of bilirubin in the blood causes a condition called jaundice, the main symptom of which is the characteristic yellow color of the skin. Jaundice itself is not a dangerous condition, but the presence of yellow-tinted skin indicates that high bilirubin levels are present. It is this high level of bilirubin which is dangerous to the newborn.
The reason why newborn babies are at risk of dangerously high levels of bilirubin is not known. One theory hinges on the fact that many infants are born with high levels of red blood cells. Bilirubin circulates in red blood cells, so when excess cells are broken down, one result may be an overload of bilirubin in the blood. In older children and adults, high bilirubin levels are not harmful. In newborn babies, bilirubin is able to cross the blood-brain barrier, where it can cause irreversible brain damage.
Jaundice is common to newborns in developed as well as developing countries. In the United States, for example, up to 60% of newborn babies are jaundiced. Most cases of newborn jaundice are easily treatable with a type of therapy called phototherapy, in which infants are exposed to light. Exposure to light causes bilirubin to alter in form, causing it to become a water-soluble non-toxic molecule. In this form, bilirubin is harmless and can be easily excreted.
In rare cases, a newborn may not respond to this treatment and may still be at risk of developing kernicterus brain damage. In such cases the infant is treated with a procedure called exchange transfusion. In this process the baby’s blood is removed and replaced with banked blood that is free from bilirubin. The exchange transfusion is carried out very gradually, over the course of several hours.
Exchange transfusion may also be carried out if an infant has symptoms which indicate that kernicterus brain damage is already occurring. Symptoms of this brain damage include lethargy and difficulty waking, changes in muscle tone, high-pitched crying, and arching of the back. When these symptoms occur treatment must begin as soon as possible to prevent any further brain damage. In addition, if kernicterus treatment begins immediately, it is sometimes possible to reverse some of the damage that has already been done.