Kernicterus in Newborn Babies
Kernicterus is a serious medical condition affecting the brain that can potentially result if infant jaundice is not managed properly and treated after childbirth.
Kernicterus is a rare type of infant brain damage that can result from excessive levels of bilirubin in the brain caused by untreated cases of jaundice. Bilirubin is a bi-product substance naturally produced in the body during the disposal of old red blood cells. When levels of bilirubin in the blood become too high, however, it can be toxic - a condition referred to as hyperbilirubinemia. Jaundice occurs when hyperbilirubinemia progresses beyond a moderate level. The excessive accumulation of bilirubin caused by jaundice can eventually damage the brain and nervous system.
Newborn babies are particularly susceptible to jaundice because their livers are not fully developed. The underdeveloped liver of a newborn can quickly become overworked. This causes bilirubin levels to increase and result in jaundice. Jaundice in newborns is a very common condition. About 60% of newborns will experience some degree of jaundice during the first few weeks of life.
Infant jaundice is typically pretty harmless and short-lived. When the baby is exposed to regular sunlight, jaundice typically goes away quickly. In some cases, however, infant jaundice does not go away easily. Then you may have a serious concern. If a case of infant jaundice becomes very severe and is not properly managed or treated, the excessive bilirubin levels in the baby's blood can cause a particular type of infant brain damage known as kernicterus.
Kernicterus is a progressive condition that gets worse as the brain damage advances. The specific symptoms of kernicterus differ depending on what the stage of progression of the the condition.
- Jaundice: severe and/or prolonged infant jaundice is the root cause of kernicterus, so anytime a newborn has a particularly serious case of infant jaundice that does not clear up on its own it can be a symptom of kernicterus.
- Poor Feeding: newborns with early-stage kernicterus will often demonstrate significant difficulties with feeding, latching on, and sucking (with both breast and bottle feeding).
- Hypotonia: hypotonia (often called "floppy baby syndrome") is a condition characterized by extreme lack of muscle tone. Babies with hypotonia may feel floppy, like a rag-doll when picked up.
- Chronic Fatigue: abnormal levels of lethargy or apparent fatigue in a newborn (e.g., lack of intense crying, not getting up at night to feed, etc.) can be early symptoms of kernicterus.
- Seizures: as the neurologic damage of kernicterus advances, babies may experience sudden, uncontrolled infant seizures.
- Head Bulge: babies with kernicterus may develop a noticeable bulge in the "soft spots" or fontanel areas of the head.
- Increased Seizures: as kernicterus reaches the most advanced stages, a baby's seizures will often increase in both frequency and intensity.
- Hearing Loss: a common symptom of advanced kernicterus is extensive high-frequency hearing loss. This is sometimes difficult to identify in newborn infants.
- Stiffness: in early stages, kernicterus may cause hypotonia (floppy baby syndrome). In the late stages, however, the condition will often result in excessive muscle stiffness and problems with movement and body control.
As explained above, kernicterus is caused by poorly managed jaundice that causes bilirubin levels in the blood to become so high that the brain is damaged. Bilirubin is continuously manufactured inside the body from the constant breakdown and disposal of dead red blood cells. When old red blood cells get broken down (a process called hemolysis) most of the byproducts such as iron are reused elsewhere by the body. Bilirubin is the one byproduct of hemolysis that the body has no use for and simply discards.
When bilirubin is initially created from red blood cell breakdown it is in the unconjugated form. Unconjugated bilirubin is toxic because it is not water-soluble and it will build up in the body's tissues. The liver filters unconjugated bilirubin out of the bloodstream and converts into conjugated bilirubin. Conjugated bilirubin from the liver is water-soluble. This means it can be removed from the body through urine.
When many babies are first born, their livers are often unable to efficiently filter and convert unconjugated bilirubin into conjugated bilirubin fast enough to keep up with production. This invariably causes a backlog of unconjugated bilirubin in the bloodstream of many newborn babies which leads to infant jaundice.
Infant jaundice is usually short-lived as the baby's liver is quickly able to get caught up with bilirubin conversion. For some babies, however, the conversion and disposal of bilirubin by the liver does not get back on pace. As a result, the child's jaundice becomes more severe. If not properly managed and treated this can cause kernicterus where unconjugated bilirubin in the blood to infiltrates and damages brain tissue. There are factors that put a baby at increased risk of severe jaundice and kernicterus:
- Premature Birth: the liver is one of the last organs to develop during gestation. So when a baby is born before week 37 their liver will be less efficient at bilirubin conversion and will take longer to get caught up.
- Poor Feeding: feeding problems can prolong infant jaundice because frequent stools and urination help accelerate bilirubin disposal.
- Genetic Predisposition: babies with a family history of severe infant jaundice (i.e. siblings or parents who had serious jaundice as an infant) are at increased risk.
- Maternal Blood Type: research has found that mothers with type O or Rh-negative blood types are more prone to have babies with high bilirubin levels.
A diagnosis of kernicterus is usually made presumptively. But a definitive diagnosis of kernicterus is almost impossible to make without an autopsy. A diagnosis of kernicterus in a newborn is a process that usually begins with a standard physical exam and the identification of jaundice indications (yellow eyes, skins discolor, etc.). A light meter and blood test can help doctor diagnose bilirubin levels suggestive of kernicterus.
Kernicterus is caused when newborn jaundice is very severe and not properly treated or managed. This allows bilirubin levels in the blood to become so high that they damage cells in the brain.
Sadly, once kernicterus occurs there is currently no effective medical treatment. Kernicterus results from damage to the brain which cannot be reversed or repaired. Treatment of kernicterus focuses on the prevention of hyperbilirubinemia/jaundice which causes the condition.
The good news is that newborn jaundice is something that can be very effectively treated. The first level of treatment for jaundice involves phototherapy (or light therapy) in which the baby is exposed to natural sunlight or a special artificial light. Light exposure accelerates the filtration and conversion of bilirubin inside the body. A second level of treatment for infant jaundice can involve blood exchange transfusions. This involves the removal of some of the baby's blood and replacement with donor blood.
No. Once the damage to the brain that characterizes kernicterus occurs it cannot be reversed and the damaged brain cells will never regenerate. There is no effective treatment for kernicterus other than prevention.
If a very severe case of infant jaundice is not treated or managed, it can potentially develop into kernicterus as quickly as 2-5 days after birth. Keep in mind, however, that kernicterus is very rare. Few cases of infant jaundice (even if not treated) will develop into kernicterus.
Kernicterus Spectrum Disorder (KSD) is a brain injury from bilirubin toxicity. Again, there is no specific cure for the resulting encephalopathy. The consequences can include cognitive deficits, hearing loss, motor impairments, auditory deficits, dental dysplasia, and potentially cognitive impairments.
Medical Literature and Studies on Kernicterus
Alkén, Jenny, et al.: "Rates of extreme neonatal hyperbilirubinemia and kernicterus in children and adherence to national guidelines for screening, diagnosis, and treatment in Sweden." JAMA network open 2.3 (2019): e190858-e190858. (This study looked at newborn hyperbilirubinemia and kernicterus rates and concluded that many hyperbilirubinemia-related brain damage cases could be avoided if healthcare providers followed the right medical practices.)
Donneborg, Mette Line, et al.: "Extreme neonatal hyperbilirubinemia and kernicterus spectrum disorder in Denmark during the years 2000–2015." Journal of Perinatology 40.2 (2020): 194-202. (This study identified ABO hemolytic disease of the newborn as the main kernicterus cause. They concluded that a systematic approach to neonatal jaundice and the surveillance of kernicterus and neonatal hyperbilirubinemia were necessary.)
McCarthy, Molly E., et al.: "Newborn metabolic profile associated with hyperbilirubinemia with and without kernicterus." Clinical and translational science 12.1 (2019): 28-38. (Study concluded that healthcare providers should consider a newborn’s metabolic profile when investigating hyperbilirubinemia causes and risks.)
Rennie, Janet M., Jeanette Beer, and Michele Upton.: "Learning from claims: hyperbilirubinaemia and kernicterus." Archives of Disease in Childhood-Fetal and Neonatal Edition 104.2 (2019): F202-F204. (Found that infants with kernicterus typically had an underlying condition.)