Kernicterus is caused by the effects of what substance?

Kernicterus is primarily caused by the accumulation of unconjugated bilirubin in the central nervous system. In conditions like hemolytic disease of the newborn, where there is excessive breakdown of red blood cells, there is an increase in bilirubin production. Normally, bilirubin is conjugated in the liver to make it water-soluble, allowing for excretion. However, when there is an excess of unconjugated bilirubin and the liver is unable to process it efficiently, it can cross the blood-brain barrier and deposit in the brain tissues, leading to kernicterus.

This condition results in significant neurological damage, which is why it's critical to monitor bilirubin levels in newborns closely. Unconjugated bilirubin is toxic to neurons and can lead to severe complications if not addressed promptly, making it the key substance associated with kernicterus.