Kernicterus is a rare but serious complication of untreated jaundice in babies. It's caused by excess bilirubin damaging the brain or central nervous system.

In newborn babies with very high levels of bilirubin in the blood (hyperbilirubinaemia), the bilirubin can cross the thin layer of tissue that separates the brain and blood (the blood-brain barrier).

The bilirubin can damage the brain and spinal cord, which can be life-threatening.

Brain damage caused by high levels of bilirubin is also called bilirubin encephalopathy.

Your baby may be at risk of developing kernicterus if:

• they have a very high level of bilirubin in their blood
• the level of bilirubin in their blood is rising rapidly
• they do not receive any treatment

Initial symptoms of kernicterus in babies include:

• poor feeding
• irritability
• a high-pitched cry
• no startle reflex
• lethargy (sleepiness)
• brief pauses in breathing (apnoea)
• their muscles becoming unusually floppy, like a rag doll

As kernicterus progresses, additional symptoms can include fits (seizures) and muscle spasms that can cause arching of the back and neck.

Treatment for kernicterus involves using an exchange transfusion as used in the treatment of newborn jaundice.

If significant brain damage occurs before treatment, a child can develop serious and permanent problems, such as:

• cerebral palsy (a condition that affects movement and co-ordination)
• hearing loss (which can range from mild to severe)
• learning disabilities
• involuntary twitching of different parts of their body
• problems maintaining normal eye movements (people affected by kernicterus have a tendency to gaze upwards or from side to side, rather than straight ahead)
• poor development of the teeth