Kernicterus (Bilirubin-Induced Brain Damage)

How kernicterus happens

Newborns break down red blood cells faster than adults, and their immature liver processes bilirubin slowly. Most babies develop mild jaundice in the first week, which is harmless (neonatal jaundice).

When unconjugated bilirubin rises very high, it can cross the blood-brain barrier and stain and damage nerve cells, especially in the basal ganglia, brainstem hearing pathways and cerebellum. The term "kernicterus" originally described the yellow staining of these brain areas.

• Acute bilirubin encephalopathy: the early, sometimes reversible, phase of toxicity in the first days
• Kernicterus (chronic bilirubin encephalopathy): the permanent damage that follows

Risk factors for severe jaundice

• blood group incompatibility between mother and baby: ABO incompatibility and Rh disease
• G6PD deficiency: an inherited enzyme deficiency common in people of African, Mediterranean, Middle Eastern and Asian ancestry
• prematurity, including babies born at 35 to 37 weeks
• bruising or cephalohematoma from a difficult birth
• poor breastfeeding with dehydration and weight loss
• sibling who needed phototherapy
• infection (sepsis)
• rare genetic disorders such as Crigler-Najjar syndrome
• early discharge without follow-up

Signs and symptoms

Acute bilirubin encephalopathy

Early:

• deep jaundice
• sleepiness and lethargy
• poor feeding and weak sucking
• reduced muscle tone

Intermediate:

• irritability and a high-pitched cry
• increased tone with arching of the neck (retrocollis) and back (opisthotonus)
• fever

Advanced:

• seizures
• inability to feed
• coma

Chronic kernicterus

Develops over the first year:

• athetoid cerebral palsy: involuntary writhing movements and dystonia
• sensorineural hearing loss or auditory neuropathy
• limited upward gaze
• dental enamel defects of baby teeth
• intellectual ability is often relatively preserved

Diagnosis

• bilirubin screening: AAP guidance recommends measuring bilirubin in every newborn before discharge using a skin (transcutaneous) or blood test, and plotting it on age-specific charts
• blood tests for blood group, direct antibody test, blood count, G6PD
• hearing tests (auditory brainstem response) for babies with severe jaundice
• MRI of the brain may show characteristic changes in the globus pallidus

Treatment of high bilirubin

• phototherapy: blue-green light converts bilirubin into forms the body can excrete. Thresholds depend on the baby's age in hours, gestational age and risk factors
• feeding support: frequent breastfeeding, sometimes with supplementation, to help bilirubin leave in stool
• IV immunoglobulin in some cases of blood group incompatibility
• exchange transfusion: replacing the baby's blood to rapidly lower dangerously high bilirubin or when there are signs of encephalopathy

Managing kernicterus

There is no cure for established brain damage. Care focuses on:

• physical and occupational therapy
• medicines for dystonia and spasticity
• hearing aids or cochlear implants
• speech and communication support, including assistive technology
• deep brain stimulation in selected cases

Prevention

• every newborn's jaundice is assessed before hospital discharge
• follow-up visit within 1 to 3 days of discharge depending on risk
• parents check skin and eye color in daylight and watch feeding and diapers
• do not rely on sunlight at home to treat jaundice
• seek care promptly for warning signs

Frequently asked questions

What is kernicterus?

Kernicterus is permanent brain damage caused by extremely high bilirubin levels in a newborn. It affects areas of the brain that control movement and hearing, leading to athetoid cerebral palsy, hearing loss and eye movement problems.

What are the early signs of kernicterus?

Early warning signs include deep jaundice, a very sleepy baby, poor feeding and floppiness. Later signs are a high-pitched cry, arching of the back and neck, stiffness, fever and seizures. Any of these need emergency care.

Can kernicterus be prevented?

Yes, almost always. Checking bilirubin in every newborn, follow-up soon after discharge, and prompt phototherapy or exchange transfusion when levels are high prevent the brain damage that causes kernicterus.

Is kernicterus reversible?

The early acute phase may be partly reversible with urgent treatment such as exchange transfusion. Once permanent brain damage has occurred, it cannot be reversed, but therapies can improve function and quality of life.

When is newborn jaundice dangerous?

Jaundice is concerning if it appears in the first 24 hours, spreads below the chest or deepens after day 3, or comes with poor feeding, extreme sleepiness, few wet diapers, or a high-pitched cry. These babies need prompt bilirubin testing.