Kernicterus
Related Subjects:Sick Neonate
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One of the most easily preventable causes of brain injury from severe neonatal jaundice. Neonatal hyperbilirubinaemia with signs of acute encephalopathy is a neurological emergency.
๐งพ About
- Kernicterus = bilirubin-induced neurological dysfunction due to severe unconjugated hyperbilirubinaemia.
- Occurs when TSB > 360 ฮผmol/L in most term infants (lower thresholds in preterm/ill neonates).
- 50โ60% of term newborns develop some jaundice in the first week; usually benign, but a minority progress to kernicterus if untreated.
- Peak bilirubin: day 3โ5 in term infants (later in Asian neonates).
โ๏ธ Aetiology & Pathophysiology
- Unconjugated bilirubin crosses the immature bloodโbrain barrier if albumin binding is exceeded.
- Albumin normally buffers bilirubin (neuroprotection).
- Excess free bilirubin โ deposits in basal ganglia (esp. globus pallidus) โ neuronal necrosis/apoptosis.
๐ฉบ Clinical Features
- Early: poor feeding, lethargy, hypotonia.
- Progression: irritability, hypertonia, opisthotonus (arching), high-pitched cry.
- Auditory damage: sensorineural hearing loss (due to cochlear nuclei involvement).
- Severe: seizures, encephalopathy, coma โ death if untreated.
โ ๏ธ Risk Factors for Neurotoxicity
- Bilirubin > albumin binding capacity.
- Albumin displacement by drugs (e.g. sulfonamides, ceftriaxone) or acidosis.
- Prematurity (immature BBB + low albumin).
- Sepsis, hypoxia, metabolic derangements.
๐ Differentials
- Sepsis/Meningitis: lethargy, encephalopathy, poor feeding.
- Hypoxic-Ischaemic Encephalopathy (HIE): abnormal tone, seizures.
- Metabolic disorders: galactosaemia, hypothyroidism.
- Intracranial haemorrhage.
- TORCH infections: congenital causes of jaundice + neuro signs.
๐งช Investigations
- Bloods: FBC, U&E, LFTs, Coombs test, sepsis screen.
- Bilirubin levels:
- < 323 ฮผmol/L: usually safe in term infants.
- > 360 ฮผmol/L: requires urgent intervention (thresholds lower in preterm).
- MRI: Kernicterus shows T2 hyperintensity in globus pallidus.
๐ Management
- Emergency: Neonatal jaundice + encephalopathy = treat immediately.
- Phototherapy: Blue light converts unconjugated bilirubin to soluble isomers excreted without conjugation. Increase intensity if rising fast.
- Exchange transfusion: If phototherapy fails or bilirubin dangerously high. Involves replacing blood in aliquots with donor blood.
- Supportive: optimise hydration, correct acidosis, treat sepsis.
๐ก Teaching Pearls
- OSCE buzzword: sleepy jaundiced baby with opisthotonus โ think kernicterus.
- Preterm babies are at risk at lower bilirubin levels.
- Ceftriaxone is contraindicated in neonates due to bilirubin displacement.
- Phototherapy works by photoisomerisation of bilirubin, not by liver metabolism.
๐ References
- NICE NG98: Neonatal jaundice (2016).
- Rennie & Robertonโs Textbook of Neonatology, 5th Ed.
- Maisels MJ. Kernicterus and bilirubin encephalopathy. N Engl J Med. 2006.
