Makindo Medical Notes

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.

About

• Neonatal jaundice with bilirubin > 360 micromoles/L.
• 50-60% of all term newborns are jaundiced in the first week of life.
• Total serum bilirubin typically peaks at age 3-5 days (later in Asian infants).

Aetiology

• Free bilirubin crosses the blood-brain barrier when the blood binding capacity is exceeded.
• Causes bilirubin-induced neurologic dysfunction.
• Most circulating bilirubin is bound to albumin, which acts as a "neuroprotective" agent.
• Bilirubin damages brain tissue cells via necrosis and apoptosis.

Clinical Features

• Infants appear sleepy and less responsive.
• Altered muscle tone: hypotonia, hypertonia, or opisthotonus.
• Sensorineural hearing loss due to damage to the cochlear nuclei.
• Severe encephalopathy in advanced cases.

Factors Predisposing to Neurotoxicity of Unconjugated Hyperbilirubinemia

• When bilirubin concentration exceeds the binding capacity of serum albumin.
• Displacement of bilirubin from albumin due to acidosis or certain drugs (e.g., sulfonamides, Ceftriaxone).
• Conditions like sepsis and prematurity increase risk due to lower serum albumin concentrations and susceptibility to acidosis and sepsis.

Differentials

• Sepsis and Meningitis: Both can cause lethargy, poor feeding, and encephalopathy, mimicking kernicterus symptoms.
• Hypoxic-Ischaemic Encephalopathy (HIE): Brain injury caused by oxygen deprivation may present with abnormal muscle tone and neurological symptoms.
• Metabolic Disorders (e.g., galactosaemia, hypothyroidism): May present with jaundice and neurological abnormalities.
• Intracranial Hemorrhage: Can lead to altered consciousness and abnormal neurological signs in newborns.
• Congenital Infections (e.g., TORCH infections): Can result in jaundice and neurologic abnormalities, similar to kernicterus.

Investigations

• Full Blood Count (FBC), Urea & Electrolytes (U&E), Liver Function Tests (LFTs), Coomb's test, and sepsis screening.
• Bilirubin levels: levels < 323 micromoles/L are generally less harmful, while levels > 360 micromoles/L require intervention. Follow local treatment thresholds.
• MR Imaging: In cases of kernicterus (bilirubin encephalopathy), T2-weighted MRI images may show high signal intensity bilaterally in the globus pallidus, an area prone to bilirubin deposition.

Management

• Neurological Emergency: Neonatal hyperbilirubinaemia with signs of acute encephalopathy is a neurological emergency. Initiate intense UV phototherapy while preparing for exchange transfusion.
• Phototherapy: Effective in reducing bilirubin levels; light therapy intensity may be increased based on severity.
• Exchange Transfusions: Balanced exchange transfusions are used if phototherapy alone is insufficient. Treatment thresholds vary with neonatal maturity and bilirubin levels.

References