Bilirubin Encephalopathy, Chronic (Kernicterus)

Key Features

• Kernicterus is an irreversible brain injury characterized by choreoathetoid cerebral palsy and hearing impairment

• Intelligence is probably normal but may be difficult to assess because of associated hearing, communication, and coordination problems

• Infants with visible jaundice on the first day of life or who develop excessive jaundice require the following:

  • Feeding and elimination history

  • Birth weight and percent weight change since birth

  • Examination for sources of excessive heme breakdown

  • Assessment of blood type, Coombs testing, complete blood cell count (CBC) with smear, serum albumin, and total serum bilirubin (TSB)

  • G6PD test if jaundice is otherwise unexplained, and in African-American infants with severe jaundice

  • Fractionated bilirubin level in infants who appear ill, those with prolonged jaundice, acholic stool, hepatosplenomegaly, or dark urine to evaluate for cholestasis

Clinical Findings

• Extrapyramidal movement disorder (choreoathetoid cerebral palsy)

• Gaze abnormality, especially limitation of upward gaze

• Auditory disturbances (deafness, failed auditory brainstem evoked response with normal evoked otoacoustic emissions, auditory neuropathy, auditory dyssynchrony)

• Dysplasia of the enamel of the deciduous teeth

Diagnosis

• Clinical but is strengthened if audiologic testing shows auditory neuropathy and auditory dyssynchrony in which the otoacoustic emission test is normal but the auditory brainstem response is absent

• Magnetic resonance imaging (MRI) scanning of the brain is nearly diagnostic if it shows abnormalities isolated to the globus pallidus or the subthalamic nuclei, or both

• TSB should be measured and interpreted based on the age of the infant in hours at the time of sampling

• Term infants with a TSB level greater than the 95th percentile for age in hours have a 40% risk of developing significant hyperbilirubinemia

Treatment

• Phototherapy

  • Most common treatment for indirect hyperbilirubinemia

  • Intensive phototherapy should decrease TSB by 30–40% in the first 24 hours, most significantly in the first 4–6 hours

  • Infant's eyes should be shielded to prevent retinal damage

  • Diarrhea, which sometimes occurs during phototherapy, can be treated if necessary by feeding a nonlactose-containing formula

• Exchange transfusion

  • Double-volume exchange transfusion (~160–200 mL/kg body weight) is most often required in infants with extreme hyperbilirubinemia secondary to Rh isoimmunization, ABO incompatibility, or hereditary spherocytosis

  • Also indicated in any infant with TSB above 30 mg/dL, in infants with signs of encephalopathy, or when intensive phototherapy has not lowered TSB by at least 0.5 mg/dL/h after 4 hours.

  • The decision to perform exchange transfusion should be based on TSB, not on the indirect fraction of bilirubin.

  • Procedure decreases serum bilirubin acutely by approximately 50% and removes about 80% of sensitized or abnormal red blood cells and offending antibody so that ongoing hemolysis is decreased

  • Procedure is invasive, potentially risky, and infrequently performed