Kernicterus Clinical Presentation

Updated: Dec 20, 2020
  • Author: Shelley C Springer, JD, MD, MSc, MBA, FAAP; Chief Editor: Ted Rosenkrantz, MD  more...
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When assessing possible kernicterus, remember that a history of risk for hemolytic disease can be an important clue to a neonate's increased risk of pathologic hyperbilirubinemia, particularly Rh antigen incompatibility between mother and baby [8] . ABO incompatibility and a family history of red blood cell (RBC) abnormalities (ie, glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis) are also concerning. A review of neonatal readmissions in Canada showed that, of 258 infants readmitted for severe hyperbilirubinemia from 2002-2004, 87 (34%) demonstrated one of these hematologic abnormalities. [21]

Certain cultural postnatal practices may also contribute to significant hyperbilirubinemia and should be inquired about if culturally relevant. In the Middle East, Peker et al reported in 2010 a case series of 10 severely hypernatremic babies who also presented with kernicterus, two of whom died. [22] Of 112 postpartum women surveyed in Jordan Hospital, Amman, Jordan, almost 50% of them admitted to "salting" their newborns as is the common custom. Women doing this practice broadly represented all socioeconomic and educational strata. [23]

Conversely, if the baby is breastfeeding well and appears healthy and vigorous, this can be reassuring. The mother may have breastfed previous babies who also developed significant jaundice. If so, she may be one of the approximately 20-40% of women who have above-average levels of beta-glucuronidase in their breast milk, which potentiates and prolongs hyperbilirubinemia in their breastfed babies.


Physical Examination

Bilirubin-induced neurologic dysfunction (BIND) is the term applied to the spectrum of neurologic abnormalities associated with hyperbilirubinemia. It can be further divided into characteristic signs and symptoms that appear in the early stages (acute) and those that evolve over a prolonged period (chronic).

Acute bilirubin encephalopathy

The clinical features of this diagnosis have been well described and can be divided into three stages. Of babies with BIND, approximately 55-65% present with these features, 20-30% may display some neurologic abnormalities, and approximately 15% have no neurologic signs.

The three stages are as follows:

  • Phase 1 (first few days of life): Decreased alertness, hypotonia, and poor feeding are the typical signs. Obviously, these are quite nonspecific and could easily be indicative of a multitude of neonatal abnormalities. A high index of suspicion of possible BIND at this stage that leads to prompt intervention can halt the progression of the illness, significantly minimizing long-term sequelae. Of note, seizure is not typically associated with acute bilirubin encephalopathy. Among infants reported in the US kernicterus registry, the mean birth weight was 3281 g. [12]

  • Phase 2 (variable onset and duration): Hypertonia of the extensor muscles is a typical sign. Patients present clinically with retrocollis (backward arching of the neck), opisthotonus (backward arching of the back), or both. Infants who progress to this phase develop long-term neurologic deficits.

  • Phase 3 (infants aged >1 week): Hypotonia is a typical sign.

Chronic bilirubin encephalopathy

The clinical features of chronic bilirubin encephalopathy evolve slowly over the first several years of life in the affected infant. The clinical features can be divided into phases; the first phase occurs in the first year of life and consists of hypotonia, hyperreflexia, and delayed acquisition of motor milestones. The tonic neck reflex can also be observed. In children older than 1 year, the more familiar clinical features develop, which include abnormalities in the extrapyramidal, visual, and auditory systems. Minor intellectual deficits can also occur.

Note the following:

  • Extrapyramidal abnormalities: Athetosis is the most common movement disorder associated with chronic bilirubin encephalopathy, although chorea can also occur. The upper extremities are usually more affected than the lower ones; bulbar functions can also be impacted. The abnormalities result from damage to the basal ganglia, the characteristic feature of chronic bilirubin encephalopathy.

  • Visual abnormalities: Ocular movements are affected, most commonly resulting in upward gaze, although horizontal gaze abnormalities and gaze palsies can also be observed. These deficits result from damage to the corresponding cranial nerve nuclei in the brain stem.

  • Auditory abnormalities: Hearing abnormalities are the most consistent feature of chronic bilirubin encephalopathy and can develop in patients who show none of the other characteristic features. The most common abnormality is high-frequency hearing loss, which can range from mild to severe. These deficits can result from damage both to the cochlear nuclei in the brain stem and to the auditory nerve, which appear to be exquisitely sensitive to the toxic effects of bilirubin, even at relatively low levels. Clinically, this deficit can manifest as delayed language acquisition. Hence, auditory function must be assessed early in any baby at risk for chronic bilirubin encephalopathy.

  • Cognitive deficits: Cognitive function is relatively spared in chronic bilirubin encephalopathy. However, individuals with chronic bilirubin encephalopathy are often mistakenly considered to have mental retardation because of their choreoathetoid movement disorders and hearing deficits. The clinician must emphasize that intellectual functioning is not typically severely affected.

  • Abnormalities of dentition: Some degree of dental enamel hypoplasia can be observed in about three quarters of patients with chronic bilirubin encephalopathy. A smaller number of individuals develop green-stained teeth.