kernicterus

Kernicterus is a form of brain injury caused by the deposition of unconjugated bilirubin in brain tissue, most often arising in the setting of severe neonatal hyperbilirubinemia. It represents the permanent, chronic phase after an episode of acute bilirubin encephalopathy.

Pathophysiology involves the ability of unconjugated bilirubin to cross the immature blood–brain barrier in newborns. Once in the central nervous system, bilirubin is neurotoxic, with preference for deep gray matter structures such as the globus pallidus, subthalamic nucleus, hippocampus, and brainstem. Risk is increased by high bilirubin levels and conditions that raise free bilirubin, such as prematurity, sepsis, acidosis, hypoxia, hypoalbuminemia, or drugs that displace bilirubin from albumin. Early detection and treatment of severe hyperbilirubinemia are crucial to prevent progression to kernicterus.

Clinical features are typically described in two stages. Acute bilirubin encephalopathy may present in newborns with lethargy, hypotonia or irritability, poor feeding, high-pitched cry, and altered sensorium. If untreated or unrecognized, permanent injury can occur, producing kernicterus with chronic movement disorders such as dystonia and choreoathetosis, gaze abnormalities, auditory dysfunction, and potential long-term neurodevelopmental impairment.

Diagnosis relies on measuring serum bilirubin and assessing the bilirubin–albumin binding, alongside neurologic examination and risk factors. Neuroimaging, especially MRI, may show symmetric signal changes in basal ganglia and related pathways in established kernicterus.

Prevention centers on early identification and prompt treatment of severe hyperbilirubinemia, primarily with phototherapy or exchange transfusion when indicated. The prognosis depends on the severity and timeliness of intervention; kernicterus is typically associated with permanent neurological deficits.