Kernikterus

Kernicterus, also known as bilirubin-induced neurologic dysfunction, is the chronic and often permanent brain injury that can follow severe unconjugated hyperbilirubinemia in newborns. It occurs when high levels of bilirubin cross the immature blood-brain barrier and deposit in brain tissue, most prominently in the basal ganglia, brainstem nuclei, hippocampus, and other deep gray matter structures.

Risk factors and pathophysiology include conditions that cause extensive neonatal jaundice or impaired bilirubin clearance, such as hemolytic diseases (for example, Rh or ABO incompatibility), glucose-6-phosphate dehydrogenase deficiency, sepsis, prematurity, metabolic disorders, asphyxia, and breastfeeding jaundice. Prolonged or markedly elevated unconjugated bilirubin increases the likelihood that bilirubin will invade brain tissue, leading to neuronal injury.

Clinical features can begin with signs of acute bilirubin encephalopathy in the first days of life, such as lethargy, poor feeding, hypotonia or irritability, high-pitched crying, and abnormal muscle tone, which may progress to seizures. In later stages, kernicterus can cause chronic movement disorders (dystonia, choreoathetosis), gaze abnormalities and oculomotor palsies, sensorineural hearing loss, dental enamel defects, and growth or cognitive impairment.

Diagnosis relies on a history of severe jaundice and elevated unconjugated bilirubin levels, supported by neurological examination and, when indicated, imaging and audiology testing. Prevention and treatment focus on early detection and reduction of bilirubin levels through phototherapy and, in severe cases, exchange transfusion, along with management of underlying causes and close neurodevelopmental follow-up to monitor for long-term sequelae. kernicterus is largely preventable with timely intervention.