*It's a state of encephalopathy due to escape of fat soluble unconjugated bilirubin from the vascular compartment through the blood brain barrier and its deposition in the basal ganglia causing cell damage and neurobal loss.
*The critical level of plasma bilirubin above which kernictrus occurs is 20 mg/dl and there are factors that help this by disturbance of BBB like hypoxia, acidosis and sepsis.
--Acute manifestations : three phases
First phase;lethargy, hypotonia, poor suckling
Second phase;Hypertonia (retrocollis and opisthotonus position that mean arching back of neck and trunk respectively)
Third phase;coma, seizures, irregular respiration
--chronic manifestations;cerebral palsy,hearing loss, mental retardation, gaze abnormalities.