Kernicterus is brain damage caused by high levels of bilirubin in the brains of newborn infants. Kernicterus is caused by high levels of bilirubin in a baby's blood, a condition known as jaundice, or hyperbilirubinemia, according to the Merck Manual for Healthcare Professionals. Jaundice is more common in premature infants, infants with blood incompatibilities, babies with certain genetic disorders and those with infection, among many other causes. Kernicterus can cause permanent brain damage if levels exceed 20 milligrams per deciliter (mg/dl), and it should be treated with phototherapy or exchange transfusion.
Acute Kernicterus Phase 1
Early symptoms of kernicterus include bilirubin levels of 20 to 25 mg/dl or higher; a depressed or absent Moro, or startle, reflex; extreme lethargy and lack of muscle tone; and poor feeding, vomiting or poor suck, according to the National Institutes of Health Medline Plus. If babies feed poorly, they take in less fluid, and fluids are necessary to wash out the bilirubin in the stool, according to Dr. Steven Shapiro of the Virginia Commonwealth University.
Acute Kernicterus Phases 2 and 3
If kernicterus progresses to phase 2, an infant may have a high-pitched, shrill cry and may also arch her back, according to Medline Plus. Seizure may occur, and the fontanel--the soft spot on top of the baby's head--which is normally flat, may be tense or bulging. Fever may be present. The baby's muscle tone may become hypertonic, which means increased muscle tone; the neck may be hyperextended, according to Dr. Shapiro. This period is followed by phase 3, in which hypotonia, or decreased muscle tone.
Chronic Bilrubin Encephalopathy
Late symptoms of kernicterus can't be reversed. Among the possible long-term consequences are mental retardation; athetoid cerebral palsy, which is characterized by muscle rigidity and slow, writhing movements; and lack of normal muscle tone without cerebral palsy. Hearing problems include possible high-frequency hearing loss or auditory neuropathy, an auditory processing issue. Speech problems and eye problems, such as an inability to gaze upward, may occur, along with stained baby teeth, according to Dr. Shapiro. Many infants with late-stage neurological damage don't survive, according to Medline Plus.
