Anemia of Prematurity - Portal Neonatal

Kernicterus
Last Updated: November 6, 2004
Synonyms and related keywords: acute bilirubin encephalopathy, chronic postkernicteric
bilirubin encephalopathy, chronic bilirubin encephalopathy, profound pathologic hyperbilirubinemia
AUTHOR INFORMATION Section 1 of 11
Author: Shelley C Springer, MD, MBA, MSc, Neonatologist, Assistant Professor of Pediatrics,
Department of Pediatrics, University of Wisconsin, Madison
Coauthor(s): David J Annibale, MD, Director of Fellowship Training Program in Neonatal-
Perinatal Medicine, Associate Professor, Department of Pediatrics, Medical University of South
Carolina
Shelley C Springer, MD, MBA, MSc, is a member of the following medical societies: American
Academy of Pediatrics, American Medical Association, Minnesota Medical Association, National
Perinatal Association, and South Carolina Medical Association
Editor(s): Oussama Itani, MD, Medical Director of Neonatology, Borgess Medical Center, Clinical
Assistant Professor, Department of Pediatrics and Human Development, Michigan State
University; Robert Konop, PharmD, Director, Clinical Account Management, Ancillary Care
Management; David A Clark, MD, Chairman, Professor, Department of Pediatrics, Albany Medical
College; Carol L Wagner, MD, Associate Professor, Department of Pediatrics, Division of
Neonatology, Medical University of South Carolina; and Neil N Finer, MD, Director, Division of
Neonatology, Professor, Department of Pediatrics, University of California at San Diego
INTRODUCTION Section 2 of 11
Background: Traditionally, the term kernicterus (literally yellow kern, with kern indicating the most
commonly afflicted region of the brain, ie, the nuclear region) refers to an anatomic diagnosis made
at autopsy based on a characteristic pattern of staining found in babies who had marked
hyperbilirubinemia before they died. Regions most commonly affected include the basal ganglia;
hippocampus; geniculate bodies; and cranial nerve nuclei, such as the oculomotor, vestibular, and
cochlear. The cerebellum can also be affected. Acute bilirubin encephalopathy, which refers to the
clinical signs associated with bilirubin toxicity, ie, hypotonia followed by hypertonia, opisthotonus or
retrocollis, or both, is usually synonymous with kernicterus.
Prevalent in the 1950s and 1960s, kernicterus had virtually disappeared from the clinical scene,
only to reappear during the 1990s. Early discharge of term infants (before their bilirubin peaks) may
be a factor in the reemergence of this devastating neurologic affliction.
Much of the traditional teaching regarding hyperbilirubinemia is now being questioned as more is
learned about bilirubin metabolism and neurologic injury. Kernicterus is now recognized to occur in
the premature infant and very rarely in the term infant in the absence of profound
hyperbilirubinemia. Conversely, physiologic jaundice (sometimes to levels previously thought to be
universally dangerous) has been recognized to be within the reference range in the first week of life
in healthy term babies, particularly those who are breastfed. Jaundice of this type resolves
spontaneously, without sequelae.
Despite the lack of a clear-cut cause-and-effect relationship between kernicterus and
hyperbilirubinemia, laboratory investigations have demonstrated that bilirubin is neurotoxic at a
cellular level. Other in vitro studies have shown bilirubin to have more antioxidant capability than
vitamin E, which is commonly assumed to be the most potent antioxidant in the human system.
This possible role of bilirubin in early protection against oxidative injury, coupled with identification
of multiple neonatal mechanisms to preserve and potentiate bilirubin production, has led to
speculation about an as-yet-unrecognized beneficial role for bilirubin in the human neonate.