MR Findings in Kernicterus Vesna Martich-Kriss, Spyros S. Kollias, and William S. Ball, Jr Summary: We describe the MR appearance of kernicterus (bil- hypotonia, early signs of choreoathetosis, developmental irubin encephalopathy). T2-weighted images show high signal delay, nystagmus, and suspected seizure activity (Fig 1B). bilaterally in the globus pallidus, a known area of cerebral dep- High signal on T2-weighted images was again found in osition of bilirubin. the globus pallidus bilaterally, with no evidence of mass effect. Follow-up MR at 1 year of age was unchanged Index terms: Brain, diseases; Brain, metabolism; Infants, (Fig 1C). diseases Kernicterus is a neurologic condition in the Discussion neonate characterized by cerebral deposition of Kernicterus is a neurologic condition result- unconjugated bilirubin (1). Also known as bil- ing from the deposition of unconjugated biliru- irubin encephalopathy, it is a rare complication bin within the brain. Bilirubin encephalopathy of infantile hyperbilirubinemia resulting from was described in 1904 by Schmorl (3), who preferential deposition of bilirubin in the globus reported the postmortem pathologic finding of pallidus, subthalamic nuclei, hippocampus, pu- yellow staining of the basal ganglia in infants to tamen, thalamus, and cranial nerve nuclei (es- be associated with neonatal jaundice. pecially III, IV, and VI) (2). We report the mag- Causes of kernicterus (hyperbilirubinemia) netic resonance (MR) findings in a neonate with include erythroblastosis fetalis or other hemo- clinical and laboratory evidence of bilirubin lytic anemias such as glucose 6-phosphate de- encephalopathy. hydrogenase deficiency. Phototherapy and ex- change transfusions are two therapeutic options in the neonate with hyperbilirubinemia that Case Report have significantly reduced the prevalence of bi- lirubin encephalopathy (2). A term neonate (uncomplicated spontaneous vaginal delivery, Apgar score of 9 at 1 and 5 minutes) was seen at The neurologic manifestations of hyperbiliru- 8 days of age with irritability, severe jaundice, and opis- binemia usually appear by 2 to 5 days of age as thotonus. Total bilirubin level was 49.4 mg/dL. Two im- serum bilirubin levels rise over 20 mg/dL in the mediate exchange transfusions reduced the total bilirubin term neonate, lower in the more susceptible to 26 mg/dL. By 13 days old, the bilirubin level had premature neonate (4). Characteristic neuro- dropped to 6.3 mg/dL. The cause of the encephalopathic logic symptoms include somnolence, hypoto- hyperbilirubinemia is unknown, but was presumed to be nia, opisthotonus, rigidity, and a high-pitched hemolytic in nature. cry. Early in the course of the disease, the Because of the increased risk of hearing loss in infants symptoms may be subtle, mimicking sepsis, with hyperbilirubinemia, a brain-stem evoked response asphyxia, or hypoglycemia (1). Initially, sei- examination was performed. This examination was con- sistent with bilateral severe sensorineural hearing loss. The zures are uncommon. Once the neurologic question of possible brain-stem injury was also raised. An complications appear, the prognosis is poor. MR examination was obtained at 18 days of age (Fig 1A). Posticteric encephalopathy often develops in T2-weighted images showed symmetric high signal in the the few survivors of kernicterus. Neurologic globus pallidus bilaterally. Another MR examination was symptoms of posticteric encephalopathy are performed 6 months later in this infant, who now exhibited mostly related to the basal ganglia and include Received July 2, 1993; accepted after revision September 30. From the Departments of Radiology (V.M.-K., S.S.K., W.S.B) and Pediatrics (V.M.-K., W.S.B.), Children’s Hospital Medical Center and the University of Cincinnati College of Medicine, Ohio. Address reprint requests to William S. Ball, Jr, MD, Department of Radiology, Children’s Hospital Medical Center, 333 Burnet Ave, Cincinnati, OH 45229-3039. AJNR 16:819–821, Apr 1995 0195-6108/95/1604–0819 q American Society of Neuroradiology 819 820 MARTICH-KRISS AJNR: 16, April 1995 Fig 1. Kernicterus. A, Axial T2-weighted MR image (spin-echo 3000/110/2 [repetition time/echo time/excitations]) obtained at 18 days of age shows bilateral hyperintense lesions involving the globi pallidi (arrows). B and C, Subsequent T2-weighted MR images obtained at ages 6 months (B) (fast spin-echo 2500/119/2) and 1 year (C) (spin-echo 3000/110) show persistence of the lesions (arrows). Low T2 signal of the further myelinated internal capsule outlines better the preferential involvement of the globi pallidi. choreoathetoid movements, asymmetric spas- icteric stained sections reveals bilirubin pigment ticity, rigidity, opisthotonus, neurogenic hearing within neurons, neuronal processes, and micro- loss, and ataxia (5, 6). glia. The selective pattern of involvement of Bilirubin is usually bound to plasma albumin, specific nuclear groups and the nature of the rendering it nontoxic. However, free bilirubin is cytotoxic action of bilirubin are not well under- toxic and can enter the brain when the concen- stood. The entrance of bilirubin into the brain tration of bilirubin exceeds normal albumin tissue was attributed to disturbances of the al- binding capacity. Hence, exchange transfusions bumin-bilirubin equilibrium, resulting in pro- are usually performed when bilirubin levels ap- longed high concentrations of bilirubin in the proach 18 to 20 mg/dL (7). Reduced albumin blood stream, as well as to the greater perme- levels can also lead to increased free bilirubin ability of the immature blood-brain barrier. An- levels, perhaps explaining the occurrence of other proposed mechanism is that bilirubin en- kernicterus at lower serum bilirubin levels in the ters the brain after damage of certain nuclear premature neonate (8). groups by asphyxia, increasing the permeability Pathologic findings of kernicterus have clas- of the blood-brain barrier in the damaged re- sically been described as preferential bilirubin gions (1). In autopsy specimens of children past (icteric) discoloration of the basal ganglia, with the newborn period, chronic changes of neuro- relative sparing of the cerebral cortex and white nal loss, gliosis, and demyelination can be seen matter (2). The pattern of involvement is sym- in the basal ganglia (9). metric and highly selective. The most common The MR findings in this neonate reflect the sites affected are the pallidum, subthalamic nu- characteristic pathologic findings of ker- cleus, and horn of Ammon; staining of the thal- nicterus. High signal seen in the globus pallidus amus and striatum is less common. Brain-stem bilaterally corresponds to known areas of pref- involvement mainly affects cranial nerve nuclei erential deposition of unconjugated bilirubin. A of the tegmentum, particularly the oculomotor recent review of imaging of bilateral basal gan- and dentate nuclei, and the cerebellar flocculi. glia lesions in the pediatric population (10) de- Associated destructive lesions in the white mat- scribes a differential that lists acute causes such ter, such as periventricular infarcts, have also as hypoxia, hypoglycemia, carbon monoxide been reported (1). Microscopic evaluation of poisoning, and encephalitis versus chronic con- AJNR: 16, April 1995 KERNICTERUS 821 ditions that include inborn errors of metabolism, 2. Turkel SB, Miller CA, Guttenberg ME, Moynes DR, Hodgman JE. dysmyelinating disorders, and degenerative dis- A clinical pathologic reappraisal of kernicterus. Pediatrics 1982; 69:267–272 eases. To this list, we should add kernicterus 3. Schmorl G. Zur Kenntnis des ikterus neonaturum, insbesondere (bilirubin encephalopathy). der dabei auftretenden gehirnveranderungen. Verh Dtsch Ges Although the MR findings of high signal in Pathol 1904;6:109–115 the basal ganglia are nonspecific, they do 4. Kliegman RM, Behrman RE. Infants of diabetic mothers. In: Behr- demonstrate evidence of irreversible central man RE, Vaughan VC, eds. Nelson Textbook of Pediatrics. Phila- delphia: Saunders, 1987:419–422 nervous system toxicity from the hyperbiliru- 5. Perlstein MA. The late clinical syndrome of posticteric encepha- binemia. Imaging findings along with the appro- lopathy. Pediatr Clin North Am 1960;7:665–687 priate clinical presentation and laboratory val- 6. Hyman CB, Keaster J, Hanson V, et al. CNS abnormalities after ues could establish the correct diagnosis of neonatal hemolytic disease or hyperbilirubinemia. Am J Dis Child kernicterus. 1969;117:395–405 7. Broderson R. Bilirubin transport in the newborn infant, reviewed with relation to kernicterus. J Pediatr 1980;96:349–356 Acknowledgment 8. Hansen TWR, Bratlid D. Bilirubin and brain toxicity. Acta Paediatr 1986;75:513–522 We thank Juanita Hunter for help with the manuscript. 9. Claireaux AE. Pathology of human kernicterus. In: Sass-Kortsak W, ed. Kernicterus. Toronto: University of Toronto Press, 1959: References 140–149 10. Ho VB, Fitz CR, Chuang SH, Geyer CA. Bilateral basal ganglia 1. Friede RL. Developmental Neuropathy. Berlin: Springer-Verlag, lesions: pediatric differential considerations. Radiographics 1993; 1989:115–121 13:269–292.