A term used pathologically to describe BILIRUBIN staining of the BASAL GANGLIA; BRAIN STEM; and CEREBELLUM and clinically to describe a syndrome associated with HYPERBILIRUBINEMIA. Clinical features include athetosis, MUSCLE SPASTICITY or hypotonia, impaired vertical gaze, and DEAFNESS. Nonconjugated bilirubin enters the brain and acts as a neurotoxin, often in association with conditions that impair the BLOOD-BRAIN BARRIER (e.g., SEPSIS). This condition occurs primarily in neonates (INFANT, NEWBORN), but may rarely occur in adults. (Menkes, Textbook of Child Neurology, 5th ed, p613).