A 5-day-old term neonate with untreated jaundice becomes progressively lethargic and stops feeding. He then develops fever, a high-pitched cry, marked neck extensor spasm pulling the head backward, and episodic arching of the trunk. Total serum bilirubin is 29 mg/dL, almost entirely indirect. Which constellation of findings defines acute bilirubin encephalopathy?

• A Generalized hypotonia with a weak cry and absent Moro reflex
• B Retrocollis and opisthotonus with hypertonia and a high-pitched cry ✓
• C Focal seizures with asymmetrical limb movements and a normal sensorium between events
• D Bulging anterior fontanelle with repeated vomiting and bradycardia

Explanation

Acute bilirubin encephalopathy progresses through phases: early lethargy and poor feeding, then intermediate-phase hypertonia with retrocollis (backward extension of the neck) progressing to opisthotonus, high-pitched cry and fever, and finally advanced phase with pronounced arching, apnea and seizures. Retrocollis with opisthotonus is the hallmark that distinguishes it from hypoxic ischemic encephalopathy and sepsis. Early hypotonia occurs but is nonspecific, making option A the tempting distractor.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.