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The setting-sun phenomenon, also known as “sundowning,” is a concerning sign that may represent a pathologic increase in intracranial pressure in the young infant. The clinical presentation consists of an upward-gaze paresis with eyes that appear to be driven downward. There is usually sclera showing between the upper eyelid and the iris. Retraction of the upper eyelids, sometimes accompanied by raising of the brow, may be seen. Although this sign is commonly seen in children with obstructive hydrocephalus, it may also be seen as a result of intracranial hypertension of other causes (trauma or ventriculoperitoneal shunt dysfunction) and occasionally in normal infants. It is thought to result from compression of the periaqueductal structures.
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The phenomena could be an important sign in early detection of elevated intracranial pressure, appearing sooner than enlarged head circumference, full fontanelle, separation of sutures, irritability, or vomiting.
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Management and Disposition
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Suspect increased intracranial pressure and obtain neuroimaging urgently. Consult neurosurgery for guidance in initial management and for definitive treatment in the operating room.
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This sign is a valuable cue for obtaining prompt neuroimaging and urgent surgical intervention.
When persistent, this sign is a frequent marker of elevated intracranial pressure, appearing in 40% of children with hydrocephalus (of any cause) and in 13% of patients with shunt dysfunction.
Ask parents to share photographs of their child taken since birth to assess for changes to head size and for the presence of sundowning.