External hydrocephalus: a probable cause for subdural hematoma in infancy.

Subdural hemorrhage is common in infancy, particularly in the first year of life. The most common cause is nonaccidental (child abuse), with accidental in second place. We present three healthy infants, ages 4, 5, and 7 months that, during an evaluation for macrocephaly, were found to have frontal subdural hematoma in association with prominent extracerebral cerebrospinal fluid spaces (external hydrocephalus). There was no history of trauma or risk factors for child abuse. Skull surveys and ophthalmologic examinations were normal. All infants were neurologically intact and achieved normal developmental milestones in one-year follow-up. We suggest that some infants with external hydrocephalus may be at risk for development of subdural hematoma with minimal or no trauma, most likely secondary to stretching of the bridging veins in the unusually widened subarachnoid spaces. Child abuse, although it should always be kept in mind and should be excluded, may not be the most common cause in this specific context.