Acute obstructive hydrocephalus caused by a migrating intraventricular calculus. Case report.

A 10-year-old boy presented with acute obstructive hydrocephalus caused by the impaction of a calculus on the cerebral aqueduct. The calculus migrated from the third ventricle to the fourth ventricle after ventricular drainage and right ventriculoperitoneal shunt placement had been performed. The nature and origin of the calculus could not be determined, although its release from the choroid plexus in the lateral ventricle is highly possible.