Posttraumatic intraventricular arachnoid cyst accompanied by pseudomeningoencephalocele in a child.

Growing skull fracture (GSF) is a rare complication of head trauma. A posttraumatic intraventricular arachnoid cyst (AC), neither isolated nor accompanied by a GSF has not been reported previously. A seven-year-old girl was admitted after a severe head injury with a separated right parieto-occipital fracture and contusion. She responded well to conservative therapy. Seven weeks after discharge, she was re-admitted with a large parieto-occipital pseudomeningoencephalocele due to herniation of cerebrospinal fluid and neural tissue to the subgaleal space through the widened fracture defect, an extra-axial cyst at the posterior interhemispheric space and an intraventricular cystic mass. She underwent open surgery, and the intraventricular cystic mass was totally removed. The histological findings were consistent with an AC. One week after dural repair, hydrocephalus developed, and a ventriculo-peritoneal shunt was inserted. She did well during two-year follow-up. The present case is unique as an intraventricular AC following head trauma. When an intraventricular cystic lesion is encountered after severe head trauma, the possibility of an AC should be considered; especially with neighboring contused neural tissue and leptomeningeal cyst formation.