Biphasic ventricular dilatation following posterior fossa subdural hematoma in the full-term neonate.

Five full-term neonates with a posterior fossa subdural hematoma caused by birth injury are reported. All of the patients were successfully treated with surgery. They all presented with biphasic ventricular dilatation as demonstrated by serial computerized tomography (CT) scanning. The initial dilatation due to obstructive hydrocephalus disappeared after removal of the hematoma; however, a second dilatation without obstruction of the ventricular system developed between 2 and 4 weeks after surgery. A ventriculoperitoneal shunt was required in one case because of progressive enlargement of the head size in the chronic stage. The other four patients showed transient dilatation of the ventricles without symptoms of increased intracranial pressure. Subarachnoid hemorrhage associated with posterior fossa subdural hematoma is considered to be the most likely causative factor for the delayed ventricular dilatation. The degree of dilatation roughly depended on the volume of the subarachnoid clot that was demonstrated on the initial CT scan.