Unusual posttraumatic porencephaly--case report.

An unusual case of posttraumatic porencephaly preceded by neither overt cerebral contusion nor hemorrhage is reported. The cerebral cortex just above the porencephalic cyst was found intra-operatively to be partially herniated into a fracture line, while the cortex elsewhere was completely intact. The porencephalic cyst communicated with the lateral ventricle. Apparently, brain herniation and the cyst-ventricle communication can be causative factors in the occurrence and growth of posttraumatic porencephaly.