[A case report of cranial bone defect with a porencephalic cyst in an adult].

A case of cranial bone defect with porencephalic cyst in an adult was reported. A 47 year-old male was admitted with epilepsy. He had a round lytic bone defect lesion in the left frontal skull. The porencephalic cyst was under the bone defect. The mechanism of bone defect is thought to be as follows. He had received some head trauma in childhood and the frontal skull bone had fractured. The contusioned brain changed to a porencephalic cyst. The linear bone fracture may have enlarged according to the mechanism of a growing skull fracture. Persistent pulsative pressure from the porencephalic cyst toward the fractured bone edge might be able to make the bone defect oval.