Chronic Subdural Hygroma Caused by Rupture of Arachnoid Cyst

Abstract

The patient was a 25-year-old male, who sustained a head injury and was found to have an asymp tomatic arachnoid cyst of the middle cranial fossa and a frontal subdural space. Complete com munication between the subdural space and the subarachnoid space was recognized on CT perform ed 5 days after the injury, but not on CT 35 days after the injury. No hemorrhage was found in the subdural space on follow-up CT. Operation was performed 42 days after the injury. It was found that the subdural space contained xanthochromic fluid and that the capsule of the hygroma was very similar histologically to that of chronic subdural hematoma in adults. In this case, tear of the arachnoid membrane and accumulation of CSF in the subdural space were considered to have been essential for the formation of chronic subdural hygroma.