Case report: Middle cranial fossa arachnoid cyst in association with subdural hygroma

Abstract

Arachnoid cysts are congenital, cerebrospinal fluid (CSF)-filled, intra-arachnoidal lesions that are a common incidental finding on routine brain imaging. While this lesion can present as a mass lesion, the vast majority is generally asymptomatic. Rarely, posttraumatic or spontaneous rupture of arachnoid cysts can result in intracystic hemorrhage, subdural hematoma, or subdural hygroma. We describe a rare presentation of an arachnoid cyst, which ruptured after a minor head injury and resulted in a subdural hygroma. Arachnoid cysts are intra-arachnoidal space-occupying lesions containing fluid similar to CSF. They are benign in nature and congenital in origin. Arachnoid cysts represent 1% of all nontraumatic intracranial masses.[1] Most arachnoid cysts are supratentorial in location and 50-65% occur in the middle cranial fossa. Arachnoid cysts can also occur less frequently in the suprasellar and quadrigeminal cisterns, cerebral convexities, cerebellopontine angle, and cisterna magna. Occasionally, arachnoid cysts are complicated by intracystic or subdural hemorrhage, with or without history of preceding trauma.[1–3] A very rare complication of arachnoid cysts is the spontaneous or traumatic development of subdural hygromas.[2,4–7] We report a patient with an intracranial arachnoid cyst that was complicated by a subdural hygroma after a minor head injury.