Spontaneous disappearance of middle fossa arachnoid cyst after head injury

A case of middle fossa arachnoid cyst is presented, which disappeared after head injury. Five days after the trauma, CT scan revealed subdural fluid collection in addition to an arachnoid cyst in the middle fossa on the same side. As the subdural fluid resorbed, the cyst became smaller and disappeared on the follow-up CT scans without surgical intervention.