Nontraumatic subdural hemorrhage due to arachnoid cyst rupture.

Arachnoid cysts (ACs) are benign congenital lesions that are often detected incidentally during imaging studies performed for various etiological reasons. These cysts are typically asymptomatic, and in most cases do not require surgical intervention. Although ACs are commonly encountered, they are rarely complicated by intracystic hemorrhage or subdural hematoma. In this report, we present a case of a nontraumatic rupture of an AC, which remained undiagnosed until the age of 52 years.