A rare case of bleeding into the Sylvian arachnoid cyst: A case report

Arachnoid cysts are primarily developmental in origin and constitute rare, benign lesions. Sylvian arachnoid cysts may infrequently present with subdural and/or intracystic hemorrhage. Hemorrhage is typically of venous origin and occurs due to stretching and tearing of bridging veins, depending on minor traumas. The annual risk of bleeding associated with Sylvian arachnoid cysts, with no additional complaints other than headache and an asymptomatic course, has been reported to be 0.04%. Symptoms can range from headache to coma, depending on the mass effect after hemorrhage. If there is no clinical evidence linking the arachnoid cyst, it is sufficient to perform surgery only for the hematoma without resecting it. In this case report, we present a rare instance of hemorrhage due to a Sylvian arachnoid cyst that developed after trauma and was observed in a patient who came to our clinic with a headache. In our patient, the cyst-dependent left parietal subdural hemorrhage was evacuated through a burr-hole craniotomy, and a closed-system drainage with a Hemovac drain was applied for 48 hours. During post-operative follow-up, complete resorption of subdural and intracystic hemorrhages was observed. A case-based surgical approach is necessary for bleeding due to arachnoid cysts in the Sylvian region.