Spontaneous Acute Subdural Hematoma Associated with Arachnoid Cyst and Intra-cystic Hemorrhage

Arachnoid cysts (ACs) are congenital, extra-axial lesions containing fluid similar to the composition of cerebrospinal fluid. Usually found incidentally, these lesions are observed with serial imaging to document their growth patterns and stability, and are then followed conservatively until clinical symptoms develop. Surgical options for symptomatic arachnoid cysts include cyst aspiration, cyst evacuation with fenestration into the subarachnoid space, and shunt procedures including cysto-peritoneal and cysto-ventricular shunts. Intra-cystic hemorrhage and subdural hematoma are rare and more emergent sequelae of ACs that may require an emergent craniotomy. This case report further documents a rare cause of spontaneous subdural hematoma, as well as serves as a pivot point for further discussion into whether continued neuroimaging surveillance in patients with ACs would prove to be beneficial.