Chronic subdural hematoma associated with type II and type III Galassi arachnoid cysts: illustrative cases

Arachnoid cysts (ACs) are congenital abnormalities that can be located anywhere within the subarachnoid space along the cerebrospinal axis, although they are most often found on the left side in the temporal fossa and sylvian fissure. ACs comprise approximately 1% of all intracranial space-occupying lesions and are considered potential risk factors for subdural hematoma (SDH) in individuals of all age groups who have experienced traumatic brain injury. Although it is uncommon for an intracystic hemorrhage of an AC to occur without evidence of head trauma, it may be more common among children and young adults. Here, the authors present three cases of spontaneous AC intracystic hemorrhage with chronic SDH. Additionally, they provide a thorough review of the existing literature.

All three patients with AC were adolescent males. In all cases, AC was identified using the Galassi classification (type II or III) and associated with spontaneous intracystic hemorrhage and chronic SDH as seen on imaging.

Spontaneous intracystic hemorrhage is a rare complication and occurs most commonly on the left side. Surgery is the definitive treatment, requiring either craniotomy or burr hole for hematoma evacuation and microsurgical fenestration to drain the cyst into the subarachnoid cisterns.