Spontaneous Disappearance of an Arachnoid Cyst after Burr Hole Drainage of Chronic Subdural Hematoma.

It is well known that the presence of arachnoid cysts (ACs) in young patients is a risk factor for developing a chronic subdural hematoma (CSDH) after a minor head injury. Although there have been controversies with the treatment, most authors recommend only draining the CSDH if the AC is asymptomatic. This judgement is based on the facts that this surgical approach has shown good clinical outcomes, and the AC usually remains unchanged after the surgery. Our case demonstrates that the AC of a young patient who developed a CSDH after a minor head injury completely disappeared after a burr hole drainage of the CSDH. Although the chances of an AC disappearing are low, this case shows that an AC might disappear after only draining a CSDH when a rupture of the AC membrane is identified. In such cases, we recommend first draining only the CSDH for the treatment of AC-associated CSDHs.