A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain. It usually results from rips in bridging veins that cross the subdural space. Subdural hematomas may cause an increase in the pressure inside the skull, which in turn can cause compression of and damage to delicate brain tissue...