Imaging depicts a relatively large subdural hematoma. This occurs when trauma, or other any other source, provides enough force to rupture the bridging veins that are surrounded by cerebrospinal fluid. The bleeding occurs between the arachnoid and the dura (both of which are part of the meninges). On a CT scan, one can see a region of the the accumulated blood that is crescent-shaped and possible mass effect on the lateral ventricles. An emergency trauma neurosurgical procedure is needed with a possible drainage system. Source: Neurosurgery (name of YouTube channel)