Extradural haematoma (EDH), also known as an epidural haematoma, is a collection of blood that forms between the inner surface of the skull and outer layer of the dura, which is called the periosteal layer. They are commonly associated with a history of trauma and associated skull fracture. The source of bleeding is usually a torn meningeal artery (most commonly, the middle meningeal artery). EDHs are typically biconvex in shape and can cause a mass effect with herniation. They are usually limited by cranial sutures, but not by venous sinuses. Both CT and MRI are suitable to evaluate EDHs. When the blood clot is evacuated promptly (or treated conservatively when small), the prognosis of EDHs is generally good.