How long after head injury does extradural haematoma occur? do you always experience symptoms?

Epidural hematoma: Extramural hematomas occur minutes to hours after head trauma. Some delayed 24 hours in children and adults over 45 years old. Extradural hematoma after a head trauma is either epidural (outside the dura but under the skull) or subgaleal (under the scalp but on top of the skull). Epidural hematomas can be life threatening because the bleeding is often arterial from a torn artery in the meninges.