The most common measures of traumatic brain injury (TBI) severity include the Glasgow Coma Scale (GCS), the duration of loss of consciousness (LOC), and the duration of post-traumatic amnesia (PTA). Post-traumatic seizures are usually divided into three categories: immediate, early seizures, and late seizures. Early seizures have a different pathogenesis than late seizures; early post-traumatic seizure (PTS) are thought to be due to mechanical damage to neurons, related to extravasated blood, brain swelling, and perioperative events from cerebral manipulation or stress from general anaesthesia and metabolic factors. The relative risks of epilepsy are raised twofold after a mild head injury and sevenfold after severe head injury, risks are slightly greater in women than in men, and are increased with older age at time of injury. Structural imaging has shown promise for improving prediction of PTS risk. Phenytoin has the most evidence to support its use to reduce early post-traumatic seizures.