Late post-traumatic epilepsy is diagnosed when a seizure occurs for the first time more than one week after a head injury. Factors that correlate with an increased risk of developing post-traumatic epilepsy include presence of a depressed skull fracture, acute intracranial hemorrhage, cerebral contusion, or unconsciousness lasting more than 24 hours. Because the risk of a subsequent seizure is approximately 75%, acute and chronic treatment with anticonvulsants is indicated. Loss of consciousness, retrograde amnesia, and vomiting are relatively common immediate consequences of head trauma. They are usually transient and are not highly correlated with a risk of subsequent post-traumatic seizures. Ref: Smith W.S., English J.D., Johnston S.C. (2012). Chapter 370. Cerebrovascular Diseases. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.