immediate and early post traumatic seizure true Posttraumatic seizures are commonly derived into three classes: ‘immediate seizures’, ‘early seizures’, and ‘late seizures’. Immediate seizures refer to those that happen at or minutes after impact; seizures that occur one week after head injury are called early seizures, and late posttraumatic seizures are defined as those occurring >1 week after injury. seizure not necessarily requiring a diagnosis of epilepsy