Cumulative incidence after 30 years of<unk>  in head injured individuals It is not clear why some patients develop<unk>  while others with very similar injuries do not. However, possible risk factors have been identified, including severity and type of injury, presence of early seizures, and genetic factors. Genetics Genetics may play a role in the risk that a person will develop<unk> ; people with the ApoE-ε4 allele may be at higher risk for<unk> . The haptoglobin Hp2-2 allele may be another genetic risk factor, possibly because it binds hemoglobin poorly and thus allows more iron to escape and damage tissues. However, most studies have found that having family members with epilepsy does not significantly increase the risk of PTS, suggesting that genetics are not a strong risk factor. Severity of trauma The more severe the brain trauma is, the more likely a person is to suffer late<unk> . Evidence suggests that mild head injuries do not confer an increased risk of developing<unk> , while more severe types do. In simple mild TBI, the risk for<unk>  is about 1.5 times that of the uninjured population. By some estimates, as many as half of sufferers of severe brain trauma experience<unk> ; other estimates place the risk at 5% for all TBI patients and 15–20% for severe TBI. One study found that the 30-year risk of developing<unk>  was 2.1% for mild TBI, 4.2% for moderate, and 16.7% for severe injuries, as shown in the chart at right. Nature of trauma The nature of the head trauma also influences the risk of<unk> . People who suffer depressed skull fractures, penetrating head trauma, early PTS, and intracerebral and subdural haematomas due to the TBI are especially likely to suffer<unk> , which occurs in more than 30% of people with any one of these findings. About 50% of patients with penetrating head trauma develop<unk> , and missile injuries and loss of brain volume are associated with an especially high likelihood of developing the condition. Injuries that occur in military settings carry higher-than-usual risk for<unk> , probably because they more commonly involve penetrating brain injury and brain damage over a more widespread area. Intracranial hematomas, in which blood accumulates inside the skull, are one of the most important risk factors for<unk> . Subdural hematoma confers a higher risk of<unk>  than does epidural hematoma, possibly because it causes more damage to brain tissue. Repeated intracranial surgery confers a high risk for late<unk> , possibly because people who need more surgery are more likely to have factors associated with worse brain trauma such as large hematomas or cerebral swelling. In addition, the chances of developing<unk>  differ by the location of the brain lesion: brain contusion that occurs on in one or the other of the frontal lobes has been found to carry a 20%<unk>  risk, while a contusion in one of the parietal lobes carries a 19% risk and one in a temporal lobe carries a 16% chance. When contusions occur in both hemispheres, the risk is 26% for the frontal lobes, 66% for the parietal, and 31% for the temporal.<unk><unk>  seizures The risk that a person will develop<unk>  is heightened but not 100% if PTS occur. Because many of the risk factors for both<unk>  and early PTS are the same, it is unknown whether the occurrence of PTS is a risk factor in and of itself. However, even independent of other common risk factors, early PTS have been found to increase the risk of<unk>  to over 25% in most studies. A person who has one late seizure is at even greater risk for having another than one who has early PTS; epilepsy occurs in 80% of people who have a late seizure. Status epilepticus, a continuous seizure or multiple seizures in rapid succession, is especially strongly correlated with the development of<unk> ; status seizures occur in 6% of all TBIs but are associated with<unk>  42% of the time, and quickly halting a status seizure reduces chances of<unk>  development.
Post-traumatic epilepsy
Musicogenic epilepsy
Generalized epilepsy
Temporal lobe epilepsy
Rolandic epilepsy
Vertiginous epilepsy
Catamenial epilepsy
Northern epilepsy syndrome