The risks of epilepsy after traumatic brain injury.

The aim of this study is to present the incidence of traumatic brain injury (TBI) and identify those characteristics of brain injuries that are associated with the development of seizures. We identified 5984 episodes of TBI (loss of consciousness, post-traumatic amnesia, or skull fracture) in Olmsted County, Minnesota, from 1935 to 1984. Of these, 4541 were followed for seizure. Injuries were classified as mild (loss of consciousness or amnesia less than 30 minutes), moderate (loss of consciousness 30 minutes to 1 day or a skull fracture), or severe (loss of consciousness of more than 1 day, subdural hematoma, or brain contusion). The incidence of TBI in the period from 1975 to 84 peaked at 800 per 100 000 in males aged 15-24. The relative risk of seizures was 1.5 (95 percent confidence interval 1.0-2.2) after mild injuries, but with no increase after 5 years; 2.9 (95 percent confidence interval 1.9-4.1) after moderate injuries; and 17.2 (95 percent confidence interval 12.3-23.6) after severe injuries. Significant risk factors were brain contusion with subdural hematoma, skull fracture, loss of consciousness or amnesia of 1 day or more, and age over 65 years. We conclude that TBI is a major public health problem and contributes to the occurrence of seizures and epilepsy.