Risk of seizure recurrence after the first late posttraumatic seizure.

OBJECTIVE: To determine the incidence and risk factors for seizure recurrence after the onset of late posttraumatic seizures (ie, seizures occurring more than 7 days after injury).
DESIGN: Longitudinal cohort design.
SETTING: Level 1 trauma center. PATIENTS: Sixty-three moderately to severely head-injured adults who developed late posttraumatic seizures during the course of their participation in a randomized, placebo-controlled study of the effectiveness of prophylactic phenytoin (Dilantin) for prevention of posttraumatic seizures. MAIN OUTCOME MEASURES: Time from the first unprovoked late seizure to time of seizure recurrence.
RESULTS: The cumulative incidence of recurrent late seizures was 86% by approximately 2 years. However, the frequency of recurrent seizures varied considerably across subjects: 52% experienced at least five late seizures, and 37% had 10 or more late seizures within 2 years of the first late seizure. The relative risk of recurrence was highest in patients with a history of acute subdural hematoma and prolonged coma (ie, longer than 7 days).
CONCLUSIONS: When late seizures develop after severe head injury, the probability of recurrence is high, which suggests that patients be treated aggressively with anticonvulsant medication after a first unprovoked late seizure.