Risk of Epilepsy Following a First Posttraumatic Seizure: A Register-Based Study.

Background and objectives: Traumatic brain injury (TBI) is a common cause of epilepsy, and the risk increases with injury severity. Whether a first posttraumatic seizure (PTS) represents epilepsy is a common clinical problem, but often unknown. Prognostication is important for providing correct patient information and consideration of antiseizure medication. Our objective was to understand how trauma severity and latency from the injury affect the risk of epilepsy after a first PTS.

Methods: The register-based cohort study including all individuals hospitalized following a TBI in Sweden 2000-2010, in addition to 3 age-matched and sex-matched controls per case. We analyzed the 10-year probability of epilepsy following a first seizure using the Kaplan-Meier estimator.

Results: The risk of an epilepsy diagnosis was 41.1% (95% CI 38.6-43.7) following a PTS, higher than the risk of 33.4% (95% CI 30.3-36.5) in those without prior TBI. The risk increased with injury severity, with the highest risk following focal cerebral injuries, 62.3% (95% CI 53.7-70.9). Mild injuries and skull fractures showed a similar risk to the group without previous TBI. In addition, the risk was higher if the seizure occurred <2 years following the trauma.

Discussion: Severity of the injury and latency are major modulators of epilepsy risk following a first PTS. The risk was high in the most severe types of TBI, but a substantial proportion did not develop epilepsy, highlighting the need for further research on prognostication and biomarkers, as well as caution in diagnosing epilepsy based on a first PTS.