Epilepsy after brain infection in adults: A register-based population-wide study.

OBJECTIVE: To describe risk and risk factors of epilepsy after hospitalization for brain infection in adults in Sweden.

METHODS: This was a matched retrospective cohort study based on the comprehensive National Patient and Cause of Death Registers. All individuals age >18 without prior epilepsy who received inpatient care in 2000-2010 for a brain infection were included, with 3 age- and sex-matched unexposed controls per exposed individual (n = 12,101 exposed and 36,228 controls). Kaplan-Meier risks of epilepsy after different brain infections were calculated and risk factors identified by Cox regression. Patients were followed until the end of 2017.

RESULTS: The 10-year risk of epilepsy was 5.9% (95% confidence interval [CI] 5.5-6.3) in cases and 1.2% (95% CI 1.0-1.4) in controls: 1.7% (95% CI 0.7-2.7) after tick-borne encephalitis, 4.1% (95% CI 3.3-4.9) after bacterial meningitis, 26.0% (95% CI 21.5-30.5) after herpes simplex virus encephalitis, and 30.2% (95% CI 27.1-33.3) after brain abscess. In Cox regression, seizure during the index admission and mechanical ventilation were epilepsy risk factors.

CONCLUSIONS: Epilepsy is common after several types of brain infections in adults. The type of infection, its severity, and propensity to cause seizures in the acute phase influence the risk of subsequent epilepsy.

CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that in adults, brain infection is associated with an increased risk of subsequent epilepsy.