To determine the predictive value of the localization of epileptiform discharges after complex febrile seizure (CFS) for future development of epilepsy.

Febrile seizures are a common illness in children but no clear consensus exists regarding the prognostic value of specific epileptiform discharges after CFS.

We conducted a retrospective study of patients seen at a large tertiary children's hospital system from 2009 to 2019, who underwent an EEG after their CFS.  Children who were started on anti-seizure medications before the CFS or had known brain abnormalities or genetic conditions were excluded.  Initiation of anti-seizure medication after the CFS excluded patients from sub-analysis regarding development of epilepsy.

Epileptiform discharges were seen in 9% (56/621) of EEGs in children with CFS.  Although the discharges occurred in multiple localizations, 51.8% of the children had midline-vertex discharges.  Midline-vertex discharges occurred at a significantly greater rate than the next most frequent localization (generalized discharges, p = 0.002).  Among the patients who received EEGs and completed at least one year of follow-up, 24.7% subsequently developed epilepsy, 20% (12/60) of whom had interictal epileptiform discharges.  Midline-vertex discharges were seen at a similar rate in children who did not develop epilepsy (55%) and those who developed epilepsy (45%).  The development of epilepsy was not associated with any localization.  A logistic regression model identified four factors as predictors of future epilepsy (p < 0.05): > 3 febrile seizures in 24 hours, interictal epileptiform discharges, family history of afebrile seizures, and age of CFS onset > 3 years.

Midline-vertex epileptiform discharges occurred at a higher rate in EEGs after CFS but their presence alone is not necessarily predictive of subsequent epilepsy. Our data did not reveal any specific localization with greater predictive value for future epilepsy. A future prospective study could elucidate outcomes in children with midline-vertex discharges.