Research in context
Evidence before this study
We searched PubMed from database inception until Feb 18, 2019, for original cohort studies describing outcomes of epilepsy surgery related to histopathology or cause, using the terms “epilepsy surgery”, “outcome OR seizure”, and “histopathology OR histopathological OR etiology OR aetiology”, without language restrictions. Cohorts focusing on specific pathologies or brain regions were excluded because direct comparison of outcomes between pathologies would not be possible, as were studies without a comparison in surgery outcomes between different causes. The search yielded 252 results. Only five identified studies had sample sizes of more than 500 patients. The largest cohort sample size was 1995. None of these studies included all pathological categories, including encephalitis and vascular malformations. Only one study included a category consistent with a brain scar. The only cause included in all five studies was hippocampal sclerosis, four looked at either focal cortical dysplasia or the total group of malformations of cortical development, and only three looked at outcomes for tumours. The identified studies did not provide detailed information on expected surgical outcomes for all classes of histopathological diagnoses, nor for specific diagnoses. Postoperative drug freedom was not reported in any of the studies. None studied the effect of duration of epilepsy in the separate diagnoses.
Added value of this study
This study provides epilepsy surgery outcomes up to 5 years after surgery, for all major classes of histopathological diagnosis and specific sub-diagnoses, for 9147 patients. For the first time, to our knowledge, evidence for a correlation between long-term seizure and drug outcomes and cause, age, and epilepsy duration was provided.
Implications of all the available evidence
Epilepsy surgery should be considered in every person with drug-resistant focal and (presumed) lesional epilepsy. Surgery renders most selected patients free from disabling seizures. Histopathology is an important determinant of seizure outcome. Other independent determinants of seizure and drug outcomes are age at surgery, location of surgery, and duration of epilepsy. Longer duration of epilepsy is associated with poorer outcomes.