Mortality in a population-based cohort of epilepsy surgery patients

Purpose: To investigate mortality and especially the incidence of sudden unexpected death in epilepsy (SUDEP) in a population-based cohort of epilepsy surgery patients. Methods: All patients who underwent epilepsy surgery treatment between January 1990 and December 1998 (surgery patients) or whose presurgical evaluation started, although not leading to an operation, during the same period (nonsurgery patients) were identified through the Swedish National Epilepsy register. All subjects were followed up through the Cause of Death Register until December 1998. Standardized mortality ratios (SMRs) for all causes of death and incidence of SUDEP were calculated. Results: During the study period, 651 surgical operations were carried out on 596 patients (316 male). Of those, 14 patients died (six in SUDEP), rendering a total SMR of 4.9 [95% confidence interval (CI), 2.7-8.3]. SUDEP incidence was 2.4 per 1,000 person years. No major differences were found in SMRs or SUDEP rates between subgroups when stratifying for type of operation and for seizure outcome 2 years after surgery. SMR and SUDEP rates were higher in right-sided temporal lobe resections for gliosis than in left-sided, but the number of deaths was small. Among 212 nonsurgery patients, five died (four in SUDEP). The SMR for all causes was 7.9 (2.6-18.4), and SUDEP incidence, 6.3 per 1,000 person years. Conclusions: In this large and strictly population-based cohort, SMR for all causes and SUDEP incidence among surgery patients were similar to those of other studies. No differences in overall mortality emerged by seizure outcome, but none of the SUDEP cases was seizure free at the time of death. Four of five deaths in the nonsurgery group occurred during the surgery evaluation period. Mortality appeared to be lower for surgery than for nonsurgery patients, and the interpretation of this finding is discussed.