SUDEP: overview of definitions and review of incidence data.

The classification, occurrence, and predictors of sudden unexpected and unexplained death in individuals with epilepsy (SUDEP) have received considerable attention over the last few years. Specific criteria for the classification of definite, probable, possible, and not SUDEP implemented in United States epidemiologic studies are presented. The incidence of SUDEP in different epilepsy populations is presented. SUDEP is a real phenomenon, because the occurrence of such deaths, especially at relatively young ages, among individuals with epilepsy is far greater (perhaps 40-fold) than among those without epilepsy. SUDEP incidence rates are lower in population-based studies, higher in referral populations and clinical trials of adjunct drugs for complex partial epilepsy, and highest for surgical series. Seizure severity appears to be the strongest risk factor for SUDEP because higher rates are reported from studies of individuals with intractable epilepsy. Other potential risk factors, including sex, seizure etiology, younger age at onset, and partial-onset seizures, are unresolved.