First seizure definitions and worldwide incidence and mortality.

While all patients with epilepsy experience seizures, not all individuals with seizures have epilepsy. Seizures may be acute symptomatic or unprovoked. Acute symptomatic seizures are seizures occurring at the time of a systemic insult or in close temporal association with a documented brain insult. Unprovoked seizures are seizures occurring in the absence of precipitating factors and may be caused by a static injury (remote symptomatic seizures) or a progressing injury (progressive symptomatic seizures). Unprovoked seizures may be single or recurrent (epilepsy). The incidence of acute symptomatic seizures is 29-39 per 100,000 per year. These predominate in men, in the youngest age class, and in the elderly. Traumatic brain injury, cerebrovascular disease, drug withdrawal, infarction, and metabolic insults are the commonest causes. The incidence of single unprovoked seizures is 23-61 per 100,000 person-years. As with epilepsy, single unprovoked seizures predominate in men and in patients less than 12 months and older than 65 years. Studies on the mortality of acute symptomatic seizures are lacking. A standardized mortality ratio (SMR) of 2.3 has been reported in patients experiencing a single unprovoked seizure. The SMR in patients with a newly diagnosed unprovoked seizure ranges from 2.5 to 4.1 according to the study population and design. The SMR is highest in the youngest patients and in those with symptomatic seizures.