An epileptic seizure is a paroxysmal event due to an excessive, usually self-limited, abnormal activity in the cerebral cortex. Epilepsy is defined by the recurrence of seizures and derives its name from the Greek verb which means ‘to be seized’. In the past it has been alternatively known as the falling sickness as falling down is a common symptom during a seizure, or the sacred disease because seizures were interpreted as an indication of demonic possession.
For centuries the study of epilepsy was mainly identified with the description of seizures. We know now that the clinical spectrum of epilepsy is extremely wide. It ranges from benign, age-related, isolated idiopathic seizures in normal individuals, to malignant symptomatic epileptic encephalopathies with major disability and cognitive impairment. Although for practical clinical purposes, epilepsy may still be a useful diagnostic category, it would be too simplistic to consider it as a single nosologic entity. Epileptic seizures represent a common response of the brain to different etiologic substrates, which can comprise conditions such as age-related ion channel dysfunction and brain tumours.
Epilepsy is one of the most frequently occurring neurological diseases. However, epidemiological studies have encountered difficulties due to methodological limitations. These are related to clinical and etiological heterogeneity as well as to the criteria used in order to define the disorder (isolated vs. repetitive seizures) and data collection (population-based studies vs. hospital-based studies or national general practice surveys).
Prevalence of active epilepsy in Rochester, Minnesota (Hauser et al., 1991) was estimated at 0.68% when either spontaneous recurring seizures had occurred or an antiepileptic drug treatment had been taken during the last 5 years. Prevalence rates at 0.5–0.8% appeared in other studies in different parts of the world. The incidence of epilepsy has been estimated to range between 17.3 and 136 per 100000 individuals. The incidence curve for epilepsy with respect to age, has a peculiar bimodal distribution (Fig. 74.1; Hauser et al., 1993). Although the incidence of various seizure types has not been clearly determined, focal seizures seem to be the more frequent. (Fig. 74.2) The incidence of the various epilepsy syndromes is still under evaluation (Commission, 1993).