Seizures and epilepsies

Epilepsy is the most common of disabling neurological conditions, and seizures are among the most common of neurological symptoms. Seizures are paroxysmal, transitory events that alter consciousness or other cortical function, and they result from episodic neurologic, psychiatric, or extracerebral (particularly cardiovascular) dysfunction. Epileptic seizures are distinguished from other such events by their abnormally synchronized electrical discharges in localized or widely distributed groups of cerebral neurons; such hypersynchronous discharges do not occur during organic or psychogenic non-epileptic seizures, certain of which may produce behaviors closely resembling those of epileptic seizures. Many individuals experience a single generalized tonic–clonic seizure at some time in life, which can be caused by electrolyte disturbances, hypoglycemia, or other extracerebral conditions. Epilepsy is diagnosed only when persisting cerebral dysfunction causes recurring epileptic seizures. Approximately 5% of the general population has one or more epileptic seizure during their lifetimes. At any point in time, 1–2% of the population has epilepsy; cumulative lifetime incidence exceeds 3%. Seizures are refractory to control with antiepileptic drugs in more than 30% of all epilepsies, but the incidence of drug refractoriness varies considerably across the wide range of epileptic syndromes.[3]