Epilepsy

Epilepsy is a chronic disorder of the brain defined by a lasting tendency to have seizures. A seizure is a brief episode, lasting seconds to minutes, in which groups of neurons fire together in an abnormal, excessive way. A single seizure, or one provoked by something like a high fever or very low blood sugar, does not by itself mean epilepsy; the usual working definition is at least two unprovoked seizures more than 24 hours apart.

Seizures look very different depending on where they start. Focal seizures begin in networks on one side of the brain and may cause odd sensations, twitching of one limb or a blank, confused spell. Generalized seizures involve both sides from the start and include brief absence seizures and tonic-clonic seizures with stiffening, jerking and loss of consciousness. Known causes include brain injury around birth, head trauma, stroke, brain infections, tumors and genetic conditions, but in about half of cases no cause is found.

Diagnosis uses the patient's history, electroencephalography (EEG), which records the brain's electrical activity, and brain imaging. Antiseizure medicines can make up to about 70 percent of people seizure-free, and surgery, special diets or nerve stimulators help some others. Around 50 million people have epilepsy worldwide.