Epilepsy is a group of neurological disorders characterized by epileptic seizures. Epileptic seizures are episodes that can vary from brief and nearly undetectable to long periods of vigorous shaking. In epilepsy, seizures tend to recur, and have no immediate underlying cause while seizures that occur due to a specific cause are not deemed to represent epilepsy.
About 1% of people worldwide (65 million) have epilepsy, and nearly 80% of cases occur in countries. Epilepsy becomes more common as people age. In the developed world, onset of new cases occurs most frequently in infants and the elderly, in the developing world this is in older children and young adults, due to differences in the frequency of the underlying causes. About 5–10% of all people will have an unprovoked seizure by the age of 80, and the chance of experiencing a second seizure is between 40 and 50%. In many areas of the world those with epilepsy either have their ability to drive restricted or disallowed, but most are able to return to driving after a period of time without seizures.