epilepsy is a brain disorder in which clusters of nerve cells or neurons in the brain sometimes signal abnormally. neurons normally generate electrochemical impulses that act on other neurons glands and muscles to produce human thoughts feelings and actions. in epilepsy the normal pattern of neuronal activity becomes disturbed causing strange sensations emotions and behavior or sometimes convulsions muscle spasms and loss of consciousness. during a seizure neurons may fire as many as 500 times a second much faster than normal. in some people this happens only occasionally; for others it may happen up to hundreds of times a day. more than 2 million people in the united states -- about 1 in 100 -- have experienced an unprovoked seizure or been diagnosed with epilepsy. for about 80 percent of those diagnosed with epilepsy seizures can be controlled with modern medicines and surgical techniques. however about 25 to 30 percent of people with epilepsy will continue to experience seizures even with the best available treatment. doctors call this situation intractable epilepsy. having a seizure does not necessarily mean that a person has epilepsy. only when a person has had two or more seizures is he or she considered to have epilepsy. epilepsy is not contagious and is not caused by mental illness or mental retardation. some people with mental retardation may experience seizures but seizures do not necessarily mean the person has or will develop mental impairment. many people with epilepsy have normal or above-average intelligence. famous people who are known or rumored to have had epilepsy include the russian writer dostoyevsky the philosopher socrates the military general napoleon and the inventor of dynamite alfred nobel who established the nobel prize. several olympic medalists and other athletes also have had epilepsy. seizures sometimes do cause brain damage particularly if they are severe. however most seizures do not seem to have a detrimental effect on the brain. any changes that do occur are usually subtle and it is often unclear whether these changes are caused by the seizures themselves or by the underlying problem that caused the seizures. while epilepsy cannot currently be cured for some people it does eventually go away. one study found that children with idiopathic epilepsy or epilepsy with an unknown cause had a 68 to 92 percent chance of becoming seizure-free by 20 years after their diagnosis. the odds of becoming seizure-free are not as good for adults or for children with severe epilepsy syndromes but it is nonetheless possible that seizures may decrease or even stop over time. this is more likely if the epilepsy has been well-controlled by medication or if the person has had epilepsy surgery.
what is epilepsy?