 Epilepsy is one of the most common neurological disorders after stroke , and affects at least 50 million people worldwide . It is diagnosed in a person having recurrent unprovoked seizures . These occur when cortical neurons fire excessively , hypersynchronously , or both , leading to temporary disruption of normal brain function . This might affect , for example , the muscles , the senses , consciousness , or a combination . A seizure can be focal ( confined to one part of the brain ) or generalised ( spread widely throughout the brain and leading to a loss of consciousness ) . Epilepsy may occur for a variety of reasons ; some forms have been classified into epileptic syndromes , most of which begin in childhood . Epilepsy is considered refractory ( not yielding to treatment ) when two or three anticonvulsant drugs have failed to control it . About 60 % of patients will achieve control of their epilepsy with the first drug they use , whereas about 30 % do not achieve control with drugs . When drugs fail , other options include epilepsy surgery , vagus nerve stimulation and the ketogenic diet . 
