Seizures occur because of sudden, abnormal electrical activity in the brain. Contrary to popular belief, not all seizures cause someone to go into convulsions. Most of these brain disturbances last from 30 seconds to 2 minutes and do not cause lasting harm. It is a medical emergency if one lasts longer than 5 minutes or if a person has many and does not wake up between them. Causes include medicines, high fevers, head injuries and certain diseases. Epilepsy is a brain disorder involving chronic seizures of any type.