When nerve cells in the brain fire electrical impulses at a rate higher than normal, this causes a sort of electrical storm in the brain, known as a seizure. A pattern of repeated seizures is often referred to as epilepsy. Known causes include head injuries, brain tumors, lead poisoning, abnormalities of the brain, genetic and infectious illnesses (like encephalitis and meningitis). But in fully half of cases, no cause can be found. Medication controls seizures for the vast majority of patients.