An epileptic seizure is a symptom of disturbed electrical brain activity and can result from many causes. Epileptic seizures may be classified as focal (partial/localised), generalised (involving both hemispheres), or unclassified. Generalised seizures may be further divided into absence (typical or atypical), myoclonic, clonic, tonic, tonic-clonic, and atonic (astatic) types.  In 2009, a task force support by the International League Against Epilepsy (ILAE) issued a report revising the system of terminology and classification used for the description of individual seizures and epilepsy syndromes.  Non-epileptic seizures (where there is no electrical disruption in the brain) may mimic epileptic seizures. Their cause may be psychogenic (e.g., due to stress) or physiological (e.g., due to metabolic derangement such as hyponatraemia or hypoglycaemia).