spread and recruitment of neurons include an increase in K+ from outside the cell, and increase of Ca2+ in the presynaptic terminals. These mechanisms blunt hyperpolarization and depolarizes nearby neurons, as well as increasing neurotransmitter release. Diagnosis Seizures may be divided into provoked and unprovoked. Provoked seizures may also be known as "acute symptomatic seizures" or "reactive seizures". Unprovoked seizures may also be known as "reflex seizures". Depending on the presumed cause blood tests and lumbar puncture may be useful. Hypoglycemia may cause seizures and should be ruled out. An electroencephalogram and brain imaging with CT scan or MRI scan is recommended in the work-up of seizures not associated with a fever. Classification Seizure types are organized by whether the source of the seizure is localized (focal seizures) or distributed (generalized seizures) within the brain. Generalized seizures are divided according to the effect on the body and include tonic-clonic (grand mal), absence (petit mal), myoclonic, clonic, tonic, and atonic seizures. Some seizures such as epileptic spasms are of an unknown type. Focal seizures (previously called partial seizures) are divided into simple partial or complex partial seizure. Current practice no longer recommends this, and instead prefers to describe what occurs during a seizure. The classification of seizures can also be made according to dynamical criteria, observable in electrophysiological measurements. It is a classification according to their type of onset and offset. Physical examination Most people are in a postictal state (drowsy or confused) following a seizure. They may show signs of other injuries. A bite mark on the side of the tongue helps confirm a seizure when present, but only a third of people who have had a seizure have such a bite. When present in people thought to have had a seizure, this physical sign tentatively increases the likelihood that a seizure was the cause. Tests An electroencephalography is only recommended in those who likely had an epileptic seizure and may help determine the type of seizure or syndrome present. In children it is typically only needed after a second seizure. It cannot be used to rule out the diagnosis and may be falsely positive in those without the disease. In certain situations it may be useful to prefer the EEG while sleeping or sleep deprived. Diagnostic imaging by CT scan and MRI is recommended after a first non-febrile seizure to detect structural problems inside the brain. MRI is generally