An epileptic seizure is defined as excessive and/or hypersynchronous neuronal electrical activity in the cerebral cortex resulting in paroxysmal episodes of abnormal consciousness, motor activity, sensory input and/or autonomic function. Essentially, seizure activity represents temporary abnormal forebrain function with clinical characteristics dependent on the location of the abnormality (see also Chapter 7). Status epilepticus (SE) is defined as continuous seizure activity lasting 20-30 minutes or longer. A clinically more practical definition would be a seizure lasting longer than 5 minutes, or two or more seizures between which the patient does not completely recover consciousness. Cluster seizures are defined as two or more seizures over a short period of time (minutes to 24 hours), between which the patient regains consciousness.