What is nonconvulsive status epilepticus, and what are its subtypes?

Prolonged nonconvulsive seizures have been recognized at least since the 19th century, although their inclusion within the rubric of status epilepticus was only formalized by Gastaut and colleagues after the Xth Marseilles Colloquium, held in 1962 (Gastaut et al., 1967). This was the first ever large meeting devoted to the topic of status epilepticus, and the concept that there were status forms for every seizure type was formulated there. The classification of status epilepticus derived from the 1962 colloquium thus mirrored exactly the newly evolved International Classification of Seizure Type (Gastaut, 1970). The main disadvantage of a classification based on seizure type is that it does not take into account the broader range of phenomenology of epilepsy, which is especially significant in regard to nonconvulsive seizures. A seizure type classification does not do justice to the variety of forms and to their widely varying pathophysiological basis, prognosis, or clinical setting.