Types of Status Epilepticus: Definitions and Classification

Abstract

Status epilepticus (SE), the “maximum expression of epilepsy” (derived etymologically from the original term status in Latin), was defined in the 1962 Xth Marseilles Colloquium to be “… a term [used for] a seizure that persists for a sufficient length of time or is repeated frequently enough to produce a fixed and enduring condition.” Although no duration was then specified, Gastaut later proposed 60 min as a minimum, and later hypothesized that the many types of status reflected the many types of epileptic seizures. SE mirrored the seizure classification and was divided into partial, generalized, or unilateral types. In 1981 “…recovery between attacks does not occur,” was added. The 2006 ILAE report defined it “mechanistically” as “the failure of the natural homeostatic seizure-suppressing mechanisms responsible for seizure termination” without noting specific duration. Timelines in clinical trials and treatment have been moved progressively to 20, then 10 min. The 2009 classification provided two dimensions: a conceptual approach from scientific evidence, and an operational frame to guide management. Hence, “Status epilepticus is a condition resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms, which lead to abnormally prolonged seizures (after time-point t1). It is a condition, which can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures.” Research suggested 5 min for generalized tonic–clonic seizures, a t1 of ~10 min for focal seizures when treatment should be considered. At t2 (~30 min) damage to neuronal networks may begin, warranting aggressive treatment. In 2015, four axes were delineated: (1) semiology, (2) etiology, (3) EEG correlates, and (4) age. Motor activity and disturbance of consciousness guide clinical management. Future research should establish t1 and t2 for different SE types.