Absence status epilepsy: Delineation of a distinct idiopathic generalized epilepsy syndrome

Purpose: Absence status epilepticus (AS) is a prolonged, generalized, and nonconvulsive seizure that may occur in various circumstances. We report a series of patients in whom recurrent, unprovoked, typical AS was the main clinical feature. Method: We retrospectively reviewed consecutive patients referred to our epileptic centers, on the following criteria: (1) recurrent, unprovoked episodes of typical AS representing the unique or the predominant seizure type, (2) at least one episode of AS recorded by video-EEG or by EEG only, and (3) clinical and EEG features fulfilling the criteria of idiopathic epilepsy. We excluded patients with situation-related AS. Results: We found 11 such cases (5F, 6M). The onset of AS was after puberty or in early adulthood in most; no clear triggering factor could account for the recurrence of AS episodes; infrequent generalized tonic-clonic seizures, and, rarely, absences, could also occur. These patients had no family history of epilepsy, normal neurological evaluation, normal neuroimaging, interictal EEG showing generalized spike- and polyspike-wave discharges on a normal background, no photoparoxysmal response, variable response of AS to intravenous benzodiazepines, and usually good seizure control with valproate. This peculiar condition was misdiagnosed in most because of the unusual clinical presentation and of some atypical interictal EEG findings, often leading to the use of inappropriate drugs. Conclusion: Although there is some overlap with previously described epilepsy syndromes, specific and shared features point to the existence of a distinct epilepsy entity that we propose to name "absence status epilepsy." This syndrome expands the spectrum of idiopathic generalized epilepsies.