02-EEG in nonconvulsive status epileptisus (NCSE)

Abstract

Nonconvulsive status epilepticus (NCSE) is a serious acute situation in neurology which is not always identified. It covers a heterogenous group of electrophysiological situations. The diagnosis of NCSE requires an electroencephalogram (EEG), since clinical signs and symptoms are often nonspecific. As EEG patterns are not always unequivocal, no reliable diagnostic test exists. To simplify the diagnosis, Salzburg EEG Criteria for NCSE were formulated in 2013, with clinical validation still in progress. According to these criteria there are three possible EEG patterns in NCSE patients without preexisting epileptic encephalopathy: (a) unequivocal finding with rythmic epileptic discharges (EDs) > 2.5/s and (b) two equivocal patterns (periodic EDs ⩽ 2.5/s or rhythmic delta/theta activity exceeding 0.5/s). In those equivocal findings at least one of the additional criteria must be present for diagnosis – clinical and EEG improvements from antiepileptic drugs, subtle clinical phenomena, or typical spatiotemporal evolution. Equivocal patterns are considered to be an ictal-interictal continuum and they may or may not be a correlate of NCSE especially in critically ill patients. For the correct assessment of the importance of these patterns one must be familiar with the new ACNS Standardized Critical Care EEG Terminology which replaces clinically unequivocal terms by neutral descriptive ones.