Identifying EEG features of nonconvulsive status epilepticus (NCSE)

Nonconvulsive status epilepticus and coma

Nonconvulsive status epilepticus (NCSE) in a comatose patient cannot be diagnosed without electroencephalography (EEG). In many advanced coma stages, the EEG exhibits continuous or periodic EEG abnormalities, but their causal role in coma remains unclear in many cases. To date there is no consensus on whether to treat NCSE in a comatose patient in order to improve the outcome or to retract from treatment, as these EEG patterns might reflect the end stages of a dying brain. On the basis of EEG, NCSE in comatose patients may be classified as generalized or lateralized. This review aims to summarize the ongoing debate of NCSE and coma and to critically reassess the available literature on coma with epileptiform EEG pattern and its prognostic and therapeutic implications. The authors suggest distinguishing NCSE proper and comatose NCSE, which includes coma with continuous lateralized discharges or generalized epileptiform discharges (coma-LED, coma-GED). Although NCSE proper is accompanied by clinical symptoms suggestive of status epilepticus and mild impairment of consciousness, such as in absence status or complex focal status epilepticus, coma-LED and coma-GED represent deep coma of various etiology without any clinical motor signs of status epilepticus but with characteristic epileptiform EEG pattern. Hence coma-LED and coma-GED can be diagnosed with EEG only. Subtle or stuporous status epilepticus and epilepsia partialis continua-like symptoms in severe acute central nervous system (CNS) disorders represent the borderland in this biologic continuum between NCSE proper and comatose NCSE (coma-LED/GED). This pragmatic differentiation could act as a starting point to solve terminologic and factual confusion.