Nonconvulsive status epilepticus: EEG analysis in a large series

We analyzed EEG characteristics comprehensively in a large series of nonconvulsive status epilepticus (NCSE) cases. Eighty-five ictal episodes in 78 patients were analyzed. The ictal discharges were generalized (group G) in 59 episodes (69%), diffuse with focal predominance (group GF) in 15 (18%), and focal (group F) in 11 (13%). The morphologies and patterns of persistence varied greatly. Frequency of ictal discharge was also variable and was almost always < 3 Hz. Demonstration of focal epileptic features in response to intravenous (i.v.) diazepam (DZP) and the presence of interictal focal epileptiform discharges in some cases in groups G and GF suggested possible focal onset secondarily generalized in these cases. This study suggests that electrographically NCSE is a highly heterogeneous epileptic state, and i.v. DZP may serve as a valuable diagnostic tool in differentiating generalized from focal onset NCSE.