EEG in Convulsive and Nonconvulsive Status Epilepticus

Seizures and status epilepticus (SE) are serious complications in intensive care unit (ICU) patients. SE is often divided into convulsive and nonconvulsive types, based on clinical features. The EEG is helpful in further dividing SE into those that are generalized from onset, or have a partial onset, because this may be difficult to do clinically. This is particularly true in patients with tonic-clonic seizures, which may be generalized from onset, or secondarily generalized. Rarely in the ICU, although not infrequently in epilepsy monitoring units, the EEG may indicate that the event is nonepileptic, such as pseudostatus epilepticus. Nonconvulsive SE is often difficult to diagnose, be it partial or generalized, and the diagnosis is usually delayed. Furthermore, although an EEG is required to verify the diagnosis, there are not widely accepted criteria to diagnose this entity, particularly in obtunded/comatose patients. For example, it is controversial whether several EEG patterns, such as periodic lateralized and generalized periodic epileptiforms, are ictal or interictal. This article reviews EEG findings in different types of SE in adults and provides numerous examples.