Électroencéphalographie dans les états de mal épileptiques : glossaire, protocole et interprétation

Electroencephalography is a useful tool in the diagnosis and management of status epilepticus (SE) and it can also give prognostic information. It can help to confirm that an episode of SE has ended. It can identify the patients who have unsuspected subclinical seizures. There is a wide range of presentations of SE. Nearly all types of seizures have the potential of occurring in a repeated or continuous form. The polymorphic EEG patterns in SE reflect this wide variety. But controversial patterns also exist in the form of periodic epileptiform discharges. While some authors considered these patterns to be interictal or postictal, others postulate that these patterns are ictal. In these cases, clinical features are very important in order to conclude. Generalized convulsive SE is a medical emergency and the EEG is not necessary to make a diagnosis. Convulsive generalized SE requires immediate treatment and in this case, EEG is used in guiding treatment especially in refractory SE that may evolve into subtle SE. In non-convulsive SE, diagnosis is not obvious on the basis of clinical signs and symptoms alone and the diagnosis must be confirmed by urgent EEG. EEG can also be used to distinguish SE from psychogenic seizures, movement disorders and in patients who have causes of persistent loss of consciousness (metabolic encephalopathy, postanoxic encephalopathy). This article proposes a protocol for the use of the EEG in SE, guidelines and simple vocabulary for a good interpretation and comprehension of the EEG.