Non-convulsive status epilepticus in adults - an overview

Abstract

Status epilepticus (SE) is the most frequent neurological emergency requiring admission on the intensive care unit (ICU). The classification of status epilepticus may be dichotomised into the and the form. Whereas the diagnosis of generalised convulsive status epilepticus (GCSE) is easily made in view of the evident manifestation, the diagnosis of non-convulsive status epilepticus (NCSE) may become very difficult according to its non-spectacular and protean presentation. Non-convulsive status epilepticus is a common cause of altered mental status and delirium; and a substantial number of comatose patients in the intensive care unit may suffer from NCSE. The most important part of making a diagnosis of NCSE is to think of it at all. The definite diagnosis of NCSE is dependent on electroencephalographic (EEG) confirmation. Repetitive or, optimally, continuous EEG recording may help to closely monitor seizure activity and to guide the therapy in order to protect the patient from under- and/or over-treatment. The interpretation of EEG recordings of NCSE may become challenging because of numerous artifacts caused by the patient, caregivers and devices, and because of trace elements of ambiguous significance and of waveforms mimicking epileptic activity. Non-convulsive status epilepticus was historically subdivided into the groups of complex-partial status epilepticus (focal; CPSE) and absence status (generalised; AS). Most recently, a classification proposed by the International League Against Epilepsy (ILAE) has subdivided focal NCSE into aura continua (non-convulsive simple partial with maintained consciousness) and into dys-cognitive (with impaired consciousness) of mesial temporal or neocortical origin. Several patients with focal NCSE or AS were known for pre-existing epilepsy. In addition, other types of NCSE have been reported, like subtle where convulsions in patients with GCSE clinically stop, but the continuous epileptic activity electroencephalographically still persists. Another variant belongs to those patients with critical illness where the serious disorder and/or medications may trigger an acute, prolonged and all too often very-hard-to-treat epileptic condition (critical illness SE [CISE]). The majority of these patients will never have had seizures before. Of note, none of the currently proposed classifications has gained broad acceptance and official approval. Since the need for immediate and intensive treatment of GCSE is beyond debate, the insidiously calm presentation of NCSE may mislead to a much less aggressive therapeutic approach. However, experimental and clinical data suggest that continuous epileptic activity in the brain during NCSE associated with consecutive (glutamatergic) hyperexcitation triggers neurotoxicity and proapoptotic mechanisms which eventually may lead to irreversible brain damage and the onset of a chronic epileptic disorder or to an irreversible neurological deficit. Thus, recent national and international guidelines and reviews recommend immediate and intensive treatment for NCSE as well as for GCSE. With a few exceptions, the first drug is an intravenous benzodiazepine, mainly lorazepam; intravenous phenytoin or valproate should be started without delay. Persistence of NCSE after administration of these two classes of drugs heralds refractory (RSE) where single or combinations of drugs in anaesthetic dosages requiring intubation and enteral antiepileptics may be added except for the cases of AS or an underlying terminal disease. The outcome of NCSE is mainly determined by the type, duration, cause and the severity of concomitant diseases.