Epileptic encephalopathy.

Abstract

Epileptic encephalopathies are conditions in which epileptic activity itself is postulated to contribute to severe cognitive and behavioural impairments above and beyond what might be expected from the underlying pathology alone. The term has been used in two ways: (1) as a generic classification term for epilepsies with severe cognitive and be-havioural outcomes and (2) as a pathophysiological process. We argue that the term is not synonymous with " severe epileptic syndrome ". Epileptic encephalopathy can complicate many different epileptic conditions. In some it is an almost constant feature (e.g., Lennox-Gastaut syndrome), in others expected but not invariable (e.g., West syndrome) whilst in yet others it may or may not occur with almost equal frequency (e.g., Doose syndrome). Epileptic encephalopathy very occasionally complicates otherwise benign epilepsies (e.g., benign rolandic epilepsy). Epileptic encephalopathy is a dynamic condition that may persist over time causing increasingly severe functional effects or else it may improve and remit, either spontaneously or with treatment which suppresses the proposed causative epileptic activity. Fundamental to the concept of epileptic encephalopathy is that the cognitive and other problems which characterise it result from epileptic activity, rather than being a consequence of any underling cerebral pathology (whether genetic, structural, metabolic inflammatory, etc.) which may itself be causing the epilepsy. However, all spontaneous epileptic phenomena in humans are a function of some kind of brain disease (genetic through to structural) and therefore it is likely that all cognitive impairments in children with epilepsy are at least in part a function of aetiology. When a brain disorder gives rise to both epilepsy and cog-nitive and behavioural problems, it should not be classed as an epileptic encephalopathy, but rather as an " epileptogenic encephalopathy ". The crucial difference being that the cogni-tive and behavioural problems are not a consequence of the epilepsy, but of the cerebral pathology. However, in epilepto-genic encephalopathies seizures may aggravate cognitive and behavioural problems and thus treatment of seizures may improve outcomes. Some disorders, mostly genetically determined and char-acterised by the onset of seizures in the first months of life and with developmental stagnation are best considered as " early onset epilepsies with encephalopathy " rather than epileptic encephalopathy. Both the epilepsy and the enceph-alopathy appear to be symptoms of a known or unknown genetic defect and there is no evidence that epileptic activity is primarily responsible for the developmental stagnation. Examples of this include disorders associated with CDKL5, …