Epileptic encephalopathies are severe brain disorders of early age that manifest with: (1) electrographic EEG paroxysmal activity that is often aggressive, (2) seizures that are usually multi-form and intractable, (3) cognitive, behavioral, and neurological deficits that may be relentless, and (4) sometimes early death.
The concept of 'epileptic encephalopathies' is based on the assumption that aggressive ictal (seizure) and electrical (electrographic) epileptogenic activity during brain maturation is the main causative factor of progressive cognitive and neuropsychological deterioration or regression. Conversely, this deleterious epileptic activity is a specific age-related brain reaction of excessive neocortical excitability to different pathological conditions, which are focal or diffuse, of symptomatic or idiopathic cause. This age-related epileptogenic reaction is peculiar to the immature brain and varies significantly in accordance with the stage of brain maturity at the time that this occurs. Thus, EEG demonstrates primarily burst-suppression patterns in the neonatal period, hypsarrhythmia in infancy, and slow generalized spike-wave discharges (GSWD) in early childhood. With advancing age, the seizure and electrographic epileptogenic features may evolve from one to another age-related stage that is from burst-suppression to hypsarrhythmia and then to slow GSWD. All epileptic encephalopathies have a tendency to abate, discontinue, or even stop in adolescence but often with serious neurocognitive residuals.
The following are syndromes of epileptic encephalopathies with onset in the neonatal period, infancy, and early childhood:
- Dravet syndrome (severe myoclonic epilepsy in infancy)
- Early myoclonic encephalopathy
- Epilepsy with continuous spike-and-waves during slow-wave sleep (other than Landau-Kleffner syndrome)
- Hypothalamic (gelastic) epilepsy (included in this section because it manifests with progressive severe seizures and cognitive and behavioral decline)
- Landau-Kleffner syndrome
- Lennox-Gastaut syndrome
- Myoclonic status in non-progressive encephalopathies
- Ohtahara syndrome
- West syndrome
The epileptic syndromes and their significance
A major advance in recent epileptology is the recognition of epileptic syndromes that allows an accurate diagnosis and management of seizure disorders.[1-3]
Medical diagnosis is the identification of a disease by investigation of its symptoms and history, which provides a solid basis for the treatment and prognosis of the individual patient. An accurate diagnosis is the golden rule in medicine, and epilepsies should not be an exception to this. Like in any other disease, the recognition of non-fortuitous clustering of symptoms and signs in epilepsies requires the study of detailed clinical and laboratory data.[1-3] However, often in current practice, the diagnosis is limited to either epilepsy or seizures, which is unsatisfactory because this cannot provide guidance on important items such as severity of the disease, prognosis, short- and long-term therapeutic decisions, and genetics (research and counselling), which are all factors that crucially affect personal, family, and social life; education; and career choices of patients. Defining the type of epilepsy should now be considered mandatory as it offers the best guide to both management and prognosis. Most epileptic syndromes and diseases are well defined and easy to diagnose. The benefits of syndromic diagnosis over seizure/symptom diagnosis or an inclusive diagnosis such as epilepsy far outweigh any morbidity from incorrect categorization that may arise in difficult cases.
Important clinical features of a syndrome include the type of seizures, their localization, frequency, sequence of events, circadian distribution, precipitating factors, age at onset, mode of inheritance, physical or mental symptoms and signs, prognosis, and response to treatment.
Epilepsies or epilepsy?
The clinical and practical significance of the syndromic diagnosis of epilepsies is well illustrated by 3 common epileptic disorders. Benign childhood focal epilepsies, juvenile myoclonic epilepsy (JME), and hippocampal epilepsy have nothing in common other than the fact that they may all be complicated by generalized tonic clonic seizures (GTCS), which are primarily GTCS in JME and secondarily GTCS in benign childhood focal epilepsies and hippocampal epilepsy.
Furthermore, the short-and long-term treatment strategies are entirely different for each disorder: benign childhood focal epilepsies may or may not require medication for a few years, appropriate anti-epileptic drug (AED) treatment is lifelong in JME while neurosurgery may be life-saving for patients with hippocampal epilepsy. What may be a life-saving drug such as carbamazepine for hippocampal epilepsy may be ill-advised for JME.
It should not be difficult to distinguish an intelligent child with benign focal seizures or childhood absence epilepsy from a child with Kozhevnikov-Rasmussen, Lennox-Gastaut, Down, or Sturge-Weber syndrome or a child with severe post-traumatic cerebral damage, brain anoxia, or catastrophic progressive myoclonic epilepsy. Describing all these children as simply having epilepsy just because they have seizures offers no more benefit than a diagnosis of febrile illness irrespective of cause, which may be a mild viral illness, a life-threatening acute bacterial meningitis, or a malignancy. Inappropriate generalizations with regard to terminology, diagnosis, and treatment are the single most important factor of mismanagement in epilepsies.
- Engel J Jr. A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: Report of the ILAE Task Force on Classification and Terminology. Epilepsia 2001;42:796-803.
- Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989;30:389-99.
- Blume WT, Luders HO, Mizrahi E, Tassinari C, van Emde BW, Engel J Jr. Glossary of descriptive terminology for ictal semiology: report of the ILAE task force on classification and terminology. Epilepsia 2001;42:1212-8.
- Panayiotopoulos CP. A clinical guide to epileptic syndromes and their treatment. Second edition. London:Springer; 2007.
For details and bibliography for these syndromes see the reference book: Panayiotopoulos CP. A clinical guide to epileptic syndromes and their treatment. Second edition. London:Springer; 2007.
This section was adapted from:
The educational kit on epilepsies: The epileptic syndromes By C. P. Panayiotopoulos Originally published by MEDICINAE, 21 Cave Street, Oxford OX4 1BA First published 2006 and reprinted in 2007. The Educational Kit on Epilepsies was produced through an unrestricted educational grant from UCB Pharma SA. UCB Pharma SA assumes no responsibility of the views expressed and recommended treatments in these volumes.