Jerome Engel

Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005-2009.

The International League Against Epilepsy (ILAE) Commission on Classification and Terminology has revised concepts, terminology, and approaches for classifying seizures and forms of epilepsy. Generalized and focal are redefined for seizures as occurring in and rapidly engaging bilaterally distributed networks (generalized) and within networks limited to one hemisphere and either discretely localized or more widely distributed (focal). Classification of generalized seizures is simplified. No natural classification for focal seizures exists; focal seizures should be described according to their manifestations (e.g., dyscognitive, focal motor). The concepts of generalized and focal do not apply to electroclinical syndromes. Genetic, structural–metabolic, and unknown represent modified concepts to replace idiopathic, symptomatic, and cryptogenic. Not all epilepsies are recognized as electroclinical syndromes. Organization of forms of epilepsy is first by specificity: electroclinical syndromes, nonsyndromic epilepsies with structural–metabolic causes, and epilepsies of unknown cause. Further organization within these divisions can be accomplished in a flexible manner depending on purpose. Natural classes (e.g., specific underlying cause, age at onset, associated seizure type), or pragmatic groupings (e.g., epileptic encephalopathies, self‐limited electroclinical syndromes) may serve as the basis for organizing knowledge about recognized forms of epilepsy and facilitate identification of new forms.

A Proposed Diagnostic Scheme for People with Epileptic Seizures and with Epilepsy: Report of the ILAE Task Force on Classification and Terminology

The International League Against Epilepsy (ILAE) made a major contribution when it established standardized classifications and terminology for epileptic seizures and syndromes. This provided a universal vocabulary that not only facilitated communication among clinicians, but also established a taxonomic foundation for performing quantitative clinical and basic research on epilepsy. Much, however, has changed since the adoption of the currently used Classification of Epileptic Seizures in 1981 (1) and the Classification of Epilepsies and Epileptic Syndromes in 1989 (2). Consequently, the Executive Committee of the ILAE, which took office in July 1997, agreed that review and revision of the current classification system would be a priority for this Executive term. A Task Force on Classification and Terminology was appointed, which divided itself into four working groups concerned with Descriptive Terminology for Ictal Events; Seizures; Syndromes and Diseases; and Impairment. During the course of several meetings and vigorous e-mail discussions, the Task Force agreed that it would not be possible to replace the current international classifications with similar revised and updated classifications that would be universally accepted and meet all the clinical and research needs such a formal organizational system would be expected to provide. Rather, the Task Force is proposing a diagnostic scheme that makes use of standardized terminology and concepts to describe individual patients (Table 1). Within this diagnostic scheme, a variety of approaches to classification are possible, and some are presented here by way of example only. The Task Force views the development of specific classifications as a continuing work in progress. Flexible and dynamic classifications will be revised periodically based not only on rapidly emerging new information, but also on the resolution of problems that will inevitably be identified through use. At this point, the proposal does include several definitive changes in concepts and terminology (Table 2), and classifications are presented as examples of what could be devised in the future.

ILAE Official Report: A practical clinical definition of epilepsy

Epilepsy was defined conceptually in 2005 as a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures. This definition is usually practically applied as having two unprovoked seizures >24 h apart. The International League Against Epilepsy (ILAE) accepted recommendations of a task force altering the practical definition for special circumstances that do not meet the two unprovoked seizures criteria. The task force proposed that epilepsy be considered to be a disease of the brain defined by any of the following conditions: (1) At least two unprovoked (or reflex) seizures occurring >24 h apart; (2) one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years; (3) diagnosis of an epilepsy syndrome. Epilepsy is considered to be resolved for individuals who either had an age‐dependent epilepsy syndrome but are now past the applicable age or who have remained seizure‐free for the last 10 years and off antiseizure medicines for at least the last 5 years. “Resolved” is not necessarily identical to the conventional view of “remission or “cure.” Different practical definitions may be formed and used for various specific purposes. This revised definition of epilepsy brings the term in concordance with common use.

Practice parameter: Temporal lobe and localized neocortical resections for epilepsy Report of the Quality Standards Subcommittee of the American Academy of Neurology, in Association with the American Epilepsy Society and the American Association of Neurological Surgeons

Objectives/Methods: To examine evidence for effectiveness of anteromesial temporal lobe and localized neocortical resections for disabling complex partial seizures by systematic review and analysis of the literature since 1990. Results: One intention-to-treat Class I randomized, controlled trial of surgery for mesial temporal lobe epilepsy found that 58% of patients randomized to be evaluated for surgical therapy (64% of those who received surgery) were free of disabling seizures and 10 to 15% were unimproved at the end of 1 year, compared with 8% free of disabling seizures in the group randomized to continued medical therapy. There was a significant improvement in quantitative quality-of-life scores and a trend toward better social function at the end of 1 year for patients in the surgical group, no surgical mortality, and infrequent morbidity. Twenty-four Class IV series of temporal lobe resections yielded essentially identical results. There are similar Class IV results for localized neocortical resections; no Class I or II studies are available. Conclusions: A single Class I study and 24 Class IV studies indicate that the benefits of anteromesial temporal lobe resection for disabling complex partial seizures is greater than continued treatment with antiepileptic drugs, and the risks are at least comparable. For patients who are compromised by such seizures, referral to an epilepsy surgery center should be strongly considered. Further studies are needed to determine if neocortical seizures benefit from surgery, and whether early surgical intervention should be the treatment of choice for certain surgically remediable epileptic syndromes.

Glossary of descriptive terminology for ictal semiology: report of the ILAE task force on classification and terminology.

INTRODUCTION PRINCIPLES FOR TERMS AND DEFINITIONS DATA SOURCES I GENERAL TERMS 1.0 SEMIOLOGY 2.0 EPILEPTIC SEIZURE 3.0 ICTUS 4.0 EPILEPSY 5.0 FOCAL 6.0 GENERALIZED 7.0 CONVULSION II TERMS DESCRIBING EPILEPTIC SEIZURE SEMIOLOGY 1.0 MOTOR 1.1 ELEMENTARY MOTOR 1.1.1 TONIC 1.1.1.1 EPILEPTIC SPASM 1.1.1.2 POSTURAL 1.1.1.2.1 VERSIVE 1.1.1.2.2 DYSTONIC 1.1.2 MYOCLONIC 1.1.2.1 NEGATIVE MYOCLONIC 1.1.2.2 CLONIC 1.1.2.2.1 JACKSONIAN MARCH 1.1.3 TONIC-CLONIC 1.1.3.1 GENERALIZED TONIC-CLONIC SEIZURE 1.1.4 ATONIC 1.1.5 ASTATIC 1.1.6 SYNCHRONOUS 1.2 AUTOMATISM 1.2.1 OROALIMENTARY 1.2.2 MIMETIC 1.2.3 MANUAL OR PEDAL 1.2.4 GESTURAL 1.2.5 HYPERKINETIC 1.2.6 HYPOKINETIC 1.2.7 DYSPHASIC 1.2.8 DYSPRAXIC 1.2.9 GELASTIC 1.2.10 DACRYSTIC 1.2.11 VOCAL 1.2.12 VERBAL 1.2.13 SPONTANEOUS 1.2.14 INTERACTIVE 2.0 NON-MOTOR 2.1 AURA 2.2 SENSORY 2.2.1 ELEMENTARY 2.2.1.1 SOMATOSENSORY 2.2.1.2 VISUAL 2.2.1.3 AUDITORY 2.2.1.4 OLFACTORY 2.2.1.5 GUSTATORY 2.2.1.6 EPIGASTRIC 2.2.1.7 CEPHALIC 2.2.1.8 AUTONOMIC 2.2.2 EXPERIENTIAL 2.2.2.1 AFFECTIVE 2.2.2.2 MNEMONIC 2.2.2.3 HALLUCINATORY 2.2.2.4 ILLUSORY 2.3 DYSCOGNITIVE 3.0 AUTONOMIC EVENTS 3.1 AUTONOMIC AURA 3.2 AUTONOMIC SEIZURE 4.0 SOMATOTOPIC MODIFIERS 4.1 LATERALITY 4.1.1 UNILATERAL 4.1.1.1 HEMI4.1.2 GENERALIZED (syn. “bilateral”) 4.1.2.1 ASYMMETRICAL 4.1.2.2 SYMMETRICAL 4.2 BODY PART 4.3 CENTRICITY 4.3.1 AXIAL Epilepsia, 42(9):1212–1218, 2001 Blackwell Science, Inc.

Hippocampal and Entorhinal Cortex High‐Frequency Oscillations (100–500 Hz) in Human Epileptic Brain and in Kainic Acid‐Treated Rats with Chronic Seizures

Summary: Purpose: Properties of oscillations with frequencies >100 Hz were studied in kainic acid (KA)‐treated rats and compared with those recorded in normal and kindled rats as well as in patients with epilepsy to determine differences associated with epilepsy.

Report of the ILAE Classification Core Group

Summary:  A Core Group of the Task Force on Classification and Terminology has evaluated the lists of epileptic seizure types and epilepsy syndromes approved by the General Assembly in Buenos Aires in 2001, and considered possible alternative systems of classification. No new classification has as yet been proposed. Because the 1981 classification of epileptic seizure types, and the 1989 classification of epilepsy syndromes and epilepsies are generally accepted and workable, they will not be discarded unless, and until, clearly better classifications have been devised, although periodic modifications to the current classifications may be suggested. At this time, however, the Core Group has focused on establishing scientifically rigorous criteria for identification of specific epileptic seizure types and specific epilepsy syndromes as unique diagnostic entities, and is considering an evidence‐based approach. The short‐term goal is to present a list of seizure types and syndromes to the ILAE Executive Committee for approval as testable working hypotheses, subject to verification, falsification, and revision. This report represents completion of this work. If sufficient evidence subsequently becomes available to disprove any hypothesis, the seizure type or syndrome will be reevaluated and revised or discarded, with Executive Committee approval. The recognition of specific seizure types and syndromes, as well as any change in classification of seizure types and syndromes, therefore, will continue to be an ongoing dynamic process. A major purpose of this approach is to identify research necessary to clarify remaining issues of uncertainty, and to pave the way for new classifications.

High-frequency oscillations in human brain

Ripples are 100–200 Hz short‐duration oscillatory field potentials that have recently been recorded in rat hippocampus and entorhinal cortex. They reflect fast IPSPs on the soma of pyramidal cells, which occur during synchronous afferent excitation of principal cells and interneuron networks. We now describe two similar types of high‐frequency field oscillations recorded from the entorhinal cortex and hippocampus of patients with mesial temporal lobe epilepsy. The first type appears be the human equivalent of normal ripples in the rat. The second, which we have termed fast ripples (FR), are in the frequency range of 250–500 Hz. FR are found in the epileptogenic region and may reflect pathological hypersynchronous population spikes of bursting pyramidal cells. Hippocampus 1999;9:137–142.

High‐frequency oscillations: What is normal and what is not?

High‐frequency oscillations (HFOs) in the 80–200 Hz range can be recorded from normal hippocampus and parahippocampal structures of humans and animals. They are believed to reflect inhibitory field potentials, which facilitate information transfer by synchronizing neuronal activity over long distances. HFOs in the range of 250–600 Hz (fast ripples, FRs) are pathologic and are readily recorded from hippocampus and parahippocampal structures of patients with mesial temporal lobe epilepsy, as well as rodent models of this disorder. These oscillations, and similar HFOs recorded from neocortex of patients, appear to identify brain tissue capable of spontaneous ictogenesis and are believed to reflect the neuronal substrates of epileptogenesis and epileptogenicity. The distinction between normal and pathologic HFOs (pHFOs), however, cannot be made on the basis of frequency alone, as oscillations in the FR frequency range can be recorded from some areas of normal neocortex, whereas oscillations in the ripple frequency range are present in epileptic dentate gyrus where normal ripples never occur and, therefore, appear to be pathologic. The suggestion that FRs may be harmonics of normal ripples is unlikely, because of their spatially distinct generators, and evidence that FRs reflect synchronized firing of abnormally bursting neurons rather than inhibitory field potentials. These synchronous population spikes, however, can fire at ripple frequencies, and their harmonics appear to give rise to FRs. Investigations into the fundamental neuronal processes responsible for pHFOs could provide insights into basic mechanisms of epilepsy. The potential for pHFOs to act as biomarkers for epileptogenesis and epileptogenicity is also discussed.

A HEALTH-RELATED QUALITY OF LIFE INSTRUMENT FOR PATIENTS EVALUATED FOR EPILEPSY SURGERY

The goals of surgery in treating intractable epilepsy are to eliminate seizures and improve quality of life. This report describes the development of the Epilepsy Surgery Inventory (ESI)-55, a 55-item measure of health-related quality of life for epilepsy patients. The ESI-55 includes the following scales (number of items in parentheses): health perceptions (9), energy/fatigue (4), overall quality of life (2), social function (2), emotional well-being (5), cognitive function (5), physical function (10), pain (2), and three separate scales of role limitations due to emotional, physical, or memory problems (5 items each). Also included is one change in health item. The ESI-55 was completed by 89% of 224 adults who had undergone a protocol evaluation for epilepsy surgery since 1974. Alpha internal consistency reliability coefficients ranged from 0.76 to 0.88 except for social function (alpha = 0.68). Multitrait scaling analyses supported item discrimination across scales. Factor analysis confirmed previously identified mental and physical health factors, and yielded a third factor defined by cognitive function and role limitations scales. Construct validity was supported by correlations of the ESI-55 with a mood profile instrument. Analysis of ESI-55 scale scores by seizure classification showed that the 44 patients who were seizure-free following surgery scored higher than did 55 patients who continued to have seizures (P<0.05 for all comparisons); 43 patients having seizures without loss of consciousness scored in between. Results of this study indicate that the ESI-55 is reliable, valid, and sensitive to differences in seizure status.