Networks and systems, conceptualizations, and research

Inter-ictal network of focal epilepsy and effects of clinical factors on network activity

OBJECTIVE

Aim of the study was to explore the inter-ictal, resting-state EEG network in patients with focal epilepsy (FE) and to specify clinical factors that influence network activity.

METHODS

Functional EEG connectivity (EEGfC) differences were computed between 232 FE patients (FE group) and 77 healthy controls. EEGfC was computed among 23 cortical regions within each hemisphere, for 25 very narrow bands from 1 to 25 Hz. We computed independent effects for six clinical factors on EEGfC in the FE group, by ANOVA and post-hoc t-statistics, corrected for multiple comparisons by false discovery rate method.

RESULTS

Robust, statistically significant EEGfC differences emerged between the FE and the healthy control groups. Etiology, seizure type, duration of the illness and antiepileptic treatment were independent factors that influenced EEGfC. Statistically significant results occurred selectively in one or a few very narrow bands and outlined networks. Most abnormal EEGfC findings occurred at frequencies that mediate integrative and motor activities.

CONCLUSIONS

FE patients have abnormal resting-state EEGfC network activity. Clinical factors significantly modify EEGfC.

SIGNIFICANCE

Delineation of the FE network and modifying factors can open the way for targeted investigations and introduction of EEGfC into epilepsy research and practice.

Modern technology calls for a modern approach to classification of epileptic seizures and the epilepsies

In the last 10-15 years the ILAE Commission on Classification and Terminology has been presenting proposals to modernize the current ILAE Classification of Epileptic Seizures and Epilepsies. These proposals were discussed extensively in a series of articles published recently in Epilepsia and Epilepsy Currents. There is almost universal consensus that the availability of new diagnostic techniques as also of a modern understanding of epilepsy calls for a complete revision of the Classification of Epileptic Seizures and Epilepsies. Unfortunately, however, the Commission is still not prepared to take a bold step ahead and completely revisit our approach to classification of epileptic seizures and epilepsies. In this manuscript we critically analyze the current proposals of the Commission and make suggestions for a classification system that reflects modern diagnostic techniques and our current understanding of epilepsy.

The new ILAE report on terminology and concepts for the organization of epilepsies: critical review and contribution

This critical review refers to the new report on terminology and concepts for the organization of epilepsies by the Commission of the International League Against Epilepsy (ILAE). It is unfortunate that most of the proposals in the Commission's report are modified interpretations and nomenclature of previous ILAE classifications; new terms are not better than the old ones, and recent advances have not been incorporated. Hence, the new ILAE report met with considerable dissatisfaction from several expert epileptologists. The Commission abandoned (1) the disease-syndrome distinction, although "disease" is generally differentiated from "syndrome" in most medical texts as well as in the ILAE classification itself; (2) the distinction of "generalized" and "focal" for epileptic syndromes, despite maintaining this distinction for epileptic seizures and despite the fact that most epileptic syndromes manifest exclusively either with generalized or focal epileptic seizures; (4) the terms "idiopathic,""symptomatic," and "cryptogenic," although these terms have been well defined in the previous ILAE classifications; reiterating their true meaning would be sufficient. Genetic epilepsy could be a new category and (5) the designation of "benign" epilepsies, despite the recommendations of experts at the Monreale workshop. In addition, the Commission proposed that "age at onset" be used as a primary dimension for organizing the epilepsies. However, (a) this runs counter to classification efforts of other diseases in medicine and neurology; (b) syndromes that are likely to be linked together on the basis of electroclinical (and often genetic) evidence are now separated and intermixed with a number of heterogeneous epilepsies; and (c) a considerable number of epileptic syndromes have a wide range of age at onset from childhood to adulthood. Furthermore, epilepsy syndromes were given by name only, without definition; thus we remain dependent on previous ILAE definitions, which are often broad and imprecise. The ILAE should commission consensus of opinion from experts in specific fields in order to define each syndrome. Areas of certainties and uncertainties and of agreements and disagreements should be identified and explained. This approach may be the only way toward achieving a scientifically sound and clinically meaningful organizational system for the epileptic seizures and the epilepsies-a process that would incorporate the tremendous advances in our field and would be accepted by the wider community of clinicians and scientists.