The term “epileptic encephalopathy” (EE) designates epileptic disorders of infancy and childhood with multiform seizures and cognitive, behavioral, and neurologic deterioration. The current hypothesis is that frequent seizures and/or severe epileptiform electroencephalography (EEG) abnormalities induce a progressive worsening of epilepsy and deterioration of brain function. Although the term EE is currently employed, its meaning is by no means unequivocally defined. One matter of discussion is whether it should include any type of epilepsy with hypothetically seizure-dependent deterioration or be limited to the infancy and childhood disorders that it classically designates. The debate is relevant to the question of the role of developmental variables in EE pathomechanisms. For example, some of the previously recognized EEs have been shown to be genetically determined, and could be defined as genetic encephalopathies with epilepsy (or epileptogenic encephalopathy) rather than EE. This is a crucial point that could challenge the boundary between EEs and the encephalopathies with epilepsy (e.g., progressive myoclonic epilepsies) in which the progressive course is due to the intrinsic nature of the underlying encephalopathy and not to the epileptic activity per se. But even excluding the conditions that may be a source of ambiguity, the mechanism(s) by which the epileptic activity could determine the progressive course of EEs is/are still to be defined and can hardly be ascribed to a unitary pathogenic process.

The preceding considerations prompted us to invite a group of experts to participate in a workshop to discuss the existing lines of evidence and to bring the contribution of their own experience in the field. The Third International Sicilian Workshop was held in Sciacca (Sicily, Italy) on April 29–30, 2012, with the participation of several experts in the field. Our focus was on EE definition and clinical spectrum; clinical and experimental evidence of epileptic activity-induced aggravation; and epileptic activity versus underlying pathology as responsible for cognitive deterioration, pathophysiology, potential biomarkers, and therapy. A fruitful discussion was held and although some controversial points are still unresolved, the group reached a consensus on several issues and identified some research lines that may provide answers to the questions that are still open. We thought that a synthetic report of the workshop could contribute to the ongoing discussion on EE nosography in the framework of the forthcoming classification of epilepsies.

We are grateful to Eisai for their unrestricted educational grant that supports this supplement, and to the former editors, Simon Shorvon and Phil Schwartzkroin, who accepted this topic as an Epilepsia supplement. We also thank the authors of the articles that appear in this supplement for their successful effort in summarizing the comprehensive and vivid discussion that they animated during the workshop.