title: The new approach to classification of focal epilepsies: Epileptic discharge and disconnectivity in relation to cognition.
abstract: The new classification of epilepsy stratifies the disease into an acute level, based on seizures, and an overarching chronic level of epileptic syndromes (Berg et al., 2010). In this new approach, seizures are considered either to originate and evolve in unilateral networks or to rapidly encompass both hemispheres. This concept extends the former vision of focal and generalized epilepsies to a genuine pathology of underlying networks. These key aspects of the new classification can be linked to the concept of cognitive curtailing in focal epilepsy. The present review will discuss the conceptual implications for acute and chronic cognitive deficits with special emphasis on transient and structural disconnectivity. Acute transient disruption of brain function is the hallmark of focal seizures. Beyond seizures, however, interictal epileptic discharges (IEDs) are increasingly recognized to interfere with physiological brain circuitry. Both concomitant EEG and high-precision neuropsychological testing are necessary to detect these subtle effects, which may concern task-specific or default-mode networks. More recent data suggest that longstanding IEDs may affect brain maturation and eventually be considered as a biomarker of pathological wiring. This brings us to the overarching level of chronic cognitive and behavioral comorbidity. We will discuss alterations in structural connectivity measured with diffusion-weighted imaging and tractography. Among focal epilepsies, much of our current insights are derived from temporal lobe epilepsy and its impact on neuropsychological and psychiatric functioning. Structural disconnectivity is maximal in the temporal lobe but also concerns widespread language circuitry. Eventually, pathological wiring may contribute to the clinical picture of cognitive dysfunction. We conclude with the extrapolation of these concepts to current research topics and to the necessity of establishing individual patient profiles of network pathology with EEG, high-precision neuropsychological testing, and state-of-the-art neuroimaging. This article is part of a Special Issue entitled "The new approach to classification: Rethinking cognition and behavior in epilepsy".
authors.affiliation: Neurology Unit, Rothschild Foundation, 25 Rue Manin, 75019, Paris, France; Centre de Recherche de l'Institut du Cerveau et de la Moëlle Épinière (CRICM), UPMC-UMR 7225 CNRS-UMRS 975 INSERM, Paris, France. Electronic address: v.dinkelacker@gmail.com.
authors.forename: Vera
authors.initials: V
authors.lastname: Dinkelacker
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moëlle Épinière (CRICM), UPMC-UMR 7225 CNRS-UMRS 975 INSERM, Paris, France; Epilepsy Unit, Pitié-Salpêtrière Hospital, 47-83 boulevard de l'Hôpital, 75013, Paris, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Dupont
authors.affiliation: Epilepsy Unit, Pitié-Salpêtrière Hospital, 47-83 boulevard de l'Hôpital, 75013, Paris, France; Laboratoire PSITEC (EA 4072), Université de Lille 3, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Samson
mesh_terms: D003071:Cognition; D003072:Cognition Disorders / Q000145:classification* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000145:classification / Q000379:methods; D004569:Electroencephalography / Q000379:methods / Q000639:trends; D004828:Epilepsies, Partial / Q000145:classification* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000145:classification / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D009483:Neuropsychological Tests; D012640:Seizures / Q000145:classification / Q000000981:diagnostic imaging / Q000503:physiopathology
keywords: Diffusion-weighted imaging; Interictal epileptic discharge; Structural connectivity; Temporal lobe epilepsy; Transient cognitive impairment