. Author manuscript; available in PMC: 2016 Aug 29.

Published in final edited form as: Lancet Neurol. 2014 Aug 10;13(9):949–960. doi: 10.1016/S1474-4422(14)70076-6

Table 1.

Definitions of key terms

	Definition
Epilepsy	Conceptual definition: a disorder of the brain characterised by an enduring predisposition to generate unprovoked epileptic seizures and by the neurobiological, cognitive, psychological, and social consequences of this condition¹⁸^* Operational definition: (i) at least two unprovoked (or reflex) seizures occurring more than 24 h apart; (ii) one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures (at least 60%) occurring over the next 10 years; and (iii) diagnosis of an epilepsy syndrome¹⁹^*
Epileptogenesis	The development and extension of tissue capable of generating spontaneous seizures, resulting in (1) development of an epileptic condition and/or (2) progression of the epilepsy after it is established²⁰
Ictogenesis	The acute neurobiological processes that result in a seizure
Epileptogenic abnormality	The pathophysiological substrate(s) responsible for the initiation and/or maintenance of epilepsy
Epilepsy comorbidity	A medical or psychiatric condition that occurs in association with epilepsy at frequencies that are substantially greater than those observed in an appropriately matched group without epilepsy A comorbidity might be a cause of epilepsy, a consequence of epilepsy, or its treatments, or a separate condition that is associated with epilepsy because there are common causes for the epilepsy and the comorbidity⁷
Drug resistance	In patients: the failure of adequate trials of two tolerated and appropriately chosen and used antiseizure medication schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom²¹^* In animal models: persistent seizure activity that does not respond to monotherapy with at least two appropriate antiseizure medications²²
Cure	The complete and permanent reversal of epilepsy, such that no seizures occur after treatment withdrawal²
Epilepsy biomarker	An objectively measurable characteristic of a biological process that reliably identifies the development, presence, severity, progression, or localisation of an epileptogenic abnormality²³
Epilepsy surrogate endpoint	A laboratory measurement or physical sign that is used in therapeutic trials as a substitute for a clinically meaningful endpoint (epileptic seizures) and is expected to predict the effect of the therapy²⁴
Therapy	Symptomatic therapy or treatment: includes antiseizure drugs or in general antiseizure treatments and anticomorbidity treatments² Disease-modifying therapy or treatment: includes antiepileptogenic and comorbidity-modifying treatments

International League Against Epilepsy (ILAE) definition. With the exception of the ILAE definitions, the table gives working definitions used for the purpose of this Personal View.