Drug-resistant epilepsy
Definition
Seizures sometimes are not controlled with antiepileptic drugs. A number of different terms may be used to describe these including: “uncontrolled,” “intractable,” “refractory,” or “drug resistant.”
The International League Against Epilepsy (ILAE) appointed a Task Force to formulate a consensus definition of drug resistant epilepsy. The overall framework of the definition has two “hierarchical” levels: Level 1 provides a general scheme to categorize response to each therapeutic intervention, including a minimum dataset of knowledge about the intervention that would be needed; Level 2 provides a core definition of drug resistant epilepsy using a set of essential criteria based on the categorization of response (from Level 1) to trials of antiepileptic drugs. It is proposed as a testable hypothesis that drug resistant epilepsy is defined as failure of adequate trials of two tolerated, appropriately chosen and used antiepileptic drug schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom. This definition can be further refined when new evidence emerges. The rationale behind the definition and the principles governing its proper use are discussed, and examples to illustrate its application in clinical practice are provided 1).
Epidemiology
Focal cortical dysplasia is a malformation of cortical development, which is the most common cause of drug resistant epilepsy in the pediatric population 2).
In a study, roughly one-third of patients (64.0%) had continued seizures despite AED management, and failure of first or second line therapies correlated with an increased likelihood to develop refractory (or drug-resistant) epilepsy. Over the ensuing 2 decades since this study, AEDs with novel mechanisms of action have expanded treatment options and many are thought to be safer with similar clinical efficacy, when used as monotherapy or as adjunctive agents 3).
Classification
Etiology
Risk Factor
Patients who have many seizures before therapy or who have an inadequate response to initial treatment with antiepileptic drugs are likely to have refractory epilepsy 4).