The identification of the aetiology of a patient's
epilepsy is instrumental in the diagnosis, prognostic counselling and management of the
epilepsies. Indeed, the aetiology can be important for determining the recurrence risk of
single seizures and so for making a diagnosis of
epilepsy. Here, we divide the aetiologies into six categories: structural, genetic, infectious, metabolic, immune (all of which are part of the International League Against
Epilepsy [ILAE] classification system) and neurodegenerative (which we have considered separately because of its growing importance in
epilepsy). These are not mutually exclusive categories and many aetiologies fall into more than one category. Indeed, genetic factors probably play a role, to varying degrees, in the risk of
seizures in all people with
epilepsy. In each of the categories, we discuss what we regard as the most important aetiologies; importance being determined not only by prevalence but also by clinical significance. The introduction contains information suitable for level 1 competency (entry level), whilst the subsequent sections contain information aimed at level 2 competency (proficiency level) as part of the new ILAE competency-based curriculum. As we move towards
precision medicine and targeted
therapies, so aetiologies will play an even greater role in the management of
epilepsy.