Chapter 18: Introduction to Seizures, Epilepsy, and Seizure Mimics

INTRODUCTION TO SEIZURES AND EPILEPSY

Seizures are relatively common; approximately 1 in 10 people will have a seizure, but not all patients go on to develop epilepsy, typically only 1 in 26.¹ There is a bimodal distribution of seizures, with the highest incidence in the very young (<12 months old) and in the adult population older than 65 years. The incidence of pediatric epilepsy has a wide range between 41 and 187 per 100,000 and can vary by country.²

The International League Against Epilepsy (ILAE) has put together continually revised consensus operational and guideline criteria for definitions and classifications of seizures and epilepsy for children and adults, with the most recent update in 2017.³ By definition, a seizure is a hyperactivation of neuronal brain cells characterized by abnormal synchronized misfiring. A seizure can broadly be classified in a few ways that are helpful for diagnostic and management steps. The first is if there is a temporal association with a provoking factor (eg, caused by a stroke, metabolic derangement such as hypoglycemia, or drug/medication intoxication) as compared to unprovoked where no clear cause is found. A seizure can also be defined by its suspected location of onset, such as focal (originating in one part of the brain), generalized (diffuse or rapid bisynchronized), or unknown (eg, if not witnessed). A third method of seizure classification is based on the reported features (or semiology) seen; that is, if there are motor (eg, tonic or generalized tonic-clonic [GTC]) or nonmotor (eg, an aura) features. ILAE has a website (epilepsydiagnosis.org) that is a very helpful resource for physicians for further review and is highly recommended as a reference for clinicians at any level of learning. Clues regarding seizure onset and type are based first and foremost upon the patient’s report and the primary eyewitness account of the events. It is paramount to ask the patient about the events because internal sensory changes such as déjà vu may not be seen. In addition, it is important to ask the primary eyewitness about the seizure because stories can change if related to another reporter. If events reoccur, we also advise families to obtain videos on a cell phone to review with the provider, but the patient’s safety and privacy should be prioritized.

Features that are highly suspicious or suggestive of an epileptic seizure include events that are consistently stereotyped, events arising out of sleep or that are nocturnal, clear tonic-clonic movements, lacerations on the lateral aspects of the tongue (for motor seizures), evolution over time if not treated, and a concordant postictal phase with the seizure. Features such as urinary or bowel incontinence are suggestive but not specific for an epileptic seizure. Preceding paroxysmal events should be explicitly asked about because often the first presentation is the one witnessed but may not be the first seizure the patient has experienced.

Per the ILAE, epilepsy is a condition ...