Seizures are a common emergency presentation, accounting for approximately 1% of all ED visits.1 Presentations include patients with epilepsy, new-onset or first-time seizure (whether provoked or unprovoked), and other diagnostic entities that can mimic seizure but are not a true epileptic seizure. Even after a detailed and comprehensive evaluation, correctly determining the diagnosis can still be a challenge.2
The International League Against Epilepsy (ILAE) defines epileptic seizures as “a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.”3 There are typically three phases of a seizure—the aural, ictal, and postictal states.
Aural Phase. Patients may or may not experience an aura prior to seizure onset. An aura can manifest as a sense of déjà vu or a rising sensation in the abdomen, abnormal taste or smell, or autonomic changes. These are not warning signs of a seizure but rather an early manifestation of a focal seizure before there has been enough electrical spread to cause cognitive or motor symptoms.
Ictal Phase. The second stage of seizure, the ictal phase, is the typical cognitive or motor manifestations of seizure activity. Seizures can last several seconds to minutes, but the majority has a duration of less than 1 minute.
Postictal Phase. The postictal period occurs after the active phase of seizure and is characterized by confusion, altered mental status, and somnolence. The postictal period can last from several minutes to hours and can result in suppression of function; including cognitive or motor deficits such as Todd’s paralysis wherein a patient experiences transient paralysis confined to one hemisphere.4
Etiology and Classification
Seizures can be subdivided based on two different categories: etiology or origin of abnormal electrical impulses within the brain. To categorize seizures based on etiology, the clinician must determine whether the seizure was brought on by an identifiable cause.
Provoked seizures are also referred to as acute symptomatic seizures, because they present within 7 days of a systemic insult, whether it be secondary to an electrolyte abnormality (eg, hyponatremia, hypoglycemia, hypercalcemia), substance withdrawal (eg, alcohol, benzodiazepines), toxic ingestion, infection, central nervous system lesions, or head injury. The aforementioned does not represent a comprehensive list, but rather some of the more common etiologies of seizures.2,5
An unprovoked seizure occurs without an identifiable acute precipitating insult. These types of seizures are generally more consistent with epilepsy or are due to a remote systemic insult greater than 7 days prior. Examples include patients who have a history of stroke, traumatic brain injury, or congenital brain malformation.2,5
Epilepsy is described as a seizure disorder where recurrent, usually unprovoked seizures occur. Determining the probable etiology of a seizure can be important when pursuing proper objective evaluation and work up, as we will discuss in this article.
Seizures can also be classified as being generalized or focal, depending on the probable origin of the abnormal electrical discharges within the brain. This classification system is widely used and was developed by the ILAE.6
Generalized seizures have bilateral cortical involvement at the onset of presentation and are associated with loss of consciousness. This is determined through electroencephalogram (EEG) monitoring because focal seizures, where the initiation of abnormal electrical discharges are located in one cortical hemisphere or localized area of the brain, may rapidly spread to both hemispheres and appear very similar to a primary generalized seizure.
Tonic-Clonic Seizures. The most colloquial type of generalized seizure is a tonic-clonic seizure. “Tonic” refers to the muscle stiffness or rigidity that occurs during this type of seizure, and “clonic” describes the rhythmic jerking of these muscles.
Nontonic-Clonic Seizures. Other types of generalized seizures include absence seizures (brief staring episodes or an arrest in behavior), atonic seizures (loss of muscle tone), and myoclonic seizures (brief, sudden muscular contractions).5
Focal seizures are diagnosed when the history, clinical presentation, and EEG findings support the localization of abnormal electrical neuronal discharges to one hemisphere of the brain. Loss of consciousness does not always occur during a focal seizure, and the ILAE recently updated the terminology in this regard to this distinction in 2017. Instead of classifying focal seizures as simple partial or complex partial in relation to the preservation of consciousness, the terminology has now changed to focal aware (no loss of consciousness) and focal impaired awareness (affected consciousness). Focal seizures can have not only motor manifestations, but may also present with sensory, autonomic, or psychic symptoms, depending on the anatomic location of the abnormal neuronal activity.5-6