eMedicine Specialties > Emergency Medicine > Neurology

Seizures

Author: M Tyson Pillow, MD, Assistant Director of Medical Education, Ben Taub General Hospital Emergency Center; Assistant Professor, Baylor College of Medicine
Coauthor(s): David S Howes, MD, Residency Program Director, Professor of Medicine, Section of Emergency Medicine, University of Chicago/Pritzker School of Medicine; Shaneen U Doctor, MD, Research Assistant, Department of Emergency Medicine, University of Chicago
Contributor Information and Disclosures

Updated: Jan 22, 2010

Introduction

Background

A seizure is an episode of neurologic dysfunction caused by abnormal neuronal activity that results in a sudden change in behavior, sensory perception, or motor activity. The clinical spectrum of seizures includes simple and complex focal or partial seizures and generalized seizures.

The term epilepsy refers to recurrent, unprovoked seizures from known or unknown causes. Ictus describes the period in which the seizure occurs, and post-ictal refers to the period after the seizure has ended but before the patient has returned to his or her baseline mental status. A focal or partial seizure describes abnormal neuronal firing that is limited to one hemisphere or area of the brain that manifests itself as seizure activity on one side of the body or one extremity. These seizures are classified as simple partial if there is no change in mental status or complex partial if there is some degree of impaired consciousness.

A generalized seizure consists of abnormal electrical activity involving both cerebral hemispheres that causes an alteration in mental status. Traditionally, the patient with 30 minutes of continuous seizure activity or a series of seizures without a return to full consciousness is defined as being in status epilepticus (SE). Newer definitions suggest that status epilepticus is defined by duration of 5 continuous minutes of generalized seizure activity or 2 or more separate seizure episodes without return to baseline.¹ This article focuses on the emergency department (ED) evaluation, management, and disposition of adult patients presenting for evaluation of seizure.

Febrile seizures in children are a distinct entity and are discussed in a separate article.

Pathophysiology

A seizure results when abnormal neuronal firing manifests clinically by changes in motor control, sensory perception, behavior, and/or autonomic function. This sudden biochemical imbalance between excitatory neurotransmitters and the NMDA receptor and inhibitory forces (GABA) at the neuronal cell membrane results in repeated, abnormal electrical discharges that may stay within a certain area of the brain or they may propagate throughout the brain resulting in generalized seizures. For example, in the event that these neuronal discharges are confined to the visual cortex, the seizure manifests itself with visual phenomena.

Seizures also produce a number of physiologic changes. Many of these systemic responses are thought to be a result of the catecholamine surge that accompanies seizures.² During a generalized seizure, there can be a period of transient apnea and subsequent hypoxia. In a physiological effort to maintain appropriate cerebral oxygenation, the patient may become hypertensive. Additionally, transient hyperthermia may occur in up to 40% of patients and is thought to result from vigorous muscle activity that occurs in a seizure.³  Hyperglycemia and lactic acidosis occur within minutes of a convulsive episode and usually resolve within 1 hour.⁴ Transient leukocytosis may also be seen but is not accompanied by bandemia (unless infection is present).

In the setting of prolonged convulsive seizure activity or status epilepticus, there is pronounced systemic decompensation including hypoxemia, hypercarbia, hypertension followed by hypotension, hyperthermia, depletion of cerebral glucose and oxygen, cardiac dysrhythmias, and rhabdomyolysis. These changes may even take place despite adequate oxygenation and ventilation. In extremis, pulmonary edema and disseminated intravascular coagulation (DIC) have also been reported.⁵

Frequency

United States

• Epilepsy and seizures affect more than 3 million American of all ages.
• Approximately 200,000 new cases occur each year, of which 40-50% will recur be classified as epilepsy.⁶
• Overall, approximately 50,000-150,000 cases will reach status epilepticus.

Mortality/Morbidity

• Up to 50% of patients with epilepsy will have recurrent seizures despite medical therapy.⁷
• Up to 25% of patients with a first-time, generalized seizure will have a recurrence within 2 years.⁸
• The overall mortality rate is about 20% for those who reach status epilepticus.
• The mortality rates are highest for those older than 75 years, reflecting an increased incidence of degenerative, neoplastic, and vascular pathologies.

Sex

• Males are slightly more likely to develop epilepsy than females.

Age

• Incidence is highest in those younger than 2 years and in those older than 65 years.

Clinical

History

• A history of epilepsy is often noted (if the patient is unconscious, family, friends, or prehospital personnel can be questioned).
• Recent noncompliance with medications
• History of CNS pathology (stroke, neoplasms, recent surgery)
• History of systemic neoplasms, infections, metabolic disorders, or toxic ingestions
• Recent trauma or fall
• Alcohol abuse
• Recent travel or immigration to the United States
• Pregnancy
• Focal symptoms (partial seizure activity) that then progressed to a generalized seizure

Physical

• A generalized seizure is recognizable at the bedside when tonic-clonic activity is present.
• If the patient is actively seizing, attempt to observe motor activity, as posturing (decerebrate/decorticate) and eye deviation may provide clues to the epileptic focus.
• A partial seizure may present as isolated seizure activity with or without loss of consciousness. The workup for partial seizures is more extensive and requires neurologic consultation.
• Identifying a partial seizure that then generalizes to a full tonic-clonic seizure may be difficult, as this may be missed as the initial presentation of a generalized seizure.
• Vital signs 
  • In a generalized, tonic-clonic seizure, accurate vital signs are difficult to obtain.
  • Low-grade fever may be present initially, but prolonged fever may be an indication of infectious etiology.
• Mental status examination 
  • As mentioned above, any seizure with loss of consciousness is termed complex.
• Neurologic examination 
  • Focal deficits may be evidence of an old lesion, new pathology, or Todd’s paralysis (transient, <24 h paralysis that mimics stroke)
  • Hyperreflexia and extensor plantar responses are indicative of a recent seizure but should resolve during the post-ictal period.

Causes

• The differential diagnosis for seizure disorder consists of a myriad of conditions.
• For patients with known seizure disorder, the most likely cause is subtherapeutic levels of antiepileptic medications, including the following: 
  • Medical noncompliance
  • Systemic derangement that may disrupt absorption, distribution, and metabolism of medication (infection)
• In addition, multiple other factors, including stress, lack of sleep, and caffeine use, may contribute to seizures in patients with known seizure disorder, but these are diagnoses of exclusion.
• For patients presenting with new-onset seizure disorder, the differential is broad: 
  • CNS pathologies (stroke, neoplasm, trauma, hypoxia, vascular abnormality)
  • Metabolic abnormalities (hypoglycemia/hyperglycemia, hyponatremia/hypernatremia, hypercalcemia, hepatic encephalopathy)
  • Toxicologic etiologies (alcohol withdrawal, cocaine, isoniazid, theophylline)
  • Infection etiologies (meningitis, encephalitis, brain abscess) – Neurocysticercosis and malaria are very common causes of seizures in the developing world and should be considered in patients with history of travel or immigrants.

• Search for CME/CE on This Topic »

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• Absence Seizures (Neurology)
• Pediatrics, Febrile Seizures (Emergency Medicine)
• Simple Partial Seizures (Neurology)
• Seizures and Epilepsy, Overview and Classification (Neurology)

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• A 65-Year-Old Woman With Possible Seizures
• Ketogenic Diet and Febrile Seizures