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For further information, see CMDT Part 24-03: Epilepsy

Key Features

Essentials of Diagnosis

  • Recurrent unprovoked seizures

  • Epilepsy should not be diagnosed on the basis of a solitary seizure

  • Characteristic electroencephalographic (EEG) changes may occur

  • Postictal confusion or focal neurologic deficits may follow and last hours

General Considerations

  • The term "epilepsy" denotes any disorder characterized by recurrent unprovoked seizures

  • A seizure is a transient disturbance of cerebral function due to an abnormal paroxysmal neuronal discharge in the brain


  • Epilepsy affects approximately 0.5% of the US population


  • According to the International League Against Epilepsy classification system, recurrent seizures should be classified by

    • Seizure type

    • Epilepsy type

    • Epilepsy syndrome

  • Seizure types

    • Focal onset seizures: classified by motor or nonmotor onset as well as by whether awareness is impaired

    • Generalized onset seizures:

      • Classified into those with motor or nonmotor features

      • Awareness is typically lost with generalized seizures, but may be retained partially in the briefest absence attacks and some myoclonic seizures

    • Unknown onset seizures: In some circumstances, seizures cannot be classified because of incomplete information or because they do not fit into any category

  • Epilepsy types

    • Focal

    • Generalized

    • Combined generalized and focal

  • Epilepsy syndromes

    • Defined by constellations of seizure types, EEG findings, and imaging features, and often also depend on age at onset and comorbidities

    • Not every patient with epilepsy can be given a syndromic diagnosis


  • The International League Against Epilepsy lists six broad etiologic categories; sometimes a patient's seizures have more than one etiology

    • Structural

      • Congenital abnormalities and perinatal injuries may result in seizures presenting in infancy or childhood

      • Hippocampal sclerosis is a recognized cause of focal and secondarily generalized seizures of uncertain etiology

      • Trauma is an important cause of seizures at any age, but especially in young adults

      • Neoplasms may lead to seizures at any age, but they are an especially important cause of seizures in middle and later life, when the incidence of neoplastic disease increases

      • Stroke and other vascular diseases become increasingly frequent causes of seizures with advancing age and are the most common cause of seizures with onset at age 60 years or older

      • Alzheimer disease and other degenerative disorders are a cause of seizures in later life

    • Genetic

      • Age at onset ranges from the neonatal period to adolescence or even later in life

      • Monogenic disorders tend to exhibit an autosomal dominant pattern of inheritance, and where the mutation is known, the responsible gene often encodes a neuronal ion channel

      • A genetic etiology may also underpin certain epilepsies with a metabolic or structural basis

    • Infectious

      • Seizures may occur with an acute infective or inflammatory illness

      • Seizures are a common sequela of supratentorial brain abscess

    • Metabolic

      • Inborn errors of metabolism and other inherited conditions may cause epilepsy as one ...

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