Epilepsy

Key Features

Essentials of Diagnosis

• Recurrent unprovoked seizures

• Epilepsy should not be diagnosed based on a solitary seizure

• Characteristic electroencephalographic (EEG) changes may occur

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

General Considerations

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

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

Demographics

• Epilepsy affects approximately 0.5% of the US population

Classification

• 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

Etiology

• 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 pathogenic variant (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 ...