Types of Seizures

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The numerous epilepsy seizure types are most commonly defined and grouped according to the International Classification of Epileptic Seizures, proposed by the International League Against Epilepsy (ILAE) in 1981 (1).

Contents

International Classification of Seizure Types (1981)

Classification of Partial Seizures

  • Simple partial seizures (consciousness not impaired)
    • EEG Seizure type: Local contralateral discharge starting over the corresponding area of cortical representation (not always recorded on the scalp)
    • EEG Interictal expression: Local contralateral discharge
    • With motor signs
      • Focal motor with march (jacksonian)
      • Versive
      • Postural
      • Phonatory (vocalization or arrest of speech)
    • With somatosensory or special-sensory symptoms (simple hallucinations, e.g. tingling, light flashes, buzzing)
      • Somatosensory
      • Visual
      • Auditory
      • Olfactory
      • Gustatory
      • Vertiginous
    • With autonomic symptoms or signs (including epigastric sensation, pallor, sweating, flushing, piloerection, and pupillary dilation)
    • With psychic symptoms (disturbance of higher cerebral function); these symptoms rarely occur without impairment of consciousness and are much more commonly experienced as complex partial seizures
      • Dysphasic
      • Dynamic (e.g. deja vu)
      • Cognitive (e.g. dreamy states, distortions of time sense)
      • Affective (fear, anger, etc.)
      • Illusions (e.g. macropsia)
      • Structured hallucinations (e.g. music, scenes)
  • Complex partial seizures (with impairment of consciousness; may sometimes begin with simple symptomology)
    • EEG Seizure type: Unilateral or, frequently, bilateral discharge, diffuse or focal in temporal or frontotemporal regions
    • EEG Interictal expression: Unilateral or bilateral generally asynchronous focus; usually in temporal or frontal regions
    • Simple partial onset followed by impairment of consciousness
      • With simple partial features followed by impaired consciousness
      • With automatisms
    • With impairment of consciousness at onset
      • With impairment of consciousness only
      • With automatisms
  • Partial seizures evolving to secondarily generalized seizures (may be generalized tonic-clonic, tonic, or clonic)
    • EEG Seizure type: Above discharges become secondarily and rapidly generalized
    • Simple partial seizures evolving to generalized seizures
    • Complex partial seizures evolving to generalized seizures
    • Simple partial seizures evolving to complex partial seizures evolving to generalized seizures

Classification of Generalized Seizures

  • Absence seizures
    • EEG Seizure type: Usually regular and symmetrical 3 Hz but may be 2- to 4-Hz spike-and-slow-wave complexes and may have multiple spike-and-slow-wave complexes; abnormalities are bilateral
    • EEG Interictal expression: Background activity usually normal, although paroxysmal activity (such as spikes or spike-and-slow-wave complexes) may occur; this activity is usually regular and symmetric
    • Impairment of consciousness only
    • With mild clonic components
    • With atonic components
    • With tonic components
    • With automatism
    • With autonomic components
  • Atypical Absence
    • EEG Seizure type: EEG more heterogenous: may include irregular spike-and-slow-wave complexes, fast activity, or other paroxysmal activity, abnormalities are bilateral but often irregular and asymmetric
    • EEG Interictal expression: Background usually abnormal; paroxysmal activity (such as spikes or spike-and-slow-wave complexes) frequently irregular and asymmetric
    • May have:
      • Changes in tone that are more pronounced than in absence seizures
      • Onset and/or cessation that is not abrupt
  • Myoclonic seizures - Myoclonic jerks (single or multiple)
    • EEG Seizure type: Polyspike and wave, or sometimes spike and wave or sharp and slow waves
    • EEG Interictal expression: Same as ictal
  • Clonic seizures - Myoclonic jerks (single or multiple)
    • EEG Seizure type: Fast activity (10 Hz or more) and slow waves: occasional spike-and-wave patterns
    • EEG Interictal expression: Spike-and-wave or polyspike-and-wave discharges
  • Clonic seizures
    • EEG Seizure type: Low voltage, fast activity or a fast rhythm of 9-10 Hz or more, decreasing in frequency and increasing in amplitude
    • EEG Interictal expression: More or less rhythmic discharges of sharp and slow waves, sometimes asymmetric, background often abnormal for age
  • Tonic-clonic seizures
    • EEG Seizure type: Rhythm at 10 Hz or more, decreasing in frequency and increasing in amplitude during tonic phase, interrupted by slow waves during clonic phase
    • EEG Interictal expression: Polyspikes and waves or spike and wave or, sometimes, sharp and slow-wave discharge
  • Atonic seizures (Astatic)
    • EEG Seizure type: Polyspikes and wave or flattening or low-voltage fast activity
    • EEG Interictal expression: Polyspikes and slow wave

References

1. Wyllie, Elaine, Ajay Gupta, and Deepak K. Lachhwani, eds. The Treatment of Epilepsy: Principles & Practice. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2006. ISBN: 978-0781749954

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