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HEMISPHERIC LATERALIZATION

Specific focal seizure features are useful in lateralizing the seizure onset or network to one hemisphere. Such features can be informative when EEG recordings are not helpful.

Features that suggest lateralization of the seizure are outlined below. These features provide strong evidence for lateralization, but it should be noted that occasionally they can be falsely lateralizing.

  • Unilateral ictal clonic activity or ictal dystonia suggests lateralization of the seizure to the contralateral hemisphere.
  • Early forced head version suggests lateralization to the hemisphere contralateral to the direction of the head version i.e. if the head turns to the right, the seizure onset is in the left hemisphere.
  • Ictal speech lateralizes to the non-dominant hemisphere.
  • Ictal aphasia lateralizes to the dominant hemisphere.
  • Postictal dysphasia lateralizes to the dominant hemisphere.
  • Preserved awareness during ictal automatisms lateralizes to the non-dominant hemisphere.
  • Post-ictal nose-wiping lateralizes to the hemisphere ipsilateral to the hand used for nose-wiping.
  • Unilateral eye-blinking lateralizes to the hemisphere ipsilateral to the eye-blinking.
  • Ictal vomiting lateralizes to the non-dominant hemisphere
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