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
- Unilateral ictal clonic activity or
ictal dystonia suggests lateralization of the seizure to the
- 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