Abstracts

Rationale: Seizure semiology and scalp EEG seizure patterns provide critical information for seizure lateralization and localization in presurgical evaluations, and they are directly correlated with intracranial seizure propagation. The aim of this study is to define patterns of intracranial seizure propagation in patients with temporal lobe epilepsy that have not been fully appreciated previously. Methods: We recorded simultaneously seizure propagation patterns using 26 channels of scalp EEG with sub-temporal supplementary electrodes and 46 to 98 channels of intracranial EEG in 17 patients with medically-intractable temporal lobe epilepsy. Subdural electrodes were implanted extensively on the anterior through mid-temporal lobe and selectively on extra-temporal cortex in all patients. Results: We observed three different seizure propagation patterns. In 11 patients, seizures propagated gradually along a mesial→basal→lateral→tempora→extratemporal pathway. Scalp EEG seizure onsets were localized to the anterior temporal region. Seizures were manifested clinically as ipsilateral motor automatisms and contralateral dystonic limb posturing. In 4 patients, seizures propagated quickly to the contralateral temporal lobe. In these patients the scalp EEG ictal onsets were poorly lateralized. Seizures were manifested as mixed bimanual motor automatisms and dystonic posturing. In 3 patients, the seizures propagated from mesio-temporal to extratemporal cortex directly and possibly through subcortical pathways. In these patients the scalp EEG ictal onsets were also poorly lateralized and localized. These seizures were manifested by hypermotor activity. Conclusions: Three seizure propagation patterns were observed in patients with temporal lobe epilepsy, and these were associated with distinct seizure semiology and scalp EEG seizure patterns. Appreciating the various pathways for seizure propagation is essential for localizing the seizure onset zone in a pre-surgical evaluation.