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False localization of ictal activity by scalp EEG in candidates for hemispherectomy


Two patients with intractable seizures and large structural lesions were candidates for hemispherectomy for seizure control. Repeated ictal EEGs recorded from scalp falsely localized seizure onset to the contralateral hemisphere. Intracarotid amobarbital study was performed during left-body epilepsia partialis continua in one subject. Amobarbital was injected in the right internal carotid artery, despite electrographic seizure activity apparently originating in the left hemisphere. Clinical and electrographic seizure activity ceased immediately at the onset of left hemiparesis, without inducing right hemiparesis, speech loss, or EEG attenuation on the left. Intracranial recordings in both patients confirmed that the clinically suspect hemisphere was the source of the seizures, and hemispherectomy produced excellent clinical results. In the presence of a large structural lesion, it appears that scalp EEG may falsely localize ictal discharges to the contralateral side. © 1993 Butterworth-Heinemann.

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