Extracranial EEG work-up in epilepsy surgery: usefulness and limitations

Extracranial interictal and ictal EEG provide essential information to diagnosis, seizure/syndrome classification and focus localization. Combined with structural and dynamic neuro-imaging and neuropsychological data, extracranial EEG will often provide sufficient information in pre-operative work-up for temporal lobectomy. Ictal EEG recordings are essential to confirm the diagnosis and classification and, above all, to exclude patients with significant non-epileptic seizures from further surgical evaluation. The advantage of sphenoidal electrodes lies first and foremost in a more favorable signal/noise ratio, while their superiority to closely placed special scalp electrodes are more debatable.