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

Area of Science:

• Neurology
• Neurophysiology

Background:

• Extracranial electroencephalography (EEG) is vital for epilepsy diagnosis, seizure classification, and localization.
• It plays a key role in the preoperative evaluation for temporal lobectomy when combined with neuro-imaging and neuropsychological data.

Purpose of the Study:

• To highlight the diagnostic and classification utility of extracranial EEG.
• To emphasize the role of ictal EEG in surgical candidate selection for temporal lobectomy.
• To discuss the specific benefits and limitations of sphenoidal electrodes.

Main Methods:

• Review of the role of extracranial EEG in epilepsy diagnosis and management.
• Analysis of the contribution of ictal EEG recordings in patient selection for surgery.
• Comparison of sphenoidal electrodes with specialized scalp electrodes.

Main Results:

• Extracranial EEG provides essential diagnostic and localization information.
• Ictal EEG is critical for confirming epileptic seizures and excluding non-epileptic seizures in surgical candidates.
• Sphenoidal electrodes offer a better signal-to-noise ratio, though their superiority over specialized scalp electrodes is debated.

Conclusions:

• Extracranial EEG is indispensable for comprehensive epilepsy assessment.
• Ictal EEG recordings are paramount for accurate diagnosis and appropriate surgical candidate selection.
• The optimal electrode choice requires careful consideration of signal quality and clinical context.