Combined depth and subdural electrode investigation in uncontrolled epilepsy

Area of Science:

• Neurosurgery
• Epileptology
• Clinical Neurophysiology

Background:

• Accurate localization of the seizure focus is critical for surgical planning in medically refractory epilepsy.
• Both depth and subdural electrodes offer distinct advantages for capturing seizure onset and propagation patterns.

Purpose of the Study:

• To compare the efficacy of depth electrodes versus subdural electrodes in localizing seizure foci in epilepsy patients.
• To investigate the relationship between seizure onset location and surgical outcomes.

Main Methods:

• Utilized both depth and subdural electrodes for ictal monitoring in 47 patients with medically refractory epilepsy.
• Analyzed seizure onset localization, propagation patterns, and correlation with post-surgical seizure control.

Main Results:

• Seizures were localized in 33 patients; depth electrodes consistently localized onset in 23, subdural electrodes in 4, and 6 showed variable/simultaneous localization.
• Eighty-seven percent of temporal lobe seizures originated in the hippocampus (depth electrodes), propagating to ipsilateral neocortex (subdural electrodes) in 80%.
• Variable or simultaneous unilateral neocortical versus hippocampal seizure onset correlated with less favorable outcomes after temporal lobectomy and hippocampectomy.

Conclusions:

• Depth electrodes are superior for detecting hippocampal seizure onset, while subdural electrodes are effective for extratemporal foci and neocortical propagation.
• Combined electrode use provides comprehensive localization, and seizure onset patterns significantly impact surgical success in temporal lobe epilepsy.