Depth electrode investigations in patients with bitemporal epileptiform abnormalities

Area of Science:

• Clinical Neurology
• Epileptology
• Neurophysiology

Background:

• Extracranial electroencephalograms (EEGs) can show bitemporal independent epileptiform abnormalities.
• Localization or lateralization of the epileptogenic zone is often challenging with noninvasive methods.
• Accurate seizure focus localization is critical for surgical treatment of epilepsy.

Purpose of the Study:

• To investigate the utility of stereotactic depth electrode recordings in patients with intractable epilepsy.
• To determine the origin and patterns of seizure onset in patients with bitemporal independent epileptiform abnormalities.
• To evaluate the effectiveness of depth electrode recordings for localizing the epileptogenic zone when noninvasive methods fail.

Main Methods:

• Stereotactic depth electrode recordings were performed in 57 patients with bitemporal independent epileptiform abnormalities on extracranial EEGs.
• Patients underwent invasive EEG monitoring to precisely identify seizure onset zones.
• Electrical stimulation studies and afterdischarge threshold determinations were also conducted.

Main Results:

• In 77% of patients (44/57), seizures originated exclusively or predominantly from one temporal lobe.
• In 23% of patients (13/57), seizures arose independently from either temporal lobe or showed diffuse patterns.
• Seizure onset patterns could vary within the same patient, and electrical stimulation had limited value for lateralization.

Conclusions:

• Stereotactic depth electrode recordings are valuable for localizing the epileptogenic zone in patients with difficult-to-localize epilepsy.
• A significant majority of patients with bitemporal abnormalities on scalp EEG have a unilateral temporal lobe seizure origin.
• Invasive monitoring provides crucial information for surgical decision-making in epilepsy management.