Accuracy and interobserver reliability of scalp ictal EEG

Area of Science:

• Neurology
• Neurophysiology
• Epileptology

Background:

• Accurate localization of seizure onset is critical for epilepsy surgery.
• Scalp electroencephalography (EEG) is a primary tool for non-invasive seizure monitoring.
• Determining the reliability of scalp EEG for lateralizing seizure origin is essential.

Purpose of the Study:

• To evaluate the accuracy and interobserver reliability of scalp EEG in lateralizing the origin of complex partial seizures.
• To compare the effectiveness of different EEG features (activity at onset of electrographic seizure, rhythmic theta and alpha, postictal findings) for seizure lateralization.

Main Methods:

• Analysis of 137 complex partial seizures (119 temporal, 18 extratemporal) in 35 patients with known seizure origins post-surgery.
• Independent review by three electroencephalographers using scalp EEG data.
• Assessment of seizure onset, rhythmic theta and alpha, and postictal findings for lateralization.

Main Results:

• Correct lateralization rates ranged from 76%–83% for temporal and 47%–65% for extratemporal seizures when all seizures were analyzed.
• When lateralization was possible, accuracy reached 93%–99% for temporal and 89%–100% for extratemporal seizures.
• Rhythmic theta and alpha and postictal findings were more accurate than activity at onset; rhythmic theta and alpha were more frequent in temporal seizures.

Conclusions:

• Scalp EEG is a highly accurate and reliable method for lateralizing the origin of complex partial seizures.
• Specific EEG patterns, particularly rhythmic theta and alpha, improve localization accuracy.
• The findings support the continued use of scalp EEG in the pre-surgical evaluation of epilepsy.