Abstracts

RATIONALE: To detect the epileptiform discharges originating specifically from the temporal lobe, we performed EEG with intravascular electrodes (intravascular EEG) as a presurgical extracranial study during the Wada procedure. Although we had used micro-guide wires as active intravascular recording electrodes, recently we used micro-sized mapping catheter. In this study of 8 patients with TLE, we evaluated the sensitivity of intravascular EEG to detect the laterality of epileptogenic foci.
METHODS: The subjects in this study were 8 patients with medically intractable TLE. After giving informed consent, we performed intravascular EEG recording in combination with the Wada test. For 2 of 8 patients, we placed guide wire electrodes into bilateral middle meningeal artery at the level of the foramen spinosum, placing the electrodes to the inferior surface of each temporal lobe. For the remaining 6 patients, we used a multilead catheter with four electrodes. The intravascular EEG was recorded in the angiography room for about one hour while scalp EEG with sphenoidal (SP) electrodes was simultaneously recorded. We evaluated the usefulness of this technique for comparison with a simultaneously recorded scalp EEG, furthermore with the results of chronic intracranial EEG recordings.
RESULTS: The intravascular EEG demonstrated clear epileptiform discharges, sometimes even when they were absent on the simultaneously recorded scalp EEG. As for the lateralization of the epileptiform discharges recorded from intravascular EEGs, in 5 of 8 patients, the epileptiform discharges were observed only at the unilateral intravascular electrode which lateralization was agreed with that of the ictal patterns obtained from subsequent intracranial recordings. In 2 patients, although epileptiform discharges were demonstrated bilaterally, most of the epileptiform discharges were predominantly observed at the unilateral intravascular electrode. The lateralization of these 2 cases was compatible with that of intracranial recordings. In the remaining 1 case intravascular EEG revealed bilateral epileptiform discharges, however, the ictal patterns from intracranial EEG also showed bilaterally.
The intravascular EEG agreed with lateralization of epileptiform discharges obtained from subsequent intracranial recordings.
CONCLUSIONS: This intravascular EEG can detect the epileptiform discharges more sensitive than SP electrode. This method of identifying epileptogenic areas is as useful as or complements the invasive techniques such as depth recording. However, we propose using intravascular EEG to aid in lateralization in patients where noninvasive.