Synchronous recording of intracranial and extracranial EEG in temporal lobe epilepsy.
OBJECTIVE
To explore the diagnostic value of intracranial electrodes in highly suspected temporal lobe epilepsy (TLE) and the value of sphenoid electrodes (PG) and the propagation patterns of ictal discharges in focus lateralization.


METHODS
Intracranial electrodes were implanted in 22 probable TLE patients through bilateral temporal burr holes. Extracranial electrodes included the 10-20 international EEG system and bilateral PGs. Intracranial and extracranial EEGs (IEEG, EEEG) were synchronously recorded. The interictal epileptic discharges (IEDs) were counted for 3h of interictal preoperative long-playing video EEG. Time intervals between electrodes recording the ictus and ictus occurring were measured and the propagation patterns were deduced.


RESULTS
By IEEG, 18 patients with confirmed TLE had surgery; 14 were seizure-free. 3 had FLE, and 1, uncertain localization. Of the 14 TLE and postoperative seizure-free patients, the ratio (left:right) of IEDs in the 3h interictal EEG was 483:211 in the 6 left TLE and 263:654 in the 8 right TLE. In 12 of the 14 cases, the side with more IEDs at PG was the epileptic focus side. In 11 of the 14 cases the earlier PG recording side was focus side. We found that the propagation sequence of ictus followed certain rules in most attacks.


CONCLUSIONS
The results indicated that IEEG was useful for final diagnosis of highly suspected TLE and that PG was helpful in focus lateralization. The propagation patterns of ictus might provide a new tool in focus lateralization and localization.
Department of Neurosurgery, Institute of Neurological Disorder, Yuquan Hospital, Tsinghua University, Tsinghua University, 5# Shijingshan Road, Beijing 100049, China. zuohc@mail.tsinghua.edu.cn
Zhang
Z
Guangming
Zuo
Z
Huancong
Zhou
Z
Wenjing
Chen
C
Guoqiang
Wang
W
Dongming
Shi
S
Yanfang
Liu
L
Xiaohua
Lin
L
Jiuluan
D000328:Adult; D001931:Brain Mapping; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D013997:Time Factors; D014741:Video Recording / Q000379:methods