Electric cortical stimulation suppresses epileptic and background activities in neocortical epilepsy and mesial temporal lobe epilepsy.
OBJECTIVE
To evaluate the suppressive effect of electric cortical stimulation upon the seizure onset zone and the non-epileptic cortex covered by subdural electrodes in patients with neocortical epilepsy and mesial temporal lobe epilepsy (MTLE).


METHODS
Four patients with medically intractable focal epilepsy had implanted subdural electrodes for preoperative evaluation. Cortical functional mapping was performed by intermittently repeating bursts of electric stimulation, which consisted of 50 Hz alternating square pulse of 0.3 ms duration, 1-15 mA, within 5 s. The effect of this stimulation on the seizure onset zones and on the non-epileptic areas was evaluated by comparing spike frequency and electrocorticogram (ECoG) power spectra before and after stimulation. A similar comparison was performed in stimulation of 0.9 Hz of the seizure onset zones for 15 min.


RESULTS
When the seizure onset zone was stimulated with high frequency, spike frequency decreased by 24.7%. Logarithmic ECoG power spectra recorded at stimulated electrode significantly decreased in 10-32 Hz band by high frequency stimulation of the seizure onset zone, and in 14-32 Hz band by high frequency stimulation of the non-epileptic area. Low frequency stimulation of the seizure onset zone produced 18.5% spike reduction and slight power decrease in 12-14 Hz.


CONCLUSIONS
Both high and low frequency electric cortical stimulation of the seizure onset zone have a suppressive effect on epileptogenicity. Reduction of ECoG fast activities after electric cortical stimulation suggests the augmentation of inhibitory mechanisms in human cortex.
Department of Neurology, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawaharacho, Sakyoku, Kyoto 606-8507, Japan.
Masako
M
Kinoshita
Akio
A
Ikeda
Masao
M
Matsuhashi
Riki
R
Matsumoto
Takefumi
T
Hitomi
Tahamina
T
Begum
Keiko
K
Usui
Motohiro
M
Takayama
Nobuhiro
N
Mikuni
Susumu
S
Miyamoto
Nobuo
N
Hashimoto
Hiroshi
H
Shibasaki
D000328:Adult; D001931:Brain Mapping; D004307:Dose-Response Relationship, Radiation; D004599:Electric Stimulation Therapy; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000145:classification / Q000628:therapy*; D005071:Evoked Potentials / Q000528:radiation effects*; D005260:Female; D006801:Humans; D019579:Neocortex / Q000503:physiopathology / Q000528:radiation effects*; D013057:Spectrum Analysis; D013355:Subdural Space; D013702:Temporal Lobe / Q000503:physiopathology / Q000528:radiation effects*; D013997:Time Factors