HIGH-FREQUENCY DIRECT CORTICAL STIMULATION AND ITS PRODUCTION OF AFTER DISCHARGES
Abstract number :
1.030
Submission category :
Year :
2002
Submission ID :
1008
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Hiroshi Shigeto, Imad Najm, Attaporn Boongird, Dileep Nair, Candice Burrier, Hans O. Luders. Neurology, The Cleveland Clinic Foundation, Cleveland, OH
RATIONALE: During the extraoperative functional mapping, direct cortical electrical stimulation (25-50 Hz) may lead to focal after discharges (ADs) that are usually focal, and stop spontaneously, but at times may spread and evolve into clinical seizure. It was previously shown that an additional focal stimulation may terminate the AD. (Lesser et al, 1999). The effect of high frequency stimulation on seizure generation and control remains unknown. In this study, we evaluated the effect of various stimulus frequencies on the threshold for generation of ADs and the duration of ADs in rat neocortex.
METHODS: Four Sprague-Dawley rats were used. Epidural stainless-steel screws were placed over bilateral frontal cortex (A: 3.5mm, L: [plusminus]2mm from bregma), bilateral motor cortex (A: -1mm, L: [plusminus]3mm), bilateral sensory cortex (A: -1mm, L: [plusminus]5mm) and bilateral occipital cortex (A: -6mm, L: [plusminus]3mm). Bipolar, biphasic square pulse constant current stimuli were given between screw electrodes on motor and sensory cortex of the same hemisphere. Pulse width was 0.2 msec. Duration of stimulus train was 5seconds. We used various stimulus frequencies 50, 100, 200, 400 and 800Hz. Simultaneous electrocorticographic recordings were performed. Stimulus intensity varied from 0.2mA and increased 0.2mA one by one at 10 minutes interval. The threshold was defined as the amplitude of the current necessary for the production of AD. Threshold and duration of after discharges were compared for each frequency using ANOVA.
RESULTS: ADs were obtained for all frequencies used. Average and standard deviation of thresholds were 2.51 [plusminus] 2.07, 2.20 [plusminus] 1.88, 1.74 [plusminus] 1.29, 1.79 [plusminus] 1.50, 2.15 [plusminus] 1.65mA corresponding to 50, 100, 200, 400, 800Hz respectively. Duration of the ADs were 10.52 [plusminus] 5.71, 7.33 [plusminus] 2.59, 8.80 [plusminus] 4.41, 8.13 [plusminus] 4.48, 8.07 [plusminus] 3.39 seconds corresponding to 50, 100, 200, 400, 800Hz respectively. No significant differences in the threshold or duration of ADs were seen at the various frequencies used.
CONCLUSIONS: Direct cortical stimulation at various stimulation frequencies may lead to ADs with no significant differences in the threshold of AD generation or its duration.
[Supported by: Medtronic]