Abstracts

RATIONALE: Cortical electrical stimulation is a standard procedure for localizing eloquent cortex before surgical resection in medically intractable epileptic patients. During stimulation, afterdischarges can interfere with further testing and clinical seizures can completely stop the procedure because of possible post-ictal effects and need for medications. Lesser et al (1999) reported that afterdischarges can be terminated by restimulation. We wished to determine whether clinical seizures can also be stopped.
METHODS: A fourteen year-old right-handed female had intractable seizures since the age of six. She had an aura of tingling on the medial portion of her left leg, followed by stiffening and extension of all extremities. Consciousness was preserved during the events, which lasted 10-15 seconds. Video-EEG monitoring with scalp electrodes localized seizures to the right medial frontal lobe. An ictal SPECT revealed increased blood flow in the cingulate and right supplementary motor regions. Two MRIs were normal. Two subdural electrode grids were placed in the right medial frontal region. Spontaneous seizures localized to the posterior portion of the posterior grid. A cortical stimulation study was then carried out at the bedside using a Grass S22 constant current stimulator to apply current through two adjacent electrodes. Five second trains of 50 Hz alternating polarity pulses were delivered, with a stimulus duration of 300 microseconds. Stimulation was started at a low current of 1-2 mA with gradual ascension of current and performed at each electrode until an afterdischarge, clinical seizure, or a functional result was noted, or until 8 mA current was reached. Immediate restimulation at the same location with the same parameters was applied as soon as an afterdischarge or clinical seizure was recognized.
RESULTS: The cortical stimulation study produced, at several electrode pairs, afterdischarges, electrographic seizures without clinical correlates, and three typical clinical seizures. The stimulated seizures were terminated within two seconds after restimulation of the same electrodes with the same current. The afterdischarges and electrographic seizures were also immediately terminated by restimulation using the same parameters.
CONCLUSIONS: Immediate restimulation of cortex can abort clinical and electrographic seizures allowing continuation of cortical stimulation studies. It may be possible to exploit this effect clinically in the future.