Intraoperative risk of seizures associated with transient direct cortical stimulation in patients with symptomatic epilepsy.

Direct cortical stimulation--either with the 60-Hz stimulation or the train-of-five technique--is commonly agreed on being the gold standard for intraoperative mapping of the motor cortex and the motor pathways but may result in an intraoperative seizure. The occurrence of intraoperative stimulation associated seizures with respect to symptomatic epilepsy was evaluated in a group of 129 patients undergoing tumor resection within the central region. Data were reviewed with respect to the frequency of seizures with both stimulation techniques and symptomatic epilepsy. Direct stimulation of the motor cortex was performed with a train of five consecutive pulses, an interstimulus interval of 4 ms, an individual pulse width of 0.5 ms, and 40 mA stimulation intensity at maximum. In 1 of 63 patients (1.6%) presenting with symptomatic epilepsy, a stimulation-associated seizure occurred, and 1 of the other 66 patients (1.5%) had a seizure (n.s., not significant). In the literature, stimulation associated seizures are reported in 1.2% with the train-of-five technique and significantly more frequently in 9.5% with the 60-Hz technique (P < 0.001). In summary, there is no increased risk of the occurrence of stimulation-associated seizures during surgery for patients with symptomatic epilepsy compared with those patients without.