Frontal Eye Field in the Precentral Sulcus: A Direct Electrical Cortical Stimulation Study With Stereo-EEG Electrodes

Background

This study aims to explore the stimulation-induced eye movements (EMs) from various branches of the precentral sulcus (PrCS) and to learn if the epileptogenic area influences EMs effects.

Methods

The high-frequency direct electrical stimulation mapping reports were completed from patients with SEEG exploration. The counts of gender, the distribution of EMs effects sites, the seizure onset age, course of epilepsy, age of stimulation, and stimulation intensity were analyzed. The correlation factors of the EMs positive cases were studied through the multivariate regression method.

Results

The PrCS through 778 contacts of 77 patients was studied from July 2015 to December 2020. A total of 18 patients showed induced EMs in the PrCS. The average stimulation intensity was 22.0 ± 1.3 mA. In positive cases, 279 contacts were explored on the PrCS, and 24.51% were positive. Overall, 60.32% sites were in the superior PrCS (SP), and 39.68% sites were in the inferior PrCS (IP). The SP was more likely to have a stimulating response to EMs than the IP (p = 0.017). The major EM effect was deviation, with a total of 39.68% positive sites in 11 cases, namely, 16 sites in the SP and 9 sites in the IP. Multiple regression analysis indicated that the positive EMs cases were only correlated with whether seizure onset zone (SOZ) was located on prCS (p = 0.004), but not with age of onset, duration, frequency of seizures, preoperative intelligence quotient (IQ), and age of stimulation.

Conclusion

Deviation was the major type of positive EMs by directly stimulating the prCS. The SP was more sensitive to stimulation than the inferior branch was. The positive EM's chance showed a certain correlation with whether the prCS was inside the SOZ or not.