Hitting the Sulcus With a More Tangential Angle May Result in Resistance Felt During Implantation of Stereotactic Electroencephalography Electrodes

BACKGROUND AND OBJECTIVES: Placement of stereotactic electroencephalography (SEEG) electrodes involves insertion of an obturator toward the target under image guidance without direct vision. Thus, tactile feedback during obturator manipulation is key to avoiding complications. Resistance encountered during advancement of the obturator that hinders planned electrode placement has prompted us to investigate the factors contributing to this resistance. METHODS: We analyzed 168 trajectories in 24 consecutive patients who underwent SEEG electrode placement between May 2019 and March 2023: 135 were placed using a 1.5-mm obturator and 33 were placed using a 0.86-mm obturator. The depth at which resistance was encountered was documented intraoperatively and compared with the preplanned trajectory to determine the structure where resistance occurred. Factors that may contribute to resistance were analyzed. RESULTS: Resistance was encountered in a total of 22 trajectories: 19 from the 1.5-mm obturator group and 3 from the 0.86-mm obturator group. Sulcal bank penetration was observed in 15 trajectories (68%) with resistance and in 42/146 trajectories (29%) without resistance. Sulcal bank penetration contributed most to resistance, more than lesion presence or trajectory length. In the 1.5-mm obturator group, insertion angles differed between trajectories with and without resistance (37.1° ± 19.0 vs 58.8° ± 15.5, 95% CI = 11.8-31.6, P = .000055). The difference remained significant when considering all pia penetrations, including at the cortical surface (37.6° ± 18.5 vs 66.1° ± 13.3, 95% CI = 21.3-35.5, P = 2.19 × 10 −13 ). CONCLUSION: Sulcal bank penetration is the main factor contributing to resistance; resistance risk increases as the insertion angle decreases. Our findings guide forecasting resistance during sulci-traversing in SEEG electrode implantation, which may be unavoidable for optimal gray matter coverage, although forceful advancement against resistance should be avoided to minimize hemorrhagic risks.