Electrode Tip Shift During the Stereotactic Electroencephalography Evaluation Period with Boltless Suture Fixation

Abstract

Electrodes for stereotactic electroencephalography (SEEG) are typically fixed to the skull with anchor bolts. When anchor bolts are unavailable, electrodes have to be fixed using other methods, carrying the possibility of electrode shift. This study, therefore, evaluated the characteristics of electrode tip shift during SEEG monitoring in patients with electrodes fixed using the suture technique. We retrospectively included patients who underwent SEEG implantation with suture fixation and evaluated the tip shift distance (TSD) of electrodes. Possible influences evaluated included: 1) implantation period, 2) lobe of entry, 3) unilateral or bilateral implantation, 4) electrode length, 5) skull thickness, and 6) scalp thickness difference. A total of 50 electrodes in 7 patients were evaluated. TSD was 1.4±2.0mm (mean±standard deviation). Implantation period was 8.1±2.2days. Entry lobe was frontal for 28 electrodes and temporal for 22 electrodes. Implantation was bilateral for 25 electrodes and unilateral for 25 electrodes. Electrode length was 45.4±14.3mm. Skull thickness was 6.0±3.7mm. Scalp thickness difference was-1.5±2.1mm, which was found greater in temporal lobe entry compared with frontal lobe entry. According to univariate analyses, neither implantation period nor electrode length correlated with TSD. Multivariate regression analysis showed that only greater scalp thickness difference correlated significantly with greater TSD (P=0.0018). Greater scalp thickness difference correlated with greater TSD. Surgeons need to consider the degree of scalp thickness difference and electrode shift when using suture fixation, especially with temporal lobe entry.