Application of intracranial electrode implantation using stereotactic frame in identification of epileptogenic zone

Objective To explore the safety and reliability of intracranial electrode implantation based on stereotactic frame. Methods Sixty patients with refractory epilepsy were retrospectively included from June 2015 to June 2016 in Beijing Tiantan-Fengtai Epilepsy Center. We analyzed relevant indexes which might influence the SEEG (stereo-electroencephalograhy) electrode implantation target deviations and complications related to the implantation. Video-EEG monitoring was conducted after the electrode implantation before operation was performed to remove the seizure focus according to the preoperative evaluation. Outcomes were followed-up. Results Sixty patients underwent a total of 474 intracranial electrodes implantation with an average electrode number of 8.0 ± 2.5 and an average application time of 13.5 ± 3.1 min per electrode. The entrance point deviation, target deviation, electrode-skull angle and electrode length in the brain were 0.0-8.3 mm (median: 1.1 mm), 0-12 mm (median: 1.4 mm), 44.0-90.0° (median: 67.5°) and 15-97 mm (median: 43 mm), respectively. The target deviation was positively correlated with the deviation of entry point (r=0.426, P<0.01). The target deviation was negatively correlated with the electrode skull angle (r=-0.247, P<0.01). The target deviation was positively correlated with the length of electrode in the brain (r=0.145, P<0.01). There are totally 6(10%) cases developing complications including small amount of cerebral hematoma in 3(5%), brain abscess in 1(2%) and electrode bending in 2(3%). Fifty-three patients were followed up for 1-2 (1.5±0.5) years post resection surgery. There was 72%(38/53) of the patients achieving seizure free (Engel Ⅰ). Meanwhile, seizures remained in the other 28%(15/53) of the patients (Engel Ⅱ-Ⅳ). Conclusion The stereotactic frame-based intracranial electrode implantation technique seems safe and reliable. Combined with postoperative video-EEG analysis, it could be applied for localization of epileptogenic zone. Key words: Epilepsy; Neurosurgical procedures; Stereoelectroencephalogram; Prognosis