Frameless Stereotactic Drilling for Placement of Depth Electrodes in Refractory Epilepsy

Abstract

For stereotactic implantation of depth electrodes in refractory epilepsy, both frame-based and frameless techniques have been developed. The higher versatility of current frameless techniques compared with framed-based methods is paid by the need of a standard burr hole for the implantation of 1 electrode. To develop a frameless method that allows convenient implantation of the electrode via a percutaneous bolt as used in frame-based methods, thereby avoiding the need for a standard burr hole. We adopted our technique from frameless stereotactic biopsy and designed the GIDE, a bone-fixated Guide for Implantation of Depth Electrodes. This reducing sleeve works as a stabilizer of the neuronavigation arm through bony contact and allows percutaneous stereotactic drilling, screwing of an implantation bolt, and placement of the depth electrode. Twenty-six electrodes in 7 patients (5 male and 2 female patients; median age, 19.6 years; range, 5.5-39.1 years) were successfully implanted. The overall accuracy was comparable to that of frameless stereotactic biopsy with a target deviation of 3.0 ± 1.9 mm (mean ± SD). All electrodes were within or touched the targeted anatomic structure with an adequate quality of the recordings. We encountered no hemorrhage or neurological deficit related to the depth electrode. Our technique combines the high versatility of frameless stereotaxy with the convenient implantation and fixation of the depth electrode via a percutaneous bolt used in frame-based stereotactic methods. Thus, our technique allows fast, efficient implantation of depth electrodes for intracranial electroencephalography recordings.