Background: 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 to framed-based methods is paid by the need of a standard burr hole for the implantation of one electrode.
Objective: To develop a frameless method that allows a convenient implantation of the electrode via a percutaneous bolt as used in frame-based methods, thereby avoiding the need for a standard burr hole.
Methods: We adopted our technique from frameless stereotactic biopsy and designed the GIDE – a bone fixated Guide for Implantation of Depth Electrodes. This is a reducing sleeve that works as a stabilizer of the neuronavigation arm through bony contact, and that allows percutaneous stereotactic drilling, screwing of an implantation bolt, and placement of the depth electrode.
Results: Twenty-six electrodes in seven patients (5 male and 2 female, median age 19.6 years, range 5.5 – 39.1) were successfully implanted. The overall accuracy was comparable to frameless stereotactic biopsy with a target deviation of 3.0 mm +/-1.9 (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.
Conclusion: 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. By this, our technique allows a fast and efficient implantation of depth electrodes for intracranial EEG recordings.
From: Frameless Stereotactic Drilling for Placement of Depth Electrodes in Refractory Epilepsy: Operative Technique and Initial Experience by Dorfer et al.