Quantification of Subdural Electrode Shift Between Initial Implantation, Postimplantation Computed Tomography, and...

Area of Science:

• Neurosurgery
• Medical Imaging
• Epileptology

Background:

• Subdural electrodes are crucial for localizing epileptic regions before surgical resection.
• Postoperative computed tomography (CT) is standard for determining electrode placement.
• Current practice assumes electrodes remain stationary between CT and surgery.

Purpose of the Study:

• To quantify the shift of subdural electrodes between implantation, CT acquisition, and resection surgery.
• To assess electrode displacement relative to both the skull and the cortical surface.

Main Methods:

• Evaluated 23 patients undergoing subdural electrode implantation.
• Coregistered preoperative MRI and postoperative CT scans to extract electrode positions.
• Utilized a stereovision system for intraoperative digitization of electrodes and cortical surface.
• Tracked cortical surface movement and calculated electrode position changes.

Main Results:

• Average electrode shift was 8.0 mm (Crani 1 to CT) and 9.2 mm (CT to Crani 2).
• Average cortical shift was 4.7 mm laterally.
• Electrode shift relative to the cortical surface averaged 5.5 mm between implantation and resection.

Conclusions:

• Subdural electrodes exhibit significant lateral shift relative to the skull and cortex.
• This displacement challenges the assumption of electrode stationarity.
• Findings have critical implications for epilepsy surgery planning and functional mapping accuracy.