Abstracts

Stereoelectroencephalography (SEEG) established its investigational role in the 1960s (Bancaud et al., 1965) and has since gained widespread adoption across Europe and North America (Khoo et al., 2020). In 2004, it was first reported that radiofrequency thermocoagulation (RF-TC) through the implanted electrodes may have a therapeutic effect on intractable epilepsy (Guénot et al., 2004). The technique has not been widely utilized due to its limited efficacy from small ablation size (Staudt et al., 2018), likely reflecting a limited impact on the seizure onset zone (SOZ). We review the evolution of SEEG at the Montreal Neurological Institute (MNI) over the past fifty years and propose an approach which permits larger more conformal lesioning via SEEG.

A PubMed search was performed for articles published between 1970 and 2024 using the following terms alone and in combination: “stereoelectroencephalography,” “epilepsy,” “SEEG-guided,” “radiofrequency,” and “thermocoagulation.” We reviewed the charts of patients who underwent SEEG-guided RF-TC at the MNI between 2013 and 2023 to report on technical aspects related to achieving a larger volume of ablation.

SEEG was first performed at the MNI in 1972 and has continually evolved by incorporating new technology from several domains, including commercially available magnetic resonance (MRI)-compatible electrodes since 2007, robotic assistance since 2011, and SEEG-guided RF-TC since 2013. A retrospective chart review identified 21 patients who underwent SEEG-guided RF-TC at our center between 2013 and 2023 with a greater proportion of SEEG cases receiving RF-TC over time. All procedures were performed by the senior author (JH) who introduced the cross-coagulation technique (Mirza et al., 2021) in 2018. Post-RF-TC MRI demonstrate that the combination of axial and cross-coagulation techniques effectively produces larger conformal ablative lesions.

Recent advancements are transforming SEEG from a purely investigational tool into a promising therapeutic modality. We propose an approach and describe technical aspects which maximize lesion volume. A priori consideration of RF-TC in SEEG planning should be considered. SEEG-guided RF-TC using more densely placed electrodes along with a tailored combination of lesion generation between adjacent contacts on a single electrode (axial coagulation) and between contacts on two adjacent electrodes (cross-coagulation) permits a larger volume of tissue in the seizure onset zone to be ablated.