SEEG in 2025: progress and pending challenges in stereotaxy methods, biomarkers and radiofrequency thermocoagulation

Technological innovations and clinical research in SEEG have dramatically increased with its worldwide dissemination. In this review, we summarize the main advances in the field from the last 5 years.

Several large series and meta-analyses have provided consistent data regarding a lower risk of serious complications with SEEG as compared to sub-dural grids, while some studies also suggest a greater diagnostic value. The safety and precision of SEEG partly depends on the type of vascular imaging and method of implantation, with some series suggesting that MR angiography might not provide an optimal delineation of electrode-vessel conflicts and that frameless stereotaxy lacks precision. Noninvasive frame coupled with robot-guided implantation might offer the best precision/invasiveness tradeoff. Small series suggest that SEEG can be safely performed from the age of 16 months, and that adding electrodes during SEEG often prove beneficial. Transhemispheric electrodes targeting the mesial frontal structures, bilaterally, proved safe and informative. Several interictal and ictal biomarkers of the epileptogenic zone have been investigated. Although high-frequency oscillations (HFOs) remain a biomarker of interest, a randomized controlled trial failed to demonstrate its diagnostic value against spikes. Furthermore, other interictal biomarkers proved to better correlate with the epileptogenic zone than HFOs rate, including spike-gamma and spike-ripples. Ictal biomarkers of interest include the so-called chirp and epileptogenic zone fingerprint. Overall, recent data suggest that high-frequency activities are not a mandatory feature of interictal and ictal biomarkers of the epileptogenic zone. Radiofrequency thermocoagulation (RFTC) performed during SEEG investigation have also progressed, with some authors reporting spectacular rates of seizure freedom in patients with localized epileptogenic lesion but also mesial temporal sclerosis. However, a systematic assessment of memory and mental health demonstrated the presence of altered memory and psychiatric complications in a significant proportion of mesial temporal lobe RFTC.

Progress has been made in the technology and methods used to perform SEEG and RFTC, with the view to increase safety and effectiveness. Several interictal and ictal biomarkers appear promising but still face challenges in their validation and implementation in clinical practice. Future research requires harmonization in the concepts of the seizure onset and epileptogenic zones, and prospective pathology-specific studies.