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Summary: Objective: Despite the increasing number of studies reporting results of stereo‐electroencephalography (SEEG)–guided radiofrequency‐thermocoagulation (SEEG‐guided RF‐TC) in the treatment of patients with drug‐resistant focal epilepsy, the exact efficacy of this approach remains unclear. The seizure‐freedom rate varies greatly across studies and the factors associated with efficacy have not been formally investigated. Methods: All prospective or retrospective studies reporting efficacy and/or safety of SEEG‐guided RF‐TC in patients with drug‐resistant focal epilepsy were included. The primary outcome was the seizure‐free rate 1 year after the procedure. Secondary outcomes were (1) the responder rate 1 year after the procedure and (2) the proportion of patients with permanent neurologic deficit 1 year after the procedure. Each outcome was assessed in all patients and in 4 groups of patients defined by the etiology of epilepsy. Each outcome was pooled using inverse variance weighting, logit transformation of proportion, and a random‐effects model. Results: No prospective study was identified and a total of 6 retrospective studies, reporting efficacy and safety data of 296 patients, were included. The pooled rate of permanent neurologic deficit was 2.5% (95% confidence interval [CI] 1.2%‐5.3%), without heterogeneity across studies. In contrast, both the seizure‐free and responder rates varied greatly across studies, and statistical heterogeneity was high. The pooled seizure‐free and responder rates were 23% (95% CI 8%‐50%) and 58% (95% CI 36%‐77%), respectively. Both for the seizure‐free and responder rates, the greatest efficacy was observed in patients with periventricular nodular heterotopia and the lowest in patients with normal magnetic resonance imaging (MRI) findings. Significance: SEEG‐guided RF‐TC is a safe procedure with low risk of complications. In contrast, the level of evidence regarding its efficacy remains low. Better identification of factors associated with seizure outcome are needed. [ABSTRACT FROM AUTHOR]

SEEG-guided radiofrequency thermocoagulation (SEEG-guided RFTC), a combination of Stereo-electroencephalography (SEEG) and radiofrequency thermocoagulation (RFTC), has been performed since 2001 in drug resistant epilepsy. The interest of this procedure is to aim at total or partial destruction of the epileptogenic zone, as tailored in each individual patient by the SEEG exploration. These multiple SEEG-guided RFTC lesions of epileptic foci are produced by using a radiofrequency generator connected to the electrode contacts. This review summarizes the results of SEEG-guided RFTC reported in 251 patients. This procedure appears to be safe since complications are rare, minor and usually reversible, which is explained by the use of functional electrical stimulations before RFTC. It makes it also possible to produce RF lesions located very close to cortical areas having a high functional value or being poorly accessible to a conventional surgical procedure. Even if seizure outcome is not as good as results of surgery, 41% of the patients are responders at 12 months with several seizure free patients. The benefit-risk ratio of the SEEG-guided RFTC procedure proved to be particularly favorable for the patients presenting with epileptogenic cortical malformation of development (nodular heterotopy as well as focal cortical dysplasia) and for those in whom surgery is not feasible or risky. For the patients in whom surgery is feasible, SEEG-guided RFTC could be used as a first step, as a predictive therapeutic test before resective surgery. [ABSTRACT FROM AUTHOR]

Summary We propose expert recommendations on the use of SEEG-guided radiofrequency thermocoagulation (RF-TC) based on an exhaustive literature review. This technique consists in performing a RF-TC lesion using a SEEG depth electrode at the end of the recording. It is indicated when conventional surgical resection of the ictal onset zone is not possible. SEEG guided RF-TC can also be considered as a diagnostic tool since an improvement, even limited, has a high positive predictive value concerning the good outcome after surgery. It is possible to perform SEEG only in the purposes of performing RF-TC. An over-implantation of the presumed ictal onset zone is possible when such a procedure is planned. The RF-TC target should only be defined based on the ictal activity, except when a type II focal cortical dysplasia electrophysiological interictal signature is recorded. A single or multiple coagulations should always be performed between contiguous electrode contacts. The power delivered by the generator should be increased until the impedance suddenly changes, which indicates that the thermocoagulation has occurred. The procedure should be performed under clinical monitoring without anesthesia and after systematically testing neurological functions by electric stimulation on each target. Multiple SEEG-guided RF-TC can be proposed in a single patient, for example, in cases of relapse after a previous effective procedure. Conventional resection surgery remains feasible after a RF-TC procedure. [ABSTRACT FROM AUTHOR]

Objective Stereo electroencephalography ( SEEG)-guided radiofrequency thermocoagulation ( SEEG-guided RF- TC) has been proposed since 2004 as a possible treatment of some focal drug-resistant epilepsy. The aim of this study is to provide extensive data about efficacy and safety of SEEG-guided RF- TC. Methods Over a 10-year period, 162 patients with drug-resistant focal epilepsy were eligible for SEEG-guided RF- TG during phase II invasive investigation by SEEG. All follow-up and safety data were collected prospectively. The primary outcome was seizure freedom at 2 months and at 1 year after SEEG-guided RF- TC. Secondary outcomes were the responders' rate (patient with at least 50% decrease in seizure frequency) and their long-term follow-up. Results Twenty-five percent of patients were seizure-free at 2 months and 7% at 1 year. We reported 67% of responders at 2 months and 48% at 1 year; 58% of responders maintained their status during the long-term follow-up. The seizure outcome was significantly better when the SEEG-guided RF- TC involved the occipital region (p = 0.007). When surgery followed an SEEG-guided RF- TC, the positive predictive value of being a responder 2 months after an SEEG-guided RF- TC and to be Engel's class I or II after surgery was 93%. We reported 1.1% of permanent deficit and 2.4% of transient side effects. Significance Our results, gathered in a large population over a 10-year period, confirm that SEEG-guided RF- TC is a safe technique, being efficient in many cases. More than two thirds of patients showed a short-term improvement, and almost half of them were responders at 1-year follow-up. The technique appears to be especially interesting for limited epileptic zone inaccessible to surgery and when epilepsy is related to a large unilateral network (network disruption by multiple RF- TC). Furthermore, SEEG-guided RF- TC effect is a predictor of outcome after conventional cortectomy in patients eligible for surgery. [ABSTRACT FROM AUTHOR]

Background Deep brain electrodes have been used for the past 10 years to produce bipolar stereo-electro-encephalography−guided radiofrequency thermocoagulation (SEEG RF-TC). However, this technique is based on empiric knowledge. The aim of this study is 3-fold: 1) provide in vivo animal data concerning the effect of bipolar RF-TC on brain and its safety; 2) assess the parameters of this procedure (current delivery and dipole selection) that produce the most efficient lesion; and 3) provide technical guidelines. Methods First we achieved in vivo RF-TC on rabbit brains with several conditions (power delivered and lesioning duration) and analyzed their influence on the lesion produced. Only a difference in terms of volume was found, and type of histologic lesions was similar whatever the settings were. We then performed multiple RF-TC in vitro on egg albumen, first with several parameters of radiofrequency and then with different dipole spatial selections. The end point was the size of the radiofrequency thermolesion produced. Results Using unfixed parameters of radiofrequency current delivery and increasing it until the power delivered by the generator collapsed produced significantly larger lesions ( P = 0.008) than other conditions. Concerning the dipole selection, the use of contiguous contacts on electrodes led to lesions with a higher volume ( P = 7.7 × 10 −13 ) than those produced with noncontiguous ones. Conclusion Besides the target selection in SEEG RF-TC, which is summarized on the basis of a literature review, we report the optimal parameters: Radiofrequency current must be increased until the power delivered collapses, and dipoles should be constituted by contiguous electrode contacts. [ABSTRACT FROM AUTHOR]

Summary Stereoelectroencephalography (SEEG) was designed and developed in the 1960s in France by J. Talairach and J. Bancaud. It is an invasive method of exploration for drug-resistant focal epilepsies, offering the advantage of a tridimensional and temporally precise study of the epileptic discharge. It allows anatomo-electrical correlations and tailored surgeries. Whereas this method has been used for decades by experts in a limited number of European centers, the last ten years have seen increasing worldwide spread of its use. Moreover in current practice, SEEG is not only a diagnostic tool but also offers a therapeutic option, i.e., thermocoagulation. In order to propose formal guidelines for best clinical practice in SEEG, a working party was formed, composed of experts from every French centre with a large SEEG experience (those performing more than 10 SEEG per year over at least a 5 year period). This group formulated recommendations, which were graded by all participants according to established methodology. The first part of this article summarizes these within the following topics: indications and limits of SEEG; planning and management of SEEG; surgical technique; electrophysiological technical procedures; interpretation of SEEG recordings; and SEEG-guided radio frequency thermocoagulation. In the second part, those different aspects are discussed in more detail by subgroups of experts, based on existing literature and their own experience. The aim of this work is to present a consensual French approach to SEEG, which could be used as a basic document for centers using this method, particularly those who are beginning SEEG practice. These guidelines are supported by the French Clinical Neurophysiology Society and the French chapter of the International League Against Epilepsy. [ABSTRACT FROM AUTHOR]