Stereo electroencephalography–guided radiofrequency thermocoagulation (SEEG‐guided RF‐TC) in drug‐resistant focal epilepsy: Results from a 10‐year experience

Abstract

SUMMARYObjective: 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.

Stereoelectroencephalography-guided radiofrequency thermocoagulation (SEEG-guided RF-TC) in patients with drug-resistant focal epilepsy

“…In conclusion, the favorable risk-benefit ratio of SEEG-guided RF-TC in comparison to conventional surgery and other palliative treatments suggests expanding the indications of SEEG-guided RF-TC, either to patients for whom surgery is risky or even not viable, or as a predictive test before resective surgery [17] .…”

“…In France, Bourdillon et al [17] adopted the following parameters: 50 V/120 mA (6 W) for 10-20 s, while the lesion generator system was from a model RFG-3, manufactured by Radionics (Radionics Medical Products, Burlington, MA, U.S.A.), and electrodes were manufactured by Dixi (Dixi Medical, Besancon, France).…”

“…It has been recently reported that SEEG-guided RF-TC was a safe and efficient technique in many cases gathered from a large population over a 10-year period [17] . In contrast to other palliative [2,3] treatments such as vagus nerve stimulation (30%-63% reduction of >50% of seizures) [4][5][6] , multiple subpial transection [32] , callosotomy [33] , or deep brain stimulation of the anterior nucleus of the thalamus (54% reduction of >50% of seizures) [6] , SEEG-guided RF-TC is a focal treatment targeted selectively at the epileptogenic zone (as is radiosurgery) [34,35] .…”

“…With the development and application of this technique in neurosurgery [16] , it was soon utilized to resect lesions by means of radiofrequency (RF). The first paper on stereotactic lesion on epilepsy was published in 1965 [17] . Since then, stereotactic lesion as a surgical treatment for focal epilepsy gained widespread use [18] , mainly as an alternative to conventional surgery in patients with mesial temporal lobe epilepsy (MTLE) [19][20][21] , especially with hippocampal sclerosis [22][23][24] and malformation of cortical development (MCD) [25][26][27] .…”

“…This technique is characterized by the following advantages [17] : (1) the RF-TC can be targeted on the seizure-onset zone delineated by SEEG recordings; (2) multiple lesions can be performed between adjacent contacts of the SEEG electrodes; (3) the electrodes used to perform the RF-TC are those implanted for the SEEG so that carrying out thermo-SEEG does not increase surgical risk, such as bleeding; (4) RF-TC can be preceded by a functional mapping through cortical stimulation, thereby preventing neurologic deficits; (5) these lesions are well tolerated by the patients and the procedure does not require anesthesia; (6) the clinical and electrophysiological condition of the patient can be monitored in real time before, during, and after the lesion is resected. Such monitoring allows for the interruption of the procedure as soon as a sensation of heat is reported [31] ; (7) RF-TC does not preclude subsequent conventional surgery in case of failure; (8) there are no additional costs for either consumables or prolonged hospitalization.…”