Abstracts

Rationale: To treat drug resistant partial epilepsy by means of stereotactic thermolesions is not a new idea. Many attempts have been reported in the late XXth century (Epilepsia 1999; 40(10):1408-16), but with rather disappointing results, probably due to the strong heterogeneity of the reported cases, and to the small size of the lesions. In this context, ten years ago, we proposed (Epilepsia 2004; 45:1368–74) to perform stereotactic radio-frequency thermo-lesion done by means of SEEG electrodes, and guided by the intracranial electrophysiological data obtained from these SEEG electrodes. Since then, Some study related to this technique, called thermoSEEG, have been published in specific indications such as periventricular heterotopia (Neurol Neurosurg Psychiatry 2014;85: 611–617) but overall results obtained from very large populations are not yet available. The aim of our study is to report the efficiency (Engel class at 2 and 12 months) and the safety of thermo-SEEG toward our ten years experience.Methods: Patients were suffering from drug resistant partial epilepsy, and were all eligible to a phase 2 pre-surgical investigations by SEEG. Thermo-lesions were performed using a radiofrequency current delivered on some of the contacts of some of the implanted SEEG electrodes. A given contact of a given electrode was considered as a target for coagulation as soon as, either spike-wave discharges, or low amplitude fast pattern at the onset of the seizures was observed, and if not any neurological impairment was observed during stimulation. The primary study endpoint was Engel class of patients at two months and one year after the procedure. Secondary study endpoints were the impact of etiology, duration of the disease and multiple thermo-SEEG sites on its efficiency.Results: From 2003 to 2013, 162 patients were included and 186 procedures performed. At two month 67% of patients were good responders (Engel 1 or 2) and 26% were seizure free. At one year 46% of patients maintained good results and half of seizure-free patients stayed Engel 1 (11.9%). No patient showed any increase in seizure frequency. 6 procedures out of 186 (3.2%) led to side effects and 5 of them had a complete recovery (0.6% of permanent neurological impairment). Patients with cryptogenic epilepsy had a worse outcome than others (p=0.03, t-val = -3). Long duration of epileptic disease was correlated with a better outcome at one year (coefficient correlation 0.28, p=0.0091). Bad results after a first procedure was predictive of the failure of a new one (p=1.2x10-5, t-val=7.5).Conclusions: Thermo-SEEG leads to good results (Engel 1 or 2) in one case out of two and should be considered as a major therapeutic option in patients who are not eligible for conventional surgery after phase 2 invasive investigations. Furthermore, with 0.6% of permanent neurological side-effect, thermo-SEEG is the safest surgical procedure for drug-resistant partial epilepsy. Such results may lead to extend indications of this procedure to patients ineligible to surgery after phase 1 investigations and to propose SEEG for the explicit purpose to perform thermo-SEEG.