Title: In Reply: Predictive Factors of Surgical Outcome in Frontal Lobe Epilepsy Explored with Stereoelectroencephalography
Abstract: To the Editor: The authors of “Predictive factors of surgical outcome in frontal lobe epilepsy explored with stereoelectroencephalography”1 appreciate the observations on our manuscript and thank the authors of the Letter to the Editor2 for their interest in our paper. We are pleased to respond to their interesting comments on our study. Concerning surgical outcome in patients undergoing dominant hemisphere surgery, in our series the majority of patients was right-handed, and we found no difference between left and right epilepsy surgery. With respect to functional cortex, less favorable outcome was observed in patients whom EZ included the central region, as previously reported.3 In the other comment, authors query about the existence, retrospectively, of disconcordance between the EZ as defined by SEEG and MRI visible lesion, and consequently about noninvasive electrophysiological data which could have accounted for this. In our cohort, for 13/20 patients with positive MRI undergoing SEEG, the EZ extended beyond the lesion, including contiguous and remote regions. In the remaining 7 cases, SEEG data were consistent with MRI findings, the EZ being restricted to the lesion. However, this was not surprising for 5 of them, since their main indication to SEEG was the proximity to eloquent (primary motor) cortex (rather than doubt as to localization with regards to the lesion), and the resulting EZ was premotor and/or precentral. The two remaining patients with EZ limited essentially to the lesion had FCD as etiology with EZ in medial prefrontal regions. Thus, a majority of lesional cases had an EZ that was demonstrated with SEEG to be larger than the lesion. Present data are not sufficient to extract general rules for identifying bias in the correlation between MRI and electroclinical data. We could however discuss that, through data and experience that has been built up over the last decade,4-6 we more often indicate direct surgery without SEEG in prefrontal and even premotor epilepsies especially in patients with FCD, when convincing and concordant metabolic and electric source-imaging data are available. Nonetheless, even with the improvement of non-invasive techniques, the decision-making process for epilepsy surgery still remains a tailored approach for individual patients, which of course benefits from all clinical and diagnostic advances. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.