In response to comments on Adverse events related to extraoperative invasive EEG monitoring with subdural grid electrodes: A systematic review and meta‐analysis

Abstract

We are thankful to Drs. Tandon and Esquenazi for interest in our work. As mentioned in our Methods section, only those studies were excluded which reported patients with only depth electrodes.1 We included the studies that provided data about both subdural and depth electrodes. The study by Tanriverdi et al.2 reports data from a total of 6,415 electrodes including 2,943 depth electrodes (45.9%) and 2,490 cortical electrodes (38.8%). The rest were reference and ground electrodes (also subdural). This study also reports data about surgical morbidity of various epilepsy surgery procedures. While calculating pooled prevalence estimates for our study, we used a value for our denominator that was imputed from the ratio of depth and other electrodes. However, we had no choice but to extrapolate their raw percentages as being applicable to both depth and cortical electrodes. For regression analysis, we evaluated different ‘adjusted’ models, but we presented only the best models based on commonly used criteria, as detailed in our paper. We have already mentioned this limitation in our study and cautioned the reader that the estimates are biased and most likely represent conservative figures. Similar argument holds true for the study by Wellmer et al.3 We agree with Drs. Tandon and Esquenazi that this is an imperfect data synthesis. However, as we have repeatedly pointed out in our paper: there is extensive variability in reporting surgical morbidity associated with invasive epilepsy evaluation and the estimates that we have generated, although biased and likely conservative, represent the currently available data and draw attention to the heterogeneity in practice and data reporting. None of the authors has any conflict of interest to disclose. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.