Background. Awake surgery is currently a safe and reliable alternative for identifying and preserving functional areas. However, this protocol has evolved over time to minimize the occurrence of electrical stimulation-induced seizures and postoperative deficits. Objective. The aim of this study is to highlight both internal and external factors influencing the language and sensorimotor thresholds of electrical stimulation mapping (ESM) during gliomas awake surgery. Material and methods. From October 2016 to April 2022, we performed a retrospective study on 74 patients underwent awake craniotomy of gliomas in two series based on ESM: group 1 and group 2. Preoperatively and three months after surgery, general performance and neurological deficits were assessed according to the type, location, and side of the tumor in correlation with ASA, BMI, Mallampati and KPS indexes. Results. The outcome shows that the median patient age was 49 years old in a range of [13-70], functional mapping was performed in language areas for 96% of patients and motor functions for 54%. In addition, 55.5% of the patients had HGG, 40.5% had LGG, and 4% had AVMs. Most lesions were in the temporal area (40.5%), followed by the frontal area (31%), 24.5% for insular area, 4% for the parietal area, and 85% of patients had left-sided lesions. The overall rate of intraoperative complications fell from 16.2% in group 2 to 1.35% in group 1. Conclusions. Under the ESM threshold of group 1, a high-quality of awake surgery can be used with optimally low complications and failure rates regardless of BMI, ASA rating, Mallampati and KPS scores or smoking status.

Background. Until the advent of new exploration techniques: functional magnetic resonance imaging (fMRI) and surgical protocols such as exeresis in awake mode, the functional recovery potential of postoperative deficits was limited by conventional tumor surgery. The use of these methods simultaneously improves the quality of life and survival medians, mainly for removing low-grade gliomas massively infiltrating subcortical networks in eloquent regions where surgery is historically not associated with high functional recovery rates. Accordingly, the results from the awake brain surgery literature motivate us to establish a new baseline on the relationship between electrical stimulation mapping (ESM) threshold, the extent of resection (EOR), neuroplastic typology, and functional recovery after intraoperative crises or postoperative care deficits using induced neuroplasticity. Materials and patients. This is a retrospective analytical study of 35 brain tumor cases of gliomas, operated by common craniotomy in awake conditions from September 2016 to July 2022. Before entering awake resection mode, all patients underwent brain mapping (ESM) by direct electrical stimulation (DES) according to standard conditions and Helsinki ethical guidelines. Analysis according to ESM was done for two groups (group 1 and group 2) of different intensities of DES. Outcomes. The ESM by threshold intensity expressed in mean ± deviation standard was: 2,45 ± 0.125 mA for sensorimotor functions against 1.35 ± 0.175 mA for cognitive mapping. These stimulation currents were optimum thresholds which allowed us during control mapping to overcome all boundary conditions, mostly false negative results. The functional recovery time (FRT) following stimulation-induced seizures was varied from 2 s to 6.26 s, marking the intraoperative neuroplasticity operated mainly by synaptic remodeling during the functional reactivation. The EOR was better for group 1 with 82.35 % gross total resection (GTR) with only 8.75% of the occurrence of transient seizures against 45.7% for group 2 and only 2.86% suffered from neurological permanent deficits in group 1 against 11.42% in group 2. Conclusions. ESM in the range of [2.35 - 2.45 mA] improved DES sensitivity without false negatives. We had a compromise of improved results between these stimulation thresholds, the duration of the craniotomy, the functional recovery time, the EOR and overall the occurrence of neurological deficits, which explain the processes involved in the success of awake surgery.

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