Samuel Luciano Caliri

Background: Glioblastomas (GBMs) in eloquent areas, particularly within the motor system, represent a significant surgical challenge due to the risk of postoperative neurological deficits. This study evaluates the effectiveness of a structured preoperative protocol, including nTMS-guided motor mapping, to optimize surgical outcomes and minimize neurological deficits, with a particular focus on the timing of adjuvant oncological therapy initiation. Methods: A retrospective analysis was conducted on 44 GBM patients, divided into two groups: 11 with motor area lesions (group A) and 33 with non-eloquent lesions (group B). All patients underwent a standardized preoperative protocol. Surgical outcomes (EORs), neurological function (MRC score and KPS index), time to oncological therapy initiation and survival (OS and PFS) were compared between groups. Results: Both groups achieved high rates of GTR without significant differences in EOR (72.7% group A vs. 78.8% group B). Although group A exhibited a higher incidence of postoperative motor deficits, motor function at three-month follow-up was similar between groups. Time to initiation of oncological therapy did not differ between groups (40.6 days group A vs. 41.9 days group B, p = 0.719), highlighting that preservation of motor function helped minimize delays in starting oncological therapy. No significant differences were found in survival outcomes. Conclusions: A structured preoperative protocol incorporating nTMS motor mapping allows for safe and aggressive resection of motor-area GBMs. This approach effectively mitigates the risk of delays in initiating adjuvant oncological therapy, optimizing the patient prognosis. Further studies are needed to explore the long-term benefits of this protocol in both functional and oncological outcomes.

Introduction: Navigated transcranial magnetic stimulation (nTMS) has emerged as one of the most innovative techniques in neurosurgical practice. However, nTMS motor mapping involves rigorous steps, and the importance of an accurate execution method has not been emphasized enough. In particular, despite strict adherence to procedural protocols, we have observed high variability in map activation according to the choice of stimulation intensity (SI) right from the early stage of hotspot localization. We present a retrospective analysis of motor mappings performed between March 2020 and July 2022, where the SI was only chosen with rigorous care in the most recent ones, under the guide of an expert neurophysiologist. Materials and methods: In order to test the ability to reduce inaccurate responses and time expenditure using selective SI, data were collected from 16 patients who underwent mapping with the random method (group A) and 15 patients who underwent mapping with the proposed method (group B). The parameters considered were resting motor threshold (%), number of stimuli, number of valid motor evoked potentials (MEPs), number of valid MEPs considered true positives (TPs), number of valid MEPs considered false positives (FPs), ratio of true-positive MEPs to total stimuli, ratio of true-positive MEPs to valid MEPs, minimum amplitude, maximum amplitude and mapping time for each patient. Results: The analysis showed statistically significant reductions in total stimulus demand, procedural time and number of false-positive MEPs. Significant increases were observed in the number of true-positive MEPs, the ratio of true-positive MEPs to total stimuli and the ratio of true-positive MEPs to valid MEPs. In the subgroups analyzed, there were similar trends, in particular, an increase in true positives and a decrease in false-positive responses. Conclusions: The precise selection of SI during hotspot search in nTMS motor mapping could provide reliable cortical maps in short time and with low employment of resources. This method seems to ensure that a MEP really represents a functionally eloquent cortical point, making mapping more intuitive even in less experienced centers.

Awake surgery and intraoperative neuromonitoring represent the gold standard for surgery of lesion located in language-eloquent areas of the dominant hemisphere, enabling the maximal safe resection while preserving language function. Nevertheless, this functional mapping is invasive; it can be executed only during surgery and in selected patients. Moreover, the number of neuro-oncological bilingual patients is constantly growing, and performing awake surgery in this group of patients can be difficult. In this scenario, the application of accurate, repeatable and non-invasive preoperative mapping procedures is needed, in order to define the anatomical distribution of both languages. Repetitive navigated transcranial magnetic stimulation (rnTMS) associated with functional subcortical fiber tracking (nTMS-based DTI-FT) represents a promising and comprehensive mapping tool to display language pathway and function reorganization in neurosurgical patients. Herein we report a case of a bilingual patient affected by brain tumor in the left temporal lobe, who underwent rnTMS mapping for both languages (Romanian and Italian), disclosing the true eloquence of the anterior part of the lesion in both tests. After surgery, language abilities were intact at follow-up in both languages. This case represents a preliminary application of nTMS-based DTI-FT in neurosurgery for brain tumor in eloquent areas in a bilingual patient.