P07.10.B Preoperative brain mapping using transcranial magnetic stimulation applied to brain tumour resection surgery

Abstract

Background Brain oncological surgery must pursue maximal tumour resection to achieve oncological benefits while preserving acceptable neurological function. Neuromonitoring techniques and brain mapping have been developed over the last decades to intraoperatively assess the exact location of neurological functions and secure their preservation. However, the fact that they cannot offer preoperative information and require in some cases the patient’s collaboration during displeasing awake surgeries raised the interest during last years on noninvasive techniques offering preoperative functional information. Navigated transcranial magnetic stimulation (nTMS) is a noninvasive technique able to create small magnetic fields and electrically stimulate brain cortex, emulating the effect obtained by cortical direct electrical stimulation (DES). It is a promising tool for performing pre-operative cortical brain mapping. Material and Methods We performed a unicenter prospective descriptive study including patients diagnosed with intra axial brain tumours neighboring cortical zones apparently implicated in motor and/or language functions who were planned for surgical resection. We performed preoperative nTMS (SofTaxic Neuro navigation system 3.0, EMS, Bologna) in all of them to define the location of these functions. Results Between November 2020 and December 2021 we included 18 patients (11 men, 7 women) with a mean age of 56 years (range 29-71). Location (8 temporal, 6 frontal, 3 parietal and 1 insular) and laterality (12 left, 6 right) of the brain tumours were registered. In all cases, cortical brain motor mapping with nTMS was performed with positive results, obtaining a mean anteroposterior diameter of the motor cortex of 22,75 mm. In 11 cases language mapping was also performed, detecting a total of 40 cortical language positive sites (31 frontal, 9 temporal) in those patient’s left hemispheres. No relevant side effects were noticed after nTMS performance. Definitive pathological results after surgery revealed high-grade glioma in 15 cases and low-grade glioma in 3. Conclusion nTMS is a recent noninvasive technique that allows the realization of preoperative cortical brain mapping. The information provided by this technique is of extreme value to better define surgical candidates and to plan brain tumour resection surgeries, according to functional cortical sites identified. The available literature describes its applications, mainly in localizing motor and language cortices, showing good concordance with intraoperative cortical DES, which is still the gold standard technique for brain mapping. Its integration in the pre-operative brain tumour assessment offers important advantages without adding relevant morbidity.