Abstract
Preoperative mapping of cortical structures prior to neurosurgical intervention can provide a roadmap of the brain with which neurosurgeons can navigate critical cortical structures. In patients undergoing surgery for brain tumors, preoperative mapping allows for improved operative planning, patient risk stratification, and personalized preoperative patient counseling. Navigated transcranial magnetic stimulation (nTMS) is one modality that allows for highly accurate, image-guided, non-invasive stimulation of the brain, thus allowing for differentiation between eloquent and non-eloquent cortical regions. Motor mapping is the best validated application of nTMS, yielding reliable maps with an accuracy similar to intraoperative cortical mapping. Language mapping is also commonly performed, although nTMS language maps are not as highly concordant with direct intraoperative cortical stimulation maps as nTMS motor maps. Additionally, nTMS has been used to localize cortical regions involved in other functions such as facial recognition, calculation, higher-order motor processing, and visuospatial orientation. In this review, we evaluate the growing literature on the applications of nTMS in the preoperative setting. First, we analyze the evidence in support of the most common clinical applications. Then we identify usages that show promise but require further validation. We also discuss developing nTMS techniques that are still in the experimental stage, such as the use of nTMS to enhance postoperative recovery. Finally, we highlight practical considerations when utilizing nTMS and, importantly, its safety profile in neurosurgical patients. In so doing, we aim to provide a comprehensive review of the role of nTMS in the neurosurgical management of a patient with a brain tumor.
Highlights
A primary tenet of neurosurgical oncology is to achieve maximal resection of pathologic lesions while preserving the surrounding eloquent brain and, protecting a patient’s functional ability
Over multiple studies, there were no positive motor mapping sites identified with direct cortical stimulation (DCS) that were unrecognized with TMS, demonstrating the high degree of sensitivity for preoperative Navigated transcranial magnetic stimulation (nTMS)
There was a corresponding decline in the rate of postoperative deficits in the group of patients who underwent nTMS. These findings suggest that the addition of preoperative nTMS mapping data to a clinical routine of preoperative fiber tractography, intraoperative neuronavigation, and intraoperative mapping/electrophysiology improves surgical outcomes for tumors in or near the motor pathways [18]
Summary
Preoperative mapping of cortical structures prior to neurosurgical intervention can provide a roadmap of the brain with which neurosurgeons can navigate critical cortical structures. Navigated transcranial magnetic stimulation (nTMS) is one modality that allows for highly accurate, image-guided, non-invasive stimulation of the brain, allowing for differentiation between eloquent and non-eloquent cortical regions. Motor mapping is the best validated application of nTMS, yielding reliable maps with an accuracy similar to intraoperative cortical mapping. Language mapping is commonly performed, nTMS language maps are not as highly concordant with direct intraoperative cortical stimulation maps as nTMS motor maps. We evaluate the growing literature on the applications of nTMS in the preoperative setting. We aim to provide a comprehensive review of the role of nTMS in the neurosurgical management of a patient with a brain tumor
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