nTMS Motor Mapping: Basic Principles and Clinical Use

Gliomas constitute a group of intrinsic brain neoplasms for which no curative therapies currently exist. Cytoreductive surgery remains the cornerstone of glioma treatment, and while surgical resection alone is not sufficient to halt tumor progression, the importance of maximizing the EOR has been increasingly recognized for low-grade gliomas (LGG) as well as high-grade gliomas (HGG). However, preservation of neurological function postoperatively is equally important because it influences not only quality of life but also survival. Many tools are available at neurosurgeons’ disposal today to help maximize the EOR. The addition of only one modality, such as DTI of the CST preoperatively or intraoperative DES and mapping, can improve the rates of complete resection by 30–40% while preserving neurological function. Preoperative mapping tools like nTMS can also help to identify eloquent cortical areas and subcortical pathways and better prepare the surgeon to achieve a maximal, safe tumor resection.