nTMS motor mapping: Basic principles and clinical use

The goal of glioma surgery is maximal safe resection. These intrinsic brain neoplasms, however, lack a clear margin and frequently infiltrate eloquent areas of the brain, thus making their surgical resection challenging. Therefore, preoperative investigations like nTMS that aid in anatomico-functional tumor characterization help to define the extent of the tumor and to determine the feasibility of complete resection, which is helpful to the surgeon. Coupled with intraoperative adjuncts like navigated cortical and subcortical mapping and monitoring techniques, preoperative nTMS maps can help to identify a tumor-infiltrated functional cortex during surgery to maximize the extent of resection. Combined use of these different modalities before and during surgery is encouraged to meet surgical goals and ensure best patient outcomes. In this chapter, we discuss the role of nTMS in motor mapping for tumors in the perirolandic region.