Navigated Transcranial Magnetic Stimulation in Tumor Surgery

Maximizing surgical removal of brain tumors while minimizing neurologic deficits is challenging. Functional brain tissue may reside close to or even within the abnormality, and inadvertent removal or disturbance of such areas can result in neurologic deficits. At present, the gold standard for identifying critical motor areas in tumor surgery is intraoperative invasive direct current stimulation (DCS) through a handpiece. More recently, new non-invasive preoperative method for brain mapping, functional magnetic resonance imaging (fMRI), may be used to identify the eloquent motor areas. fMRI signals used in localization of the motor areas are generated when the brain is activated during the performance of specific motor tasks. However, as fMRI signals are also generated by sensory input, the resulting fMRI map may include sensory as well as motor areas. Nexstim has developed a Navigated Brain Stimulation (NBS) system that uses TMS with a software based Navigational System that together may have more specific spatial accuracy. This study aims to determine whether navigated TMS is able to identify the eloquent motor cortical areas in patients with brain tumors and to determine the clinical accuracy of the procedure by comparing it to results obtained by intraoperative DCS and fMRI.