A Standardized Protocol for Functional Motor Mapping Using Navigated Transcranial Magnetic Stimulation

Navigated transcranial magnetic stimulation (nTMS) is based on the integration of individual brain imaging data to determine the precise positioning of the stimulation coil, thus enabling anatomically guided stimulation of cortical targets. The interest of neuronavigation systems is well recognized in the optimization of coil positioning during repetitive TMS (rTMS) treatments. Furthermore, nTMS is increasingly applied for functional mapping of brain regions in different applications, such as the identification and delineation of eloquent motor and language areas before tumor resection. Besides its usefulness in optimizing neurosurgical procedures, nTMS mapping can also be a tool for monitoring cortical plasticity and quantifying the integrity of the motor system in various neurological diseases. This methodological paper presents a standardized protocol for motor mapping using nTMS, in combination with diffusion tensor imaging (DTI)-based reconstruction of the corticospinal tract (CST). This approach allows for precise delineation of eloquent motor cortical regions and their subcortical projections, and the detection of functional reorganizations in patients with adjacent lesions. When integrated into presurgical planning, this method provides guidance for individualized surgical strategies aimed at maximizing lesion resection while preserving motor function. The protocol presented here is reproducible, clinically applicable, and suitable for integration into routine workflows. It constitutes a promising tool for neuroplasticity research and rehabilitation planning.