Combined use of tractography-integrated functional neuronavigation and direct fiber stimulation

Object. The aim of this study was better preoperative planning and direct application to intraoperative procedures through accurate coregistration of diffusion-tensor (DT) imaging-based tractography results and anatomical three-dimensional magnetic resonance images and subsequent importation of the combined images to a neuronavigation system (functional neuronavigation). Methods. Six patients with brain lesions adjacent to the corticospinal tract (CST) were studied. During surgery, direct fiber stimulation was used to evoke motor responses to confirm the accuracy of CST depicted on functional neuronavigation. In three patients, Stimulation of the supposed CST elicited the expected motor evoked potentials. In the other three, stimulation at the resection borders more than 1 cm away from the supposed CST showed no motor response. All patients underwent appropriate tumor resection with preservation of the CST. Conclusions. Integration of the DT imaging-based tractography information into a traditional neuronavigation system demonstrated spatial relationships between lesions and the CST, allowing for the avoidance of tract injury during lesion resection. Direct fiber stimulation was used for real-time reliable white matter mapping, which served to adjust for any discrepancy between the neuronavigation system data and potentially shifted positions of the brain structures. The combination of these techniques enabled the authors to identify accurate positions of the CST during surgery and to accomplish optimal tumor resections.