Identification of the pyramidal tract by neuronavigation based on intraoperative diffusion-weighted imaging combined with subcortical stimulation

Background/Aims: To identify the pyramidal tract by neuronavigation based on intraoperative diffusion-weighted imaging (iDWI) combined with subcortical stimulation. Methods: Seven patients with brain tumors near the deep white matter underwent resection surgery using neuronavigation based on iDWI to visualize white matter bundles. Subcortical electrical stimulation was performed and electromyography was measured at the extremities when surgical manipulation came near the position corresponding to the depicted bundle. We validated the bundle depicted on iDWI by considering the responses to subcortical stimulation and the distance between the stimulation site and the depicted bundle. Results: Positive motor-evoked potentials were detected in 5 of 7 patients (8 stimulations) and the distance from the stimulation site to the depicted bundle was 0-4.7 mm (mean ± SD, 1.4 ± 2.1 mm). Negative (no) responses were obtained in all patients when the distance was more than 5 mm. The neuronavigation system had an average error of 0.79 ± 0.25 mm and a maximum error of 2.0 mm (n = 16). Conclusion: Neuronavigation based on iDWI combined with subcortical stimulation allowed surgeons to identify the pyramidal tract and avoid inadvertent injury. Our findings demonstrate that the white matter bundles depicted by iDWI can contain the pyramidal tract.