Verification of the DTI-Fiber Tracked Tractus Corticospinalis during Neurosurgical Procedures – First Results

Object: Our aim was to validate the via DTI constructed pyramidal tract by intraoperative monitoring modalities – only nice images or rendering of a functional sytem? Methods: With help of measurements of the isotropy, white matter tracts could be detected. The pyramidal tract was reconstructed by choosing ROIs within its well known anatomic sites. These results were imported in two neuronavigation systems (either BrainLab® or SonoWand®). During tumor resections the cortical and/or subcortical sites as displayed in the navigation systems were stimulated with an Ojemann cortical stimulator and/or Oxford Medelec Synergy using different patterns. The patient's postoperative clinical status was examined. Results: In 5 of 11 cases the direct subcortical stimulation of the position of the pyramidal tract displayed in the neuronavigation led to contralateral limb movements and/or electromyographic potential recording. In 4 cases cortical stimulation in the gyrus to which the fiber tracking led was successful. The precentral gyrus was here also identified by phase reversal. In 3 patients there was no motor response in stimulation and no phase reversal detected. The cause was either the large distance to the pyramidal tract or in one case of a recurrent glioma a marked fibrosis in the resection cavity, probably acting as an isolation. Only one patient experienced a postoperative neurological deterioration. Conclusion: The intraoperative electrophysiological findings of the neuronavigation implemented DTI detected pyramidal tract seem to support its correlation with its anatomic sites. In case of confirmation in further investigations, the fiber tracking may be a valuable supplement to neuronavigation and may help to make performance of resections near the motor system safer.