Three-dimensional visualization of the pyramidal tract in a neuronavigation system during brain tumor surgery: first experiences and technical note.

Objective: To integrate spatial three-dimensional information concerning the pyramidal tracts into a customized system for frameless neuronavigation during brain tumor surgery.

Methods: Four consecutive patients with intracranial tumors in eloquent areas underwent diffusion-weighted and anatomic magnetic resonance imaging studies within 48 hours before surgery. Diffusion-weighted datasets were merged with anatomic data for navigation purposes. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. The reconstruction results, together with the fused-image dataset, were available during surgery in the environment of a customized neuronavigation system.

Results: In all four patients, the combination of reconstructed data and fused images was a helpful additional source of information concerning the tumor seat and topographical interaction with the pyramidal tract. In two patients, intraoperative motor cortex stimulation verified the tumor seat with regard to the precentral gyrus.

Conclusion: Diffusion-weighted magnetic resonance imaging allows individual estimation of large fiber tracts applicable as important information in intraoperative neuronavigation and in planning brain tumor resection. A three-dimensional representation of fibers associated with the pyramidal tract during brain tumor surgery is feasible with the presented technique and is a helpful adjunct for the neurosurgeon. The main drawbacks include the length of time required for the segmentation procedure, the lack of direct intraoperative control of the pyramidal tract position, and brain shift. However, mapping of large fiber tracts and its intraoperative use for neuronavigation have the potential to increase the safety of neurosurgical procedures and to reduce surgical morbidity.