gms | German Medical Science

Objective: To determine the relationship of the distance of a tumor to the pyramidal tract in respect to neurological outcome of surgery of intracranial lesions and to visualize hulls representing safety margins around the pyramidal tract for integration into a navigation system.

Methods: In 64 patients (37 f, 27 m) with intracerebral lesions (52 gliomas, 6 cavernomas, 6 other) adjacent to the pyramidal tract, diffusion tensor imaging (DTI) data were integrated in a navigational setup. Diffusion data (b=0) were rigidly registered with standard T1-weighted 3-D images. Fiber tracking was performed applying a tensor-defection algorithm using a multiple volume of interest approach as seed regions for tracking. fMRI data identifying the motor gyrus were applied as selection criteria to define the fibers of interest. After tracking, a 3-D object was generated representing the pyramidal tract. Additionally, hulls wrapping all fiber structures representing safety margins were visualized. The minimum distance of the pyramidal tract to the lesion was measured in the 3-D space.

Results: In all patients the pyramidal tract could be visualized in the operative field by applying the heads-up display of the operating microscope. In 7 patients (11%) a new or worsened postoperative paresis was seen, which was transient in 5 of them; thus, in only 2 patients (3,1%) was there a new permanent neurological deficit. 6 of these patients were in the group where the pyramidal tract reached the lesion (total n=33). The risk for an at least transient postoperative deficit was: 18.2%, 14.3%, 0%, and 0% respectively in the groups with a distance of the pyramidal tract to the lesion of: 0, 0-5, 5-10, and >10 mm. These safety margins could be visualized by additional hulls wrapping the fibers of the pyramidal tract.

Conclusions: DTI fiber tracking data can be reliably integrated into navigational systems providing an intraoperative visualization of the pyramidal tract. A safety margin representing the critical distance of 5 mm around the pyramidal tract is visualized by wrapping hulls. This technique allowed the resection of lesions adjacent to the pyramidal tract with a low morbidity.