gms | German Medical Science

Objective: To prevent postoperative neurological deficits in patients with tumors close to language related brain areas not only the cortical eloquent brain areas but also the major white matter tracts connecting Broca and Wernicke areas have to be preserved during surgery. The aim of this study was to visualize these language pathways intraoperatively to prevent new postoperative language deficits.

Methods: Single-shot spin-echo diffusion weighted echo planar imaging was used for diffusion tensor imaging based fiber tracking. Functional MRI data (applying silent reading and naming paradigms) to identify the motor and sensor speech areas were used as seed regions for tracking. Tracking was initiated in both retro- and orthograde directions according to the direction of the principal eigenvector in each voxel. The reconstructed fiber tracts were integrated into 3-D navigation by rigid registration of the B0 diffusion images with 3-D T1-weighted anatomical datasets; co-registered with the functional data. In addition a probabilistic tracking approach (A*-algorithm) was applied for validating the reconstructed tract data. Hulls wrapping the selected fiber tract bundle were generated and visualized in the surgical field.

Results: In 14 patients with lesions adjacent to language pathways, the language fiber tracts and the representation of the eloquent cortical areas could be visualized successfully. Fiber tract generation and integration into the navigation required 25-30 minutes in each case. Registration of fibertracking with 3-D datasets was possible with an error of less than 2 mm adjacent to the lesion. Co-registration with fMRI was consistent in all cases, and the probabilistic tracking confirmed the displayed course of the fibers as well. In two patients we observed a temporary speech deterioration which resolved completely one week after surgery in each case.

Conclusions: Language pathways can be reliably visualized by fiber tracking and integrated into functional neuronavigation, thereby supporting the removal of tumors adjacent to language areas, which results in alow morbidity.