Reconstruction of the Corticospinal Tract in Patients with Motor-Eloquent High-Grade Gliomas Using Multilevel Fiber Tractography Combined with Functional Motor Cortex Mapping

Abstract

BACKGROUND AND PURPOSE: Tractography of the corticospinal tract is paramount to presurgical planning and guidance of intraoperative resection in patients with motor-eloquent gliomas. It is well-known that DTI-based tractography as the most frequently used technique has relevant shortcomings, particularly for resolving complex fiber architecture. The purpose of this study was to evaluate multilevel fiber tractography combined with functional motor cortex mapping in comparison with conventional deterministic tractography algorithms.MATERIALS AND METHODS: Thirty-one patients (mean age, 61.5 [SD, 12.2] years) with motor-eloquent high-grade gliomas underwent MR imaging with DWI (TR/TE ¼ 5000/78 ms, voxel size ¼ 2 Â 2 Â 2 mm 3 , 1 volume at b ¼ 0 s/mm 2 , 32 volumes at b ¼ 1000 s/mm 2 ). DTI, constrained spherical deconvolution, and multilevel fiber tractography-based reconstruction of the corticospinal tract within the tumor-affected hemispheres were performed. The functional motor cortex was enclosed by navigated transcranial magnetic stimulation motor mapping before tumor resection and used for seeding. A range of angular deviation and fractional anisotropy thresholds (for DTI) was tested.RESULTS: For all investigated thresholds, multilevel fiber tractography achieved the highest mean coverage of the motor maps (eg, angular threshold = 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold ¼ 71.8%, 22.6%, and 11.7%) and the most extensive corticospinal tract reconstructions (eg, angular threshold ¼ 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold ¼ 26,485 mm 3 , 6308 mm 3 , and 4270 mm 3 ).CONCLUSIONS: Multilevel fiber tractography may improve the coverage of the motor cortex by corticospinal tract fibers compared with conventional deterministic algorithms. Thus, it could provide a more detailed and complete visualization of corticospinal tract architecture, particularly by visualizing fiber trajectories with acute angles that might be of high relevance in patients with gliomas and distorted anatomy.ABBREVIATIONS: ADT ¼ angular deviation threshold; CSD ¼ constrained spherical deconvolution; CST ¼ corticospinal tract; FAT ¼ fractional anisotropy threshold; FOD ¼ fiber orientation distribution; MLFT ¼ multilevel fiber tractography; nTMS ¼ navigated transcranial magnetic stimulation G liomas are the most prevalent malignant brain tumors in adults, and particularly anaplastic astrocytoma and glioblastoma as representatives of high-grade gliomas have poor prognoses. [1][2][3] Contemporary treatment combines neurosurgical tumor resection with extended focal radiation therapy and adjuvant chemotherapy. [4][5][6] Specifically, a maximum extent of resection correlates to

Reconstructing the somatotopic organization of the corticospinal tract remains a challenge for modern tractography methods

“…Over the past two decades, many diffusion magnetic resonance imaging (dMRI) tractography methods have been proposed for the reconstruction of the CST, including single-and multi-fiber modeling, deterministic and probabilistic methods, and machine-learning-based methods. Despite many recent advances, dMRI tractography of the CST still faces challenges in adequately depicting all portions of the CST (Petersen & McIntyre, 2023;Pujol et al, 2015;Zhylka et al, 2023).…”

“…Despite many recent advances, dMRI tractography of the CST still faces challenges in adequately depicting all portions of the CST (Petersen & McIntyre, 2023 ; Pujol et al, 2015 ; Zhylka et al, 2023 ). An ideal tractography reconstruction of the CST should produce streamlines that cover (intersect) all regions of the primary motor cortex.…”