Motor and language DTI Fiber Tracking combined with intraoperative subcortical mapping for surgical removal of gliomas

Preoperative DTI Fiber Tracking (DTI-FT) reconstruction of functional tracts combined with intraoperative subcortical mapping (ISM) is potentially useful to improve surgical procedures in gliomas located in eloquent areas. Aims of the study are: (1) to evaluate the modifications of fiber trajectory induced by the tumor; (2) to validate preoperative DTI-FT results with intraoperative identification of functional subcortical sites through direct subcortical stimulation; (3) to evaluate the impact of preoperative DTI-FT reconstructions in a neuronavigational setup combined with ISM technique on duration and modalities of surgical procedures, and on functional outcome of the patients. Data are available on 64 patients (52 low-grade and 12 high-grade gliomas). DTI-FT was acquired by a 3-T MR scanner with a single-shot EPI sequence (TR/TE 8986/80 ms, b=1000 s/mm) with gradients applied along 32 non-collinear directions. 3D Fast Field Echo (FFE) T1-weighted imaging (TR/TE 8/4 ms) was performed for anatomic guidance. The corticospinal tract (CST), superior longitudinal, inferior fronto-occipital and uncinatus fasciculi were reconstructed. Data were transferred to the neuronavigational system. Functional subcortical sites identified during ISM were correlated with fiber tracts depicted by DTI-FT. In high-grade gliomas, DTI-FT depicted tracts mostly at the tumor periphery; in low-grade gliomas, fibers were frequently located inside the tumor mass. There was a high correlation between DTI-FT and ISM (sensitivity for CST=95%, language tracts=97%). For a proper reconstruction of the tracts, it was necessary to use a low FA threshold of fiber tracking algorithm and to position additional regions of interest (ROIs). The combination of DTI-FT and ISM decreased the duration of surgery, patient fatigue, and intraoperative seizures. Combination of DTI-FT and ISM allows accurate identification of eloquent fiber tracts and enhances surgical performance and safety maintaining a high rate of functional preservation.