Deterministic Tractography of the Descending Tract of the Spinal Trigeminal Nerve Using Diffusion Tensor Imaging.

BACKGROUND AND PURPOSE: Pain information from the face enters the pons via the trigeminal nerve before creating an anatomical "elbow" that turns caudally into the spinal trigeminal tract (SpTV). Visualization of the descending tract of the trigeminal nerve as it begins its descent from the nerve root entry zone (NREZ) in the pons would improve the accuracy of current procedures aimed at altering or lesioning the trigeminal nerve within the brainstem. The focus of this study was to develop a standardized protocol using diffusion tensor imaging (DTI) and deterministic tractography methods to image the SpTV. There are currently no standard techniques used to visualize the trigeminal nerve using DTI.

METHODS: DTI and tractography were performed on 20 patients: 17 with trigeminal neuralgia (TN), 1 with hemifacial spasm, 1 with a facial nerve tumor, and 1 with an arteriovenous malformation. A standardized protocol was developed using regions of interest (ROIs) located at the SpTV, as determined by a brainstem atlas, and the NREZ.

RESULTS: Using our standardized protocol, the descending tract of the trigeminal nerve was successfully visualized in all 20 patients. Trigeminal fibers entered the pons at the NREZ and descended through the SpTV. The accuracy of the visualized tract was confirmed through coregistration with a stereotactic atlas and anatomical scan.

CONCLUSION: A successful, robust DTI imaging and postprocessing protocol of the SpTV contributes to our understanding of its anatomical distribution within the brainstem and is a potentially new neurosurgical planning tool.