Introduction: The hyperdirect pathway, connecting the primary motor cortex to the subthalamic nucleus (STN), is hypothesized to play a role in movement inhibition and is believed to mediate the effects of deep brain stimulation in Parkinson’s disease (PD). This study outlines a methodological approach for generating the hyperdirect tract using diffusion MRI tractography and the selection of regions of interest (ROIs) for the STN and primary motor cortex.
Methods: We included 6 patients with PD who underwent MRI including diffusion-tensor images (DTI). DTI were pre-processed and whole-brain tractograms were generated. ROIs for the STN were manually segmented using SWI images on the axial and coronal views in ITK-SNAP, while ROIs for the primary motor cortex were manually segmented from T1-weighted images on the axial view. Hyperdirect tracts were delineated using ROIs from the brain tractogram using MRtrix3. Tract quality was assessed through visual inspection and anatomical consistency. The results were reviewed by one board-certified neurosurgeon and one neurosurgery resident.
Results: The hyperdirect tracts successfully connected the STN and primary motor cortex with high anatomical consistency in all 6 patients. Across all patients, a total of 105 streamlines (18 per patient) were identified. Of these, 93 % passed dorsolateral STN.
Conclusion : This study presents a rigorous approach for identifying the hyperdirect pathway using diffusion MRI tractography. The results align with established anatomical features. These methods provide a strong foundation for future studies aimed at integrating clinical outcomes to further explore the role of the hyperdirect pathway in neurological disorders and therapeutic interventions.
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