Abstract
The corticospinal tract (CST) is one of the most well-studied tracts in human neuroanatomy. Its clinical significance can be demonstrated in many notable traumatic conditions and diseases such as stroke, spinal cord injury (SCI) or amyotrophic lateral sclerosis (ALS). With the advent of diffusion MRI and tractography the computational representation of the human CST in a 3D model became available. However, the representation of the entire CST and, specifically, the hand motor area has remained elusive. In this paper we proposed a novel method, using manually-drawn ROIs based on robustly identifiable neuroanatomic structures to delineate the entire CST and isolate its hand motor representation as well as to estimate their variability and generate a database of their volume, length and biophysical parameters. Using 37 healthy human subjects we performed a qualitative and quantitative analysis of the CST and the hand-related motor fiber tracts (HMFTs). Finally, we have created variability heatmaps from 37 subjects for both the aforementioned tracts, which could be utilized as reference for clinicians to explore neuropathology in both trauma and disease states.
Highlights
A new method based on three neuroanatomical landmarks using higher-order diffusion MRI tractography for the complete corticospinal tract (CST) delineation is proposed.
Focus on the clinically significant hand motor area with description of a novel method to isolate and quantify the hand-related motor fiber tracts (HMFTs).
It is suggested that crossing fibers like the superior longitudinal fascicle are restricting the full representation of the CST in the hand motor area.
Qualitative and quantitative analysis is performed and variability heatmaps of the human CST and HMFTs are provided based on healthy human subjects from the Human Connectome Project.
Clinical applications of the CST and the HMFTs tractographic analyses are discussed, along with the historical aspects related to the CST, given its clinical importance for neurology/neurosurgery, neurorehabilitation and regenerative medicine.
Abbreviations
- CST
- corticospinal tract
- HMFTs
- hand-related motor fiber tracts
- PT
- pyramidal tract
- BA
- Brodmann’s area
- dMRI
- diffusion magnetic resonance imaging
- DTI
- diffusion tensor imaging
- HARDI
- high angular resolution diffusion imaging
- IC
- internal capsule
- SCI
- spinal cord injury
- TBI
- traumatic brain injury
- MS
- Multiple sclerosis
- ALS
- Amyotrophic Lateral Sclerosis
- AF
- arcuate fascicle
- SLF
- superior longitudinal fascicle
- CC
- corpus callosum
- HCP
- Human Connectome Project
- UKF deterministic tractography
- unscented Kalman filter deterministic tractography
- FA
- fractional anisotropy
- AD
- axial diffusivity
- RD
- radial diffusivity
- SD
- standard deviation
- WU-Minn HCP consortium
- Washington University-University of Minnesota and Oxford University Human Connectome Project consortium
- ROIs
- regions of interest
- WMQL
- White Matter Query Language
- AC
- anterior commissure
- SI
- Symmetry index
- WashU
- Washington University
- MNI
- Montreal Neurological Institute
- CBPS
- congenital bilateral perisylvian syndrome
- OFF
- occipitofrontal fascicle