Precise diagnosis of cervical spondylotic myelopathy based on quantitative fiber tractography

Abstract

INTRODUCTION: The insidious onset and variety of clinical symptoms and signs of cervical spondylotic myelopathy (CSM) pose a big challenges to clinician for early diagnosis and precise prognostication. The gross morphological and signal changes in T2-weighted magnetic resonance images (MRI) did not necessarily correlate with the severity of chronic compressive injuries of cervical spinal cord. In the present study, we aimed to employ a relatively novel diffusion MRI imaging and fiber tractography techniques to quantify the damages of nerve fibers in spinal cord in CSM patients. METHODS: Total 14 volunteers were recruited in this study with informed consent, including 5 adult healthy subjects (group A, 25 ± 2 years), 5 elderly healthy subjects (group B, 53 ± 3 years) and 4 CSM patients (group C, 53 ± 8 years). Diffusion MR Imaging MR imaging of cervical spinal cord were performed with a 3T Philips MR system (Philips Medical System, Netherlands). T1 and T2-weighted images were obtained and diffusion MRI images were also taken using pulsed gradient, spin-echo-echo-planar imaging (SE-EPI) sequence(data acquisition parameters: TR/TS = 5000/60 ms; 13 slices (7 mm slice thickness, 2.2 mm gap); field of view (FOV) = 80 (RL) 9 36 (AP) mm; matrix size = 128 9 128; non-collinear diffusion encoding directions = 16, b = 600 s/mm2; reconstruction resolution = 0.63 9 0.64 9 7.0 mm3; acquisition time = 8 min). Fiber trachtography was done via TrackVis. The density of nerve fibers (unit/mm2) ventral, lateral and dorsal column of white matter in the cord, was calculated, respectively. RESULTS: It was revealed in T2-weighted image of four CSM patients that the spinal cords were compressed by degenerated disc from ventrally. Yet it was found that the nerve fiber density was significantly lower in dorsal column of spinal cord in these four patients as compared with adult and elderly healthy subjects (group A: 0.432 ± 0.033; B: 0.418 ± 0.023; C: 0.276 ± 0.028; p﹤0.05). There were no significant differences in either ventral (group A: 0.315 ± 0.037; B: 0.368 ± 0.026; C: 0.359 ± 0.020) or lateral columns among groups (group A: 0.368 ± 0.032; B: 0.380 ± 0.031; C: 0.364 ± 0.012). CONCLUSION: The discontinuity of nerve fibers were present in dorsal column of spinal cord with ventral compression in CSM patients. It suggested the underlying mechanism of CSM might not result from the effect of direct compression.