Introduction
Cervical myelopathy (CM) is a common degenerative condition caused by compression on the spinal cord. Currently, decompression surgery is considered to be the most immediate way to provide relief from the spinal cord compression and to promote neurological recovery. The purpose of this study is to identify whether there were differences in spinal cord integrity based on individual tract after the decompression surgery in CM patients using diffusion tensor imaging (DTI).
Methods
Twenty CM patients (mean age 56.8years) and 12 healthy subjects (mean age 34.7 years) were recruited for this study. DTI was acquired once in controls and twice in CM patients (before and 2 weeks after laminoplasty). 3-T MRI scanner was used to acquire T2 structural image, magnetization transfer image and DTI. DTI analysis was done using neuropoly software. Before analysis, images were flipped if right side was the lesion side. Twelve areas were selected as region-of-interest (ROI): main motor and sensory pathways of white matter. Fractional anisotropy (FA) and mean diffusivity (MD) were extracted at each ROIs at the lesion level and above the lesion level before and after surgery. We performed independent t-test to analyze difference in each value between patient and control. Two way ANOVA test was done with two factors (time (pre vs post-op), lesion (above vs lesion level)). Pearson correlation was conducted between modified Japanese Orthopaedic Association (mJOA) scale and diffusion metrics.
Results
1. On the lesion level, the ventral corticospinal tract (vCST), tectospinal tract (TST), ventral reticulospinal tract (vReST), lateral vestibulospinal tract (lVST) and spino-olivary tract (SOT) showed significant high FA and low MD value (except: TST of the MD) in the CM patients compared to controls in the preoperative condition, which was maintained after surgery. On above the lesion level, same tracts showed significant changes in FA and MD except TST in preop. condition, however, after surgery, only the vReST remained to be significant.
2. Significant interaction effect between time and lesion was in FA of the rubrospinal tract, lateral CST (lCST), fasciculus gracilis tract, fasciculus cuneatus tract, ventral spinocerebellar tract, which was significantly increased on the lesion level and decreased on the above the lesion level of CM patients postoperatively.
3. FA and MD of the left lCST showed significant correlation with vCST on the lesion level only after surgery.
4. FA and MD of the TST showed significant correlation with mJOA scale on the lesion level postoperatively.
Conclusion
We found compensatory increase in diffusion metrics of vCST and extrapyramidal tract, mostly located at the anterior portion of spinal cord in CM patient. Decompression effect of surgery was prominent in the posterolateral sensorimotor tracts. As the TST was well correlated with behavioral outcome, it could be used as a biomarker for prognosis in the CM patient. |
