Matching relationship between cervical spinal cord and spinal canal and dynamic change analysis on spinal cord compression factors of patients with cervical spondylotic myelopathy

English Keywords:Cervical spondylotic myelopathy  Dynamic MRI  Spinal cord  Dural sac  Matching relationgship

English Abstract:

  【Abstract】 Objectives: To observe the dynamic changes of the matching relationship between cervical spinal cord and cervical canal, and investigate the relationship of the risk of spinal cord compression with matching relationship and spinal cord compression factors. Methods: The imaging data of the patients with cervical spondylotic myelopathy(CSM) who underwent dynamic magnetic resonance imaging(DMRI) in our hospital from January 2018 to July 2021 were collected, and those with unclear images and unsatisfactory flexion and extension angles were excluded. A total of 63 patients, 37 males and 26 females, were included. The age ranged from 50 to 67 years old (56.6±4.9 years old). The horizontal spinal cord area and dural sac area of C3 to C7 intervertebral disc in cross section on DMRI T2 images were measured at anteflexion position, neutral position, and rear protraction position. The ratio of spinal cord to dural sac area(spinal cord occupancy ratio) was calculated. The degree of intervertebral disc herniation on the transverse section of T2 image and the thickness of ligamentum flavum on the sagittal plane of T2 image were measured. The degree of spinal cord compression was observed on T2 images in cross section, and the spinal cord compression was graded with the modified Muhle classification standard. The degree of intervertebral disc degeneration was observed and scored by Pfirrmann grading standard. All C3-C7 segments were divided into group with disc herniation and group without disc herniation for comparison, so as to analyze whether the herniated disc would affect the matching relationship of spinal canal and the change of ligamentum flavum thickness. Results: A total of 252 cervical vertebra segments were measured, including 33 non-herniated C3/4 disc segments and 30 herniated disc segments; 21 C4/5 non-protruding segments and 42 protruding segments; 17 C5/6 non-protruding segments and 46 protruding segments; 27 C6/7 non-protruding segments and 36 protruding segments. In groups without and with disc herniation, for the area of spinal cord, it was: rear protraction position>neutral position>anteflexion position; for the area of dural sac, it was: anteflexion position>neutral position>rear protraction position; the spinal canal occupancy was: rear protraction position>neutral position>anteflexion position. The difference was statistically significant(P<0.05). In groups with disc herniation, the spinal cord occupancy ratio of C5/6 in the neutral position was the highest in the four segments of C3-C7. In groups without disc herniation, the spinal cord occupancy ratio of C5/6 in the anterior flexion position and the neutral position was the highest in the four segments of C3-C7. The degree of disc herniation was: rear protraction position>neutral position>anteflexion position, and the grade of spinal cord compression was: rear protraction position>neutral position>anteflexion position, and the difference was statistically significant(P<0.05). The thickness of ligamentum flavum was: rear protraction position>neutral position>anteflexion position. The grade of disc degeneration in the group with disc herniation was higher than that in the group without disc herniation, and the difference was statistically significant(P<0.05). The thickness of ligamentum flavum in the group with disc herniation was statistically significant compared with that in the group without disc herniation(P<0.05). Conclusions: DMRI can show the dynamic changes of the matching relationship between cervical spinal cord and spinal canal. When the cervical spine moves from flexion to extension, the spinal canal occupancy increases and the risk of spinal cord compression increases, especially at the C5/6 segment.