The magnetic resonance imaging grading of spinal cord compression in cervical spondylotic myeopathy and its clinical significance

English Keywords:Cervical spondylotic myeopathy  Spinal cord compression  Dural sac  Magnetic resonance imaging grading

English Abstract:

  【Abstract】 Objectives: To establish a magnetic resonance imaging(MRI) grading system of spinal cord compression in cervical spondylotic myelopathy（CSM）, and to investigate its clinical significance and the correlation with age, duration of disease and JOA scores. Methods: From January 2010 to September 2011, a retrospective study of 78 consecutive patients with multi-level CSM, who were referred to our hospital and underwent MRI examination of the cervical spine, was carried out. There were 51 males and 27 females with an average age of 55.1 years(range, 42-77 years) and an average duration of disease of 48.8 months(range, 0.25-276 months). The spinal cord morphology, spinal cord signal and relationship between spinal cord and dural sac in the MRI were regarded as grading signs. Each sign was divided into three types on the basis of severity degrees, and corresponding scores were 0 to 2. The grades of spinal cord compression on MRI were scored on the same four-point scale according to total scores： grade 0, 0 score; grade 1, 1-2 scores; grade 2, 3-4 scores; grade 3, 5-6 scores. Three independent spine surgeons(ranking as senior, middle, and primary) evaluated twice respectively and together for the third time, the MRI of CSM from the C2/3 through C6/7 levels of 78 consecutive patients. Kappa analysis was used to evaluate the consistency of the first and second results of grading. The Spearman correlation among three grading signs and the correlation of age, duration of disease and the JOA scores were investigated according to the third results of grading. Results: A total of 390 levels from 78 consecutive patients was evaluated by three independent spine surgeons twice respectively, 82-94 levels (21.03%-24.10%) were considered to be grade 0, 112-126 (28.72%-32.31%) grade 1, 111-137 (28.46%-35.13%) grade 2, 47-70(12.05%-17.95%) grade 3. The Kappa values of intraobserver were ranged from 0.657 to 0.706, representing substantial or excellent agreement in 74.6%-78.5% of 390 levels. The Kappa values of interobserver were ranged from 0.614 to 0.683, representing substantial or excellent agreement in 71.5%-76.7% of 390 levels. There were positive correlations among three grading signs(r=0.552, 0.603, 0.577, P<0.05). Age and duration of disease had positive correlations with the MRI grading of spinal cord compression in CSM(r=0.372-0.511, 0.388-0.498, P<0.05). The preoperative JOA scores had negative correlations with the MRI grading of spinal cord compression in CSM(r=-0.409--0.546, P<0.05). Conclusions: MRI grading system of spinal cord compression in CSM according to spinal cord morphology, spinal cord signal and relationship between spinal cord and dural sac is presented with good reliability, which can be useful for assessment and research of spinal cord compression. The magnetic resonance imaging grading of spinal cord compression in CSM exists a positive correlation with age and duration of disease, but has a negative correlation with preoperative JOA scores.