Study design: Transverse areas of the spinal canal, the dural tube and the spinal cord of the cervical spine of normal adults and patients with cervical spondylotic myelopathy (CSM) were analyzed by magnetic resonance imaging (MRI).
Objectives: Correlations of the results of MRI to clarify the pathogenesis of CSM.
Summary of background data: Relationships between the area of the spinal cord and that of the dural tube or the spinal canal have been reported, but there is no report to compare the relationships among the three in patients with CSM and normal adults.
Methods: T1-weighted MR images of the cervical spine of 96 normal adults and 74 patients with CSM were evaluated by measuring the transverse areas of the three structures mentioned above in the axial plane.
Results: In normal adults, the maximal transverse area of the spinal cord was 85.8 mm2 at C4/5 and the minimal transverse areas of the dural tube and the spinal canal were 186.0 mm2 at C5/6 and 236.1 mm2 at C4, respectively. At the unaffected level of C3, the ratio of the canal to the spinal cord was significantly higher in CSM patients than in age-matched normal adults. The transverse area of the spinal cord and the ratio at the maximal compression level showed significant correlations with the severity of neurological symptoms.
Conclusion: These results suggest that the narrow area and high ratio of the spinal canal to the spinal cord are responsible for a static factor in CSM.