Relatively Large Cervical Spinal Cord for Spinal Canal is a Risk factor for Development of Cervical Spinal Cord Compression: A Cross-Sectional Study of 1211 Subjects.

STUDY DESIGN A cross-sectional study. OBJECTIVE This study aims to investigate the correlation of the cervical canal and spinal cord size, and evaluate whether the size of the spinal cord relative to the spinal canal is a risk factor for development of cervical spinal cord compression (SCC). SUMMARY OF BACKGROUND DATA There is little knowledge regarding the relationship between cervical bony canal and spinal cord diameters. Although developmental canal stenosis has been recognized as a risk factor for SCC, the size of the spinal cord relative to the spinal canal has not been similarly discussed. METHODS Cervical canal anteroposterior (AP) diameters on X-rays and AP diameters and cross-sectional areas of dural sacs and spinal cords on magnetic resonance imaging (MRI) were measured in 1211 healthy volunteers. Correlation between cervical canal diameter on X-rays and AP diameter and cross-sectional area of dural sacs and spinal cords on MRI were assessed. The ratio of the AP diameter of the spinal cord/dural sac was compared between subjects with and without SCC. RESULTS Spinal canal diameters were not highly correlated with spinal cord AP diameters and cross-sectional areas, although spinal canal diameters were significantly correlated with dural sac AP diameters. The individual difference in the ratio of the AP diameter of the spinal cord/dural sac was large (35%-93%), and the ratio was significantly larger in the subjects with SCC. An AP diameter ratio more than 62% at the C2 to C3 disc level is a risk factor for developing SCC. CONCLUSION The spinal cord diameter was independent of the spinal canal diameter and the relative size of a spinal cord and spinal canal differed on an individual basis. In addition, the ratio of spinal cord/dural sac in subjects with SCC was significantly larger. Therefore, a relatively large spinal cord could be a risk factor for SCC.