The Influence of Changes in Cervical Lordosis on Bulging Disk and Spinal Stenosis: Functional MR Imaging

ABSTRACT

PURPOSE: To assess the effect of lordotic curve change of the cervical spine on disk bulging and spinal stenosis by means of functional cervical MR imaging at the flexion and extension position. MATERIALS AND METHODS: Using a 1.5T imager, kinematic MR examinations of 25 patients with degenerative spondylosis (average age, 41 years) were performed at the neutral, flexed and extended position of the cervical spine. Sagittal T2-weighted turbo spin-echo images were obtained during each of the three phases. Lordotic an-gle, bulging thickness of the disk, AP diameter of the spinal canal, and distance between the disk and spinal cord were measured on the workstation at each disk level. After qualitative independent observation of disk bulging, one of four grades(0, normal; 1, mild; 2, moderate; 3, marked) was assigned at each phase, and after further comparative observation, one of five scores (-2, prominent decrease; -1, mild decrease; 0, no change; 1, notable increase; 2 prominent increase) was also assigned. In addition, bulging thickness of the disk was measured and compared at the neutral, flexed, and extended positions. RESULTS: Average angles of the cervical spine were 160.5+/-5.9 degrees (neutral position, lordotic angle); 185.4+/-8.5 degrees (flexion, kyphotic angle); and 143.7+/-6.7 degrees (extension, lordotic angle). Average grades of disk bulging were 0.55 at the neutral position, 0.16 at flexion, and 0.7 at extension. Comparative observation showed that average scores of disk bulging were -0.39 at flexion and 0.31 at extension. The bulging thickness of the disk decreased by 24.2% at flexion and increased by 30.3% at extension, while the diameter of the spinal canal increased by 4.5% at flexion and decreased by 3.6% at extension. The distance from the posterior margin of the disk to the anterior margin of the spinal cord decreased at both flexion(6.6%) and extension(19.1%). CONCLUSION: Functional MRI showed that compared with the neutral position, disk bulging and spinal stenosis are less prominent at flexion and accentuated at extension. The results demonstrate the need to consider the extent to which changes in the cervical lordotic curve affect the degree of disk bulging and spinal stenosis.