Dynamic Changes in Dural Sac and Spinal Cord Cross-Sectional Area in Patients With Cervical Spondylotic Myelopathy

Study Design. Prospective imaging study of patients with cervical spondylotic myelopathy (CSM). Objectives. To measure dural sac and spinal cord cross-sectional area during flexion and extension in patients with CSM using multidetector-row CT (MDCT) and to investigate the influence of dynamic factors on the spinal cord. Summary of Background Data. In patients with CSM, the spinal cord is likely to be compressed during neck extension, because the ligamentum flavum and intervertebral discs protrude into the spinal canal during neck extension. Generally, spinal cord cross-sectional area becomes narrower during extension due to dynamic factors. There are few reports that have assessed the dural sac and spinal cord cross-sectional area during flexion and extension. Methods. A total of 100 patients with CSM were prospectively enrolled. Patients with rheumatoid arthritis, cerebral palsy, thoracic spondylotic myelopathy, and lumbar spinal canal stenosis were excluded. Magnetic resonance imaging in a neutral position, and MDCT scan during flexion and extension after myelography were taken in all patients before surgery. Dural sac and spinal cord cross-sectional area at each disc level between C2-C3 and C7-T1 were measured using Scion imaging software. Results. The average dural sac and spinal cord cross-sectional area were less during extension than during flexion from the C3-C4 to C7-T1 disc levels. The decreasing changes during extension occurred mostly at the C5-C6 disc level. The differences in spinal cord cross-sectional area were statistically significant at each disc level between C3-C4 and C7-T1. Conclusion. MDCT demonstrated dynamic factors in patients with CSM. The spinal cord cross-sectional area became narrower during extension in patients with CSM. The decreasing change during extension occurred mostly at the C5-C6 disc level among all disc levels evaluated.