Computed tomography of the upper cervical spine in Down syndrome.

Axial CT of the upper cervical spine was performed on 25 Down syndrome patients. Measurements of the degree of atlantoaxial displacement, the sagittal diameters of the spinal canal and spinal cord, thickness of the transverse ligament, and the ratio of sagittal diameter of spinal cord to canal were made. Thirty-six percent of the group showed evidence of cord compression. These patients demonstrated a significant decrease in the anteroposterior diameter of the spinal canal and the cord with an increase in the degree of subluxation and the cord:canal ratio when compared with the remainder.