Canal diameter, anteroposterior compression ratio, and spondylotic myelopathy of the cervical spine.

Nine patients with cervical spondylotic myelopathy, diagnosed during life, were subjected to detailed clinicopathologic study. The degree of cord destruction was in good correlation with the ratio of the anteroposterior diameter to the transverse diameter, designated as an anteroposterior compression ratio. Within the factors responsible for decrease in the ratio, developmental narrowing of the spinal canal was the most significant, and multiplicity of spondylotic protrusion less so. The former resulted in an extensive demyelination of the posterolateral funiculus and infarction of the gray matter. Recurrent trauma proved to cause distinct manifestations and cord pathology. Clinicopathologic correlations were also examined from the neurologic findings at the terminal stage.