Computer-assisted myelography in cervical spondylotic myelopathy and radiculopathy. Clinical correlations and pathogenetic mechanisms.

A total of 53 patients with cervical spondylotic myelopathy and/or radiculopathy were studied with computer-assisted myelography following metrizamide myelography. Cervical cord deformities resulting from spondylotic protrusions were classified into four groups. The A shape (anterior central concavity) is the commonest and is often associated clinically with bilateral anterolateral and posterior column deficits. In the B shape (lateral deformity on one side), unilateral anterolateral column and root signs, usually mild, predominate. The symptomatology of the C shape (lateral deformity on both sides) and the D shape (flattened anterior surface) is bilateral, although not often symmetrical, and includes anterolateral and posterior column disturbances and root signs. Radiculopathy may, however, occur in the absence of cord deformity if the spondylotic lesion is close to or inside the intervertebral foramen. As there is some relationship between cord shapes and symptomatology, the decision as to whether a particular deformity is responsible for the clinical presentation may be made with more confidence. Moreover, the degree of cord deformity correlates well with the severity of symptomatology. Those with mild deformity had relatively few or mild cord signs, whereas in those with severe deformity cord signs were numerous and severe. Certain observations on cord deformity in vivo support the view that compression is an important pathogenetic mechanism in cervical spondylotic myelopathy. Most patients had anterior cord compression and the anterolateral signs were more frequent and marked. Severity of cord signs is associated with the degree of compression. Removal of the compression is followed by re-expansion of the cord and clinical improvement. In a small number of cases where cord compression by osteophytic protrusion was mild, and where clinical improvement followed the removal of the protrusion, the theory of cord traction and friction appears to apply. The contribution of other mechanical factors and of ischaemia to cord damage is also discussed.