pathophysiology

Last reviewed 07/2023

• in cervical spondylosis, degeneration of one or more of the cervical intervertebral discs leads to narrowing of the disc space and the production of bony and cartilaginous osteophytes. The disc changes are the earliest, but the facet joints and the unco-vertebral joints soon become involved. The osteophytes, or spurs, project backwards into the spinal canal, or laterally into the intervertebral foramina. There is also degeneration of the nucleus pulposus and protrusion of the disc
• osteophytic outgrowths and the disc protrusion may compress the spinal cord, producing a myelopathy, and/or the adjacent nerve roots producing a radiculopathy
• C5-C6, C6-7 and C7-T1 are most frequently involved
• in patients with spondylotic features compromising the spinal/root canals without neurological signs, a sudden deterioration of symptoms and the development of neurological signs, may suggest a recent disc herniation with or without pain
• cervical spondylosis is a progressive condition
  • spondylotic changes on plain radiographs will be seen in around 50% of people over the age of 50 years, and around 75% over the age of 65 years - however, only a small proportion will develop clinical neurological features
  • people who have a pre-existing narrow spinal canal are particularly vulnerable to cord compression
  • features of myelopathy are seen in cases where there is a greater than ~30% reduction in the cross-sectional area of the spinal canal
    • in the average person, this occurs when the sagittal diameter of the spinal canal is less than 14 mm (1)
• neurological features correspond with the segmental level of bony changes, and cord compression occurs in only 50% of cases (1)
• spinal cord ischaemia, caused by reduction of arterial flow or venous stasis, may contribute to the development of clinical features
  • anterior spinal artery and the microcirculation of the cord may be directly compressed or develop spasm secondary to chronic mechanical distortion

The pathophysiology of spondylotic myelopathy is multifactorial, but spinal stenosis, biomechanical aspects, disc herniation and vascular compromise all potentially play a part in the development of the problem (1).

Reference:

1. ARC. Rheumatic Disease In Practice January 2002.