Spondylosis - Cervical Spondylsis
Cervical spondylosis refers to a degenerative process of the cervical spine producing narrowing of the spinal canal and neural foramina, producing compression of the spinal cord and nerve roots, respectively. Through wear and tear with aging, the following processes occur:
- Bony ridges (osteophytes) develop on the vertebral bodies adjacent to the areas of motion at the intervertebral discs.
- The facets undergo degeneration and hypertrophy, as in the lumbar spine.
- The ligamentum flavum undergoes hypertrophy and buckling, again as in the lumbar spine.
The symptoms and the mechanisms which produce them are similar to those associated with herniated cervical discs. However, the two processes are fundamentally different in that disc herniation is an acute event while spondylosis is a chronic, slowly progressive process which may be punctuated by episodes of worsening. The manifestations of radiculopathy were discussed in the previous section. The following discussion focuses on cervical spondylotic myelopathy (CSM).
Myelopathy refers to dysfunction of the long tracts of the spinal cord. It may manifest as weakness and spasticity, sensory loss, position sense loss, and incontinence. Myelopathy develops in only 5-10% of patients with symptomatic spondylosis. Interestingly, coexistent neck and radicular pain are unusual.
Several syndromes of cervical spondylotic myelopathy have been delineated (Gregorius):
- Transverse syndrome: corticospinal, spinothalamic, and dorsal column dysfunction.
- Motor system syndrome: corticospinal and anterior horn cell dysfunction.
- Mixed radicular and long tract syndrome.
- partial Brown-Sequard syndrome.
- Central cord syndrome.
The central cord syndrome frequently occurs with minor trauma, especially involving hyperextension. A typical history is a fall, striking the forehead or chin, with hyperextension and immediate weakness of the arms, and to a variable degree of the legs, with variable sensory loss. The presumed mechanism of spinal cord injury is contusion, compression, or ischemia of the cord against a bony spondylotic ridge. In retrospect, there has often been a history of gradual worsening of myelopathic symptoms prior to the fall.
plain X-rays of the cervical spine disclose osteophytes at the involved level, loss of disc height, and often a narrow spinal canal. It must be emphasized that some degree of spondylotic changes are seen in 25-50% of the population over the age of 50 years, and in 75% of people over 75 years! Obviously, most people do not develop symptoms from these processes; a patient's clinical picture must be assessed carefully to determine which symptoms may be caused by spondylosis, and to what degree. This must be individualized for each patient.
Myelogram with CT, as discussed previously, provides the best bony detail. In most cases MRI may be unnecessary.
Unlike the case with cervical disc herniation, most patients do not improve with nonoperative treatment, because of the progressive degenerative nature of spondylotic disease. patients who are poor medical candidates or for another reason are treated nonoperatively must be followed closely for worsening of myelopathy.
The surgical options are anterior or posterior decompression. Anterior approaches are similar to that described for herniated cervical disc and may be performed at multiple levels as appropriate. Alternatively, the entire vertebral body may be removed (corpectomy) between adjacent levels of spondylosis, or several bodies may be removed. A bony graft is placed for fusion. With long grafts, a plate and screws are usually placed. posterior decompression involves laminectomy at the affected levels. The effectiveness of posterior decompression is contoversial, but most surgeons today would probably prefer an anterior procedure when feasible.
Overall, improvement following anterior decompression with interbody fusion is seen in 60-84% of patients. When myelopathy alone was present, 40% improved in one study. When myelopathy and radiculopathy were both present, the myelopathy was improved in 60% and completely relieved in another 12%.
Several factors have been shown to impact negatively on the degreee of improvement from surgery:
- Age greater than 50
- Duration of symptoms greater than 12 months
- Involvement of multiple levels
The effect of age is probably related to advanced disease.