Degenerative Cervical Myelopathy
Article information
To the editor
I read the abovementioned article as it directly relates with my clinical interest.
Wilson et al. [1] have reviewed the subject of ‘degenerative cervical myelopathy’ and have discussed the ‘latest’ advances in the subject and have evaluated the future trends in its management. I am troubled by the fact that our several PubMed and MEDLINE indexed articles on the subject published in leading journals dedicated to the study of spine have not found any place in the huge reference list of 137 articles [2-7]. Moreover, I am convinced that our articles will have significant impact on the future of surgery for degenerative cervical spondylotic radiculopathy and/or myelopathy (DCM).
Disc space reduction due to loss of its water content related to ‘old’ age has been identified uniformly in literature to be the nodal point of pathogenesis of spinal degeneration. Osteophyte formation, ligamentum flavum hypertrophy, and bulging disc eventually result in reduction in a single or multiple spinal levels and cause symptoms related to radiculopathy and/or myelopathy. The various vascular events identified by Wilson et al. [1] could be the ultimate cause of neurological symptoms.
In 2010, we proposed an alternative concept of pathogenesis of cervical spondylotic myelopathy [6,7]. We identified that weakness of muscles responsible for standing human position due to disuse, abuse or injury leads to ‘vertical’ spinal instability and listhesis of facet of rostral cervical vertebra over the facet of caudal vertebra. Buckling of the intervertebral ligaments that include posterior longitudinal ligament and ligamentum flavum, osteophyte formation and disc space reduction are a result of reduction in the vertical height of the spinal segment. Reduction in the spinal and neural canal dimensions are ultimate consequence of spinal instability. On the basis of this hypothesis we proposed distraction of facet using ‘Goel facet spacers’ and arthrodesis of involved spinal segments as a treatment for both radiculopathy and myelopathy for single or multiple level DCM [2]. Our article on the subject is the first in the literature wherein no direct decompression of the neural structures by bone, soft tissue, osteophyte or disc removal formed the basis of surgical treatment. Restoration of all secondary features identified with DCM following a single act of facet distraction gives credence to our hypothesis. Other authors have validated this concept [8-10]. We also used the same concept in the surgical treatment of degenerative lumbar spondylotic disease [11].
As our understanding in the subject matured further, we realized that it is not compression or deformation but it is subtle instability related microinjury to neural structures that is the cause of symptoms in DCM. Accordingly, we resorted to ‘only fixation’ of the involved spinal segments using transarticular technique of fixation [4,5,12,13]. No direct or indirect decompression of bone or soft tissue and no resection of osteophyte or disc material were done. Our remarkable clinical result gives credence to the concept. We have treated cases with lumbar canal ‘stenosis’ with the same concept of only fixation without any decompression [14].
The other crucial observation was that the atlantoaxial instability of ‘central’ or ‘axial’ variety is ‘frequently’ associated with multilevel DCM, particularly when the patient is ‘old’ and when the neurological deficits related to myelopathy are ‘severe’ [15-17]. Ignoring atlantoaxial instability can be a major cause of failure of surgical treatment. We recently reported gratifying clinical outcome in patients presenting with symptoms related to severe myelopathy treated by multilevel spinal fixation that included atlantoaxial joint in a majority of cases [18]. No ‘decompression’ was done.
Our studies have identified that spinal instability forms the nodal point of pathogenesis of cervical myelopathy related to ossification of posterior longitudinal ligament [19]. We reported remarkably gratifying clinical outcome following only fixation of cervical segments by transarticular technique of fixation without any anterior or posterior decompression. Atlantoaxial joint was included in the fixation construct in a number of cases. Our observations on the basis of our increasing experience is that multilevel spinal fixation that includes atlantoaxial joint can revolutionize the treatment for cervical myelopathy related to ossification of posterior longitudinal ligament [20].
Wilson et al. [1] have identified the advancements in the imaging technology for identification and treatment of DCM. We observed that vertical instability and telescoping of spinal segments might not be identified on direct imaging due to their lateral location away from the neural structures. Direct visual assessment of instability of spinal segments by manual manipulation of bone on the basis of high level of suspicion based of guiding clinical and radiological parameters can be important in determining the levels of required fixation [21].
Notes
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