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Study design:Systematic review.
Study rationale:Cervical spondylotic myelopathy (CSM) is a common cause of spinal cord dysfunction that may be asymptomatic or may present with severe symptoms. Since CSM has an insidious manifestation, identification of risk factors associated with this condition may aid clinicians in monitoring high-risk patients and implementing appropriate management strategies.
Objective:To assess sociodemographic, clinical, radiographic, and genetic risk factors associated with presence of CSM in patients 18 years or older.
Methods:A systematic review of the literature was performed using PubMed, the National Guideline Clearinghouse Databases, and bibliographies of key articles to assess risk factors associated with CSM. Articles were reviewed by two independent reviewers based on predetermined inclusion and exclusion criteria. Each article was evaluated using a predefined quality-rating scheme.
Results:From 486 citations, eight articles met all inclusion and exclusion criteria. Larger vertebral body and smaller spinal canal and Torg/Pavlov ratio were associated with CSM diagnosis, while gender was not associated with a CSM diagnosis across multiple studies. There were inconsistent reports with respect to increased age as a risk factor for CSM diagnosis.
Conclusion:The limited data available suggests that inherent anatomical features that may contribute to congenital cervical stenosis may be associated with CSM. This systematic review is limited by the small number of high-quality studies evaluating prognostic factors for CSM. The overall strength of evidence for all risk factors evaluated is low.
Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction in patients 55 years or older. This disease is caused by the degeneration of various components of the vertebra including the vertebral body, intervertebral disc, supporting ligaments, and the facet and other true joints. These anatomical changes, specifically the development of osteophytic spurs, may lead to the narrowing of the spinal canal and potentially to mechanical compression of the neural elements. Long-standing compression of the spinal cord, in turn, can result in irreversible damage including demyelination and necrosis of the gray matter. The onset of CSM is insidious and usually progresses in a stepwise fashion. Furthermore, CSM may be asymptomatic or may present with a wide range of symptoms, from numb clumsy hands to severe gait impairment.1,2 Since CSM has an insidious manifestation, it is essential to determine risk factors associated with this condition. Identification of these factors will allow clinicians to monitor their high-risk patients and implement appropriate management strategies.
To assess sociodemographic, patient, behavioral, environmental, or inborn risk factors associated with the presence of CSM in patients 18 years or older.
Study design: Systematic review.
Search: PubMed and National Guideline Clearinghouse Databases; bibliographies of key articles (Fig. 1).
Dates searched: 1950 through December 2011.
Inclusion criteria: Patients diagnosed with CSM. Studies explicitly designed to evaluate risk factors (sociodemographic, behaviors, occupational or lifestyle, environmental, inborn or inherited characteristics) for CSM in patients older than 18 years were sought. Studies were considered if CSM and evaluation of risk factors were described in the title and/or abstract. Studies which explicitly compared groups which had CSM with those who did not were considered for inclusion. Only studies in which factors logically preceded (or were measured prior to) development of CSM were included.
Exclusion criteria: Cervical radiculopathy diagnosis, cervical spondylosis only with no myelopathy, thoracic and/or lumbar myelopathy, CSM patients with history of acute trauma or tumor, patients younger than 18 years, factors related to recovery after treatment or progress after treatment; factors that related to criteria for CSM diagnosis, clinical assessment, physiological testing; factors that are along the continuum of spondylosis, degenerative spinal disease/processes or its progression; cost-of-care analyses, case series or case reports.
Risk factors: Sociodemographic, patient characteristics, occupational, lifestyle, behavioral, environmental, congenital, inherited and/or genetic factors for CSM.
Outcomes: Cervical spondylotic myelopathy.
Analysis: Descriptive statistics; statistics and effect estimates as reported by authors.
Details about methods can be found in the Web Appendix at www.aospine.org/ebsj
The initial search yielded 486 citations, 21 of which underwent full-text review. Eight studies met the inclusion criteria for assessing prognostic factors associated with CSM diagnosis. One study was a poor quality cohort (Level of Evidence [LoE] III),3 and seven were considered case-control studies (LoE III).4,5,6,7,8,9,10 Additional details regarding the critical appraisal and study exclusion criteria are available in the Web Appendix.
Table 1 describes the characteristics of included studies with criteria used for determining the presence (diagnosis) of CSM. Table 2 summarizes the primary factors evaluated in the studies and effect size estimates reported in the studies.
Only age and gender were evaluated across multiple studies.
Findings from single studies:
The following measurements were assessed in multiple studies:
Findings from isolated studies included:
Support for this work was provided by Spectrum Research Inc with funding from AOSpine.
This is a high-quality systematic review that truly highlights the weakness of available evidence in defining risk factors for cervical spondylotic myelopathy. I recommend publication in its present form.
It is interesting to note that a smaller Torg/Pavlov ratio was found to be associated with CSM diagnosis, but not CSM development. It seems intuitive that patients with small Torg/Pavlov ratios at some point in their lives were not myelopathic, and at some point became myelopathic or developed myelopathy. Thus, it would seem that risk factors associated with CSM diagnosis would likely also be risk factors linked to CSM development. In any event, this is most likely reflective of low level of evidence available in the literature.
This systematic review would provide the basis for the background and introduction for a prospective longitudinal study examining risk factors for the development of CSM, or a prospective natural history study of patients with asymptomatic stenosis.