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Cervical Spondylotic Myelopathy: Current State of the Art and Future Directions

Fehlings, Michael G., MD, PhD, FRCSC*; Tetreault, Lindsay A., HBSc*; Wilson, Jefferson R., MD; Skelly, Andrea C., PhD, MPH

doi: 10.1097/BRS.0b013e3182a7e9e0
Introduction
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Study Design. Narrative overview of the focus issue on cervical spondylotic myelopathy (CSM).

Objective. To provide an introduction to this special focus issue of Spine journal that deals with CSM.

Summary of Background Data. CSM is a progressive spine disease and the leading cause of spinal cord dysfunction worldwide. The shift in population demographics in many parts of the world has motivated the development of this focus issue. With the overall aging of the population, we can predict that global health care systems will be confronted with an increase in patients presenting with degenerative spine changes and various stages of cervical myelopathy.

Methods. The articles in this issue vary in their methods—there are systematic reviews, narrative reviews, a study protocol, and 2 primary research articles.

Results. A summary of the findings of each article is provided as a table within this introduction.

Conclusion. By way of this issue, we have summarized current knowledge gaps and limitations in the evidence to provide direction for future research and investigation. These include the need for a unified nomenclature for referring to CSM, the need to specify the incidence of myelopathy and the prevalence of ossification of the posterior longitudinal ligament, and the need to explore both the safety and efficacy of neuroprotective and neuroreparative pharmacological strategies. Further work is also required to optimize the management of patients with minimal symptoms.

This introduction to the Spine focus issue on cervical spondylotic myelopathy summarizes the reason for the issue and the findings of the articles.

*Toronto Western Hospital, University Health Network, Toronto, Ontario

Department of Surgery, Divisions of Neurosurgery and Orthopedic Surgery, Spinal Program, University of Toronto, Toronto, Ontario; and

Evidence-Based Practice Division, Spectrum Research, Inc., Tacoma, WA.

Address correspondence and reprint requests to Michael G. Fehlings, MD, PhD, FRCSC, Toronto Western Hospital, University Health Network, Room 4W-449, 399 Bathurst St, Toronto, Ontario M5T 2S8; E-mail: Michael.Fehlings@uhn.on.ca

Acknowledgment date: June 18, 2013. First revision date: July 23, 2013. Acceptance date: August 2, 2013.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Supported by AOSpine North America, Inc. Analytic support for this work was provided by Spectrum Research, Inc., with funding from the AOSpine North America.

Relevant financial activities outside the submitted work: support for travel, fees for participation in review activities, and payment for writing or reviewing the manuscript.

Cervical spondylotic myelopathy (CSM) is a progressive spine disease and the leading cause of spinal cord dysfunction worldwide.1 It is caused by the degeneration of the cervical vertebral column leading to compression of the spinal cord.2 Although the majority of individuals will experience degenerative changes of the spinal axis as they age, a small fraction of this group will present with neurological signs and symptoms of myelopathy.3

Traditionally, the term CSM has been used to describe spinal cord compression secondary to the development and protrusion of osteophytic spurs. As the spine ages, intervertebral discs begin to degenerate and can no longer fulfill their weight-bearing and load-transferring functions.4 In turn, the uncovertebral processes become flattened, altering the load-bearing function of the intervertebral joint, and putting increased stress on the articular cartilage endplates. To stabilize hypermobility in adjacent segments and increase the weight-bearing surface area of the endplates, osteophytic spurs develop. In addition, the ligamentum flavum between adjacent lamina may stiffen and buckle dorsally because of loss of disc height and straightening of cervical lordosis.1,4 Disc degeneration, associated spondylosis, and hypertrophy of the ligamentum flavum are the 3 static factors that may lead to the narrowing of the spinal canal and potentially to mechanical compression of the neural elements.

There is controversy in the literature as to whether ossification of the posterior longitudinal ligament (OPLL) should be categorized as CSM or should be considered a separate entity. It is more prevalent in the Japanese population (1.9%–4.3%) and is present in approximately 25% of patients diagnosed with cervical myelopathy.5 In contrast to CSM, OPLL occurs more frequently in younger patients and is suspected to have a familial predisposition and genetic association.5 Given that the occurrence and progression of OPLL is tied to the aging process of the spine, and because it presents with similar signs and symptoms as CSM, we have devised a new term, “degenerative cervical myelopathy,” to encompass both diseases. Under this umbrella, we consider both osteoarthritic changes including spondylosis, disc herniation, and facet arthropathy as well as ligamentous aberrations such as hypertrophy or calcification of the ligamentum flavum and OPLL. Many of the systematic reviews in this focus issue have considered both CSM and OPLL.

The shift in population demographics in many parts of the world has motivated the development of this focus issue. With the overall aging of the population, we can predict that global health care systems will be confronted with an increase in patients presenting with degenerative spine changes and various stages of cervical myelopathy. In anticipation of an increase in disease prevalence, we undertook this project to heighten physicians’ awareness of this condition, to provide guidelines for its accurate diagnosis and management and to summarize important predictors of development, progression, and surgical outcome. We expect clinicians will use the results and recommendations from these studies, in combination with their own views and past experience, as an aid to facilitate diagnosis and treatment decision making and to manage patient expectations for the future. Moreover, we anticipate this issue will contribute to an increased emphasis in medical schools on the study of CSM as a common cause of spinal cord dysfunction. Finally, we trust that our contribution will lead to a greater urgency among primary care physicians, neurologists, rheumatologists, and other health care practitioners in diagnosing and establishing appropriate treatment programs for CSM.

This focus issue consists of 15 articles developed to address key clinical questions surrounding the natural history, diagnosis, conservative and surgical management, prognosis, and outcome assessment of CSM. Of these, 2 were narrative reviews, 10 were systematic reviews, 2 were primary research studies, and 1 was a research protocol. The first article outlines the methodology used for each study, including an in-depth description of the systematic review methodology. After the methodology article, the focus issue is divided into 4 comprehensive sections based on topic. Table 1 presents a list of all the articles and summarizes the clinical objective for each study as well as the evidence-based recommendations or summary statements. In addition, each section has its own consensus statement outlining the objectives and clinical recommendations for every article and for the entire section.

TABLE 1-a

TABLE 1-a

TABLE 1-b

TABLE 1-b

TABLE 1-c

TABLE 1-c

TABLE 1-d

TABLE 1-d

TABLE 1-e

TABLE 1-e

TABLE 1

TABLE 1

Section 1 provides an introduction and overview of CSM by summarizing its pathophysiology and natural history, exploring nonoperative management and predictors of neurological deterioration in asymptomatic patients, and presenting the protocol for the ongoing CSM-Protect trial involving a promising neuroprotective agent, riluzole, which is a sodium-glutamate antagonist. The objective of these articles is to increase awareness of important risk factors of neurological deterioration and to emphasise the need to maintain open patient-physician communication. The recommendations focus on monitoring high-risk asymptomatic patients or those with mild myelopathy and counseling them regarding the progressive nature of this disease and surgical options. Patients with moderate to severe myelopathy, on the contrary, should be considered for surgical intervention because timely operation is necessary to optimize patient outcomes.

Section 2 summarizes important concepts in the diagnosis and outcome assessment of patients with cervical myelopathy and reports on important genetic and imaging predictors of disease development and postsurgical outcomes. With respect to accurate diagnosis, magnetic resonance imaging and plain film radiographs should be used to confirm the presence of degenerative myelopathy and to exclude differential diagnoses after an inconclusive physical examination. From the standpoint of genetics, whereas CSM has not consistently been associated with any one genetic polymorphism, OPLL may be associated with 2 single nucleotide polymorphisms on collagen-encoding genes. The recommendations provided in this section focus on the value of magnetic resonance imaging in predicting disease progression and surgical outcome and the utility of outcome measures in the assessment of myelopathy severity and recovery. The authors strongly recommend that the Neck Disability Index and the modified Japanese Orthopaedic Association score be used routinely to evaluate patients with CSM, with a view to standardizing clinical practice and international research.

The objective of section 3 is to explore the topic of spinal deformity in relation to the diagnosis and management of CSM. From the 2 original articles presented in this section, the authors recommend that physicians assess regional cervical and relative spinal alignment in the preoperative setting, and that they consider correcting cervical kyphosis and sagittal imbalance during decompressive surgery to help optimize postoperative outcomes.

Finally, section 4 includes several systematic reviews addressing the surgical management of CSM and the relative effectiveness of various techniques. Given similar documented efficacy between posterior and anterior approaches and between laminoplasty and laminectomy and fusion, the authors recommend using an individualized approach, accounting for either pathoanatomical variations or familiarity with each procedure, when attempting to decide on the most appropriate surgical approach for a given patient. With respect to various anterior surgical options, it is recommended that patients with minimal retrovertebral disease should be treated by multiple discectomy rather than corpectomy or hybrid procedures, whereas those with significant retrovertebral disease should undergo a hybrid discectomy-corpectomy rather than a multiple corpectomy. Furthermore, when examining alternative procedures for the treatment of CSM, we cannot recommend artificial disc replacement over anterior cervical discectomy and fusion, or laminoplasty over skip laminectomy, after considering the existing evidence pertaining to their relative impact on postoperative outcomes.

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CONCLUSION

By way of this focus issue, we have summarized current knowledge gaps and limitations in the evidence to provide direction for future research and investigation. For one, the nomenclature for CSM needs to be internationally unified and perhaps should be expanded to encompass all degenerative forms of cervical myelopathy, including OPLL. We suggest that the terminology introduced here, “degenerative cervical myelopathy,” may be an appropriate starting point for harmonizing parlance in this domain. Second, the global and regional burden of this disease needs to be better defined, especially the incidence of myelopathy caused by degenerative changes and the prevalence of OPLL in the Western population. Third, it is important to develop improved disease screening tools, to determine predictors of neurological deterioration, and to refine and standardize existing functional scores. Fourth, as outlined by CSM-Protect protocol, it is also essential to explore both the safety and efficacy of neuroprotective and neuroreparative pharmacological strategies, which may, one day, augment the effects of decompressive surgery to help optimize patient outcomes. Finally, further work is required to determine the appropriate management of minimally symptomatic patients with cervical spondylosis and cord compression as well as to further delineate the risk of spinal cord injury with minor trauma in this setting.

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Key Points

  • CSM is a progressive spine disease and the leading cause of spinal cord dysfunction worldwide.
  • This focus issue consists of 15 manuscripts developed to address key clinical questions surrounding the natural history, diagnosis, conservative and surgical management, prognosis, and outcome assessment of CSM.
  • The nomenclature used when referring to CSM needs to be unified.
  • There needs to be a greater urgency among primary care physicians, neurologists, rheumatologists, and other health care practitioners in diagnosing and establishing appropriate treatment programs for CSM.
  • Further work is required to clarify the optimal way to manage patients with mildly symptomatic CSM.
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References

1. Kalsi-Ryan S, Karadimas SK, Fehlings MG. Cervical spondylotic myelopathy: the clinical phenomenon and the current pathobiology of an increasingly prevalent and devastating disorder. [published online ahead of print November 30, 2012] Neuroscientist 2012;19:409–21. doi: 10.1177/1073858412467377.
2. Tracy JA, Bartleson BJ. Cervical spondylotic myelopathy. Neurologist 2010;16:176–87. doi: 10.1097/NRL.0b013e3181da3a29.
3. Bednarik J, Kadanka Z, Dusek L, et al. Presymptomatic spondylotic cervical cord compression. Spine 2004;29:2260–69.
4. Baptiste DC, Fehlings MG. Pathophysiology of cervical myelopathy. Spine J 2006;6(suppl 6):190S–97S. doi: 10.1016/j.spinee.2006.04.024.
5. Smith ZA, Buchanan CC, Raphael D, et al. Ossification of the posterior longitudinal ligament: pathogenesis, management, and current surgical approaches: a review. Neurosurg 2011;30:E10. doi: 10.3171/2011.1.FOCUS10256.
Keywords:

cervical spondylotic myelopathy; CSM; spinal cord injury; spinal cord dysfunction

© 2013 by Lippincott Williams & Wilkins