Preface: Current Knowledge in Degenerative Cervical Myelopathy

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1 Cervical Myelopathy Preface: Current Knowledge in Degenerative Cervical Myelopathy Michael G. Fehlings xiii Epidemiology and Overview of the Clinical Spectrum of Degenerative Cervical Myelopathy 1 Satoshi Yamaguchi, Takafumi Mitsuhara, Masaru Abiko, Masaaki Takeda, and Kaoru Kurisu Degenerative cervical spondylosis (DCM) is an umbrella term used to describe myelopathy caused by various degenerative changes in the cervical spine. This article outlines the spectrum of DCM and reviews the epidemiology of each factor composing DCM. The uniform term of DCM is expected to elucidate the epidemiology of myelopathy caused by degenerative changes of the cervical spine. Pathobiology of Degenerative Cervical Myelopathy 13 Farhana Akter and Mark Kotter Degenerative cervical myelopathy (DCM) is a common spinal cord disease caused by chronic mechanical compression of the spinal cord. The mechanism by which mechanical stress results in spinal cord injury is poorly understood. The most common mechanisms involved in the pathobiology of DCM include apoptosis, inflammation, and vascular changes leading to loss of neurons, axonal degeneration, and myelin changes. However, the exact pathophysiologic mechanisms of DCM are unclear. A better understanding of the pathogenesis of DCM is required for the development of treatments to improve outcomes. This article highlights the mechanisms of injury and pathology in DCM. The Natural History of Degenerative Cervical Myelopathy 21 Jetan H. Badhiwala and Jefferson R. Wilson Although degenerative cervical myelopathy (DCM) is the leading cause of spinal cord dysfunction among adults worldwide, little is known about its natural history. There is mounting evidence of the effectiveness of surgery for DCM in halting progression of symptoms and, in fact, in improving neurologic outcomes, functional status, and quality of life. However, surgical decision making relies on a weighing of the risks and benefits of alternative strategies. The authors reviewed the available literature pertaining to the natural course of DCM and the predictors of outcome of nonoperative approaches. Imaging Evaluation of Degenerative Cervical Myelopathy: Current State of the Art and Future Directions 33 Allan R. Martin, Nobuaki Tadokoro, Lindsay Tetreault, Elsa V. Arocho-Quinones, Matthew D. Budde, Shekar N. Kurpad, and Michael G. Fehlings Degenerative cervical myelopathy (DCM) is a common neurologic condition that is often treated with surgery. Imaging plays a central role in the management of DCM, including diagnosis, preoperative planning, postoperative assessment, and prognostication. Radiographs, computed tomography, and MRI offer unique and complementary assessments, and all have important uses in current clinical practice.

2 viii Emerging microstructural and functional MRI techniques have the potential to have a major impact, potentially transforming practice by offering earlier and more accurate diagnosis, monitoring for deterioration, and prediction of outcomes. In the future, it can be expected that imaging will play an even greater role in DCM management. Pathophysiology of Calcification and Ossification of the Ligamentum Flavum in the Cervical Spine 47 Toshiyuki Takahashi, Junya Hanakita, and Manabu Minami Calcification of the ligamentum flavum (CLF) and ossification of the ligamentum flavum (OLF) in the cervical spine are differential diagnoses in patients with posterior extradural compressive lesions related to cervical degenerative disease. Preoperative computed tomography can facilitate the detection of characteristic findings and help one to distinguish between CLF and OLF. Although these are rare entities in the cervical spine, adequately timed surgical decompression is required in most patients who present with radiculomyelopathy. Radiologic Evaluation of Ossification of the Posterior Longitudinal Ligament with Dural Ossification 55 Junichi Mizuno There are 3 basic radiologic patterns of dural ossification (DO). Although doublelayer DO is most common, when examining neuroimaging of ossification of the posterior longitudinal ligament (OPLL), isolated DO or masse DO should be kept in mind. Bone window computed tomography (CT) is most sufficient in identifying any type of DO associated with OPLL. Sagittal reformation of CT has replaced polytomography. MRI is not optimal for the identification of DO and OPLL. Surgical approaches should be determined based on this important radiologic information to avoid an unexpected complication. Expansive laminoplasty is the procedure of choice when DO is predominant. Ossification of the Ligaments in the Cervical Spine, Including Ossification of the Anterior Longitudinal Ligament, Ossification of the Posterior Longitudinal Ligament, and Ossification of the Ligamentum Flavum 63 Yukoh Ohara Ossification of the posterior longitudinal ligament (OPLL), ossification of the anterior longitudinal ligament (OALL), and ossification of the ligamentum flavum (OLF) sometimes are seen in the same patients, but the exact coexisting frequencies are not clear, especially in the cervical region. The most frequent combination is OPLL and OALL. Cervical OPLL can coexist with thoracic OLF but is rarely associated with cervical OLF. All of these ossifying diseases of the cervical spinal ligaments are influenced by dynamic factors of the spinal column. The most frequent levels in the cervical spine affected by OPLL, OALL, and OLF are different because of anatomic differences inherent to each ligament. Importance of Sagittal Alignment of the Cervical Spine in the Management of Degenerative Cervical Myelopathy 69 Thomas J. Buell, Avery L. Buchholz, John C. Quinn, Christopher I. Shaffrey, and Justin S. Smith Cervical spine sagittal malalignment correlates with worse symptoms and outcomes in patients with degenerative cervical myelopathy (DCM) and should influence surgical management. An anterior versus posterior surgical approach may not

3 ix significantly change outcomes in patients with preoperative lordosis; however, most studies suggest improved neurologic recovery among kyphotic patients after adequate correction of local sagittal alignment through an anterior or combined anteroposterior approach. There are no comprehensive guidelines for DCM management in the setting of cervical malalignment; therefore, surgical management should be tailored to individual patients and decisions made at the discretion of treating surgeons with attention to basic principles. Anterior Cervical Option to Manage Degenerative Cervical Myelopathy 83 Zoher Ghogawala Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord dysfunction in the world. There are multiple types of anterior approaches for treating patients with DCM. Many strategies have been developed to reduce complications for multilevel anterior surgery. Posterior approaches are sometimes used to supplement more extensive anterior approaches. More recently, multilevel cervical arthroplasty has been used for this condition. More data will be available soon comparing anterior and posterior approaches with the goal of optimizing patient-related quality of life and reducing complications, which include dysphagia, weakness, and instrumentation failure in some cases. Laminectomy with or Without Fusion to Manage Degenerative Cervical Myelopathy 91 Fahad H. Abduljabbar, Alisson R. Teles, Rakan Bokhari, Michael Weber, and Carlo Santaguida Stand-alone cervical laminectomy for degenerative cervical myelopathy (DCM) has become increasingly rare because of risk of postlaminectomy kyphosis. This article discusses the biomechanics of cervical degeneration and how laminectomy effects spine stability and summarizes relevant clinical studies to help guide surgical decision making for the posterior treatment of DCM. Laminectomy and fusion remains a safe and efficacious treatment. Stand-alone laminectomy should be used only for a highly selected patient population with relative stiff lordotic cervical spines, using care to not disrupt facets and C2 and C7 muscle attachments. History and Evolution of Laminoplasty 107 Yoshitaka Hirano, Yukoh Ohara, Junichi Mizuno, and Yasunobu Itoh Techniques of expansive laminoplasty for degenerative cervical myelopathy and ossified posterior longitudinal ligament are described, focusing on the history of the surgical procedure. Laminectomy was the only approach for posterior decompression before Japanese orthopedic surgeons introduced laminoplasty from the 1970s to the 1980s to overcome the poor outcomes of laminectomy. Recent laminoplasty techniques offer less invasive maneuvers to the posterior cervical muscle structures to reduce axial neck pain and to obtain better functional outcome, but every operation is carried out based on the unchanged initial concept. Some recent attempts to improve the surgical results are also discussed. Significant Predictors of Outcome Following Surgery for the Treatment of Degenerative Cervical Myelopathy: A Systematic Review of the Literature 115 Lindsay Tetreault, Lisa M. Palubiski, Michael Kryshtalskyj, Randy K. Idler, Allan R. Martin, Mario Ganau, Jefferson R. Wilson, Mark Kotter, and Michael G. Fehlings This systematic review aims to summarize important clinical predictors of outcomes in patients undergoing surgery for the treatment of degenerative cervical

4 x myelopathy. Based on the results of this article, patients with a longer duration of symptoms and more severe myelopathy are likely to have worse surgical outcomes. With respect to age, several studies have indicated that elderly patients are less likely to translate neurologic recovery into functional improvements. However, many other studies have failed to identify a significant association between age and outcomes. Finally, smoking status and presence of comorbidities may be important predictors of outcomes. Neurologic Complications in Managing Degenerative Cervical Myelopathy: Pathogenesis, Prevention, and Management 129 Taku Sugawara Degenerative cervical myelopathy is a common neurologic condition induced by the compression of the spinal cord due to degenerative changes of the cervical spine. It is one of the leading causes of acquired disability in adults and manifests as a slow deterioration of the symptoms in most patients. A variety of nonsurgical and surgical treatments have been performed to ameliorate or halt the symptoms, and a number of articles describe their methods, efficacy, and complications. In this article, the pathogenesis, prevention, and management of the neurologic complications are reviewed. Options of Management of the Patient with Mild Degenerative Cervical Myelopathy 139 Izumi Koyanagi Surgical management of patients with mild degenerative cervical myelopathy (DCM) is controversial. This article reviews 84 subjects with cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL) who underwent surgical treatment. Nine had mild myelopathy: 6 CSM and 3 OPLL. Seven presented with pain or numbness of upper extremities. MRI revealed intramedullary hyperintensity in 55.6%. Five underwent anterior decompression and fusion, whereas 4 were operated posteriorly. Pain and intramedullary signal change on MRI are important. Management of patients with mild DCM should be determined individually, considering benefits and risks in long-term conservative treatment and surgery. Management of the Patient with Cervical Cord Compression but no Evidence of Myelopathy: What Should We do? 145 Kentaro Naito, Toru Yamagata, Kenji Ohata, and Toshihiro Takami Degenerative cervical myelopathy (DCM) eventually affects not only activities of daily living but also quality of life. DCM is usually a gradually progressive, sometimes irreversible, disease of the cervical spinal cord, although there is always a risk of acute deterioration caused by minor trauma. There is still not enough evidence regarding the prognosis of mild DCM without surgical treatment, and conservative treatment seems a reasonable option, although patients need to be followed up closely because some do deteriorate over time. However, surgeons need to understand the importance of decision making in the surgical management of mild DCM. Clinical Characteristics and Management of C3-4 Degenerative Cervical Myelopathy 153 Masato Tomii and Junichi Mizuno Single-level anterior cervical discectomy and fusion (ACDF) was performed at C3-4; non C3-4 ACDF patients of the authors random sample of ACDF were compared

5 xi with C3-4 ACDF patients. The radiologic study of C3-4 ACDF patients shows that they had significant cervical lordosis, and cervical motion was dependent on the C3-4 segment, which accounted for 39.8% of C2-7 range of intervertebral motion (total motion). In C3-4 ACDF patients, not only static factors but also dynamic factors (instability) at the C3-4 level contributed to the major causes of degenerative cervical myelopathy. Intraoperative Neurophysiologic Monitoring for Degenerative Cervical Myelopathy 159 Masaaki Takeda, Satoshi Yamaguchi, Takafumi Mitsuhara, Masaru Abiko, and Kaoru Kurisu Multimodal intraoperative neurophysiologic monitoring is a reliable tool for detecting intraoperative spine injury and is recommended during surgery for degenerative cervical myopathy (DCM). Somatosensory evoked potential (SEP) can be used to monitor spine and peripheral nerve injury during positioning in surgery for DCM. Compensation technique for transcranial evoked muscle action potentials (tcmeps) should be adopted in intraoperative monitoring during surgery for DCM. Free-running electromyography is a useful real-time monitoring add-on modality in addition to SEP and tcmep. Health Economics and the Management of Degenerative Cervical Myelopathy 169 Christopher D. Witiw, Fabrice Smieliauskas, and Michael G. Fehlings Degenerative cervical myelopathy (DCM) is the leading cause of spinal cord impairment worldwide. Surgical intervention has been demonstrated to be effective and is becoming standard of care. Spine surgery, however, is costly, and value needs to be demonstrated. This article serves to summarize the key health economic concepts as they relate to the assessment of the value of surgery for DCM. This is followed by a discussion of current health economic research on DCM, which suggests that surgery is likely to be cost-effective. The article concludes with a summary of future questions that remain unanswered, such as which patient subgroups derive the most value from surgery and which surgical approaches are the most cost-effective. Managing the Complex Patient with Degenerative Cervical Myelopathy: How to Handle the Aging Spine, the Obese Patient, and Individuals with Medical Comorbidities 177 Geoffrey Stricsek, John Gillick, George Rymarczuk, and James S. Harrop Degenerative cervical myelopathy (DCM) is the most common cause of nontraumatic spinal cord injury worldwide. Even relatively mild impairment in functional scores can significantly affect daily activities. Surgery is an effective treatment for DCM, but outcomes are dependent on more than technique and preoperative neurologic deficits. Future Directions and New Technologies for the Management of Degenerative Cervical Myelopathy 185 Mario Ganau, Langston T. Holly, Junichi Mizuno, and Michael G. Fehlings The diagnosis and treatment of degenerative cervical myelopathy (DCM) has been evolving over the past 5 decades as a result of collaborations between clinicians and scientists. The most recent trends in basic and clinical research include advances in imaging, clinical diagnostic tools, molecular genetics, surgical techniques, and reparative/regenerative strategies. Spine surgeons are witnessing a fast-paced evolution, which is reshaping the management strategies available for an aging population that suffers increasingly from this degenerative condition.