Pathophysiology and natural history of cervical spondylotic myelopathy

A global perspective on the outcomes of surgical decompression in patients with cervical spondylotic myelopathy: results from the prospective multicenter AOSpine international study on 479 patients

STUDY DESIGN

Prospective, multicenter international cohort.

OBJECTIVE

To evaluate outcomes of surgical decompression for cervical spondylotic myelopathy (CSM) at a global level.

SUMMARY OF BACKGROUND DATA

CSM is a degenerative spine disease and the most common cause of spinal cord dysfunction worldwide. Surgery is increasingly recommended as the preferred treatment strategy for CSM to improve neurological and functional status and quality of life. The outcomes of surgical intervention for CSM have never been evaluated at an international level.

METHODS

Between October 2007 and January 2011, 479 symptomatic patients with image evidence of CSM were enrolled in the prospective, multicenter AOSpine CSM-International study from 16 global sites. Preoperative and postoperative clinical status, functional impairment, and quality of life were evaluated using the modified Japanese Orthopaedic Assessment Scale, Nurick Scale, Neck Disability Index, and Short-Form-36v2. Preoperative and 12- and 24-month postoperative outcomes were compared using mixed-model analysis of covariance for repeated measurements.

RESULTS

The study cohort consisted of 310 males and 169 females, with a mean age of 56.37 ± 11.91 years. There were significant differences in age, etiology, and surgical approaches between the regions. At 24 months postoperatively, the mean modified Japanese Orthopaedic Assessment Scale score improved from 12.50 (95% confidence interval [CI], 12.24-12.76) to 14.90 (95% CI, 14.64-15.16); the Neck Disability Index improved from 36.38 (95% CI, 34.33-38.43) to 23.20 (95% CI, 21.24-25.15); and the SF36v2 Physical Component Score and Mental Composite Score improved from 34.28 (95% CI, 33.46-35.10) to 40.76 (95% CI, 39.71-41.81) and 39.45 (95% CI, 38.25-40.64) to 46.24 (95% CI, 44.94-47.55), respectively. The rate of neurological complications was 3.13%.

CONCLUSION

Surgical decompression for CSM is safe and results in improved functional status and quality of life in patients around the world, irrespective of differences in medical systems and sociocultural determinants of health.

LEVEL OF EVIDENCE

3.

Perioperative Risks Associated with Cervical Spondylotic Myelopathy Based on Surgical Treatment Strategies

BACKGROUND

Few studies have provided nationwide estimates of patient characteristics and procedure-related complications, or examined postsurgical outcomes for patients with cervical spondylotic myelopathy (CSM) comparatively with respect to surgical approach. The objective of this study is to identify patients at risk for morbidity and mortality directly related with the selected approach, report an overall nation-wide complication rate for each approach against which surgeons can compare themselves, and direct future research to improve patient outcomes.

METHODS

Patients surgically treated for CSM were retrospectively identified using ICD-9-CM codes from the Nationwide Inpatient Sample (NIS) database. Four cohorts were compared for demographics and hospital system-related data: anterior (ACDF, ACCF), posterior decompression without fusion, decompression with posterior fusion, and combined anterior-posterior. Multivariate analysis was also used to determine the odds ratio of morbidity and mortality among the cohorts.

RESULTS

54,416 discharges were identified between 2001 and 2010: 34,400 anterior, 9,014 decompression procedures without fusion, 8,741 decompression procedures with posterior fusion, and 2,261 combined anterior-posterior. Groups were statistically different with respect to age, length of hospital stay, mortality, and complications. Groups were statistically different for Deyo score except between posterior decompression only and combined approaches. Using multivariate analysis and adjusting for covariates, the combined (2.74[2.18-3.44]) and laminectomy (1.22[1.04-1.44]) cohorts had an increased risk of mortality when compared to anterior alone.

CONCLUSION

These findings are the first to determine the rates and odds of perioperative risks directly related to combined anterior-posterior procedures. This study provides clinically useful data for surgeons to educate patients and direct future research to improve patient outcomes.

Posterior atlantoaxial 'facetal' instability associated with cervical spondylotic disease

Aim:

The association of single or multiple level cervical spondylotic disease with atlantoaxial instability is assessed. The implications of identifying and treating atlantoaxial instability in such an association are highlighted.

Materials and Methods:

The analysis is based on an experience with 11 patients treated during the period June 2013-June 2014. All patients had single or multilevel cervical spondylotic disease. The spinal canal compromise and evidence of cord compression was evident on imaging in the cervical subaxial spine and was related to disc bulges and osteophytic bars. There was no or relatively insignificant compression of the cervicomedullary cord by the odontoid process. There was no evidence of odontoid process-related instability on dynamic imaging. Apart from presence of features of cervical spondylosis, investigations and surgical exploration and direct manual handling of the facets revealed evidence of Type B (posterior) atlantoaxial ‘facetal’ instability in all patients. Our 5-point clinical grading system and Japanese Orthopaedic Association (JOA) scores were used to monitor the patients both before and after surgery and at follow-up. Surgery involved both at lantoaxial and subaxial cervical fixation. During the average period of follow-up of 9 months (5-17 months), all patients showed remarkable and gratifying neurological recovery.

Conclusion:

We conclude that atlantoaxial facetal instability can be ‘frequently’ associated with cervical spondylosis and needs surgical stabilization. Our surgical outcome analysis suggests that missing or ignoring the presence of atlantoaxial facetal instability can be an important cause of suboptimal result or failure of surgery for cervical spondylotic myelopathy.

Proteomic analysis of cerebrospinal fluid in canine cervical spondylomyelopathy

STUDY DESIGN

Prospective study.

OBJECTIVE

To identify proteins with differential expression in the cerebrospinal fluid (CSF) from 15 clinically normal (control) dogs and 15 dogs with cervical spondylomyelopathy (CSM).

SUMMARY OF BACKGROUND DATA

Canine CSM is a spontaneous, chronic, compressive cervical myelopathy similar to human cervical spondylotic myelopathy. There is a limited knowledge of the molecular mechanisms underlying these conditions. Differentially expressed CSF proteins may contribute with novel information about the disease pathogenesis in both dogs and humans.

METHODS

Protein separation was performed with 2-dimensional electrophoresis. A Student t test was used to detect significant differences between groups (P < 0.05). Three comparisons were made: (1) control versus CSM-affected dogs, (2) control versus non-corticosteroid-treated CSM-affected dogs, and (3) non-corticosteroid-treated CSM-affected versus corticosteroid-treated CSM-affected dogs. Protein spots exhibiting at least a statistically significant 1.25-fold change between groups were selected for subsequent identification with capillary-liquid chromatography tandem mass spectrometry.

RESULTS

A total of 96 spots had a significant average change of at least 1.25-fold in 1 of the 3 comparisons. Compared with the CSF of control dogs, CSM-affected dogs demonstrated increased CSF expression of 8 proteins including vitamin D-binding protein, gelsolin, creatine kinase B-type, angiotensinogen, α-2-HS-glycoprotein, SPARC (secreted protein, acidic, rich in cysteine), calsyntenin-1, and complement C3, and decreased expression of pigment epithelium-derived factor, prostaglandin-H2 D-isomerase, apolipoprotein E, and clusterin. In the CSF of CSM-affected dogs, corticosteroid treatment increased the expression of haptoglobin, transthyretin isoform 2, cystatin C-like, apolipoprotein E, and clusterin, and decreased the expression of angiotensinogen, α-2-HS-glycoprotein, and gelsolin.

CONCLUSION

Many of the differentially expressed proteins are associated with damaged neural tissue, bone turnover, and/or compromised blood-spinal cord barrier. The knowledge of the protein changes that occur in CSM and upon corticosteroid treatment of CSM-affected patients will aid in further understanding the pathomechanisms underlying this disease.

LEVEL OF EVIDENCE

N/A.

Abnormal findings on magnetic resonance images of the cervical spines in 1211 asymptomatic subjects

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

The purpose of this study was to determine the prevalence and distribution of abnormal findings on cervical spine magnetic resonance image (MRI).

SUMMARY OF BACKGROUND DATA

Neurological symptoms and abnormal findings on MR images are keys to diagnose the spinal diseases. To determine the significance of MRI abnormalities, we must take into account the (1) frequency and (2) spectrum of structural abnormalities, which may be asymptomatic. However, no large-scale study has documented abnormal findings of the cervical spine on MR image in asymptomatic subjects.

METHODS

MR images were analyzed for the anteroposterior spinal cord diameter, disc bulging diameter, and axial cross-sectional area of the spinal cord in 1211 healthy volunteers. The age of healthy volunteers prospectively enrolled in this study ranged from 20 to 70 years, with approximately 100 individuals per decade, per sex. These data were used to determine the spectrum and degree of disc bulging, spinal cord compression (SCC), and increased signal intensity changes in the spinal cord.

RESULTS

Most subjects presented with disc bulging (87.6%), which significantly increased with age in terms of frequency, severity, and number of levels. Even most subjects in their 20s had bulging discs, with 73.3% and 78.0% of males and females, respectively. In contrast, few asymptomatic subjects were diagnosed with SCC (5.3%) or increased signal intensity (2.3%). These numbers increased with age, particularly after age 50 years. SCC mainly involved 1 level (58%) or 2 levels (38%), and predominantly occurred at C5-C6 (41%) and C6-C7 (27%).

CONCLUSION

Disc bulging was frequently observed in asymptomatic subjects, even including those in their 20s. The number of patients with minor disc bulging increased from age 20 to 50 years. In contrast, the frequency of SCC and increased signal intensity increased after age 50 years, and this was accompanied by increased severity of disc bulging.

LEVEL OF EVIDENCE

2.

A clinical prediction model to assess surgical outcome in patients with cervical spondylotic myelopathy: internal and external validations using the prospective multicenter AOSpine North American and international datasets of 743 patients

BACKGROUND CONTEXT

Clinical prediction rules are valuable tools in a surgical setting but should not be used to guide clinical practice until validated in other populations.

PURPOSE

The objective of this study was to validate a clinical prediction rule developed to determine surgical outcome in patients with cervical spondylotic myelopathy (CSM). The study will also identify key clinical predictors of outcome at a global level.

STUDY DESIGN/SETTING

This is a prospective multicenter cohort study.

PATIENT SAMPLE

Two-hundred seventy-eight and 479 surgical CSM patients enrolled in the AOSpine CSM-North American (CSM-NA) and CSM-International (CSM-I) studies, respectively.

OUTCOME MEASURES

The outcome measure was a Modified Japanese Orthopedic Association (mJOA) Scale.

METHODS

A clinical prediction model was built using data from 272 patients enrolled in the CSM-NA study. Bootstrapping was used for internal validation. The original model was externally validated using data on 471 patients participating in the CSM-I study. The predictive performance of the model was evaluated, including its discrimination, measured by area under the receiver-operating curve (AUC), and calibration, assessed by calibration slope, observed:expected ratios, and Hosmer-Lemeshow goodness-of-fit test.

RESULTS

The modified original model consisted of six covariates: age (odds ratio [OR], 0.96), duration of symptoms (0.76), baseline severity score (1.21), psychiatric comorbidities (0.44), impairment of gait (2.48), and smoking status (0.50). The AUC for the original model was 0.77 (95% confidence interval [CI]: 0.71, 0.82) and across the bootstrap replicates was 0.77 (95% CI: 0.76, 0.77), reflecting good discrimination and internal validity. The model tested on the CSM-I dataset yielded an AUC of 0.74 (95% CI: 0.69, 0.79), a calibration slope of 0.75, and an insignificant Hosmer-Lemeshow test. The ORs generated for baseline mJOA (OR, 1.26), impairment of gait (2.67), age (0.97), and smoking (0.55) were very similar to the original values of 1.28, 2.39, and 0.97, respectively. Duration of symptoms (OR, 0.94) had a significantly different odds ratio than in the original model, but the direction of its relationship with outcome was the same. Psychiatric comorbidities was not a significant predictor at an international level, likely because of underreporting: only six patients outside of North American centers were diagnosed with depression or bipolar.

CONCLUSIONS

The parameter estimates generated from the original analysis were internally valid. The original model was also externally valid. The most significant global predictors of surgical outcome were baseline myelopathy severity, age, smoking status and impaired gait.

Posterior surgical treatment of cervical spondylotic myelopathy: review article

BACKGROUND

Cervical spondylosis is now recognised as the leading cause of myelopathy and spinal cord dysfunction worldwide. Chronic spinal cord compression results in chronic inflammation, cellular apoptosis, and microvacular insufficiency, which are thought to the biologic basis for cervical spondylotic myelopathy (CSM).

QUESTIONS/PURPOSES

Our purpose was to address the key principles of CSM, including natural history and presentation, pathogenesis, optimal surgical approach, results and complication rates of posterior surgical approaches for CSM so that the rationale for addressing CSM by a posterior approach can be fully understood.

METHODS

We conducted a systematic search of PubMed/MEDLINE and the Cochrane Collaboration Library for literature published through February 2014 to identify articles that evaluated CSM and its management. Reasons for exclusion included patients with ossification of the posterior longitudinal ligament (OPLL), patients with degenerative disc disease without CSM, and patients with spine tumor, trauma and infection. Meeting abstracts/proceedings, white articles and editorials were additionally excluded.

RESULTS

The search strategy yielded 1,292 articles, which was reduced to 52 articles, after our exclusion criteria were introduced. CSM is considered to be a surgical disorder due to its progressive nature. There is currently no consensus in the literature whether multilevel spondylotic compression is best treated via an anterior or posterior surgical approach.

CONCLUSION

Multilevel CSM may be safely and effectively treated using a posterior approach, either by laminoplasty or with a laminectomy and fusion technique.

Is cervical decompression beneficial in patients with coexistent cervical stenosis and multiple sclerosis?

Cervical stenosis (CS) and multiple sclerosis (MS) are two common conditions with distinctive pathophysiology but overlapping clinical manifestations. The uncertainty involved in attributing worsening symptoms to CS in patients with MS due to extremely high prevalence of asymptomatic radiological CS makes treatment decisions challenging. A retrospective review was performed analyzing the medical records of all patients with confirmed diagnosis of MS who had coexistent CS and underwent surgery for cervical radiculopathy/myeloradiculopathy. Eighteen patients with coexistent CS and MS who had undergone cervical spine decompression and fusion were identified. There were six men and 12 women with an average age of 52.7 years (range 40-72 years). Pre-operative symptoms included progressive myelopathy (14 patients), neck pain (seven patients), radiculopathy (five patients), and bladder dysfunction (seven patients). Thirteen of the 14 patients (92.9%) with myelopathy showed either improvement (4/14, 28.6%) or stabilization (9/14, 64.3%) in their symptoms with neck pain and radiculopathy improving in 100% and 80% of patients, respectively. None of the seven patients with urinary dysfunction had improvement in urinary symptoms after surgery. To conclude, cervical spine decompression and fusion can improve or stabilize myelopathy, and significantly relieve neck pain and radiculopathy in the majority of patients with coexistent CS and MS. Urinary dysfunctions appear unlikely to improve after surgery. The low rate of surgical complications in our cohort demonstrates that cervical spine surgery can be safely performed in carefully selected patients with concomitant CS and MS with a good clinical outcome and also eliminate CS as a confounding factor in the long-term management of MS patients.

Cytokine concentrations in the cerebrospinal fluid of great danes with cervical spondylomyelopathy

Background

Chronic inflammation is involved in the pathogenesis of human cervical spondylotic myelopathy and could also play a role in cervical spondylomyelopathy (CSM) in dogs.

Hypothesis/Objectives

That cerebrospinal fluid (CSF) cytokine concentrations would differ between clinically normal (control) and CSM‐affected Great Danes (GDs), with affected GDs showing higher levels of inflammatory cytokines, such as interleukin (IL)‐6 and monocyte chemoattractant protein‐1/chemokine ligand 2 (MCP‐1/CCL2).

Animals

Client‐owned GDs: 15 control, 15 CSM‐affected.

Methods

Prospective study. Dogs underwent cervical vertebral column magnetic resonance imaging and collection of CSF from the cerebellomedullary cistern. Cytokine concentrations were measured using a commercially available canine multiplex immunoassay. Cytokine concentrations were compared between groups. Associations with the administration of anti‐inflammatory medications, disease duration and severity, severity of spinal cord (SC) compression, and SC signal changes were investigated in affected GDs.

Results

Affected GDs had significantly lower MCP‐1/CCL2 (mean 138.03 pg/mL, 95% confidence interval [CI] = 114.85–161.20) than control GDs (212.89 pg/mL, 95% CI = 165.68–260.11, P = .028). In affected GDs, MCP‐1/CCL2 concentrations correlated inversely with the severity of SC compression. There were no associations with administration of anti‐inflammatory medications, disease duration, or disease severity. IL‐6 concentrations were significantly higher (2.20 pg/mL, 95% CI = 1.92–2.47, P < .001) in GDs with SC signal changes.

Conclusions and Clinical Importance

Lower MCP‐1/CCL2 in CSM‐affected GDs might compromise clearance of axonal and myelin debris, delay axon regeneration, and affect recovery. Higher IL‐6 in CSM‐affected GDs with SC signal changes suggests more severe inflammation in this group.