Pathophysiology of cervical myelopathy

Socioeconomic and regional differences in the treatment of cervical spondylotic myelopathy

BACKGROUND

Cervical spondylotic myelopathy (CSM) is the leading cause of spinal cord dysfunction in the world. Surgical treatment is both medically and economically advantageous, and can be achieved through multiple approaches, with or without fusion. We used the Nationwide Inpatient Sample (NIS) database to better elucidate regional and socioeconomic variances in the treatment of CSM.

METHODS

The NIS database was queried for elective admissions with a primary diagnosis of CSM (ICD-9 721.1). This was evaluated for patients who also carried a diagnosis of anterior (ICD-9 81.02) or posterior cervical fusion (ICD-9 81.03), posterior cervical laminectomy (ICD 03.09), or a combination. We then investigated variances including regional trends and disparities according to hospital and insurance types.

RESULTS

During 2002-2012, 50605 patients were electively admitted with a diagnosis of CSM. Anterior fusions were more common in Midwestern states and in nonteaching hospitals. Fusion procedures were used more frequently than other treatments in private hospitals and with private insurance. Median hospital charges were also expectedly higher for fusion procedures and combined surgical approaches. Combined approaches were found to be significantly greater in patients with concurrent diagnoses of ossification of the posterior longitudinal ligament (OPLL) and CSM. Ultimately, there has been an increased utilization of fusion procedures versus nonfusion treatments, over the past decade, for patients with cervical myelopathy.

CONCLUSIONS

Fusion surgery is being increasingly used for the treatment of CSM. Expensive procedures are being performed more frequently in both private hospitals and for those with private insurance, whereas the most economical procedure, posterior cervical laminectomy, was underutilized.

Ex vivo 1H MR spectroscopy and histology after experimental chronic spinal cord compression

BACKGROUND

Proton magnetic resonance imaging (MRS) is used increasingly to image the spinal cord in compressive cervical myelopathy (CSM). However, detailed analyses of the underlying histomorphological changes leading to MRS alterations are still lacking. The aim of our study was to correlate neuroimaging and neuropathologic alterations in a rabbit myelopathy model.

METHODS

Chronic spinal cord compression was induced in a rabbit model (n=16) allowing for a gradual 270° compression of the spinal cord. Spinal cord compression core areas were divided into two samples for (A) 1H MRS and (B) histopathological analyses. Postoperatively the animals underwent a neurological examination twice a day and outcome was categorized in pattern of injury and amount of recovery.

RESULTS

Three groups were observed and categorized: (I) animals with severe deficits and no or minimal recovery; (II) animals with severe deficits and complete or almost complete recovery; (III) animals with mild to moderate deficits and a complete recovery. Significant differences in the lesioned spinal cords between the different recovery groups were found for N-acetyl-aspartate and choline. NAA/Cr was detected significantly (P<0.001, ANOVA) less in the group that did show permanent neurological deficits. To the contrary, choline was detected significantly (P<0.001, ANOVA) more in the group that did show permanent neurological deficits. Histologically the first group showed more apoptosis and necrosis than the second and third group.

CONCLUSIONS

MR spectroscopy (MRS) may be helpful for clinicians in improving the prognostic accuracy in cervical myelopathies since this method nicely reflects the extent and severity of spinal cord damage.

Patient Dose in Fluoroscopically Guided Cervical Discectomy and Fusion

Cervical discectomy and fusion (CDF) is a minimally invasive procedure, where the accurate placement of the implants is accomplished using fluoroscopic guidance. Therefore, the evaluation of the radiation dose becomes mandatory. The purpose of the current study was to assess patient dose during fluoroscopically guided anterior and/or posterior CDF procedures. Thirty-three patients undergoing single or multiple-level CDF were studied using a mobile C-arm system. Data regarding fluoroscopy time (FT), air kerma area product (KAP) and cumulative dose (CD) were recorded. Patient entrance surface dose (ESD), thyroid absorbed dose and effective dose (ED) were calculated from KAP measurements, utilizing the CALDoseX software. The average FT was 0.12 min (range 0.02-0.48 min), resulting to a KAP value of 0.21 Gy cm2 (range 0.01-1.46 Gy cm2) and a CD value of 0.96 mGy (range 0.04-6.58 mGy). The ESD ranged between 0.08 and 13.58 mGy (average 1.95 mGy), the ED between 0.001 and 0.097 mSv (average 0.015 mSv), while the dose absorbed by the thyroid ranged between 0.01 and 1.12 mGy (average 0.194 mGy). The dose associated with the CDF procedure is very low, comparable to that delivered by a lateral X-ray radiograph of the cervical spine. However, higher doses can be revealed, due to the non-optimum use of the X-ray system and extended FTs, mainly affected by complex clinical conditions, as well as the experience of the neurosurgeon. Additional studies need to be conducted for further investigation of the patient dose from the CDF procedure.

Utility of the clivo-axial angle in assessing brainstem deformity: pilot study and literature review

There is growing recognition of the kyphotic clivo-axial angle (CXA) as an index of risk of brainstem deformity and craniocervical instability. This review of literature and prospective pilot study is the first to address the potential correlation between correction of the pathological CXA and postoperative clinical outcome. The CXA is a useful sentinel to alert the radiologist and surgeon to the possibility of brainstem deformity or instability. Ten adult subjects with ventral brainstem compression, radiographically manifest as a kyphotic CXA, underwent correction of deformity (normalization of the CXA) prior to fusion and occipito-cervical stabilization. The subjects were assessed preoperatively and at one, three, six, and twelve months after surgery, using established clinical metrics: the visual analog pain scale (VAS), American Spinal InjuryAssociation Impairment Scale (ASIA), Oswestry Neck Disability Index, SF 36, and Karnofsky Index. Parametric and non-parametric statistical tests were performed to correlate clinical outcome with CXA. No major complications were observed. Two patients showed pedicle screws adjacent to but not deforming the vertebral artery on post-operative CT scan. All clinical metrics showed statistically significant improvement. Mean CXA was normalized from 135.8° to 163.7°. Correction of abnormal CXA correlated with statistically significant clinical improvement in this cohort of patients. The study supports the thesis that the CXA maybe an important metric for predicting the risk of brainstem and upper spinal cord deformation. Further study is feasible and warranted.

Magnetic resonance imaging assessment of degenerative cervical myelopathy: a review of structural changes and measurement techniques

Degenerative cervical myelopathy encompasses a spectrum of age-related structural changes of the cervical spine that result in static and dynamic injury to the spinal cord and collectively represent the most common cause of myelopathy in adults. Although cervical myelopathy is determined clinically, the diagnosis requires confirmation via imaging, and MRI is the preferred modality. Because of the heterogeneity of the condition and evolution of MRI technology, multiple techniques have been developed over the years in an attempt to quantify the degree of baseline severity and potential for neurological recovery. In this review, these techniques are categorized anatomically into those that focus on bone, ligaments, discs, and the spinal cord. In addition, measurements for the cervical spine canal size and sagittal alignment are also described briefly. These tools have resulted collectively in the identification of numerous useful parameters. However, the development of multiple techniques for assessing the same feature, such as cord compression, has also resulted in a number of challenges, including introducing ambiguity in terms of which methods to use and hindering effective comparisons of analysis in the literature. In addition, newer techniques that use advanced MRI are emerging and providing exciting new tools for assessing the spinal cord in patients with degenerative cervical myelopathy.

Evaluation of DTI Parameter Ratios and Diffusion Tensor Tractography Grading in the Diagnosis and Prognosis Prediction of Cervical Spondylotic Myelopathy

STUDY DESIGN

Prospective cohort.

OBJECTIVE

To explore the correlations between diffusion tensor imaging (DTI) ratios and diffusion tensor tractography (DTT) grading with clinical symptoms and outcomes of cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

In addition to magnetic resonance imaging (MRI) and computed tomography, DTI may be useful in understanding pathophysiology of spinal cord in earlier stages of the CSM but it may be confounded by age and cervical level, and previous studies had small sample sizes.

METHODS

Controls (n = 36) and patients with CSM (n = 93) underwent magnetic resonance imaging (MRI) and DTI at the Changhai Hospital of Shanghai between September 2011 and March 2013. Apparent diffusion coefficient (ADC), fractional anisotropy (FA) of white matter (WM), and central grey matter (GM) were assessed. Patients were divided into three MRI grades: no abnormal signals; increased T2WI; and increased T2WI and low T1WI. DTT images were divided into three grades: no abnormal signals; abnormal local signal cord and disordered fiber tracts; and distortion of the spinal cord and interrupted fiber tracts.

RESULTS

FA and ADC both correlated with age in all three bilateral WM funiculi and GM, whereas FA and ADC ratios only showed correlation with age in the ventral funiculus (VF) and central GM. Differences were observed in ADC ratios and FA ratios from different Japanese Orthopedic Association (JOA) score subgroups and JOA recovery subgroups. For the three WM funiculi and GM, correlations between DTI ratios, JOA scores, and JOA recovery rates were consistently higher than those between DTI values, JOA scores, and JOA recovery rates (all P < 0.05). MRI grading was correlated with the JOA scores (r = -0.674, P < 0.001) but not JOA recovery rates (r = -0.197, P = 0.058), whereas DTT grading was correlated with both JOA scores (r = -0.813, P < 0.001) and JOA recovery rate (r = -0.429, P < 0.001).

CONCLUSION

DTI parameter ratios seemed to be less influenced by age than raw DTI results and could be more valuable than absolute DTI parameters for the evaluation of CSM. DTT grading is more valuable than MRI grading for diagnosis and prognostic prediction in CSM patients.

LEVEL OF EVIDENCE

3.

Surgical treatment of multilevel cervical spondylosis in patients with or without a history of syringomyelia

PURPOSE

Cervical spondylotic myelopathy (CSM) is the commonest spinal cord disease in adults. This paper compares patients who developed CSM after successful treatment of syringomyelia to those with CSM exclusively related to degenerative spinal disease.

METHODS

In this prospective study, 70 consecutive patients with CSM and spondylotic changes in at least three levels underwent 73 operations between 2005 and 2015 (mean follow-up: 39 ± 36 months). Patients with treated syringomyelia (group A, n = 30) and those without (group B, n = 40) were distinguished. Japanese Orthopaedic Association (JOA) and European Myelopathy scores (EMS), Karnofksy scores, and scores for individual symptoms were compared. Long-term outcomes were analyzed with progression-free survival rates.

RESULTS

Patients of group A were significantly younger with a significantly longer history and lower functional scores compared to group B. 59 laminectomies C3-C6 plus lateral mass fixations, six ventral decompressions with fusion, and eight combined approaches were performed. In both groups, mean JOA (A 9.5 ± 4.3-10.0 ± 4.7; B 11.3 ± 3.7-12.3 ± 4.3), EMS (A 11.4 ± 2.9-12.0 ± 3.1; B 12.2 ± 3.1-13.5 ± 3.3), and Karnofsky scores (A 59 ± 18-62 ± 18; B 68 ± 13-72 ± 15) increased in the first postoperative year with lower scores in group A throughout. Rates for progression-free survival for 5 years were similar in both groups (A 64.2%, B 65.6%).

CONCLUSION

Patients with CSM benefit from decompressive surgery. Surgery should be advocated early for all symptomatic patients with a history of syringomyelia. These patients are at risk for diagnostic delay and worse postoperative results.

An unusual case of rapidly progressed cervical compression myelopathy caused by overnight inappropriate usage of Smartphone device

A 38-year-old man was healthy before presenting to our clinic with pain and marked weakness in the right upper extremity. He stated that the symptoms developed the day after he accidentally fell asleep while playing with his Smartphone half-lying on his back with two thick pillows supporting his upper back. Physical examination revealed significant increase in deep tendon reflexes in the lower extremities and clonus. Hoffman's sign was positive in the left upper extremity. Magnetic resonance image showed high signal change on T2-weighted images of the left spinal cord at the C4-5 level, which was indicative of compression myelopathy.

The Role of Gait Analysis in the Evaluation of Patients with Cervical Myelopathy: A Literature Review Study

BACKGROUND

Gait analysis represents one of the newest methodologies used in the clinical evaluation of patients with cervical myelopathy (CM).

OBJECTIVE

To describe the role of gait analysis in the clinical evaluation of patients with CM, as well as its potential role in the evaluation of the functional outcome of any surgical intervention.

METHODS

A literature review was performed in the PubMed, OVID, and Google Scholar medical databases, from January 1995 to August 2016, using the terms "analysis," "anterior," "cervical myelopathy," "gait," "posterior," and "surgery." Clinical series comparing the gait patterns of patients with CM with healthy controls, as well as series evaluating gait and walk changes before and after surgical decompression, were reviewed. Case studies were excluded.

RESULTS

Nine prospective and 3 retrospective studies were found. Most of the retrieved studies showed the presence of characteristic, abnormal gait patterns among patients with CM, consisting of decreased gait speed, cadence, step length, stride length, and single-limb support time. In addition, patients with CM routinely present increased step and stride time, double-limb support time, and step width, and they have altered knee and ankle joint range of motion, compared with healthy controls. Moreover, gait and walk analysis may provide accurate functional assessment of the functional outcome of patients with CM undergoing surgical decompression.

CONCLUSIONS

Gait analysis may well be a valuable and objective tool along with other parameters in the evaluation of functionality in patients with CM, as well as in the assessment of the outcome of any surgical intervention in these patients.

Non-invasive Mapping of Face Processing by Navigated Transcranial Magnetic Stimulation

Background: Besides motor and language function, tumor resections within the frontal and parietal lobe have also been reported to cause neuropsychological impairment like prosopagnosia.

Objective: Since non-navigated transcranial magnetic stimulation (TMS) has previously been used to map neuropsychological cortical function, this study aims to evaluate the feasibility and spatial discrimination of repetitive navigated TMS (rTMS) mapping for detection of face processing impairment in healthy volunteers. The study was also designed to establish this examination for preoperative mapping in brain tumor patients.

Methods: Twenty healthy and purely right-handed volunteers (11 female, 9 male) underwent rTMS mapping for cortical face processing function using 5 Hz/10 pulses. Both hemispheres were investigated randomly with an interval of 2 weeks between mapping sessions. Fifty-two predetermined cortical spots of the whole hemispheres were mapped after baseline measurement. The task consisted of 80 portraits of popular persons, which had to be named while rTMS was applied.

Results: In 80% of all subjects rTMS elicited naming errors in the right middle middle frontal gyrus (mMFG). Concerning anomia errors, the highest error rate (35%) was achieved in the bilateral triangular inferior frontal gyrus (trIFG). With regard to similarly or wrongly named persons, we observed 10% error rates mainly in the bilateral frontal lobes.

Conclusion: It seems feasible to map the cortical face processing function and to generate face processing impairment via rTMS. The observed localizations are well in accordance with the contemporary literature, and the mapping did not interfere with rTMS-induced language impairment. The clinical usefulness of preoperative mapping has to be evaluated subsequently.

Prevalence and Imaging Characteristics of Nonmyelopathic and Myelopathic Spondylotic Cervical Cord Compression

STUDY DESIGN

Cross-sectional population-based observational study.

OBJECTIVE

To estimate the prevalence of nonmyelopathic spondylotic cervical cord compression (NMSCCC) and cervical spondylotic myelopathy (CSM) in a population older than 40 years and to evaluate the magnetic resonance imaging (MRI) characteristics of these conditions.

SUMMARY OF BACKGROUND DATA

The prevalence of neither NMSCCC nor CSM is known and there exists no commonly accepted quantitative MRI definition of cervical cord compression.

METHODS

A group of 183 randomly recruited volunteers, 93 women, median age 66 years, range 40-80 years, underwent MRI examination of the cervical spine and spinal cord on a 1.5 T device using conventional sequences from disc levels C2/C3 to C6/C7. The imaging criterion for cervical cord compression was defined as a change in spinal cord contour at the level of an intervertebral disc on axial or sagittal MRI scan.

RESULTS

MRI signs of cervical cord compression were found in 108 individuals (59.0%; 95% CI: 51.5%-66.2%); their numbers increased with age from 31.6% in the fifth decade to 66.8% in the eighth. Clinical signs of symptomatic CSM were found in two cases (1.1%), and 75 cases (41.0%) were without compression. An anteroposterior cervical canal diameter at the level of intervertebral disc (CDdisc) of less than 9.9 mm was associated with the highest probability of NMSCCC-odds ratio (OR) = 32.5, followed by a compression ratio of ≤0.5: OR = 11.1.

CONCLUSION

The prevalence of NMSCCC in a population older than 40 years is higher than previously reported and increases with age. CDdisc and compression ratio had the highest capacity to discriminate between subjects with and without asymptomatic compression, and their cut-off values could be used to objectify criteria for cervical cord compression.

LEVEL OF EVIDENCE

2.

Genetics Underlying an Individualized Approach to Adult Spinal Disorders

Adult spinal disorders are a significant cause of morbidity across the world and carry significant health and economic burdens. Genetic predispositions are increasingly considered for these conditions and are becoming understood. Advances in molecular technologies since the mid-1990s have made possible genetic characterizations of these diseases in many populations, and recent findings have provided insight into the underlying pathophysiologic mechanisms. These studies have made clear the genetic heterogeneity producing clinical phenotypes and suggest that individualized treatments are possible in the future. We review the genetics and heritability of cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament and perform a systematic review of the genetics of adult lumbar degenerative scoliotic deformity, highlighting recent discoveries and the potential for personalized future therapeutics for these patients.

Cervical Spondylotic Myelopathy: What the Neurologist Should Know

Cervical spondylotic myelopathy is a well-known cause of disability among older people. A significant amount of these patients is asymptomatic. Once the symptoms start, the worsening may follow a progressive manner. We should suspect of spondylotic myelopathy in any individual over 55 years presenting progressive changes in gait or losing fine motor control of the upper limbs. Despite its frequent prevalence, this condition is still neglected and many times confused with other supratentorial lesions regarding diagnostic. Here we address some of most important aspects of this disease, calling attention to pathophysiology, the natural history, presentation, differential diagnosis, clinical assessment, and treatment.

Does Tobacco Use Attenuate Benefits of Early Decompression in Patients With Cervical Myelopathy?

STUDY DESIGN

A retrospective cohort.

OBJECTIVE

This study investigates the interplay between duration of preoperative symptoms and smoking status with respect to postoperative outcomes in patients with cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

Many studies have established the harms of smoking and several have identified the benefits of early decompression in patients with cervical myelopathy, but to our knowledge, none have assessed the relationship between these two variables.

METHODS

The medical records of all 212 patients operated on by the senior author between March 2005 and July 2012 were reviewed. Inclusion criteria were the diagnosis of CSM with a Nurick score, surgical intervention, and at least 2 years of follow-up. Patients were categorized according to smoking status and quantification of tobacco use by packs per day and pack-years, and duration of symptoms according to thresholds of 6, 12, or 24 months. Age, sex, preoperative Nurick score, duration of preoperative symptoms, duration of follow-up, procedure performed, prior surgery, number of levels operated on, diabetes status, ethanol use, and signal change on preoperative magnetic resonance imaging were also recorded for ordered logistical regression analysis.

RESULTS

One hundred twenty-five patients met all criteria. Eighty patients were smokers and 45 were nonsmokers. The median change in Nurick score for nonsmokers was 2 compared with 1 in smokers. Nonsmokers had a statistically significant likelihood of decreased change in Nurick score for symptom duration of greater than 24 months (odds ratio = 0.06, P = 0.0025). Smokers did not show a significant difference in the change in Nurick score for any threshold of symptom duration.

CONCLUSION

Increased duration of symptoms significantly affects outcomes in surgical decompression of CSM. A history of cigarette use may attenuate the benefit of early decompression and results in lower improvement in Nurick score regardless of symptom duration.

LEVEL OF EVIDENCE

3.

Riluzole blocks perioperative ischemia-reperfusion injury and enhances postdecompression outcomes in cervical spondylotic myelopathy

Although surgical decompression is considered the gold standard treatment for cervical spondylotic myelopathy (CSM), a proportion of cases show postoperative decline or continue to exhibit substantial neurological dysfunction. To investigate this further, we first examined data from the prospective multicenter AOSpine North America CSM study, finding that 9.3% of patients exhibited postoperative functional decline (ΔmJOA, ≤-1) and that 44% of patients were left with substantial neurological impairment 6 months postoperatively. Notably, 4% of patients experienced perioperative neurological complications within 20 days after surgery in otherwise uneventful surgeries. To shed light on the mechanisms underlying this phenomenon and to test a combination therapeutic strategy for CSM, we performed surgical decompression in a rat model of CSM, randomizing some animals to also receive the U.S. Food and Drug Administration-approved drug riluzole. Spinal cord blood flow measurements increased after decompression surgery in rats. CSM rats showed a transient postoperative neurological decline akin to that seen in some CSM patients, suggesting that ischemia-reperfusion injury may occur after decompression surgery. Riluzole treatment attenuated oxidative DNA damage in the spinal cord and postoperative decline after decompression surgery. Mechanistic in vitro studies also demonstrated that riluzole preserved mitochondrial function and reduced oxidative damage in neurons. Rats receiving combined decompression surgery and riluzole treatment displayed long-term improvements in forelimb function associated with preservation of cervical motor neurons and corticospinal tracts compared to rats treated with decompression surgery alone.

The Influence of Diabetes on Surgical Outcomes in Cervical Myelopathy

STUDY DESIGN

A retrospective cohort.

OBJECTIVE

The objective of the study was to determine what effect, if any, diabetes has on surgical outcomes in patients with cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

Diabetes is known to impair healing and has been shown to affect outcomes in lumbar surgery, but few studies have assessed outcomes in cervical surgery, and cervical myelopathy in particular.

METHODS

The records of 113 patients operated on by one surgeon were reviewed. Inclusion criteria were a diagnosis of CSM with a Nurick score, surgical interventions, and minimum 2 years follow-up. Patients were divided into two groups according to diabetes status (33 diabetic patients vs. 80 controls) and diabetic patients were further categorized by degree of perioperative glucose control. Simple and multiple regression analyses were done to compare outcomes as recorded by the Nurick score, controlling for age, gender, duration of symptoms, alcohol use, cocaine use, surgical approach, prior surgery, and signal change on preoperative magnetic resonance imaging.

RESULTS

There was no relationship between diabetes status and preoperative Nurick score. However, diabetes status was associated with impaired improvement in Nurick score. Average perioperative glucose in diabetic individuals was linearly associated with impaired improvement in Nurick score.

CONCLUSION

We conclude that hyperglycemia may impair postoperative healing of the spinal cord in patients with CSM.

LEVEL OF EVIDENCE

3.

Axonal plasticity underpins the functional recovery following surgical decompression in a rat model of cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is the most common spinal cord disorder and a major cause of disability in adults. Improvements following surgical decompression are limited and patients often remain severely disabled. Post mortem studies indicate that CSM is associated with profound axonal loss. However, our understanding of the pathophysiology of CSM remains limited.To investigate the hypothesis that axonal plasticity plays a role in the recovery following surgical decompression, we adopted a novel preclinical model of mild to moderate CSM. Spinal cord compression resulted in significant locomotor deterioration, increased expression of the axonal injury marker APP, and loss of serotonergic fibres. Surgical decompression partially reversed the deficits and attenuated APP expression. Decompression was also associated with axonal sprouting, reflected in the restoration of serotonergic fibres and an increase of GAP43 expression. The re-expression of synaptophysin indicated the restoration of functional synapses following decompression. Promoting axonal plasticity may therefore be a therapeutic strategy for promoting neurological recovery in CSM.

RESULTS OF TREATMENT OF CERVICAL DISCOPATHY WITH PEEK INTERBODY CAGES AT THREE LEVELS WITHOUT PLATE FIXATION

ABSTRACT Objective: To present the results of treatment of patients with cervical discopathy by anterior cervical approach, discectomy and placement of a PEEK interbody cage without anterior plate fixation. Methods: Retrospective, cross-sectional study from March 2013 to March 2015. Sixteen patients with radiculopathy or clinical signs of myelopathy were included; all patients underwent cervical surgery through anterior approach, discectomy, and placement of PEEK cages on three levels. Decompression levels were determined according to the correlation between preoperative radiological and clinical findings. Results: Sixteen patients predominantly male were included, with mean age of 50 years at the onset of the condition. Ten patients had involvement of C4-C5, C5-C6, C6-C7 levels, and six patients C3-C4, C4-C5 and C5-C6. Fourteen patients had cervicobrachialgia and two myelopathy. The preoperative visual analog scale average was 8/10 and the average postoperative value at 6 months was 3/10. At 6 months, there was no radiological evidence of recurrence. One patient had non-fatal complications. Conclusions: The treatment of cervical discopathy by anterior approach with interbody fusion with PEEK cage on three levels, with no plate fixation seemed to be safe and effective with better long-term results in terms of pain and myelopathy. The clinical results compare favorably with other similar series and, most importantly, the complications associated with anterior fixation plate are avoided.

Surgical outcomes of cervical spondylotic myelopathy: an analysis of a national, administrative, longitudinal database

OBJECTIVE

The authors performed a population-based analysis of national trends, costs, and outcomes associated with cervical spondylotic myelopathy (CSM) in the United States. They assessed postoperative complications, resource utilization, and predictors of costs, in this surgically treated CSM population.

METHODS

MarketScan data (2006–2010) were used to retrospectively analyze the complications and costs of different spine surgeries for CSM. The authors determined outcomes following anterior cervical discectomy and fusion (ACDF), posterior fusion, combined anterior/posterior fusion, and laminoplasty procedures.

RESULTS

The authors identified 35,962 CSM patients, comprising 5154 elderly (age ≥ 65 years) patients (mean 72.2 years, 54.9% male) and 30,808 nonelderly patients (mean 51.1 years, 49.3% male). They found an overall complication rate of 15.6% after ACDF, 29.2% after posterior fusion, 41.1% after combined anterior and posterior fusion, and 22.4% after laminoplasty. Following ACDF and posterior fusion, a significantly higher risk of complication was seen in the elderly compared with the nonelderly (reference group). The fusion level and comorbidity-adjusted ORs with 95% CIs for these groups were 1.54 (1.40–1.68) and 1.25 (1.06–1.46), respectively. In contrast, the elderly population had lower 30-day readmission rates in all 4 surgical cohorts (ACDF, 2.6%; posterior fusion, 5.3%; anterior/posterior fusion, 3.4%; and laminoplasty, 3.6%). The fusion level and comorbidity-adjusted odds ratios for 30-day readmissions for ACDF, posterior fusion, combined anterior and posterior fusion, and laminoplasty were 0.54 (0.44–0.68), 0.32 (0.24–0.44), 0.17 (0.08–0.38), and 0.39 (0.18–0.85), respectively.

CONCLUSIONS

The authors' analysis of the MarketScan database suggests a higher complication rate in the surgical treatment of CSM than previous national estimates. They found that elderly age (≥ 65 years) significantly increased complication risk following ACDF and posterior fusion. Elderly patients were less likely to experience a readmission within 30 days of surgery. Postoperative complication occurrence, and 30-day readmission were significant drivers of total cost within 90 days of the index surgical procedure.

Kinematic analysis of cervical spine canal diameter and its association with grade of degeneration

OBJECTIVES

To investigate the cervical spinal canal diameters variance under positional MRI, and also the relationship between cervical canal diameter variance rate and grade of degeneration.

METHODS

From January 2013 to January 2015, a consecutive of 273 symptomatic patients (166 males and 207 females) with an average age of 44.6 years (range 21-89 years) underwent positional cervical MRI. T2-weighted sagittal images of 1638 cervical intervertebral discs from 273 subjects were classified into five grades. The canal diameter and canal diameter variance rate at three positions and their comparison among five grade of degeneration were evaluated. The measurements were tabulated and analyzed using SPSS. 13.0. p values less than 0.05 were considered to indicate a statistically significant difference.

RESULTS

The sagittal cervical canal diameter at the C5/6 level were the smallest compared with the other levels regardless of neutral, flexion or extension positions, C5/6 level had the largest canal diameter variance rate in both flexion and extension (8.14 ∓ 0.38 and 7.81 ∓ 0.31 %, respectively), second was C4/5 level (7.65 ∓ 0.39 and 7.67 ∓ 0.32 %, respectively). A total of 1638 discs were classified into 5 groups, each level showed the similar tendency that no matter what position, with the increasing grade of degenerative disc degree, spine canal diameter decreased gradually. For C5/6 under extension and flexion position, significant difference was also noted between grade 2 and 3; For C4/5 under extension position, significant difference existed between grade 1 and 2, grade 1 and 3, while under flexion position, significant difference existed between grade 2 and 4, and the results also showed no significant difference at the same degree of degeneration on both levels between extension and flexion position.

CONCLUSIONS

C5/6 and C4/5 is of higher risk of suffering SCI than other levels, C4/5 level predispose SCI at earlier stage than C5/6, patients presenting with intermediate signal and slight decreased disc height on T2 weighted MRI at C4/5 level should be paid attention.

Narrow cervical canal in 1211 asymptomatic healthy subjects: the relationship with spinal cord compression on MRI

PURPOSE

Narrow cervical canal (NCC) has been a suspected risk factor for later development of cervical myelopathy. However, few studies have evaluated the prevalence in asymptomatic subjects. The purpose of this study was to investigate the prevalence of NCC in a large cohort of asymptomatic volunteers.

METHODS

This study was a cross-sectional study of 1211 asymptomatic volunteers. Approximately 100 men and 100 women representing each decade of life from the 20s to the 70s were included in this study. Cervical canal anteroposterior diameters at C5 midvertebral level on X-rays, and the prevalence of spinal cord compression (SCC) and increased signal intensity (ISI) changes on MRI were evaluated. Receiver operating characteristic analysis was performed to determine the cut-off value of the severity of canal stenosis resulting in SCC.

RESULTS

NCC (<14 mm) was observed in 123 (10.2 %) subjects. SCC and ISI were found in 64 (5.3 %) and 28 (2.3 %) subjects, respectively. The prevalence of NCC was significantly higher in females and older subjects, but the occurrence of severe NCC (<12 mm) did not increase with age. The canal size in subjects with SCC or ISI was significantly smaller than in those without SCC (p < 0.0001). The cut-off values of cervical canal stenosis resulting in SCC were 14.8 and 13.9 mm in males and females, respectively.

CONCLUSIONS

The prevalence of NCC was considerably lower among asymptomatic healthy volunteers; the cervical canal diameter in subjects with SCC or ISI was significantly smaller than in asymptomatic subjects; NCC is a risk factor for SCC.

Imaging of Spinal Cord Injury: Acute Cervical Spinal Cord Injury, Cervical Spondylotic Myelopathy, and Cord Herniation

We review the pathophysiology and imaging findings of acute traumatic spinal cord injury (SCI), cervical spondylotic myelopathy, and briefly review the much less common cord herniation as a unique cause of myelopathy. Acute traumatic SCI is devastating to the patient and the costs to society are staggering. There are currently no "cures" for SCI and the only accepted pharmacologic treatment regimen for traumatic SCI is currently being questioned. Evaluation and prognostication of SCI is a demanding area with significant deficiencies, including lack of biomarkers. Accurate classification of SCI is heavily dependent on a good clinical examination, the results of which can vary substantially based upon the patient׳s condition or comorbidities and the skills of the examiner. Moreover, the full extent of a patients׳ neurologic injury may not become apparent for days after injury; by then, therapeutic response may be limited. Although magnetic resonance imaging (MRI) is the best imaging modality for the evaluation of spinal cord parenchyma, conventional MR techniques do not appear to differentiate edema from axonal injury. Recently, it is proposed that in addition to characterizing the anatomic extent of injury, metrics derived from conventional MRI and diffusion tensor imaging, in conjunction with the neurological examination, can serve as a reliable objective biomarker for determination of the extent of neurologic injury and early identification of patients who would benefit from treatment. Cervical spondylosis is a common disorder affecting predominantly the elderly with a potential to narrow the spinal canal and thereby impinge or compress upon the neural elements leading to cervical spondylotic myelopathy and radiculopathy. It is the commonest nontraumatic cause of spinal cord disorder in adults. Imaging plays an important role in grading the severity of spondylosis and detecting cord abnormalities suggesting myelopathy.

Fractional anisotropy to quantify cervical spondylotic myelopathy severity

BACKGROUND

A number of clinical tools exist for measuring the severity of cervical spondylotic myelopathy (CSM). Several studies have recently described the use of non-invasive imaging biomarkers to assess severity of disease. These imaging markers may provide an additional tool to measure disease progression and represent a surrogate marker of response to therapy. Correlating these imaging biomarkers with clinical quantitative measures is critical for accurate therapeutic stratification and quantification of axonal injury.

METHODS

Fourteen patients and seven healthy control subjects were enrolled. Patients were classified as mildly (7) or moderately (7) impaired based on Modified Japanese Orthopedic Association Scale. All patients underwent diffusion tensor imaging (DTI) and diffusion basis spectrum imaging (DBSI) analyses. In addition to standard neurological examination, all participants underwent 30-m Walking Test, 9-hole Peg Test (9HPT), grip strength, key pinch, and vibration sensation thresholds in the index finger and great toe. Differences in assessment scores between controls, mild and moderate CSM patients were correlated with DTI and DBSI derived fractional anisotropy (FA).

RESULTS

Clinically, 30-meter walking times were significantly longer in the moderately impaired group than in the control group. Maximum 9HPT times were significantly longer in both the mildly and moderately impaired groups as compared to normal controls. Scores on great toe vibration sensation thresholds were lower in the mildly impaired and moderately impaired groups as compared to controls. We found no clear evidence for any differences in minimum grip strength, minimum key pinch, or index finger vibration sensation thresholds. There were moderately strong associations between DTI and DBSI FA values and 30-meter walking times and 9HPT.

CONCLUSIONS

The 30-m Walking Test and 9HPT were both moderately to strongly associated with DTI/DBSI FA values. FA may represent an additional measure to help differentiate and stratify patients with mild or moderate CSM.

Relatively Large Cervical Spinal Cord for Spinal Canal is a Risk factor for Development of Cervical Spinal Cord Compression: A Cross-Sectional Study of 1211 Subjects

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

This study aims to investigate the correlation of the cervical canal and spinal cord size, and evaluate whether the size of the spinal cord relative to the spinal canal is a risk factor for development of cervical spinal cord compression (SCC).

SUMMARY OF BACKGROUND DATA

There is little knowledge regarding the relationship between cervical bony canal and spinal cord diameters. Although developmental canal stenosis has been recognized as a risk factor for SCC, the size of the spinal cord relative to the spinal canal has not been similarly discussed.

METHODS

Cervical canal anteroposterior (AP) diameters on X-rays and AP diameters and cross-sectional areas of dural sacs and spinal cords on magnetic resonance imaging (MRI) were measured in 1211 healthy volunteers. Correlation between cervical canal diameter on X-rays and AP diameter and cross-sectional area of dural sacs and spinal cords on MRI were assessed. The ratio of the AP diameter of the spinal cord/dural sac was compared between subjects with and without SCC.

RESULTS

Spinal canal diameters were not highly correlated with spinal cord AP diameters and cross-sectional areas, although spinal canal diameters were significantly correlated with dural sac AP diameters. The individual difference in the ratio of the AP diameter of the spinal cord/dural sac was large (35%-93%), and the ratio was significantly larger in the subjects with SCC. An AP diameter ratio more than 62% at the C2 to C3 disc level is a risk factor for developing SCC.

CONCLUSION

The spinal cord diameter was independent of the spinal canal diameter and the relative size of a spinal cord and spinal canal differed on an individual basis. In addition, the ratio of spinal cord/dural sac in subjects with SCC was significantly larger. Therefore, a relatively large spinal cord could be a risk factor for SCC.

Mechanical and cellular processes driving cervical myelopathy

Cervical myelopathy is a well-described clinical syndrome that may evolve from a combination of etiological mechanisms. It is traditionally classified by cervical spinal cord and/or nerve root compression which varies in severity and number of levels involved. The vast array of clinical manifestations of cervical myelopathy cannot fully be explained by the simple concept that a narrowed spinal canal causes compression of the cord, local tissue ischemia, injury and neurological impairment. Despite advances in surgical technology and treatment innovations, there are limited neuro-protective treatments for cervical myelopathy, which reflects an incomplete understanding of the pathophysiological processes involved in this disease. The aim of this review is to provide a comprehensive overview of the key pathophysiological processes at play in the development of cervical myelopathy.

Non-invasive mapping of calculation function by repetitive navigated transcranial magnetic stimulation

Concerning calculation function, studies have already reported on localizing computational function in patients and volunteers by functional magnetic resonance imaging and transcranial magnetic stimulation. However, the development of accurate repetitive navigated TMS (rTMS) with a considerably higher spatial resolution opens a new field in cognitive neuroscience. This study was therefore designed to evaluate the feasibility of rTMS for locating cortical calculation function in healthy volunteers, and to establish this technique for future scientific applications as well as preoperative mapping in brain tumor patients. Twenty healthy subjects underwent rTMS calculation mapping using 5 Hz/10 pulses. Fifty-two previously determined cortical spots of the whole hemispheres were stimulated on both sides. The subjects were instructed to perform the calculation task composed of 80 simple arithmetic operations while rTMS pulses were applied. The highest error rate (80 %) for all errors of all subjects was observed in the right ventral precentral gyrus. Concerning division task, a 45 % error rate was achieved in the left middle frontal gyrus. The subtraction task showed its highest error rate (40 %) in the right angular gyrus (anG). In the addition task a 35 % error rate was observed in the left anterior superior temporal gyrus. Lastly, the multiplication task induced a maximum error rate of 30 % in the left anG. rTMS seems feasible as a way to locate cortical calculation function. Besides language function, the cortical localizations are well in accordance with the current literature for other modalities or lesion studies.

Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression

Objective

To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings.

Materials and Methods

A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD∩FA (considered positive when both the MD and FA results were positive), LD∩FA (considered positive when both the LD and FA results were positive), and RD∩FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard.

Results

The MD, LD, and RD cut-off values were 1.079 × 10^-3, 1.719 × 10^-3, and 0.749 × 10^-3 mm²/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (p = 0.003), FA and LD∩FA (p < 0.001), FA and RD∩FA (p < 0.001), MD and LD∩FA (p = 0.024) and MD and RD∩FA (p = 0.024).

Conclusion

Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.

Early detection of cervical spondylotic myelopathy using diffusion tensor imaging: Experiences in 1.5-tesla magnetic resonance imaging

The purpose of this study was to investigate the usefulness of diffusion tensor imaging (DTI) for early detection of pathological alterations in the myelon in patients with cervical spondylotic myelopathy (CSM) without T2-weighted imaging (T2W) signal abnormalities but with a narrowed spinal canal with corresponding clinical correlation. Axial DTI at 1.5T together with routine magnetic resonance imaging was performed on 18 patients fulfilling above mentioned criteria. Quantitative fractional anisotropy (FA) and apparent diffusion coefficient (ADC) maps were generated. Values at the narrowest cervical levels were compared to pre- and poststenotic levels and the interindividual means were tested for statistically significant differences by means of paired t-tests. The correlation between the grade and width of canal stenosis in the axial plane was measured. FA was significantly reduced at the stenotic level, compared to prestenotic level, whereas no significant differences were found when compared to poststenotic level. No significant differences between ADC values at stenotic level versus both adjacent non-stenotic levels were found, suggesting very early stage of degeneration. ADC values correlated significantly with the width of the spinal canal at the prestenotic level, but not at the poststenotic level. Findings indicate sufficient robustness of routine implementation of DTI at 1.5T to detect abnormalities in the spinal cord of CSM patients, before apparent T2W signal abnormalities and marked clinical deterioration. Therefore, larger and long-term studies should be conducted to establish the DTI scalar metrics that would indicate early intervention for a better clinical outcome in patients with clinical signs of CSM.

Prediction of Neurological Impairment in Cervical Spondylotic Myelopathy using a Combination of Diffusion MRI and Proton MR Spectroscopy

PURPOSE

In the present study we investigated a combination of diffusion tensor imaging (DTI) and magnetic resonance spectroscopic (MRS) biomarkers in order to predict neurological impairment in patients with cervical spondylosis.

METHODS

Twenty-seven patients with cervical spondylosis were evaluated. DTI and single voxel MRS were performed in the cervical cord. N-acetylaspartate (NAA) and choline (Cho) metabolite concentration ratios with respect to creatine were quantified, as well as the ratio of choline to NAA. The modified mJOA scale was used as a measure of neurologic deficit. Linear regression was performed between DTI and MRS parameters and mJOA scores. Significant predictors from linear regression were used in a multiple linear regression model in order to improve prediction of mJOA. Parameters that did not add value to model performance were removed, then an optimized multiparametric model was established to predict mJOA.

RESULTS

Significant correlations were observed between the Torg-Pavlov ratio and FA (R2 = 0.2021, P = 0.019); DTI fiber tract density and FA, MD, Cho/NAA (R2 = 0.3412, P = 0.0014; R2 = 0.2112, P = 0.016; and R2 = 0.2352, P = 0.010 respectively); along with FA and Cho/NAA (R2 = 0.1695, P = 0.033). DTI fiber tract density, MD and FA at the site of compression, along with Cho/NAA at C2, were significantly correlated with mJOA score (R2 = 0.05939, P < 0.0001; R2 = 0.4739, P < 0.0001; R2 = 0.7034, P < 0.0001; R2 = 0.4649, P < 0.0001). A combination biomarker consisting of DTI fiber tract density, MD, and Cho/NAA showed the best prediction of mJOA (R2 = 0.8274, P<0.0001), with post-hoc tests suggesting fiber tract density, MD, and Cho/NAA were all significant contributors to predicting mJOA (P = 0.00053, P = 0.00085, and P = 0.0019, respectively).

CONCLUSION

A linear combination of DTI and MRS measurements within the cervical spinal cord may be useful for accurately predicting neurological deficits in patients with cervical spondylosis. Additional studies may be necessary to validate these observations.

The Effect of Smoking on Spinal Cord Healing Following Surgical Treatment of Cervical Myelopathy

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

The purpose of this study was to compare outcomes of surgical treatment of cervical myelopathy between smokers and nonsmokers as assessed by the Nurick score.

SUMMARY OF BACKGROUND DATA

The harmful effects of smoking on healing have been well established. However, the effect of smoking on postoperative outcomes for cervical myelopathy has not been specifically evaluated.

METHODS

The medical records of 212 patients who underwent surgery for cervical spondylotic myelopathy were reviewed. Inclusion criteria were the diagnosis of cervical spondylotic myelopathy with a Nurick score, surgical intervention, and at least 2 years of follow-up. The patients were categorized into 2 groups according to smoking status and stratified according to pack years and packs per day. Age at presentation, sex, preoperative and postoperative Nurick score, duration of symptoms preoperatively, duration of follow-up, procedure performed, surgical approach, number of levels fused, diabetes status, cocaine use, ethanol use, preoperative magnetic resonance imaging signal change, and whether the patient belonged to the Veterans Administration (VA) were recorded. Analysis was done using simple linear regression and multiple regression.

RESULTS

Univariate analysis demonstrated a postoperative improvement in nonsmokers of 1.53 points on the Nurick scale compared with 0.6 points in smokers (P < 0.001). There is a progressive decrease in improvement as the number of pack years and packs per day increase (P < 0.001). There is a greater improvement in Nurick score with greater (worse) preoperative score but only in patients with fewer than 25 pack years. Smoking status is not associated with preoperative Nurick score.

CONCLUSION

Smoking status is associated with poor improvement in Nurick score after surgical treatment of cervical myelopathy. Smoking may have a directly toxic effect on the intrinsic healing capability of the spinal cord, particularly beyond 25 pack years.

LEVEL OF EVIDENCE

3.

Degenerative Cervical Myelopathy: Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Review.

OBJECTIVE

To formally introduce "degenerative cervical myelopathy" (DCM) as the overarching term to describe the various degenerative conditions of the cervical spine that cause myelopathy. Herein, the epidemiology, pathogenesis, and genetics of conditions falling under this hypernym are carefully described.

SUMMARY OF BACKGROUND DATA

Nontraumatic, degenerative forms of cervical myelopathy represent the commonest cause of spinal cord impairment in adults and include cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, and degenerative disc disease. Unfortunately, there is neither a specific term nor a specific diagnostic International Classification of Diseases, Tenth Revision code to describe this collection of clinical entities. This has resulted in the inconsistent use of diagnostic terms when referring to patients with myelopathy due to degenerative disease of the cervical spine.

METHODS

Narrative review.

RESULTS

The incidence and prevalence of myelopathy due to degeneration of the spine are estimated at a minimum of 41 and 605 per million in North America, respectively. Incidence of cervical spondylotic myelopathy-related hospitalizations has been estimated at 4.04/100,000 person-years, and surgical rates seem to be rising. Pathophysiologically, myelopathy results from static compression, spinal malalignment leading to altered cord tension and vascular supply, and dynamic injury mechanisms. Occupational hazards, including transportation of goods by weight bearing on top of the head, and other risk factors may accelerate DCM development. Potential genetic factors include those related to MMP-2 and collagen IX for degenerative disc disease, and collagen VI and XI for ossification of the posterior longitudinal ligament. In addition, congenital anomalies including spinal stenosis, Down syndrome, and Klippel-Feil syndrome may predispose to the development of DCM.

CONCLUSION

Although DCMs can present as separate diagnostic entities, they are highly interrelated, frequently manifest concomitantly, present similarly from a clinical standpoint, and seem to be in part a response to compensate and improve stability due to progressive age and wear of the cervical spine. The use of the term "degenerative cervical myelopathy" is advocated.

LEVEL OF EVIDENCE

5.

Trial-to-trial latency variability of somatosensory evoked potentials as a prognostic indicator for surgical management of cervical spondylotic myelopathy

Background

Early detection of neural conductivity changes at the compressed spinal cord is important for predicting the surgical outcomes of patients with cervical spondylotic myelopathy (CSM). The prognostic value of median nerve somatosensory evoked potential (SEP) has been proposed previously. The present prospective study evaluates the use of trial-to-trial variability in SEP as a valuable predictor of neurological recovery after surgery of CSM.

Methods

A total of 35 CSM patients who underwent surgery with up to 6-month follow-up were recruited in this study. SEP signals were recorded preoperatively. The single trial SEP was extracted by a newly developed second-order blind identification method. The postoperative recovery was assessed using the modified Japanese Orthopaedic Association. The correlation between the latency variability of trial-to-trial SEP and post-operative recovery ratio was analyzed. The prognostic value of trial-to-trial SEP for CSM was evaluated using a receiver operator characteristic curve which can accurately reflect the relationship between sensitivity and specificity of a diagnostic method and represent the accuracy of prognosis.

Results

The correlation coefficient of trial-to-trial latency variability and the 6-month recovery ratio was statistically significant (r = −0.82, P < 0.01). The trial-to-trial SEP had a higher prognostic accuracy (AUC = 0.928, P < 0.001) with an optimal prognostic value of 9.25 % compared with averaged SEP when the threshold of recovery ratio was 40 %, and was more sensitive (93.80 %) than the averaged SEP (43.80 %).

Conclusions

These findings indicate that the latency variability of trial-to-trial SEP reflect the recovery ratio of CSM patients after surgery. It is suggested that the latency variability of trial-to-trial SEP is useful for predicting the surgical outcomes for patients with CSM, which would be a potential indication of surgical treatment for CSM to help decision making of surgical planning for CSM patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-015-0042-4) contains supplementary material, which is available to authorized users.

Comparison of anterior approach versus posterior approach for the treatment of multilevel cervical spondylotic myelopathy

PURPOSE

The purpose of this study is to evaluate the clinical outcomes, complications, and surgical trauma between anterior and posterior approaches for the treatment of multilevel cervical spondylotic myelopathy (CSM).

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

Randomized controlled trials or non-randomized controlled trials published up to November 2014 that compared the clinical effectiveness of anterior and posterior surgical approaches for the treatment of multilevel CSM were acquired by a comprehensive search in four electronic databases (PubMed, EMBASE, Cochrane Controlled Trial Register and MEDLINE). Exclusion criteria were non-controlled studies, combined anterior and posterior surgery and cervical myelopathy caused by ossification of the posterior longitudinal ligament. The main end points included: recovery rate; Japanese Orthopedic Association (JOA) score; complication rate; reoperation rate; blood loss; operation time and length of stay.

RESULTS

A total of ten studies were included in the meta-analysis; none of which were randomized controlled trials. All of the selected studies were of high quality as indicated by the Newcastle-Ottawa scale. In six studies involving 467 patients, there was no significant difference in the preoperative JOA score between the anterior surgery group and the posterior group [P > 0.05, WMD -0.00 (-0.50, 0.50)]. In four studies involving 268 patients, the postoperative JOA score was significantly higher in the anterior surgery group compared with the posterior surgery group [P < 0.05, WMD 0.79 (0.16, 1.42)]. In five studies involving 420 patients, there was no statistically significant difference in recovery rate between the anterior and posterior surgery groups [P > 0.05, WMD 2.73 (-8.69, 14.15)]. In nine studies involving 804 patients, the postoperative complication rate was significantly higher in the anterior surgery group compared with the posterior surgery group [P = 0.009, OR 1.65 (1.13, 2.39)]. In five studies involving 294 patients, the reoperation rate was significantly higher in the anterior surgery group compared with the posterior surgery group [P = 0.0001, OR 8.67 (2.85, 26.34)]. In the four studies involving 252 patients, the intraoperative blood loss and operation time was significantly higher in the anterior surgery group compared with the posterior surgery group [P < 0.05, WMD -40.25 (-76.96, -3.53) and P < 0.00001, WMD 61.3 (52.33, 70.28)]. In the three studies involving 192 patients, the length of stay was significantly lower in the anterior surgery group compared with the posterior surgery group [P < 0.00001, WMD -1.07 (-2.23, -1.17)].

CONCLUSIONS

In summary, our meta-analysis suggested that a definitive conclusion could not be reached regarding which surgical approach is more effective for the treatment of multilevel CSM. Although anterior approach was associated with better postoperative neural function than posterior approach in the treatment of multilevel CSM, there was no apparent difference in the neural function recovery rate between the two approaches. Higher rates of surgery-related complication and reoperation should be taken into consideration when anterior approach is used for patients with multilevel CSM.

Diffusion tensor imaging studies of cervical spondylotic myelopathy: a systemic review and meta-analysis

A meta-analysis was conducted to assess alterations in measures of diffusion tensor imaging (DTI) in the patients of cervical spondylotic myelopathy (CSM), exploring the potential role of DTI as a diagnosis biomarker. A systematic search of all related studies written in English was conducted using PubMed, Web of Science, EMBASE, CINAHL, and Cochrane comparing CSM patients with healthy controls. Key details for each study regarding participants, imaging techniques, and results were extracted. DTI measurements, such as fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean diffusivity (MD) were pooled to calculate the effect size (ES) by fixed or random effects meta-analysis. 14 studies involving 479 CSM patients and 278 controls were identified. Meta-analysis of the most compressed levels (MCL) of CSM patients demonstrated that FA was significantly reduced (ES -1.52, 95% CI -1.87 to -1.16, P < 0.001) and ADC was significantly increased (ES 1.09, 95% CI 0.89 to 1.28, P < 0.001). In addition, a notable ES was found for lowered FA at C2-C3 for CSM vs. controls (ES -0.83, 95% CI -1.09 to -0.570, P < 0.001). Meta-regression analysis revealed that male ratio of CSM patients had a significant effect on reduction of FA at MCL (P = 0.03). The meta-analysis of DTI studies of CSM patients clearly demonstrated a significant FA reduction and ADC increase compared with healthy subjects. This result supports the use of DTI parameters in differentiating CSM patients from health subjects. Future researches are required to investigate the diagnosis performance of DTI in cervical spondylotic myelopathy.

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.

Acute complications of spinal cord injuries

The aim of this paper is to give an overview of acute complications of spinal cord injury (SCI). Along with motor and sensory deficits, instabilities of the cardiovascular, thermoregulatory and broncho-pulmonary system are common after a SCI. Disturbances of the urinary and gastrointestinal systems are typical as well as sexual dysfunction. Frequent complications of cervical and high thoracic SCI are neurogenic shock, bradyarrhythmias, hypotension, ectopic beats, abnormal temperature control and disturbance of sweating, vasodilatation and autonomic dysreflexia. Autonomic dysreflexia is an abrupt, uncontrolled sympathetic response, elicited by stimuli below the level of injury. The symptoms may be mild like skin rash or slight headache, but can cause severe hypertension, cerebral haemorrhage and death. All personnel caring for the patient should be able to recognize the symptoms and be able to intervene promptly. Disturbance of respiratory function are frequent in tetraplegia and a primary cause of both short and long-term morbidity and mortality is pulmonary complications. Due to physical inactivity and altered haemostasis, patients with SCI have a higher risk of venous thromboembolism and pressure ulcers. Spasticity and pain are frequent complications which need to be addressed. The psychological stress associated with SCI may lead to anxiety and depression. Knowledge of possible complications during the acute phase is important because they may be life threatening and/ or may lead to prolonged rehabilitation.

Diffusion tensor imaging of the spinal cord: insights from animal and human studies

Diffusion tensor imaging (DTI) provides a measure of the directional diffusion of water molecules in tissues. The measurement of DTI indexes within the spinal cord provides a quantitative assessment of neural damage in various spinal cord pathologies. DTI studies in animal models of spinal cord injury indicate that DTI is a reliable imaging technique with important histological and functional correlates. These studies demonstrate that DTI is a noninvasive marker of microstructural change within the spinal cord. In human studies, spinal cord DTI shows definite changes in subjects with acute and chronic spinal cord injury, as well as cervical spondylotic myelopathy. Interestingly, changes in DTI indexes are visualized in regions of the cord, which appear normal on conventional magnetic resonance imaging and are remote from the site of cord compression. Spinal cord DTI provides data that can help us understand underlying microstructural changes within the cord and assist in prognostication and planning of therapies. In this article, we review the use of DTI to investigate spinal cord pathology in animals and humans and describe advances in this technique that establish DTI as a promising biomarker for spinal cord disorders.

Do quantitative magnetic resonance imaging parameters correlate with the clinical presentation and functional outcomes after surgery in cervical spondylotic myelopathy? A prospective multicenter study

STUDY DESIGN

A prospective multicenter cohort study.

OBJECTIVE

To establish the relationship between preoperative quantitative magnetic resonance imaging (MRI) parameters and clinical presentation and postoperative outcomes in patients with cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

Correlation of magnetic resonance imaging with clinical presentation and outcomes in cervical spondylotic myelopathy is poorly understood.

METHODS

A total of 134 magnetic resonance imaging scans were reviewed from 12 sites across North America. The transverse area (TA) of the spinal cord at the site of maximal compression was computed, and spinal cord signal intensity (SI) changes on T1-/T2-weighted imaging (WI) were evaluated. Detailed clinical assessments--neurological signs, symptoms, Nurick grade, modified Japanese Orthopaedic Association, segmental-tract score, and long-tract score of modified Japanese Orthopaedic Association, 30-m walk test, Short-Form 36 questionnaire, and neck disability index were performed at admission, 6 months, and 12 months postoperatively.

RESULTS

The total number of neurological signs in a patient correlated with TA (P = 0.01) and SI changes on T1-/T2WI (P = 0.05). Pre- and postoperative Nurick grade (P = 0.03, P = 0.02), modified Japanese Orthopaedic Association score (P = 0.005, P = 0.001), segmental-tract score (P = 0.05, P = 0.006), and long-tract score (P = 0.006, P = 0.002), 30-m walk test (P = 0.002, P = 0.01) correlated with TA. There was no significant difference in pre- and postoperative clinical scores in patients with/without SI changes. Patients with severe cord compression showed SI changes on T1-/T2WI more frequently (r =-0.27, r =-0.38). Pyramidal signs--plantar response, Hoffmann reflex and hyper-reflexia correlated with TA (P = 0.003, P = 0.0004, P = 0.024, respectively) and SI changes on T1/T2WI (P = 0.02).

CONCLUSION

TA closely mirrors the clinical presentation of cervical spondylotic myelopathy and may be used in predicting surgical outcomes. Pyramidal signs correlated with TA and/or SI changes on T1-/T2WI. The total number of neurological signs in a patient correlated with TA. There was no significant relationship between TA, age and duration of symptoms.

LEVEL OF EVIDENCE

3.

Value of micro-CT for monitoring spinal microvascular changes after chronic spinal cord compression

Neurological degeneration can occur after compression of the spinal cord. It is widely accepted that spinal cord compression leads to ischemic lesions and ultimately neurological dysfunction due to a narrowed spinal canal. Therefore, an in-depth understanding of the pathogenesis of spinal cord compression injury is required to help develop effective clinical interventions. In the present study, we propose a new method of quantitative 3D micro-CT to observe microvascular events in a chronic spinal cord compression rat model. A total of 36 rats were divided into two groups: sham control group (n = 12) and compressive spinal cord injury group (n = 24). Rats were scarified at four weeks after surgery. In each group, CD34 micro-vessel immunohistochemical staining was performed in half of the animals, while micro-CT scanning was performed in the other half. Microvessel density (MVD) was measured after immunohistochemical staining, while the vascular index (VI) was measured in 3D micro-CT. In comparison with sham control, abnormal somatosensory evoked potentials (SEP) can be seen in all 24 cases of the compression group, and VI shows the amount of microvessels reduced consistently and significantly (p < 0.01). A significant correlation is also found between MVD and VI (r = 0.95, p < 0.01). These data suggest that quantitative 3D micro-CT is a sensitive and promising tool for investigating microvascular changes during chronic compressive spinal cord injury.

Ethical issues in states of impaired communication with intact consciousness and language

Acute and chronic peripheral and/or central disorders of the voluntary motor system can produce profound paresis or paralysis, at times with ophthalmoplegia, while preserving consciousness and language function. Although at times appearing to be unconscious, these patients are awake and alert but unable to communicate, manipulate their environment, or participate in medical decision-making. Clinicians caring for these patients are ethically tasked with recognizing this clinical reality, enacting measures to facilitate communication, and abiding by ethical and legal principles that support autonomous patient-centered decision-making. This chapter reviews the various disorders that may cause this state while using three exemplary disorders - locked-in syndrome, caused by an anterior pontine lesion; high cervical spinal cord lesion; and amyotrophic lateral sclerosis - to discuss the management of these patients.

Relation between cervical and thoracic spinal canal stenosis and the development of spinal cord decompression sickness in recreational scuba divers

STUDY DESIGN

Retrospective case-control study.

OBJECTIVES

The intent of this study was to investigate the relationships between vertebral degenerative changes resulting in spinal canal stenosis, spinal cord lesions and the development of spinal cord decompression sickness (DCS) in scuba divers.

SETTING

Referral hyperbaric facility, Toulon, France.

METHODS

We examined 33 injured divers less than 50 years old by cervical and thoracic MRI and compared them with 34 matched control divers. The number of intervertebral disk abnormalities and the degree of canal compression were analyzed on T2-weighted sagittal images using a validated grading system developed recently. The presence and the distribution of hyperintense cord lesions in relation with the accident and the recovery status at 6 months were also assessed.

RESULTS

Canal spinal narrowing was more common in injured divers than in controls (79% vs. 50%, OR=3.7 [95% CI, 1.3-10.8], P=0.021). We found a significant linear association between the extent of canal stenosis, multisegmental findings and the development of spinal cord decompression sickness. MRI intramedullary lesions were significantly more frequent in divers with incomplete recovery (OR=16 [95% CI, 2.6-99], P=0.0014), but statistical analysis failed to demonstrate a significant relationship between canal compression, signal cord abnormalities and a negative clinical outcome.

CONCLUSIONS

These results suggest that divers with cervical and thoracic spinal canal stenosis, mainly due to disk degeneration, are at increased risk for the occurrence of spinal cord decompression sickness.