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degenerative_cervical_spondylotic_myelopathy

Degenerative cervical spondylotic myelopathy

Degenerative cervical spondylotic myelopathy (DCSM) has been defined as a chronic degenerative process caused by compression of the spinal cord by surrounding bony or ligamentous structures.

Cervical spinal stenosis is a defining feature of cervical spondylotic myelopathy (CSM).


Tetreault et al. proposed a new term named degenerative cervical myelopathy (DCM) 1).

DCM comprises both osteoarthritic changes to the spine, including cervical spondylosis, cervical disc herniation, and facet arthropathy (collectively referred to as cervical spondylotic myelopathy), and ligamentous aberrations such as ossification of the posterior longitudinal ligament and hypertrophy of the ligamentum flavum.

A review of Tetreault et al. summarizes current knowledge of the pathophysiology of DCM and describes the cascade of events that occur after compression of the spinal cord, including ischemia, destruction of the blood-spinal cord barrier, demyelination, and neuronal apoptosis. Important features of the diagnosis of DCM are discussed in detail, and relevant clinical and imaging findings are highlighted. Furthermore, this review outlines valuable assessment tools for evaluating functional status and quality of life in these patients and summarizes the advantages and disadvantages of each. Other topics of this review include epidemiology, the prevalence of degenerative changes in the asymptomatic population, the natural history and rates of progression, risk factors of diagnosis (clinical, imaging and genetic), and management strategies 2).

Epidemiology

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction in adults 3).

It can be identified in the majority of people older than 50 years, and is widely prevalent in the population, estimated to affect 75% of the population older than 65 years 4).

The incidence of cervical spine degenerative disease has been rising owing to the increasing aging population.

Etiology

Cervical myelopathy due to cervical spondylosis is a progressive degenerative spine disease.

Develops in almost all patients with ≥ 30 % narrowing of the cross sectional area of the cervical spinal canal.

Clinical features

Diagnosing DCSM has traditionally relied on presence of clinical symptoms, including clumsy hands, paralysis of the lower extremities, gait disturbances, urinary/bowel incontinence and severe neurological dysfunction disturbances, urinary/bowel incontinence, and severe neurological dysfunction 5) 6).

Many people with cervical spondylosis or CSM are asymptomatic. However, patients with CSM are at higher risk of spinal cord injury (SCI) following minor injury.

Only a small percentage of people with spondylosis go on to develop symptoms consistent with cervical spondylotic myelopathy (CSM), which can cause significant and disabling neurological deficits, leading to loss of function, morbidity, and mortality.

In addition, diabetes mellitus (DM) is a frequent comorbidity for people of this age and may impact the severity of CCM.

Scales

Diagnosis

The timeline of neurological decline and loss of function can be gleaned from the history, whereas important physical examination findings include hyperreflexia, presence of pathological reflexes, weakness, difficulty with gait, or dysdiadochokinesia.

A major shortcoming in the management of CSM is the lack of an effective diagnostic approach to stratify treatments and to predict outcomes. No current clinical diagnostic imaging approach is capable of accurately reflecting underlying spinal cord pathologies.

Radiographs

Plain radiographs can reveal degenerative changes with osteophyte formation and disc height loss.

Magnetic resonance imaging

The advent of high-quality magnetic resonance imaging (MRI), has enabled the detailed recognition of pathology both extrinsic and intrinsic to the spinal cord.

An important finding of intrinsic pathology is the presence of increased signal in the cervical spinal cord on T2 weighted image, or cord signal change (CSC). This was first noted in the late 1980s and early 1990s 7) 8) 9).

Signal intensity on preoperative cervical magnetic resonance imaging (MRI) of the spinal cord has been shown to be a potential predictor of outcome of surgery for cervical compressive myelopathy. However, the prognostic value of such signal remains controversial. One reason for the controversy is the lack of proper quantitative methods to assess MRI signal intensity.

The relationship of the presence, absence or extent of intramedullary T2 weighted signal change to clinical myelopathy, and to the likely outcome after surgery, remains complex and controversial.

More recent publications tend to indicate that T2 weighted signal change, particularly if multisegmental, is a poor prognostic feature for response to surgery 10) 11).

Low intensity signal on preoperative T1-WIs but not T2-WIs correlated with poor postoperative neurologic outcome. Furthermore, decreased signal intensity on postoperative T1-WIs and increased signal intensity on postoperative T2-WIs are predictors of poor neurologic outcome 12).


A significant increase in muscle fatty infiltration and cross-sectional area (CSA) asymmetry at the level below the compression was observed in patients with Degenerative Cervical Myelopathy (DCM). Results also suggest an association between cervical muscle morphology and DCM clinical symptoms and functional status 13).


Preoperative sensory-evoked potentials may be considered for patients in whom clinical factors do not provide clear guidance if such information would potentially change therapeutic decisions 14).

Results suggest that Motor evoked potentials (MEPs), peripheral conduction time (PCT), and central motor conduction time (CMCT) parameters each reveal abnormalities in the upper and lower motor neurons even in patients with diabetes mellitus (DM). The results also show a prolonged PCT in compressive cervical myelopathy (CCM)-DM patients, despite having no history of diabetic neuropathy. Corticospinal tract impairments are similar between CCM and CCM-DM patients, while the JOA score of the CCM-DM patients is lower than that in the CCM patients. The JOA score in CCM-DM patients may be influenced by additional impairments in peripheral nerves or other diabetic complications. These electrophysiological studies may be useful for screening motor pathway function for CCM in patients with DM 15).

Treatment

Outcome

The impact of the changes in myelopathic signs following cervical decompression surgery and their relationship to functional outcome measures remains unclear.

Case series

2016

Fifteen patients with CSM were enrolled in this prospective study. Clinical data and scores from standard outcomes questionnaires were obtained before and after surgery. Patients also participated in experimental test protocols consisting of standard kinematic gait testing, the Purdue pegboard test, and the novel single leg squat test (SLS).

The SLS test protocol was well tolerated by CSM patients and generated objective performance data over short test periods. In patients who participated in postoperative testing, the group measures of mean SLS errors decreased following surgery. Gait velocity measures followed a similar pattern of group improvement postoperatively. Practical barriers to implementing this extensive battery of tests resulted in subject attrition over time. Compared with kinematic gait testing, the SLS protocol required less space and could be effectively implemented more efficiently.

The SLS test provides a practical means of obtaining objective measures of leg motor sensory functions in patients with CSM. Additional testing with a larger cohort of patients is required to use SLS data to rigorously examine group treatment effects 16).


Goncalves et al., hypothesized that changes in the concentration of N acetylaspartate (NAA) in the motor and sensory cortices in the brain would emulate the time course of neurological recovery following decompression surgery for cervical spondylotic myelopathy (CSM). Their aim was to compare and contrast how metabolite levels in the motor and sensory cortices change after surgery to reverse downstream spinal cord compression.

Twenty-four patients with CSM and 8 control subjects were studied using proton magnetic resonance spectroscopic imaging (1H-MRS) acquired on a 3.0-T Siemens MRI unit. The 1H-MRS data (TE 135 msec, TR 2000 msec) were acquired to measure absolute levels of NAA from the motor and sensory cortices in the cerebral hemisphere contralateral to the side of greater deficit at baseline in each subject. Data were also acquired at 6 weeks and 6 months following surgery. Control subjects were also evaluated at 6 weeks and 6 months following baseline data acquisition. Neurological function was measured in each subject at all time points using the Neck Disability Index (NDI), Modified Japanese Orthopaedic Association scale (mJOA), and the ASIA impairment scale.

In the motor cortex of patients, NAA levels decreased significantly (p < 0.05) at 6 weeks and 6 months postsurgery compared with baseline levels. In the sensory cortex of patients, NAA levels decreased significantly (p < 0.05) only at 6 months after surgery compared with baseline and 6-week levels. No significant changes in NAA were found in control subjects. Clinical scores demonstrated significant (p < 0.05) motor recovery by 6 weeks, whereas sensory improvements (p < 0.05) appeared at only 6 months.

Findings suggest that metabolite changes in both the motor and sensory cortices mimic the time course of functional motor and sensory recovery in patients with CSM. The temporal course of neurological recovery may be influenced by metabolic changes in respective cortical regions 17).


Twenty-four patients with CSM and 8 control subjects were studied using proton magnetic resonance spectroscopic imaging (1H-MRS) acquired on a 3.0-T Siemens MRI unit. The 1H-MRS data (TE 135 msec, TR 2000 msec) were acquired to measure absolute levels of NAA from the motor and sensory cortices in the cerebral hemisphere contralateral to the side of greater deficit at baseline in each subject. Data were also acquired at 6 weeks and 6 months following surgery. Control subjects were also evaluated at 6 weeks and 6 months following baseline data acquisition. Neurological function was measured in each subject at all time points using the Neck Disability Index (NDI), Modified Japanese Orthopaedic Association scale (mJOA), and the ASIA impairment scale.

In the motor cortex of patients, NAA levels decreased significantly (p < 0.05) at 6 weeks and 6 months postsurgery compared with baseline levels. In the sensory cortex of patients, NAA levels decreased significantly (p < 0.05) only at 6 months after surgery compared with baseline and 6-week levels. No significant changes in NAA were found in control subjects. Clinical scores demonstrated significant (p < 0.05) motor recovery by 6 weeks, whereas sensory improvements (p < 0.05) appeared at only 6 months.

Findings suggest that metabolite changes in both the motor and sensory cortices mimic the time course of functional motor and sensory recovery in patients with CSM. The temporal course of neurological recovery may be influenced by metabolic changes in respective cortical regions 18).


Between 2008 and 2011, 36 patients with CSM were observed following cervical decompression surgery. Patient data including mJOA and a new MS scores were prospectively collected and analyzed preoperatively and at 1 year after surgery.

In this cohort, reflex, Babinski, and proprioception signs showed statistically significant improvement following surgery at 1 year (p = < 0.001, p = 0.008, and p = 0.015, respectively). A lesser degree of improvement was observed with the Hoffman sign (p = 0.091). No statistically significant improvement in clonus occurred (p = 0.368). There was a significant improvement in mJOA (p ≤ 0.001) and MS (p ≤ 0.001) scores at 1 year compared with the preoperative scores. The results showed an inverse correlation between MS and mJOA scores both pre- and postoperatively (Spearman's correlation coefficient = -0.202 preoperatively and -0.361 postoperatively).

Improvement in myelopathic signs was noted following cervical decompression surgery in patients with CSM. The newly devised MS scale demonstrated these findings, and the new MS scale correlates with improvement in mJOA scores in this patient cohort 19).


Four hundred and seventy-nine patients with symptomatic Cervical spondylotic myelopathy were enrolled in the prospective AOSpine CSM-International study at 16 global sites. Preoperatively and at each follow-up, patients were evaluated using the modified Japanese Orthopaedic Association scale (mJOA), the Nurick scale, the Neck Disability Index (NDI), and the Short- Form 36 (SF-36) Health Survey. A mixed model analytic approach was used to evaluate differences in outcomes between races at 24 months postoperatively, while controlling for relevant baseline characteristics and surgical factors.

Three hundred and twenty-four (67.64%) patients were Caucasian and 106 (22.13%) were East Asian. There was no difference in the incidence of ossification of the posterior longitudinal ligament (OPLL) between the two races; however a greater percentage of Caucasians in India (46.15%) and Turkey (41.38%) displayed evidence of OPLL than Caucasians in other regions (p < 0.001). The frequency of spondylosis was significantly higher in Caucasians (p < 0.001). Caucasians had a longer duration of symptoms (27.33 ± 34.47 months) than East Asians (23.11 ± 35.68 months) (p < 0.001), and a lower preoperative score on the SF-36 Physical Component Score (33.85 ± 9.04) compared to East Asians (37.47 ± 8.67) (p < 0.001). At 24-months after surgery, there were no differences in functional status or QOL between East Asians and Caucasians, after adjusting for baseline characteristics, surgical preferences and disease causation. Rates of perioperative complications were not significantly different between the races (p = 0.261).

Decompressive surgery results in comparable functional gains and is equally safe in Caucasians and East Asians 20).

1986

Sixty-nine patients with cervical spondylotic myelopathy (CSM), radiculopathy (CSR), or both (CSMR) were studied with computed tomography (CT). Computer-assisted myelography (CAM) accurately determines the site and nature of spondylotic protrusions and provides good visualisation of the subarachnoid space and cord deformities even in areas with dilute metrizamide. However, excessive vertebral movement and bulging ligamenta flava with their effects on cord deformity, so easily visualised in myelograms, are completely or partially missed. In the assessment of CSM, metrizamide myelography (MM) followed by CAM should be performed, particularly when the myelographic images are unsatisfactory due to contrast dilution or blockage, when cord compression cannot be ascertained with MM and when cord atrophy is suspected. In CSR, the diagnostic information from MM and CAM is comparable. The diagnostic criteria in CAM are, however, less direct and since MM is adequate in uncomplicated cases, CAM is generally not necessary. The APD, APD/TD ratio, area and circularity are sensitive indices of cord deformity and the first two should be used more often to assist visual assessment of cord deformity. The relation between cord parameters and treatment response is better reflected in CSM cases managed conservatively and the results suggest that the degree of cord deformity is helpful in determining the outcome and hence the choice between surgical and conservative treatment. In plain CT, the osteophytes and calcified discs are adequately visualised and canal dimensions measured with accuracy, but the cervical cord and roots cannot be properly assessed and the diagnosis of CSM or CSR cannot be ascertained. At present, its role in cervical spondylosis is therefore limited 21).

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degenerative_cervical_spondylotic_myelopathy.txt · Last modified: 2018/04/16 13:33 by administrador