- Cervical Spondylotic Myelopathy (CSM) is a progressive degenerative process involving the components of the cervical spine, with narrowing of the central spinal canal and resulting compression of the spinal cord. It can occur either directly by traumatic compression and abnormal movement, or indirectly by ischemia due to arterial compression or venous stasis.
- Recent studies have defined CSM by the presence of at least one neurological sign and at least one neurological symptom in addition to a positive MRI for compression of the spinal cord. Ultimately, unless all three of these elements are present one cannot be diagnosed with CSM.1
- CSM results from degenerative changes in the cervical spine, including the vertebrae, uncovertebral and facet joints, intervertebral discs, ligaments (ligamentum flavum hypertrophy, posterior longitudinal ligament ossification) and connective tissue. It usually develops insidiously, but may be precipitated by trauma.
- A congenitally narrow canal lowers the threshold by which trivial trauma or degenerative changes may cause myelopathy.
- Congenital anomalies of the cervical spine such as Klippel-Feil syndrome can lead to accelerated spondylosis.2
- Surgical fusion of cervical vertebrae can lead to increased spondylosis in adjacent segments.3
Epidemiology including risk factors and primary prevention
- CSM is the most common cause of spinal cord dysfunction in adults over age 55 in North America, and is the most common diagnosis of non-traumatic spastic paraparesis and tetraparesis.
- Men are affected more than women (2.7:1).4
- The more mobile mid-cervical segments, C5 to C7, are most frequently involved.
- Patients over age 60 often have multi-segmental disease, with C5 and C6 being the most frequent levels at which compression occurs.4
- The average anterior-posterior (AP) diameter of the canal measures about 17 mm from C3-C7. The space required by the spinal cord averages 10 mm. Absolute spinal canal stenosis exists with a sagittal diameter below 10 mm. Stenosis is relative if the diameter is 10-13 mm.
- Both static and dynamic factors contribute to myelopathy.
- Static factors:
- Decreased height of desiccated intervertebral discs leads to increased sagittal diameter and disc bulging.
- Reactive hypertrophy occurs and osteophytes form at the vertebral end plates.
- Osteophytes can project from the uncovertebral and facet joints.
- Hypertrophy of facet capsules
- Ossification, hypertrophy or laxity of ligamentum flavum
- Dynamic factors:
- In neck flexion, the spinal cord stretches and can be compressed against osteophytic spurs and intervertebral discs protruding into the canal. With a kyphotic sagittal alignment, the cord can become tethered over spondylotic anterior elements during flexion even though canal diameter is increased.
- Hyperextension can also compress the spinal cord between the posterior margin of a vertebrae or a degenerative protruding disc anteriorly, and the laminae or ligamentum flavum posteriorly. The ligamentum flavum buckles into the canal, and the degenerative disc bulges posteriorly
- As spinal segments are stiffened by spondylotic change, adjacent segments may develop relative hypermobility and subluxation, causing cord impingement.
- Histopathological and cellular changes:
- Pressure from constant spinal cord compression can result in neuroischemia and rearrangement of blood supply, infarction, oligodendrocyte apoptosis and subsequent demyelination of adjacent neurons.
- Mechanical compression on the spinal cord’s microvascular structures may result in cystic cavitation, gliosis, central gray and medial white matter degeneration, and Wallerian degeneration of posterior columns and posterolateral tracts and anterior horn cell loss1,5-7
- Chronic demyelination of the neurons in the spinal cord can lead to permanent nerve damage even after surgical decompression.
- Secondary neural injury likely involves glutamate toxicity, free radical mediated cell injury and apoptosis.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
- Natural history of CSM is variable and inadequately defined.
- Onset is typically insidious but may be acute (e.g., after a fall with hyperextension injury).
- Some patients experience a benign clinical course with neurological improvement; complete resolution is infrequent.
- Many do not improve spontaneously and experience neurological deterioration over time. Stepwise neurological worsening with interspersed periods of quiescent stability is common; less commonly, slow, steady progression may occur.
- Motor symptoms are more progressive and less likely to improve than are sensory abnormalities.
- Balance loss is usually the first symptom patients notice, and it can become quite profound before it is addressed. The recovery of balance after surgical intervention is a slow and arduous process.
Specific secondary or associated conditions and complications
- Cervical radiculopathy often occurs concomitantly with CSM.
- Co-existing lumbar stenosis has been reported in a subset of patients.
- Acute cord compression with central cord syndrome may occur with relatively minor hyperextension trauma.
- Differential diagnoses include: amyotrophic lateral sclerosis (ALS), multiple sclerosis and other demyelinating conditions, other causes of spinal cord dysfunction (tumors; syringomyelia; infectious myelopathy; toxic, inflammatory and nutritional myelopathies), movement disorders, peripheral and entrapment neuropathies, intracranial pathology, systemic causes of hyperreflexia.
2. ESSENTIALS OF ASSESSMENT
- Symptoms depend on the magnitude and chronicity of the spinal cord dysfunction.
- Early symptoms include neck pain and stiffness, diminished hand dexterity and subtle changes in balance and gait with leg stiffness, incoordination, and/or weakness
- Patients may present with frequent falls.
- Initial sensory complaints often predominate in the upper extremities.
- Compromised bladder or bowel function is less common, and occurs with greater disease severity.
- Occipital headache, neck and/or upper extremity pain from associated radiculopathy is common.
- Limited range of motion reflects underlying spondylosis.
- Motor exam
- Patients with CSM and hyperextension injury typically present with central cord syndrome (weaker upper limbs compared to lower limbs, and sacral sparing)
- Finger escape sign: when patient holds fingers extended and adducted, the small finger spontaneously abducts due to weakness of intrinsic muscle
- Grip and release test: have the patient make a fist and release 20 times in 10 seconds. Myelopathic patients may struggle to perform this task8
- Upper motor neuron signs
- Spastic paraparesis is typical, reflecting early involvement of the corticospinal tracts.
- Pathological reflexes such as Hoffman sign, Babinski sign, lower extremity hyperreflexia, and clonus indicate cord compression. A normal jaw reflex distinguishes from intracranial pathology. Concomitant lumbar stenosis may mask lower extremity hyperreflexia.
- Upper motor neuron signs may be accompanied by lower motor neuron signs at the level of cord or root compression (e.g., intrinsic atrophy of hand muscle or muscle wasting and fasciculations of shoulder girdle).
- Sensory exam
- Altered vibratory and proprioceptive changes are common. Posterior column dysfunction may cause sensory ataxia.
- Gait and balance
- Impaired toe-to-heel walk
- Positive Romberg test
- Lhermitte sign may be positive
- Gait, balance, and fall risk should be assessed.
- Activities of daily living should be evaluated with upper extremity involvement.
- The Functional Independence Measure (FIM) is commonly used during rehabilitation and follow-up.
- The myelopathy disability index (MDI) assesses activities of daily living.
Laboratory studies are done to rule out other conditions.
- Radiographs of the Cervical Spine
- Degenerative changes are very common (more than 60% of patients aged 55 or older, and increasing with age), and positive radiograph findings should be not be interpreted in isolation, but clinically correlated
- Anterior-posterior (AP), lateral, and oblique views should be performed.
- The absolute sagittal diameter of the spinal canal is measured from the posterior aspect of the mid-vertebral body to the spinolaminar line. A reduction to 13 mm or less at C3-C7, or a ratio of canal diameter to mid-vertebral body diameter of 0.8 or less is stenotic.
- Oblique views can reveal foraminal stenosis
- Lateral flexion and extension views assess range of motion and instability.
- Magnetic resonance imaging (MRI) is the study of choice to evaluate degree of spinal cord and nerve root compression, as it assesses soft tissues and neural elements.
- Effacement of CSF indicates functional stenosis
- Clinical severity of CSM have a good correlation with high intensity signals in T2-weighted MR images (myelomalacia)
- Signal changes on T1-weighted images correlate with poorer prognosis following surgical decompression.
- Computerized tomography (CT)
- CT without contrast can provide complementary information to MRI, and more useful in evaluating bony structures, including ossified posterior longitudinal ligament.
- CT myelography may be considered in patients that cannot have an MRI or have artifact from local hardware
Supplemental assessment tools
- Electrodiagnostic testing evaluates root involvement and excludes conditions such as ALS or neuropathies. It is associated with a high false negative rate.8
- Lumbar spinal imaging assesses concomitant lumbar spinal stenosis.
Early predictions of outcomes
- Favorable prognostic indicators: symptoms for less than one year, mild myelopathic symptoms, and younger age at initial presentation.
- Motor symptoms tend to be more progressive and less likely to improve than sensory abnormalities.
Given a high risk of falls, environmental interventions such as eliminating loose rugs to prevent tripping, optimizing ambient lighting, and installing grab bars in the bathroom are important.
Social role and social support system
Old age and associated co-morbidities contribute to a high risk of loss of independence especially without an adequate social support system.
Symptoms of CSM are often subtle and varied, thus the diagnosis may be missed or misattributed to other conditions.
3. REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
Lack of high quality, randomized studies and varied natural history of the disease contribute to paucity of definitive treatment guidelines.
At different disease stages
- Patients without major neurological deficits but with radiological evidence of cord compression may be treated conservatively and monitored. Function is a more important determinant for surgery than imaging or physical exam findings. The role of surgical decompression in this population remains controversial.
- Symptomatic treatment with non-steroidal anti-inflammatory drugs (NSAIDs) and gabapentin or other similar medications for neuropathic pain
- Lifestyle changes include avoiding high-impact activities associated with hyperextension, and avoiding aggressive manipulation such as chiropractic treatment or high velocity osteopathic manipulation. Traction has not been proven to improve symptoms or outcomes
- A soft cervical collar may prevent additional injury by providing sensory feedback to restrain extremes of movement; proof of effectiveness is limited. Rigid collars with the cervical spine in slight flexion may show improvement in patients with very mild symptoms (8)
- Surgical decompression should be considered in the setting of progressive neurological deterioration. The long-term effectiveness of surgery remains inconclusive:
- Both anterior and posterior surgical approaches have been used. Choice of technique depends upon factors including location of the primary compressive lesion, presence of spinal instability, spinal alignment, number of levels involved, and surgeon preference.
- Anterior approaches include anterior cervical discectomy and fusion, or cervical corporectomy. The presence of cervical kyphosis usually requires an anterior approach.
- Patients with widespread stenosis and multi-segment cord compression, ligamentum flavum buckling, or with technical/mechanical factors that interfere with an anterior approach, may be candidates for posterior decompression.
- Laminectomy alone carries the risk of developing postoperative kyphotic deformity, which is decreased with laminoplasty or laminectomy with fusion.
- Rehabilitation interventions depend on the extent and type of deficits. Mobility assessment, gait training, and fall risk management are essential. Patients with upper extremity weakness and impaired hand dexterity need ADL assessment and training and prescription of appropriate adaptive equipment.
- Complications of myelopathy such as urinary infections, incontinence, and pressure ulcers should be prevented and promptly managed.
Coordination of care
CSM typically occurs in older individuals with co-morbidities that cumulatively impact function, thus a coordinated, interdisciplinary approach to care is important.
Patient & family education
Patients should be informed of the risks, benefits, and limitations of various surgical and nonsurgical treatment options.
- Gait analysis, particularly walking speed.
- Impairment-based measurement:
- Grip strength evaluation with a dynamometer
- 10-second step test
- 10-second open-and-close-hand test
- Modified Japanese Orthopedic Association (mJOA) scale
Translation into practice: practice “pearls
- CSM should be considered if unexplained subtle gait abnormalities or hyperreflexia are present in elderly patients.
- Do not assume that CSM is the primary cause of neurological impairment, just because there is radiological evidence of cervical spondylosis. One still needs to evaluate for other conditions that may explain the patient’s impairment.
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Cutting edge concepts and practice
- Initial results of disc arthroplasty in conjunction with decompression procedures have been promising; longer follow-up is needed.
- Advances in neuroimaging techniques including spinal diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) may play a key future role in assessment and management.
- Minimally invasive techniques can make surgery less invasive in the future.
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Gaps in the evidence-based knowledge
- Controversies persist about the natural history of CSM, the role of conservative versus surgical treatment in patients with mild symptoms, and the comparative merits of various surgical approaches. Randomized clinical studies are needed.
- Research is needed to evaluate specific interventions to optimize rehabilitation outcomes.
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Sabharwal S. Cervical Spondylotic Myelopathy. In: Sabharwal S, ed. Essentials of Spinal Cord Medicine. New York, NY: Demos Medical Publishing; 2014.
Original Version of the Topic
Sunil Sabharwal, MD. Cervical Spondylotic Myelopathy. 06/07/2013
Sunil Sabharwal, MD
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