Cervical spondylotic myelopathy

INTRODUCTION — Cervical spondylosis refers to a progressive degenerative process affecting the cervical vertebral bodies and intervertebral discs. This process can lead to narrowing (stenosis) of the central spinal canal, ie, cervical spinal stenosis. If sufficiently severe, the cervical spinal cord is compressed, producing a syndrome of spinal cord dysfunction known as cervical spondylotic myelopathy. Myelopathy occurs in 5 to 10 percent of patients with symptomatic cervical spondylosis. Other clinical syndromes associated with cervical spondylosis include neck pain and cervical radiculopathy.

Cervical spondylotic myelopathy is the most common cause of myelopathy in adults over 55 years, causing progressive disability and impairing the quality of life [1-5].

Issues related to cervical spondylotic myelopathy will be reviewed here. Neck pain, cervical radiculopathy, spinal cord syndromes, and other spinal cord disorders are discussed separately. (See "Evaluation of the adult patient with neck pain" and "Clinical features and diagnosis of cervical radiculopathy" and "Anatomy and localization of spinal cord disorders" and "Disorders affecting the spinal cord".)

PATHOPHYSIOLOGY — Cervical spondylosis is a general term for nonspecific, degenerative changes of the cervical spine that are common in older adults. These changes include degeneration of the intervertebral discs resulting in disc herniation; facet, uncovertebral, and vertebral body osteophyte formation; and ossification and hypertrophy of the posterior longitudinal ligament and ligamenta flava. The pathogenesis of cervical spondylosis is discussed separately. (See "Clinical features and diagnosis of cervical radiculopathy", section on 'Cervical spondylosis'.)

These processes can lead to narrowing of the central cervical canal, ie, cervical spinal stenosis. This in turn can produce dysfunction of the adjacent spinal cord, as the combined result of mechanical compression of neural elements and spinal cord ischemia due to compression of the arterial and/or venous blood supply to the cord [3]. Flexion and extension of the neck may exacerbate compression; the canal diameter is reduced by 2 to 3 mm in flexion, while extension can cause inward buckling of the ligamentum flavum.

The neurologic syndrome of cervical spondylotic myelopathy is sometimes referred to as a radiculomyelopathy because the spondylotic process can simultaneously damage spinal nerve roots as well as the cord itself. Injury to the anterior horn cells in the spinal cord gray matter can also cause lower motor neuron deficits at the level of spinal cord involvement (see 'Clinical presentation' below). Because the C5-7 regions are most commonly affected, the lower motor neuron or segmental signs are generally observed in these myotomes.

CLINICAL PRESENTATION — Cervical spinal cord compression can give rise to weakness in the arms, legs, or both; sensory loss with a high thoracic or cervical sensory level; and urinary and rectal sphincter dysfunction [1].

There is no well-defined pattern of neurologic deficits in cervical spondylotic myelopathy. Patients present with varying signs and symptoms that can include:

●Pain in the neck, subscapular region, or shoulder, often radiating into the arms.

●Numbness or paresthesias in the arms. The sensory loss may follow a dermatomal pattern (figure 1), and often underlies complaints of loss of fine motor control in the hands.

●Gait disturbance, usually characterized by a spastic, scissoring quality.

●Sensory deficits, usually related to dorsal column function (reduced joint position and vibratory sense) and loss of pain sensation, can be elicited in the lower extremities and may contribute to the gait impairment.

●Weakness in the lower extremities with upper motor neuron characteristics: increased reflexes, increased tone, and present Babinski signs.

●Lower motor neuron findings (weakness, atrophy, and suppressed reflexes) in a myotomal distribution in the arms or hands. The C5-7 myotomes are most often affected (table 1).

●Bladder dysfunction, urgency, frequency, and/or retention.

●Lhermitte sign. An electric shock-like sensation in the neck, radiating down the spine or into the arms, produced by forward flexion of the neck.

Symptoms usually begin insidiously. Gait impairment is a common early symptom [6-8]. This is often ill described by the patient, who may complain of leg weakness or stiffness or of a vague unsteadiness. By the time a patient presents for surgical intervention, sensory deficits in the hands causing functional impairment are also a common complaint in 80 percent [7,9]. Clinical bladder dysfunction is less common, occurring in less than 20 percent [3,9]. The examination may also reveal crepitus of the neck with restriction of lateral flexion and rotation.

Patients with cervical spondylotic myelopathy may present with progressive bilateral sensory loss and motor dysfunction in the hands, without other neurologic symptoms. These symptoms can be misdiagnosed as carpal tunnel syndrome, but electrodiagnostic studies (nerve conduction studies and electromyography) will fail to support that diagnosis.

Some patients with cervical spondylotic myelopathy will present acutely, often after minor neck trauma (such as from a fall or a whiplash injury in a motor vehicle accident), with a central cord syndrome characterized by disproportionately greater motor impairment in the upper compared with the lower extremities, bladder dysfunction, and a variable degree of sensory loss below the level of injury [8,10,11] (see "Anatomy and localization of spinal cord disorders", section on 'Central cord syndromes'). It was previously thought that the injury in these cases was the result of a concussion of the cord with stasis of axoplasmic flow, causing edematous injury. However, autopsy studies have demonstrated that bleeding into the central cord is a more likely mechanism [10,11]. This is a rare event in patients who are asymptomatic prior to the trauma [12].

DIAGNOSIS — The diagnosis requires a careful correlation between findings from the history, physical examination, and imaging studies.

Imaging — Both magnetic resonance imaging (MRI) and computed tomography (CT) with myelography can be used to diagnose cervical spondylotic myelopathy, providing a quantitative assessment of central canal narrowing [13]. MRI is superior in providing intramedullary detail of spinal cord pathology, but CT provides better images of bone and other calcified tissues. Because it is noninvasive, MRI is generally considered the test of choice [6,13]. MRI is also useful to exclude other potential causes of cervical myelopathy. (See "Disorders affecting the spinal cord".)

Various measures of canal narrowing are used clinically and in research studies. The simplest of these, and perhaps the most commonly used in routine clinical practice, is a measure of the anterior-posterior diameter. Cervical spondylotic myelopathy is considered unlikely if the diameter exceeds 16 mm, and probable if less than 10 mm. Others use measures of canal area as a potentially more reliable measure of disease severity [14,15].

Spondylotic cord compression can be seen at one or more levels. One-third to one-half of patients have multilevel disease (image 1) [9,16]. Compression at more than one level usually correlates with more severe neurologic deficits and perhaps a worse prognosis [17].

Another potentially important marker of disease severity and prognosis is a finding of signal abnormality within the cord (intramedullary). However, investigators report mixed results when attempting to correlate neurologic impairment with this finding [4,17-20]. Hypointensity on T1-weighted images, though less frequently seen than hyperintensity on T2-weighted images, may be a more reliable marker of disease severity (image 1) [4,21]. Signal abnormality at multiple cord levels also appears to be a more significant finding than more restricted areas of signal change. Some studies have found that diffusion tensor imaging provided a better correlation with clinical findings compared with more traditional MRI techniques; however, its precise clinical utility remains to be established [22-24].

There is a high incidence of MRI abnormalities of the cervical spine in asymptomatic older individuals [25,26]. One study showed disc bulge or herniation in 57 percent, spinal cord impingement in 26 percent, and frank cord compression in 4 percent of patients over 64 years [25]. These findings worsen over time in most patients [26]. Careful clinical correlation between imaging studies and clinical features is necessary to diagnose cervical spondylotic myelopathy.

Electrophysiology — Electromyography and nerve conduction studies usually do not add to the diagnosis of cervical spondylotic myelopathy. However, these tests can provide information regarding the presence and degree of anterior horn cell or spinal nerve route damage and are useful to exclude other diagnoses, particularly amyotrophic lateral sclerosis (ALS). (See "Diagnosis of amyotrophic lateral sclerosis and other forms of motor neuron disease".)

Motor- and somatosensory-evoked potentials do not have a defined role in the clinical diagnosis of cervical spondylotic myelopathy. Though often giving abnormal results, sensitivities are low, and the observed abnormalities are not specific to cervical spondylotic myelopathy [7]. However, investigators are studying a potential role for these tests as well as transcranial magnetic stimulation in determining prognosis in patients with cervical spondylotic myelopathy both with and without surgical intervention [14,27-30].

DIFFERENTIAL DIAGNOSIS — Cervical spondylotic myelopathy is often unrecognized in its early stages. In later stages, when impairments are clinically evident, several alternative diagnoses may be suggested.

Amyotrophic lateral sclerosis — Both amyotrophic lateral sclerosis (ALS) and cervical spondylotic myelopathy present in older adults. The neurologic examination in both disorders often demonstrates mixed upper and lower motor neuron deficits. With cervical spondylotic myelopathy, lower motor neuron deficits and fasciculations are isolated to the affected cervical myotomes, but in ALS they often appear in the legs and cranial muscles (eg, tongue) as well. Sensory deficits are not expected in ALS, but these are also often subtle or absent in patients with cervical spondylotic myelopathy.

Further complicating this issue is that radiologic evidence of cervical spondylosis in asymptomatic adults with normal neurologic examinations is well documented [27], and may be an incidental and misleading finding in a patient with ALS. Cases are reported in which continued neurologic deterioration after surgical decompression for putative cervical spondylotic myelopathy was later attributed to ALS [31]. Electromyography is an important diagnostic aid in ALS. (See "Clinical features of amyotrophic lateral sclerosis and other forms of motor neuron disease" and "Diagnosis of amyotrophic lateral sclerosis and other forms of motor neuron disease".)

Other cervical cord disorders — Other pathologies can affect the cervical spinal cord and produce a syndrome similar to cervical spondylotic myelopathy. Some of the more common of these disorders are summarized in the table (table 2) and are discussed in detail separately. (See "Disorders affecting the spinal cord".)

Guillain-Barré syndrome — Guillain-Barré syndrome (GBS) and cervical spondylotic myelopathy can both present as a subacute progressive paraparesis or quadriparesis. Patients with GBS typically have reduced or absent reflexes and may have cranial nerve involvement, while patients with cervical spondylotic myelopathy usually have hyperreflexia and do not have cranial nerve involvement. However, these clinical signs may be absent early on in presentation and neuroimaging may be required to distinguish these diagnoses. (See "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis".)

Normal pressure hydrocephalus — Sharing clinical features of gait impairment and bladder dysfunction, normal pressure hydrocephalus (NPH) can superficially resemble cervical spondylotic myelopathy. However, in NPH, some degree of cognitive dysfunction is usually apparent, the gait disorder is usually apractic rather than spastic in quality, and urinary dysfunction is accompanied by an indifference representing its probable frontal lobe origin. These features are distinct from those of cervical spondylotic myelopathy. (See "Normal pressure hydrocephalus".)

PROGNOSIS — The natural history of cervical spondylotic myelopathy is not well characterized [8]. Some patients experience a slow and stepwise deterioration, with worsening gait, leg and arm weakness, sensory changes, and pain [6]. Some patients experience prolonged periods of stability; however, abrupt worsening can occur, often following minor neck injuries [32-34].

Identification of clinical or radiographic risk factors for neurologic deterioration has been somewhat elusive. In one study of 45 patients treated conservatively, female gender and higher degrees of cervical mobility appeared to be risk factors for deterioration [35]. A larger canal area was predictive of a good outcome in one study, but not another [14,27]. Intramedullary signal abnormality on magnetic resonance imaging (MRI) was found not to be associated with deterioration in two studies [18,27]. Others have found that abnormal motor- and somatosensory-evoked potentials identify patients at risk for neurologic progression [7,14,27].

TREATMENT — Treatment options for cervical spondylotic myelopathy, specifically when and if to operate, remain controversial.

Conservative measures — Nonsurgical treatment often includes some form of cervical immobilization (soft collar or brace), restriction of high-risk activities and environments (eg, slippery surfaces, vigorous neck movement, heavy lifting, action sports), and pain management [18,28,36,37]. Patients should also take precautions to avoid whiplash while in vehicles, by adjusting the headrest to a position at the level of the occiput. Although some regimens also include exercises and cervical traction, other clinicians suggest that these are contraindicated in cervical spondylotic myelopathy [38-40]. There are no published data supporting the efficacy of any of these measures.

Pain control for neck pain in cervical spondylotic myelopathy may be achieved using various pharmacologic strategies including nonsteroidal anti-inflammatory agents and other analgesics, muscle relaxants, and antidepressant medications. This is discussed separately. (See "Management of nonradicular neck pain in adults".)

For the patient who defers surgical intervention or whose lesion is not severe, routine reassessment of symptoms and serial neurologic examinations are potentially valuable to identify clinical evidence of increasing cord compression. Patients should be advised to report symptoms suggesting increasing myelopathy, such as increasing bowel/bladder dysfunction, weakness, sensory loss, or gait instability. Repeat imaging should be considered when there are increasing neurologic deficits.

Surgical decompression — There is no consensus regarding the indications and timing for surgical treatment of cervical spondylotic myelopathy [1]. Although unsupported by clinical trial data, it is common clinical practice to consider surgical decompression in patients with progressive deterioration and/or a moderate or severe myelopathy causing disabling neurologic deficits [3]. For patients with mild clinical features of myelopathy, surgical consultation is recommended for those at risk for deterioration; examples include those with severe spinal cord compression on magnetic resonance imaging (MRI) and those with active lifestyles. When surgery is deferred, there should be close neurologic follow-up to assess for progressive deficits. Surgery to prevent neurologic injury in patients with asymptomatic cervical spondylotic disease is generally not recommended [12].

A number of different surgical procedures are used to treat cervical spondylotic myelopathy [1]. Anterior surgeries include cervical discectomy and corpectomy (removal of the central portion of the vertebral body) alone or in combination at single or multiple levels, often combined with a strut reconstruction (bridging the space between the end plates of the vertebral bodies) using bone or synthetic materials and plate fixation [16,41]. Posterior surgeries include laminectomy and laminoplasty (decompression and reconstruction of the laminae) [41,42]. It is not known which type of surgical procedure is best, as high-quality randomized trials are lacking [43-49]. Anterior surgeries directly decompress the pathologic lesion, but can be associated with complications such as dysphagia, graft extrusion, and cerebrospinal leaks and appear to be associated with higher reoperation rates [50]. Laminoplasty produces a more flexible spine but is not always technically possible and is associated with higher rates of C5 root injury.

Overall, 50 to 80 percent of patients are reported to be improved after surgery, while 5 to 30 percent are worse or subsequently deteriorate [9,16,42,51-55]. In one retrospective case series, benefit was apparent in the first postoperative week and maximized at approximately six months, after which recovery was marginal [56].

Investigators have attempted to identify factors that predict a good or poor response to surgery. However, for every clinical and radiologic feature reported to identify patients likely or not to benefit from surgery, there are studies both confirming and refuting an association [9,17,20,21,29,51-53,55,57-66]. Factors reported in some studies to predict a poor response to surgery include:

●Older age

●Intramedullary signal abnormality on MRI, especially if multisegmental and with abnormalities on T1- as well as T2-weighted images

●More severe disability at the time of operation

●Longer duration of symptoms preoperatively

●Narrow canal size preoperatively

●Multisegmental compression

Surgical complications occur in up to 16 percent of patients and include death in approximately 1 percent [9,16,41,42,52,53,60,67-71]. Cardiopulmonary complications are more common in older patients [72]. Common complications more specific to the surgery include:

●Nerve or nerve root injury, usually C5 or C6, recurrent laryngeal nerve, may be permanent or temporary

●Wound infections

●Epidural hematoma

●Dural tear

●Failure of instrumentation (eg, nonunion)

Studies comparing surgical and conservative treatments are limited to two small, randomized trials in patients with mild disease and one nonrandomized prospective cohort study in patients with a broader range of disease severity [73]:

●A prospective but nonrandomized study in 43 patients with cervical spondylotic myelopathy found that the 20 patients who had surgery had improved functional status, pain, and neurologic symptoms at one year compared with those who were treated conservatively [39]. Surgically treated patients had worse baseline deficits.

●In another study, 49 patients with a mild functional deficit associated with mild to moderate cervical spondylotic myelopathy were assigned by coin toss to surgical versus conservative treatment [28]. Patients assigned to conservative treatment had a significantly better gait at six months but not at two years after treatment. A nearly statistically significant better gait at baseline in the conservatively treated group may have biased the results.

●Another randomized trial of 68 patients with mild to moderate signs of myelopathy identified no differences in neurologic outcomes at two or three years between those who received medical versus surgical treatment [14,37,74].

Conservative measures should remain in place after surgical therapy. Reported cases suggest that postsurgical patients remain vulnerable to the effects of high degrees of cervical mobility and to the effects of minor neck injuries [62,75]. One study reported that recurrent spondylosis occurred at unoperated levels at a rate of 2 percent per year [9].

Patients with acute deterioration — The development of acute myelopathy may occur in patients with cervical spondylotic myelopathy, even with only mild or no baseline deficits. An acute myelopathy may also be the first presentation for a patient with cervical spondylotic myelopathy. Relatively minor neck trauma may be sufficient to produce significant spinal cord injury in this setting, although this appears to be relatively rare in patients who were previously asymptomatic [12,76]. Among a cohort of 199 patients with asymptomatic cervical spondylosis, 14 traumatic episodes occurred over a 44-month median follow-up period with no association with the development of symptomatic myelopathy [12].

This is a neurologic emergency, requiring immediate neuroimaging for anatomic confirmation and prompt neurosurgical or orthopedic consultation [76,77]. High-dose intravenous corticosteroid treatment reduces cord edema and has been shown to improve outcomes in patients with acute spinal cord injury when given within eight hours of the injury [78]. The typical regimen is 30 mg/kg methylprednisolone, followed by an infusion of 5.4 mg/kg per hour for the first 23 hours.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Upper spine and neck disorders".)

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SUMMARY AND RECOMMENDATIONS — Cervical spondylotic myelopathy is the most common cause of myelopathy in older adults.

●Cervical spondylotic myelopathy results from a progressive degenerative process affecting the cervical vertebral bodies and intervertebral discs and causing compression of the neural and vascular elements in the adjacent cord. (See 'Pathophysiology' above.)

●There is no specific stereotyped presentation of cervical spondylotic myelopathy. Usually symptoms begin with an insidious onset of gait disturbance. Other common symptoms include sensory loss, and weakness and muscle atrophy in the hands, along with neck and arm pain. The examination usually reveals other myelopathic features. (See 'Clinical presentation' above.)

●Cervical spondylotic myelopathy must be distinguished from amyotrophic lateral sclerosis (ALS) and other cervical cord disorders. (See 'Differential diagnosis' above.)

●The diagnosis of cervical spondylotic myelopathy is made by correlating the clinical features with findings of cervical spondylosis and cord compression seen on a neuroimaging study, usually magnetic resonance imaging (MRI). (See 'Diagnosis' above.)

●The clinical course and prognosis of cervical spondylotic myelopathy is not well characterized. Patients can deteriorate progressively or in a stepwise fashion with long periods of stability. Some patients may deteriorate abruptly in association with a minor neck injury. (See 'Prognosis' above.)

●There are no large randomized trials on which to base treatment recommendations. For patients with mild, nondebilitating myelopathy we suggest surgical consultation for those at risk of neurologic deterioration (eg, active lifestyle, severe radiologic cord compression) (Grade 2C). Close neurologic follow-up should assess for deterioration when surgery is deferred. Conservative measures include intermittent neck immobilization, pain management, and restriction of high-risk or aggravating activities. For patients with more severe myelopathy or progressing deficits, we suggest surgical decompression (Grade 2C). (See 'Treatment' above.)

●Acute deterioration or an acute presentation with myelopathy in a patient with cervical spondylosis is a neurologic emergency. After confirmation of the diagnosis with MRI, patients should receive a surgical consultation. We suggest administration of intravenous methylprednisolone within eight hours of acute deterioration (Grade 2C). The standard dose is 30 mg/kg intravenous bolus, followed by an infusion of 5.4 mg/kg per hour for the first 23 hours. (See 'Patients with acute deterioration' above.)