The majority of literature available for this topic is composed of case reports, case series, small cohort studies, narrative reviews, and information from textbooks. Case series and reports are considered class of evidence IV. Nonetheless, these reports provided valuable information on factors pertaining to differential diagnosis. Formal critical appraisal was not performed for included citations because all the articles were case reports or case series.
Objective 1: Primary Diagnostic Features of CSM
The onset of CSM is insidious and usually progresses in a stepwise fashion.1 Diagnosis is based on history, physical examination, and imaging findings, but patients with CSM may be asymptomatic or may experience only slight arm or neck pain. The most common symptoms include numb or clumsy hands, impaired gait, neck and leg stiffness, and sensory disturbances in the arms or legs. Other signs include atrophy of intrinsic hand muscles, a positive Hoffman and/or Babinski sign, motor deficits, hyper-reflexia, a broad-based unstable gait, and bowel and bladder dysfunction.
Imaging studies are critical in the diagnosis and confirmation of CSM, and for visualizing the extent of cord compression. After plain radiographs, magnetic resonance imaging (MRI) is typically used as the first modality because it can determine the dimensions of the spinal canal and vertebra, the severity of spondylosis or other degenerative changes, the extent of cord compression, and anatomical defects.
As noted previously, CSM can present with a wide range of signs and symptoms and differing levels of severity, making it difficult to distinguish it from other conditions. It is therefore essential to identify the key differences between CSM and other diagnoses, using demographics, components of the physical examination, MRI, and other imaging modalities and tests, as well as pertinent patient history.
Objective 2: Conditions That Have Been Described in the Literature That Present Similarly to CSM
Table 1 summarizes reports on pathologies that may be confused with CSM and the general methods used for differentiation.
Congenital or Anatomic Conditions
Two reports, totaling 4 patients, attributed congenital anomalies as the cause for myelopathy; specifically, hypoplasia of the atlas and congenital cervical stenosis.2,3 In all cases, lateral radiographs raised suspicion for congenital anomalies, and MRI or computed tomography was used to confirm the diagnosis and better define the anatomy. In addition, MR image revealed myelomalacia in all patients as evidenced by areas of hyperintensity on T2-weighted and hypointensity on T1-weighted images of the spinal cord. Mean spinal canal diameters in cases of congenital stenosis were in the range from 7 to 9 mm.
Three reports presented atypical degenerative conditions as the etiology for progressive cervical myelopathic symptoms. Three cases of retro-odontoid disc herniation were reported in 2 studies, all of which were diagnosed by MRI, which revealed a soft-tissue mass compressing the medulla and upper cervical cord posteriorly, and confirmed by tissue diagnosis.4,5 The third study reported on 3 cases of synovial cysts, and found that contrast-enhanced MRI was a sensitive means of localizing the lesion in all patients.6 Specifically, an enhancing extradural lesion was seen located posterolateral to the cord and in close proximity to a facet joint, which was displacing the cord anteriorly. Tissue diagnosis was used to confirm the diagnosis. In all 3 reports, plain radiographs were used that revealed extensive degenerative changes in all patients.
Five reports presented 5 cases where the differential included neoplastic processes. In general, although some MRI findings were atypical for CSM, histological evaluation was needed for diagnosis confirmation.
Two of the reports described findings suggestive of intramedullary lesions.7,8 In the first report, severe multilevel spinal cord compression secondary to multilevel degeneration led to an initial diagnosis of CSM, and bilateral laminectomy was performed. Successive follow-up MRI demonstrated high signal intensities on T2; contrast enhancement was continually noted at C3–C4 and thought to be related to myelopathy progression at the stage of gliosis. The patient's neurological deficit progressively increased, and MRI was done 1.5 years after the initial surgery, revealing a 40-mm intramedullary lesion. At the second surgery (a cervical myelotomy), complete excision of a grade II intramedullary ependymoma was done.8 In the second report, findings of spinal stenosis and associated disc protrusions suggested CSM; however, absence of cord atrophy and extension of an intramedullary T2 signal beyond the spondylolotic region was considered atypical of CSM. Biopsy during laminectomy led to the diagnosis of primary intramedullary lymphoma.7
Three other reports described various other neoplastic processes.9–11 Patient age and prior history may have provided insight into the differential diagnosis relative to CSM for 2 of these. In one report, a 23-year-old patient with a history of quadriparesis secondary to infectious myelitis (at 13 yr) and surgery for osteochondroma of the left greater trochanter (at 15 yr) experienced severe neurological deterioration. Cervical MR image showed a mass measuring 22 mm, which had narrowed the spinal canal to 3 mm, compressing the cord, and showed an associated syrinx measuring 10 mm in craniocaudal diameter. Excisional biopsy of the mass led to the diagnosis of osteochondroma without abnormalities, suggesting malignant transformation. Consideration of patient history and age in this case may dissuade one from a diagnosis of CSM.9
In the second report, a 36-year-old female presented with a 2-month history of progressive quadriparesis and a previous episode of acute quadriplegia 14 months earlier, after a fall at home. MRI of the brain and spinal cord at that time revealed a hyperintense lesion on T2-weighted sequences from the midbrain to C5 with no contrast enhancement. The findings were considered secondary to the trauma. At the time of symptom recurrence, 10 months later, T2 MR images demonstrated lesions in the thalamus, which extended to the brainstem and C5 cord. Smaller lesions were seen in the cerebellar vermis and left hemisphere, and an initial diagnosis of recurrent myelitis was made. The patient became tetraplegic and developed respiratory failure. No abnormalities were found after evaluation for infectious or autoimmune disease. Brain biopsy revealed grade II astrocytoma with gliomatosis cerebri.11
In the third report, MRI and computed tomographic findings of a 63-year-old patient with a 10-year history of progressive weakness was consistent with ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum. At the time of cervical laminectomy, the dura had a woody quality and the ligamentum flavum was attached to the dura. Frozen section analysis confirmed a diagnosis of a calcified dural meningioma that mimicked ossification of the ligamentum flavum.10
Inflammatory or Autoimmune Diagnoses
Nine studies reported inflammatory or autoimmune processes that resulted in a symptom presentation similar to that of CSM.
Two studies reported one case each of pseudogout in the odontoid region.12,13 On MRI, the lesions were found to be nonenhanced and isointense to neural tissue on T1-weighted images, heterogeneous and hyperintense on T2-weighted images, and demonstrated peripheral enhancement with gadolinium. Computed tomographic scan showed linear calcification within the mass, and tissue diagnosis was used to confirm the diagnosis in both cases.
Three studies presented a total of 14 cases of spinal sarcoidosis mimicking CSM. In all 3 studies, a distinct high signal intensity area within the spinal cord was observed on T2-weighted MR image. In one study, gadolinium-enhanced T1-weighted MR image also revealed areas of focal enhancement, and lymph node biopsy confirmed the diagnosis in all 3 cases.14 In the second study, a subsequent radiograph showed bilateral hilar lymphadenopathy, establishing a diagnosis of sarcoidosis in the patient.15 In the third study, the standard uptake value of the FDG-PET (fluorodeoxyglucose positron emission tomography) scan was found to be of value in distinguishing sarcoidosis from other noninflammatory lesions in 10 patients: those with spinal sarcoidosis had significantly higher standard uptake value than patients with other diseases.16
Three reports described bacteria-related pathologies.17–19 One report described 2 cases of cervical epidural abscess resulting from Staphylocccus aureus infection.19 MRI was the diagnostic modality of choice in distinguishing the etiology of cord compression. In another case, a large area of edema from C1–T1 and atypically extended high T2 signal intensity on MR image, together with progressive neurological symptoms, favored a diagnosis of a neoplastic process. Histological examination, however, excluded tumor or myelitis and suggested an inflammatory reactive process.20
Six studies reported on idiopathic disease processes mimicking CSM, 4 of which investigated various electrophysiological methods of differentiating amyotrophic lateral sclerosis (ALS) from CSM. The first study measured motor-evoked potentials (MEP) from the trapezius muscle and found that although limb MEPs were abnormal in almost all patients (both ALS and CSM), trapezius MEPs were abnormal in all patients with ALS but normal in patients with CSM.21 The second study explored the diagnostic utility of electromyography (EMG) findings, and found that the distribution of EMG abnormalities differed between the 2 groups such that those with ALS had EMG findings in both the upper and lower limbs, whereas those with ALS-like symptoms caused by CSM had EMG findings only in the upper limbs.22 The third study evaluated sternocleidomastoid muscle EMG (SCM-EMG) and dermatomal somatosensory-evoked potentials and found that they were valuable diagnostic aids in differentiating between ALS and CSM: SCM-EMGs were abnormal in patients with ALS and normal in patients with CSM, whereas the opposite was true for dermatomal somatosensory-evoked potentials.23 The fourth study recorded responses of masseter muscles to transcranial magnetic stimulation and found that the activation of corticobulbar descending fibers was absent or delayed in the majority of patients with ALS but normal in all patients with CSM, providing a means of distinguishing the 2 conditions.24
One study reported a case of ALS coupled with an arachnoid cyst that presented with symptoms of CSM. Myelography was not helpful in distinguishing CSM from ALS; instead, a careful neurological examination, biopsy of the gastrocnemius muscle, and EMG ultimately led to the proper diagnosis.25
Another study reported a patient who was originally diagnosed with ALS.26 Thirteen years later, after a cervical MRI and androgen gene analysis (prompted by the presentation of gynecomastia), the patient was diagnosed as having coexisting CSM and Kennedy syndrome. Kennedy syndrome is caused by androgen receptor gene mutations, resulting in damage to the brainstem and spinal cord motor neurons as well as spinal bulbar muscular atrophy. The CSM was identified by both the presence of spondylosis and intramedullary signal changes on the T2-weighted image.
Eight reports described cases of vascular pathologies.27–34
Three reports described findings of altered vascular anatomy on MRI that would help differentiate AVM, AV fistula, and other anomalous vasculature from CSM.28–30 Angiographic findings confirmed the diagnosis in all but one report.29 MR angiography was used in that particular case to verify the presence of an intradural AVM.
Two cases of dural AV fistula presented with diffuse swelling and hyperintensity of the spinal cord with flow void signals. Angiography was then used to further delineate the vascular abnormality.33
Two reports on 3 cases of spontaneous spinal epidural hematoma were based on MRI findings of fluid collections.31,32
Findings in an older (1974) case of arteritis included description of “chalky-white” paleness of the spinal cord during laminectomy. Random, patchy areas of demyelination with abnormalities in intra- and extramedullary vasculature as well as minimal spondylosis were found at autopsy leading to the conclusion that myelopathy was because of nonhemorrhagic vascular disease.27
Two studies reported on one case each of intraspinal tumoral calcinosis of the cervical spine causing progressive myelopathy.35,36 MRI revealed a posterior extradural mass resulting in spinal cord compression that seemed isointense and heterogeneous on T1- and T2-weighted images, with marked enhancement after the administration of gadolinium. Tissue analysis showed calcium deposits and foreign body giant cells inside a fibrous capsule, features indicative of tumoral calcinosis.
Objective 3: Role and Limitations of Various Diagnostic Tests in the Assessment of CSM
The role of a thorough neurological and radiographical evaluation of a patient with suspected CSM plays an integral role in arriving at the correct diagnosis. However, no diagnostic test is 100% sensitive or specific in diagnosing a given disease process, and recognition of the limitations of the neurological and radiographical evaluation is important to ensure less common diagnoses are not overlooked.
A thorough neurological examination in evaluating a patient with CSM includes motor and sensory examination in addition to a reflex examination and an assessment of provocative signs. The presence of hyper-reflexia and/or provocative signs may indicate CSM. A prospective study by Rhee et al37 demonstrated that although provocative signs such as the Hoffman and inverted brachioradialis reflex were more prevalent in patients with cervical myelopathy, hyper-reflexia was not. In addition, up to 20% of patients did not have these provocative signs despite having myelopathy. This calls attention to the importance of having corresponding radiographical findings in addition to pertinent physical examination findings.
Radiographical evaluation in patients with CSM usually demonstrates cord compression with or without signal change within the spinal cord. There are conflicting reports on the significance of cord compression with cord signal change on patient presentation and prognosis. Although it is generally accepted that the presence of T1 hypointensity with concurrent T2 hyperintensity is a sign of more severe disease states, the presence of isolated T2 hyperintensity is of uncertain significance.
Cerebrospinal fluid (CSF) profiles are important in differentiating several neurological diagnoses.38 Although several biomarkers and substances have been identified, clinical decisions are primarily based on general findings including pigmentation, leukocyte count, protein content, and glucose levels. Table 2 presents the CSF profile for pathologies presenting similar to CSM.38–46
In the context of diseases of the spine and spinal cord, CSF profiles can help distinguish between neoplastic, vascular, infectious, inflammatory, or degenerative disorders.38 In the absence of infection, an elevated WBC count is representative of an inflammatory or demyelinating disorder.38 These can include systemic lupus erythematosus, Sjogren syndrome, sarcoidosis, neuromyelitis optica, or multiple sclerosis (MS).
Electrodiagnosis using either EMG, electroneurography or NCS, or evoked potentials may aid in differentiating between patients with spondylotic neural compression and those with mimicking diagnoses. Table 2 present common electrodiagnostic findings in diagnoses that often present similar to CSM.47,48
EMG assesses the activity of muscle cells by repeatedly stimulating receptors of the sensory system and measuring resultant cortical activity.47,48 On the EMG in pathological states at rest, insertion activity may be absent in the case of various neuromuscular disorders, reduced in metabolic disorders, or prolonged in denervated muscle.47 Although fasciculation potentials may be present in normal muscle, they are also useful in diagnosing patients with chronic partial denervations, including ALS. Alterations in motor unit potentials may also aid in diagnosing certain disease: double discharges occurring at the beginning of voluntary contractions may indicate disorders of the anterior horn cells, roots, and peripheral nerves; myokymic discharges may reflect patients with radiation myelopathy, MS, chronic radiculopathy, entrapment neuropathy, or syringomyelia; and neuromyotonic discharges may be present in patients with peripheral axonal or demyelinated neuropathy.47
NCS are valuable in quantifying motor and sensory conduction velocities of peripheral nerves.47,48 This is done by placing 2 electrodes at different points along a peripheral nerve: the interval between the stimulus and recorded response is measured and divided by the distance between the 2.47,48 NCS are less important in detecting CSM but can help delineate underlying sensory radiculopathies and peripheral nerve entrapment syndromes such as carpal tunnel syndrome.47 Patients with bilateral sensory complaints in the hands should be presumed to have cervical cord pathology and should undergo cervical MRI even if the EMG/NCS suggest bilateral carpal tunnel syndrome. Electrodiagnostics can lead to false positives and are frequently done and misinterpreted—leading to delays to diagnosis and treatment.
Objective 4: Entities That Are Most Likely to be Confused With CSM and Distinguishing Diagnostic Features Between the Differential Diagnosis
As suggested by 2 textbooks, Harrison Internal Medicine and Clark Cervical Spine, the 4 major differential diagnoses of CSM include ALS, MS, syringomyelia, and metabolic disorders such as vitamin B12 deficiency (Tables 2, 3).49,50
ALS is a debilitating upper and lower motor neuron disease that manifests in the fourth to sixth decade of life, similarly to CSM.49 It often presents with symmetrical muscular weakness of the shoulders, fasciculation and atrophy of the upper limbs, and muscular spasticity.49,50 The absence of pain and sensory changes; the presence of tongue fasciculations; normal bladder and bowel function; and unimpressive roentgenographic studies of the spine all favor ALS over CSM.50 A recent study of protein contents in the CSF identified 3 biomarkers that are specific to patients with ALS. In one study, cystatin C, a proteolytic fragment of VGF, and a third protein species were found to be significantly lower in patients with ALS than in control subjects.51 In a second study, Ranganathan et al42 reported that patients with ALS had decreased levels of cystatin C along with decreased transthyretin and increased carboxy-terminal fragment of neuroendocrine protein 7B2. The best biomarkers for distinguishing ALS from other neurodegenerative diseases and healthy subjects are erythropoietin (decreased),39 hepatocyte growth factor (upregulated),45 monocytic chemotactic protein (increased),46 neurofilament light and heavy subunits (upregulated), and cystatin C and transthyretin.41
MS presents much earlier than CSM, in young adults 20 to 40 years of age, but still resembles CSM in terms of signs and symptoms.49 For example, patients with MS display relapsing symptoms involving the white matter tracts and, similarly to CSM, may present with L'Hermitte phenomena, and motor, sensory, and bladder/bowel dysfunction.50 Diagnosis may not be MS if (1) symptoms are localized to the spinal cord; (2) patients are younger than 15 or older than 60 years of age; (3) the disease is progressive in nature; and (4) there is a lack of visual dysfunction.50
Syringomyelia refers to a disorder in which abnormal fluid-filled cavities or cysts form in the spinal cord.49,50 The symptoms begin earlier than those of CSM, but, like CSM, its onset is insidious and progresses irregularly.50 Symptoms include sensory loss, aflexic weakness and atrophy in the upper limb, leg spasticity, bladder and bowel dysfunction, and Horner syndrome.50 On the basis of a number of overlapping symptoms, it is apparent that syringomyelia should be included in the differential diagnosis of CSM.
Vitamin B12 deficiency can also lead to symptoms similar to CSM including sensory and motor deficiencies and gait ataxia. Deep tendon reflexes are usually absent or severely diminished, whereas pathological reflexes (Babinski sign) are present. Usually these neurological findings are present with symptoms of dementia and/or other psychiatric symptoms. Patients with a history of pernicious anemia or GI abnormalities who present with symptoms of gait ataxia and motor or sensory deficits should have a high index of suspicion for Vitamin B12 deficiency.
Finally, spinal tumors compressing the cord may also produce signs and symptoms similar to CSM.50 Other important diagnoses include any condition that can result in cord compression, including compressive, noncompressive, and chronic myelopathies.49,50
Evidence-based clinical recommendations are not possible from this review because the topic and approach did not lend itself to formal systematic review based on accepted methodological principles. However, our review of selected literature provides valuable insight into diagnostic methods for distinguishing CSM from other types of pathology.
It is clear that initial radiographs and MRI are invaluable tools for arriving at the correct diagnosis of CSM. If a patient presents with physical examination findings consistent with myelopathy, and MRI findings that correspond to spondylosis as the cause of spinal cord compression, the diagnosis of CSM can almost always be confirmed. In those instances where the MRI does not correspond to the physical examination findings, further imaging and workup is necessary. Contrast studies with MRI can also be valuable because tumors and circulatory and inflammatory processes can have distinct patterns of enhancement in patients without CSM, whereas patients with CSM will not show any. Plain radiographs are useful for identifying spondylosis, although quantifying the extent of spinal cord compression is difficult with plain radiographs alone. In addition, the visualization of the anatomy on plain radiographs can heighten suspicion for congenital stenosis. Specifically, the location of the posterior arch of C1 lamina should be more posterior with respect to the C2 lamina. In the subaxial cervical spine, if the spinous processes in the subaxial cervical spine are directly adjacent to the facet joints on the lateral radiograph, this may be a sign of congenital stenosis.
In deciphering ALS from CSM, our literature review consistently revealed that the reoccurring characteristic unique to ALS was the presence of findings cranial to the cervical spine. Specifically, electrodiagnostic studies such as EMG of the SCM and the upper and lower extremity, as well as monitoring of somatosensory-evoked potentials, can be distinguishing characteristics. These studies can be used if a patient presenting with myelopathic symptoms demonstrates an absence of spondylosis in the cervical spine and a completely open spinal canal without any areas of compression. In ALS, EMG will demonstrate findings in both the upper and lower extremity, whereas patients with CSM will usually only exhibit findings in the upper extremities. Of course, this can be confusing if patients also have concurrent lumbar spondylosis because they too may have EMG findings in the lower extremity.21,22,24 In such cases, electrodiagnostic studies of the SCM or somatosensory-evoked potentials can be useful in distinguishing the diagnosis. Specifically, patients with ALS will have an abnormal SCM study. These characteristic features can guide the spine physician's diagnostic workup.
In MS, patients will usually have a history of visual symptoms. In addition, patients with MS are usually of a different epidemiological cohort—usually younger females between the ages of 20 and 40 years.49 In addition, areas of high signal intensity can be found within the brain as well. These findings can distinguish CSM pathology from MS.
It is important to be mindful that pathologies can exist concurrently with CSM. There have been reports on patients with bilateral carpal tunnel syndrome who underwent carpal tunnel release without relief, who subsequently were diagnosed as having CSM.52,53 In some cases, the conditions coexisted, and despite carpal tunnel release, relief of symptoms was not obtained. Such situations may demonstrate carpal tunnel syndrome on EMG studies; however, this does not necessarily eliminate the possibility where CSM is coexistent. Distinguishing bilateral carpal tunnel syndrome from CSM is based on the absence of signs of cord compression seen in patients with carpal tunnel syndrome. Specifically, proximal lower extremity weakness, hyper-reflexia, Hoffman sign, and a positive Rhomberg test might provide an indication that the patient may have CSM. In addition, inspection of the hand in carpal tunnel syndrome can demonstrate thenar wasting but will not usually demonstrate concurrent atrophy of the lumbrical muscles. This is because the motor fibers to the abductor pollicis brevis are located in the ventrolateral aspect of the median nerve and are therefore more prone to compression, whereas the motor fibers to the lumbricals are located more dorsally.54
Vitamin B12 deficiency can also lead to symptoms similar to CSM, including sensory and motor deficiencies and gait ataxia. Deep tendon reflexes are usually absent or severely diminished, whereas pathological reflexes (Babinski sign) are present. Usually these neurological findings are present with symptoms of dementia and/or other psychiatric symptoms. Patients with a history of pernicious anemia or GI abnormalities who present with symptoms of gait ataxia and motor or sensory deficits should have a high index of suspicion for vitamin B12 deficiency.
In most cases, CSM can be diagnosed with confidence based on the physical examination findings and correlative radiographical findings on plain radiograph and MRI. In cases where a thorough neurological examination reveals findings that are inconsistent, or if radiographs are inconsistent with cord compression, a thorough knowledge of pathologies that are in the differential diagnosis for CSM is paramount for arriving at the correct diagnosis (Table 2).
Summary Statements. Physical examination findings are not always consistent with severity of disease in CSM; therefore, correlation to plain radiographs, MRI, and patient symptomatology is essential for arriving at the correct diagnosis. In some cases where these studies are still equivocal, use of other studies should be considered including electrodiagnostic studies as well as cerebrospinal fluid examination.
- MRI is an invaluable tool in the diagnosis of CSM.
- ALS is distinct from CSM in the presence of cranial nerve involvement (CN XI) and the absence of pain or sensory changes.
- Electrodiagnostic studies demonstrate distinct characteristics in ALS vs. CSM.
- MS can be distinguished from CSM in the presence of visual symptomatology as well as a patient demographic that is much younger.
- Physical examination findings are not always consistent with severity of disease in CSM; therefore, correlation with plain radiographs, MRI and patient symptomatology is essential for arriving at the correct diagnosis.
- Patients with bilateral sensory complaints in the hands should be presumed to have cervical cord pathology and should have cervical MR imaging even if the EMG/NCS suggest bilateral carpal tunnel syndrome.
The authors thank Nancy Holmes and Ms. Chi Lam, for their administrative assistance (and others at authors’ discretion).
Author contributions are as follows: H.J.K.: Literature search and evaluation, manuscript drafting, and revision; K.D.R.: Literature evaluation, manuscript drafting, and revision; E.M.M.: Literature evaluation, manuscript drafting, and revision; P.M.A.: Literature evaluation, manuscript drafting, and revision; L.T.: Literature search and evaluation, manuscript drafting, and revision; A.C.S.: Literature search and evaluation, manuscript drafting and revision; and E.D.B.: Literature search and evaluation, manuscript drafting and revision.
Supplemental digital content is available for this article. Direct URL citation appearing in the printed text is provided in the HTML and PDF version of this article on the journal's web site (www.spinejournal.com).
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