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13 Articles in Volume 12, Issue #11
“Doc” Holliday: A Story of Tuberculosis, Pain, and Self-medication in the Wild West
"Doc's" Woman: Doc Holliday's Wife
Activation of Latent Lyme Disease Following Epidural Steroid Injection: Case Challenge
An Overview of Complex Regional Pain Syndrome and its Management
Extracorporeal Shock Wave Therapy: Applications in Tendon-related Injuries
Mission Impossible—Developing a Program to Help Chronic Pain Patients
New Ideas for Helping Difficult Pain Patients
Postoperative Pain Relief After Knee and Hip Replacement: A Review
Using Dynamic MRI to Diagnose Neck Pain: The Importance of Positional Cervical Cord Compression (PC3)
December 2012 Pain Research Updates
Best Practices For High-dose Opioid Prescribing
Does Sulindac Affect Renal Function Less Than Other NSAIDs?
The Bewildering Terminology of Genetic Testing

Using Dynamic MRI to Diagnose Neck Pain: The Importance of Positional Cervical Cord Compression (PC3)

It has become axiomatic that cervical pain and regional imaging often correlate poorly. Both degenerative disc disease and cervical pain are common among our patients. Yet, many have one apparently without the other. One diagnostic response is to discount the informative value of cervical imaging and rely more on history, symptoms, and physical signs. Another is to consider how to better image this area of complex anatomy, without discounting the primary importance of clinical findings.

As a dynamic structure, the cervical spine anatomy may be suspected of varying in conformation, depending on its orientation in flexion, extension, rotation, and lateral bending. However, accepted diagnostic imaging, especially by magnetic resonance imaging (MRI), most often has been static and limited to neutral positioning. Such convention ultimately may prove deceptive and fraught with bias.

Neck Pain and the Spinal Cord
General medical reviews describing “neck pain” often omit mention of any role attributable to the cervical spinal cord. Abnormalities of discs, facet joints, ligaments, nerve roots, and muscles are considered, but abnormalities of the cord itself generally are not.

Such abnormalities are discussed in reviews on cervical spondylotic myelopathy (CSM). Malcolm eloquently reviewed five different CSM syndromes: “the transverse lesion syndrome, the motor system syndrome, the central cord syndrome, the Brown Sequard syndrome, and the brachalgia and cord syndrome.”1 Each is associated with a different set of clinical signs and symptoms. Figure 1 provides an excellent example of cord compression using a traditional, static, neutral C-spine MRI protocol. In Dr. Malcolm’s review, he describes a case where the cervical spinal cord was compressed at 2 disc levels; after decompression, the cord was freed and there was evidence of cerebral spinal fluid flowing unimpeded within a widened cervical canal. If we accept these images as indicative of—or at least consistent with—CSM followed by resolution of its symptoms, then one may argue that we are compelled to similarly judge identical images obtained through dynamic imaging.

Figure 1. Sagittal MRI shows disc space collapse

Over 50 years ago, Olsson reported how position influenced cervical spinal canal diameter in the canine model.2 Penning expanded this evaluation to human spondylitic myelopathy in 1966.3 Much later, after the discovery of MRI, Muhle et al examined a cohort of 46 patients to assess the effect of conformational changes to the cervical canal in extension (30°) and flexion (50°).4 Cervical spinal stenosis was more commonly found at extension (48%) compared to flexion (24%, P<0.05). Further, 11% of the 46 patients had cord compression in flexion compared to 20% in extension. “Concerning the number of patients with cervical cord compression at flexion and extension, significant differences [P<0.05] were found in patients with degenerative changes at 4 segments compared with patients with 1 segment involvement,” noted the authors.

Classifying CSM
In an enlarged subsequent analysis (n=81), many of these authors collaborated with esteemed radiologist Donald Resnick to develop a classification system correlating the kinematic (positional) MRI with the degree of CSM.5 In patients with progressive degenerative disease of the cervical spine (stage I-IV spinal stenosis varied between a score of 0 [normal diameter canal and anatomy] to 3 [anterior and posterior impingement they call a “pincer effect”]). In neutral, advancing degenerative stage (I-IV) correlated with a 3 score of spinal cord compression: stage I (46%), stage II (26%), stage III (54%), stage IV (87%). This pincer appearance was accentuated in extension and reduced in flexion. Further, they remarked: “On the assumption that a reliable diagnostic indicator of the genesis of CSM is the demonstration of cord compression at the site of the cord lesion, kinematic MRI showed functional cord impingement in 4 of 6 patients [with stage IV disease], whereas no cervical cord compression was seen at the neutral position.” The authors suggest that the usefulness of obtaining additional flexion and extension MRI sagittal views reveals greater functional cervical cord impingement in extension, as well as better recognition of unsuspected cord compromise, which becomes more likely with advancing degenerative spondylitic stage.

In 2003, Chen et al reported similar findings.6 For 62 patients with cervical degenerative disease, 31% demonstrated functional cord compression in extension compared to 3% in flexion. Degenerative stage (P<0.001) and a neutral canal diameter of ≤10 mm (P<0.037) were predictive of cord compression.

Upright MRI also demonstrated similar findings,7 with more readily apparent cord compression in extension, along with recognition of reduced angular mobility, particularly at C4/5 and C5/6, in a study of 459 patients with cervical degenerative disc disease.8

Analogously, Muhle and Resnick also reported in 1998 how position affected neuroforaminal patency in patients with cervical radiculopathy.9 Dynamic MRI demonstrated that ipsilateral rotation and lateral bending increased nerve root compression consistent with what clinicians might expect with a positive Spurling test.

Use in Rheumatoid Arthritis
Another application of dynamic MRI is in very advanced rheumatoid arthritis (RA), which can lead to a potentially fatal atlantoaxial dislocation or subluxation from progressive destruction/laxity of the transverse ligament. In flexion, the odontoid process may compress the upper cervical cord, which is clinically expressed as Lhermitte’s sign, and if sufficiently forceful, can cause death. Traditionally, radiographs (x-rays) have been employed to identify this condition, but flexion-extension MRI views also have been studied. Dedicated MRI positioning devices have been engineered for patients with RA,10 as they have for patients with degenerative diseases,11,12 and some authors suggest that this imaging technique should be the diagnostic “study of choice for the upper rheumatoid C-spine” for presurgical staging.13

Positional Spinal Cord Compression Linked With FM
In 2002, Heffez also advocated viewing the cervical cord more dynamically with MRI. His suggestion was presented in the context of sorting out another complex presentation, fibromyalgia (FM), at a small meeting of the National Fibromyalgia Research Association, in Portland, Oregon. His analysis found that symptoms of FM and cervical myelopathy overlapped for many patients with FM. Further, he noted that when he surgically decompressed severe, comorbid myelopathy, FM symptoms (allodynia, fatigue, central sensitization, pain, dyscognition, sleep disturbance) often abated.14 Similar observations were made for FM combined with Chiari malformation.15

Figure 2. Sagittal neutral, flexion, and extension MR cervical spine images in a patient

To say that Heffez’s message was received with mixed responses would be overly generous. A furor built quickly to relegate it to near oblivion. Nary a clinician wanted to consider the specter of surgical intervention for 6 to 10 million American patients with FM.

In light of the above findings, beginning in 2003, radiologists working with the Pacific Rheumatology Associates began obtaining flexion-extension cervical spine MRI routinely for patients without additional charge. Positional cervical cord compression (PC3) was defined as clear, visually-confirmed abutment of the cervical cord, with a canal diameter measured at 10 mm or less
(Figure 2). (Of note, the typical cervical spinal canal can average 14 to 16 mm in men and 13 to 15 mm in women, depending on disc level and patient size.) Compression or abutment of the cord was often intermittent, and consistent with prior studies, with PC3 much more evident in extension rather than in flexion.

From a database that now exceeds 3,000 patients, a random two-month experience was reported in The Journal of Pain in 2008.16 Of 107 referrals to a suburban rheumatology office, 53 had FM by 2001 American College of Rheumatology (ACR) classification criteria,17 32 had an autoimmune or connective tissue disease, and 22 had chronic widespread pain (CWP) without sufficient allodynia (tender points) to confirm FM. PC3 was identified by flexion-extension C-spine MRI in 71% of the FM group and in 85% of the CWP group. Also, in only 15 of 52 patients identified with PC3 (21%) could the cord compression be visualized on the traditional, neutral sagittal MRI view. Thus, 80% of patients in this study with PC3 would not have been diagnosed using the MRI protocol available to most practicing clinicians.

Table 1. Neurologic Deficits commonly Found with PC3

A variety of symptoms suggestive of a myelopathic process were described by Heffez and were later seen in Seattle, WA, and in Portland, at Oregon Health and Sciences University. In addition to pain in an extended cervical position, patients reported having poor balance, variable dysesthesias, weakness, muscular cramping, headaches, widespread and migratory regional pains, fatigue, and poor sleep in both studies. Examination findings often revealed motor and sensory deficits (Table 1). Patients also characteristically reported dysautonomic features, including thermoregulatory, cardiovascular, gastrointestinal, and urological issues as well as mood disturbances (Table 2).

At least for the FM cohort, these findings have been supported independently. Hryciw found that 54% of her clinic patients with FM had PC3 by flexion-extension MRI.18 She also reported that 50% of those with PC3 had obstructive sleep apnea (OSA), a linkage of the cervical myelopathy with OSA also suggested by others. Parenthetically, 7 months after surgical decompression for Chiari malformation (without FM), the apnea hypopnea index was reduced significantly (80%) in 16 patients with a comorbid mixture of central and obstructive sleep apnea.19

Table 2. Dysautonomic Features Commonly Found with PC3

Neurologic deficits also have been reported in a controlled FM study, and PC3 was proposed as a reasonable explanation.20 In fact, these authors later suggested that in patients with FM, only a flexion-extension C-spine MRI protocol is acceptable, especially when a patient is being evaluated for a Chiari malformation.21

Such observations raise the prospect that while it is visually and, in many ways, clinically similar to CSM, PC3 may offer a twist. The intermittent component of compression documented by a flexion-extension MRI may add a dimension worth studying and discriminate PC3 from CSM. Certainly, there are many important clinical and therapeutic features that distinguish intermittent from chronic peripheral nerve compression/entrapment. The same may very well be true for the cervical spinal cord. Unfortunately, available data are insufficient to be conclusive. Yet, in animal models, intermittent abutment of the cervical cord (without injury or ischemia) is a potent trigger of autonomic arousal.22 And of note, similar abutment to thoracic and lumbar levels are not. Hence, there appears to be a curious connection between autonomic arousal and cervical cord irritation, and this observation may provide a rationale as to why FM—a potent dysautonomic, hyperexcitatory state—often is temporally related to cervical spine trauma.23,24

Summary
Regardless of whether there is a true connection between autonomic arousal and cervical cord irritation, dynamic imaging of structures confers more information and may assist in elucidating why there seem to be so many discrepancies between anatomy (as we see it so far) and symptoms. Application of enhanced imaging has had profound implications for many other areas of medicine. Those first steps were taken just as gingerly and sometimes as skeptically received. Yet, with further independent evaluation, the flexion-extension C-spine MRI may help ferret out a bit more of the mystical conundrum that is the cervical spine.

To learn about how to do a flexion-extension C-spine MRI, call Pacific Rheumatology Associates for video instruction. MRI technical settings are given in reference 16, Table 1.

Last updated on: December 20, 2012
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