Background/Purpose:

In 1998, C Muhle and D Resnick proposed a corollary to cervical spinal stenosis caused by intermittent abutment of the cervical spinal cord from dynamic shifting of degenerative discs with flexion and extension of the neck.¹ This positional cervical cord compression (PC3) has been documented in 54-71% of patients with fibromyalgia (FM)^2,3 and was an exclusion criterion in the pramipexole FM randomized controlled trial⁴.  In animal models, PC3 is a potent sympathetic nervous system arousal⁵. 

In humans, PC3 is so difficult to distinguish from FM (without dynamic imaging) that its validity and impact have been questioned. Given PC3 and FM symptom overlap, a blinded study was conducted.

Methods: Patients diagnosed with fibromyalgia per American College of Rheumatology 1990 classification criteria were recruited from the Seattle area and after consent, were provided standard, non-contrast cervical spine magnetic resonance imaging (MRI) with two additional saggital flexion and extension views with spinal canal diameter measurement at each disc level.  PC3 was defined by a canal narrowing below 10 mm at any level WITH clear visual abutment of the cervical spinal cord by the commensurate disc and ligamentum flavum².

Double-blinded to the MRI results, subjects were assessed by history, physical examination, and a variety of surveys, including the Multidimensional Health Assessment  Questionnaire (MDHAQ), Fibromyalgia Impact Questionnaire (FIQ), Short Form Health Survey (SF-36), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), Health Assessment Questionnaire (HAQ), 16-item Quick Inventory of  Depressive Symptoms (QIDS) as well as autonomic nervous system (ANS) assessment by 5-minute, frequency domain, heart rate variability (HRV) of parasympathetic, sympathetic and total power measures (Omegawave Ltd, Espoo, Finland).  Statistical analysis was conducted using Wilcoxon rank-sum for continuous variables and Fisher’s exact test for categorical variables.

Results: Fifty-four patients with FM participated in this study (92% women, mean age 45.2 years).  PC3 was identified in 31 of 54 subjects (57.4%).  All three ANS HRV measures demonstrated statistical significance.  Consistent with animal model data, parasympathetic score was lower 0.145 ± 0.067 for PC3+ patients and higher 0.198 ± 0.098 for PC3- patients (p=0.029).  Sympathetic score was higher 61.0 ± 17.5 for PC3+ patients and lower 46.2 ± 15.8 for PC3- patients (p=0.005).  Total power score was lower 440 ± 492 for PC3+ patients and higher 1633 ±4232 for PC3- patients (p=0.022).  No clinical, historical or survey measures distinguished PC3-FM+ patients from PC3+FM+ patients.

Conclusion: This study provides the first evidence that intermittent, positional abutment of the cervical cord is a potent sympathetic arousal in humans.  It also highlights the challenge of diagnosing and addressing PC3 without imaging.  Further investigation will to sort out the role of PC3 in the diagnostic conundrum of FM, its pathogenesis and its treatment algorithms.

1.  Am J Neuroradiol.  1998;19(9):1763-71.  2. J Pain 2008;9(7):613-22.  3. Presented at MYOPAIN 2010, Toledo, Spain.  4. Arthritis Rheum 2005;52(8):2495-2505.  5. Neuroscience 1999;88(3):959-973.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fibromyalgia-and-positional-cervical-cord-compression-differ-only-by-autonomic-nervous-system-consequences-a-double-blinded-prospective-study/