Research review: Observed patterns of cervical radiculopathy vs. standard ‘netter-diagram’ distributions

Shawn Thistle
April 16, 2019
Written by
Study Title:Observed Patterns of Cervical Radiculopathy: How Often do They Differ from a Standard, "Netter-diagram" Distribution?
Authors:
McAnany SJ, Rhee JM, Baird EO et al.

Publication Information:
The Spine Journal 2018; pii: S1529-9430(18)31090-8. doi: 10.1016/j.spinee.2018.08.002. [Epub ahead of print]

 

Background info
Clinicians are traditionally taught that cervical radiculopathy presents in reproducible, consistent myotomal and dermatomal patterns, with the pattern attributable to the involved cervical nerve root (1-3). The presentation of radicular symptoms, confirmed by advanced imaging, is a cornerstone of diagnosis, especially in patients seeking surgical treatment for refractory radicular syndromes. 

In clinical practice, however, patients often do not fit the standard, textbook definition of symptomatology (i.e. per the ‘Netter diagram’ standard we were taught) (4). As such, identification of the affected nerve root level can be difficult, leading to potential misdiagnosis and/or inappropriate or ineffective treatment. 

Anatomical brachial plexus variability has been suggested as a potential explanation for the non-standard presentation of radicular symptoms. To illustrate, anatomic dissections suggest that a typical ‘textbook’ brachial plexus is only observed in 37-77% of humans (6-8)! Likewise, there is limited data available on the magnitude and frequency of this variability in real-world settings. Therefore, the purpose of this study was to examine cervical radicular patterns in a surgical population of patients undergoing single-level anterior cervical discectomy and fusion (ACDF).

Pertinent results
239 patient records were reviewed and found to meet the complete set of inclusion criteria. Cervical levels involved within this patient group included: C3-4: 15; C4-5: 24; C5-6: 108; C6-7: 85; C7-T1: 7 (of course, C5-6 and C6-7 are the most common levels for cervical radiculopathy). There were no differences between the two groups (standard ‘Netter’ presentation vs. non-standard) with respect to average age, weight, BMI, gender or duration of symptoms. Significantly more patients in the standard group presented with right-sided symptoms (p = 0.0003). 

Distribution of Symptoms Relative to ‘Netter’ Standard:

  • Only 129 patients (54%) fit the standard (‘Netter’) presentation; 110 (46%) had a non-standard presentation. The 2 most common levels were C5-6 and C6-7, at which 50.9% and 44.7% of patterns were non-standard (p = 0.35).
  • Ipsilateral neck pain was the most prevalent presenting symptom, found in 193 (81%) patients – this did not differ by cervical level (p = 0.72). Shoulder pain was reported in 142 (59.4%) patients and also did not differ by cervical level (p = 0.21).
  • 46 patients (19.2%) presented with isolated neck/shoulder pain with no distal radiation, most commonly at C3-4, occurring in 60% of those patients (p = 0.001). At C5-6 and C6-7, pain without distal radiation was present in only 16.7% and 13.3% of patients, respectively. Conversely, at C3-4 and C4-5, distal symptoms were present in 40% and 66.7% of patients, respectively, with 9/24 (37.5%) of C4-5 patients displaying symptoms below the elbow.
  • Binary logistic regression indicated that the model itself is valid for the analysis being performed (X2 = 16.5, p = 0.04). None of the demographic variables were found to significantly impact the likelihood of presenting with non-standard radicular patterns.
Clinical application & conclusions
Standard, ‘Netter-diagram’ patterns of cervical radiculopathy were observed in only 54% of patients undergoing single-level ACDF. As such, the need for careful assessment of associated symptoms (neurological, physical, radiological, etc.) is underscored. Non-standard presentation in patients with C3-4 and C4-5 pathologies was relatively common and patients with C3-4 or C4-5 radiculopathy complained largely of only proximal symptoms. Clinicians must take care in identifying the causative levels of injury, as radicular symptom presentation does not regularly adhere to the accepted patterns we are taught!

Study methods
Records from patients with single-level radiculopathy who underwent anterior cervical discectomy and fusion (ACDF) performed by one of six surgeons at an academic medical centre between March, 2011 and March, 2016 were examined. 

Inclusion criteria (all were required):

  • age 18+
  • advanced imaging showing nerve root compression at the level of surgery
  • no cervical spinal cord compression on advanced imaging
  • refractory symptoms involving upper limb/neck
  • minimum 75% reduction in pre-operative symptoms after primary ACDF by the six-month post-op follow-up
Eligible patients also were required to have undergone a minimum 3-month course of non-operative treatment prior to being considered surgical candidates. 

Demographic variables including age, gender, weight, BMI, laterality of symptoms, duration of symptoms and presence of diabetes mellitus were collected. Observed patterns of radiculopathy were compared to standard textbook patterns as defined by Keegan and Garrett (4) used in Frank Netter’s anatomic drawings (5).

Strengths:

  • Reasonable sample size for this type of study
  • High threshold for degree of improvement of symptoms
  • Strong statistical analysis plan
Weaknesses:

  • Retrospective design (however, for this topic it should not be considered a fatal flaw)
Additional references
  1. Carette S, Fehlings MG. Clinical practice. Cervical radiculopathy. The New England journal of medicine 2005; 353: 392-399 DOI: 10.1056/NEJMcp04388.
  2. Ellenberg MR, Honet JC, Treanor WJ. Cervical radiculopathy. Archives of physical medicine and rehabilitation 1994; 75: 342-352.
  3. Fouyas IP, Statham PF, Sandercock PA. Cochrane review on the role of surgery in cervical spondylotic radiculomyelopathy. Spine 2002; 27: 736-747.
  4. Keegan JJ, Garrett FD. The segmental distribution of the cutaneous nerves in the limbs of man. Anat Rec 1948; 102: 409-437.
  5. Netter FH. Atlas of Human Anatomy. 6th ed. Philadelphia: Saunders/Elsevier; 2015.
  6. Lee HY, Chung IH, Sir WS et al. Variations of the ventral rami of the brachial plexus. J Korean Med Sci 1992; 7: 19-24 DOI: 10.3346/jkms.1992.7.1.19
  7. Matejcik V. Variations of nerve roots of the brachial plexus. Bratisl Lek Listy 2005; 106: 34-36.
  8. Uysal, II, Seker M, Karabulut AK et al. Brachial plexus variations in human fetuses. Neurosurgery 2003; 53: 676-684; discussion 684.

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