Research Review By Dr. Rob Rodine©

Date Posted:

February 2010

Study Title:

Pain patterns and descriptions in patients with radicular pain: Does the pain necessarily follow a specific dermatome?

Authors:

Murphy DR, Hurwitz EL, Gerrard JK & Clary R

Author's Affiliations:

Rhode Island Spine Center; Department of Community Health, Alpert Medical School of Brown University; Department of Research, New York Chiropractic College

Publication Information:

BMC Chiropractic & Osteopathy 2009; 17: 9.

Background Information:

With the exception of rare causes (such as a synovial cyst) and more ominous space occupying lesions, the most common causes of radiculopathy are herniated intervertebral discs (IVD) and lateral canal stenosis (LCS). As a quick review, LCS can occur as a result of osteophyte formation and/or hypertrophy of the ligamentum flavum or zygapophyseal joints (facets).

In the acute herniated disc presentation, radicular pain is caused primarily by chemical reactions (remember embryology and the notochord?), although pressure on the nerve root can also play a role. In chronic discogenic and lateral canal stenosis patterns, pain is thought to be caused more by fibrotic changes that infringe upon the nerve roots, or through vascular congestion. Often, as in cervical radiculopathy, cases involve a combination of both discogenic and spondylotic components (1).

The challenge for clinicians is to distinguish radicular pain and radiculopathy – these terms are not synonomous. Radiculopathy is a symptom complex involving pain, motor loss and sensory changes. Radicular pain (or “nerve root pain”) may be a component of radiculopathy, but can occur on its own. This does not even take into account “referred pain” – which can be nociceptive, neurogenic, or psychological, and can occur in all regions of the body.

Whether discogenic, referred or spondylotic, extremity pain is often detailed by patients through the use of pain drawings which are designed to assist the clinician to visualize the symptom pattern they are experiencing. Even in the absence of pain drawings, it is common practice for clinicians to ask the patient to ‘identify’ where they feel the pain. This is then classified by the clinician as being referred pain, radicular pain or even psychogenic.

This classification is often done based on knowledge of basic anatomical science and on assumptions made from practical experience. A common assumption is that if the pain is not experienced within a specific dermatomal pattern, the pain is not radicular. A major fault of this assumption however, is that it is based on little clinical evidence.

Therefore, the purpose of this study was to determine whether radicular pain patterns correlated with dermatomal maps, and to assess the overall diagnostic utility of pain distribution patterns in patients with cervical and lumbar radicular pain.

Pertinent Results:

A total of 222 patients diagnosed with radicular pain at the Rhode Island Spine Center were identified. Fifty-three were excluded, most commonly for the absence of confirmatory imaging/EMG studies. 169 patients remained in the study, with 226 total involved nerve roots. Aside from reporting a 70% female distribution, no demographic analysis is provided.

Of the 226 involved nerve roots, the most common levels were:
  • L5 = 49
  • C6 = 40
  • S1 = 37
  • C7 = 37
  • L4 = 28
  • L3 = 13
  • C5 = 12
  • L2 = 5
  • C4 = 5
Multiple levels of involvement were demonstrated on special imaging in 24% of cases. Overall, 69.7% of cervical radicular pain and 64.1% of lumbar radicular pain was deemed to be non-radicular. However, when analyzed by level, C4 and S1 involvement were deemed to be dermatomal more frequently than other levels. For a more specific breakdown, observe the following: (D = dermatomal; Non-D = non-dermatomal):
  • C4 = 60% D, 40% Non-D
  • C5 = 25% D, 75% Non-D
  • C6 = 35% D, 65% Non-D
  • C7 = 34.2% D, 67.6% Non-D
  • L2 = 40% D, 60% Non-D
  • L3 = 30.8% D, 69.2% Non-D
  • L4 = 28.6% D, 71.4% Non-D
  • L5 = 16.3% D, 83.7% Non-D
  • S1 = 64.9% D, 35.1% Non-D
Scapular pain was present in only 51.6% of cervical radicular pain cases. A trend was observed that scapular pain was more frequent in patients with radicular involvement at the lower cervical levels, though this trend was not statistically significant.

There was however a significant correlate in the clinical cause of the radicular pain as 78.8% of patients with scapular pain were classified as having a herniated intervertebral disc (with or without lateral stenosis) as compared to 21.2% who were classified as having only lateral canal stenosis.

A total of 85% of patients described their pain as either aching or sharp, with no statistical difference noted between either at any noted level. Burning pain was reported in cervical radiculopathy in only 3.9% of cases, and in 8.4% of lumbar radiculopathy.

Clinical Application & Conclusions:

Three interesting clinical applications from this study are detailed: the first is that scapular pain is more commonly associated with disc herniations, as compared to lateral stenosis.

Second, the character of radicular pain is most commonly aching or sharp, as compared to a burning sensation. This correlates well to the work of Bove et al. (4) who looked at patient descriptions of radicular pain compared to clinical examination.

This study found that most patients described pain as deep in nature, compared to superficial, when provoked through nerve root tension tests. Combining this research, clinicians could speculate radicular pain more frequently when described as aching or sharp, and deep.

Additionally, with the exception of C4 and S1, the majority of radicular pain was experienced in a non-dermatomal pattern, calling into question the basic science assumptions of how clinicians typically classify pain. Therefore, clinicians should rely more heavily on pain description and positive nerve root tension tests that clinically correlate to special diagnostic testing, such as MRI and EMG, to more accurately diagnose radicular pain.

Lastly, while C4 most frequently demonstrated a radicular pain pattern, only five patients had radicular pain confirmed to this level, calling into question the strength of these findings.

Study Methods:

Patients who were seen at the Rhode Island Spine Center and deemed to have radicular pain from either the cervical or lumbar spine were eligible for inclusion in this retrospective chart review. Radicular pain was defined as extremity pain that was clinically determined to be caused by a nerve root (given evidence of a disc protrustion or lateral canal stenosis demonstrated on special imaging), or EMG documentation showing nerve root dysfunction combined with positive nerve root provocation tests which reproduced the extremity pain.

Provocation tests used to determine radicular pain included: the brachial plexus tension test, Spurling’s test, active cervical rotation, cervical distraction test (which aims to relieve pain), the straight leg raise and the femoral nerve stretch test. As tests such as the brachial plexus tension test, straight leg raise and femoral nerve stretch can produce results less specific to nerve root pain, structural differentiation maneuvers were used to increase the specificity of the tests towards nerve root pain. An example of this would be plantar flexion of the ankle (Braggard’s test) with the straight leg raise.

Patients also underwent thorough neurological assessment which covered sensory, motor and reflexive components. These test results were not used to classify pain as being caused by a nerve root, however their results were used to help identify/confirm the level of involvement and cross-correlate with special imaging.

Patients were excluded from the study if their extremity pain was not reproduced by nerve root provocation tests or if pain characteristics were not clearly drawn or detailed when collected in the retrospective chart review.

The pain drawings of included patients were examined by two individuals and compared to two reference dermatome maps (2-3). Pain was deemed to be dermatomal if it was contained within the designated areas from one of the two sources and correlated to the nerve root level involved. If part of the pain (or all) did not correlate with the designated dermatomal area, it was deemed non-dermatomal. When multiple levels were involved, combined patterns were used.

In addition to pain drawings, descriptive characteristics of pain quality, as well as the presence or absence of scapular pain in cases of cervical involvement were retrieved from file information.

Study Strengths / Weaknesses:

One shortcoming of this study is the omission of basic demographic information for the included patients. No details, other than gender, are provided on their demographics. Most importantly, no information is provided on how many patients demonstrated lateral canal stenosis, disc herniation or a combination of both, with the exception of those cases related to the presence of scapular pain. This data would draw needed epidemiological comparison to other research.

Aside from this, the study is strong in its approach and detail. Included patients were seen by one of two chiropractors (one the primary author of the paper who is a very well respected and published clinician). This author also performed the retrospective file review, identifying patients with radicular pain. Pain drawings were interpreted by two individuals who reached a consensus during disagreement. Statistical details on this agreement however were not presented, offering another methodological flaw.

Additional References:

  1. Radhakrishnan K, Litchy W, O'Fallon W, Kurland L. Epidemiology of cervical radiculopathy. A population-based study from Rochester, Minnesota, 1976 through 1990. Brain: A Journal Of Neurology 1994; 117 (Pt 2): 325-335.
  2. Martin & Jessell. Anatomy of the somatic sensory system. In Principles of Neural Science, 3rd ed. Edited by Kendel et al: Appleton & Lange; 1991: 353-66.
  3. Bates. A guide to physical examination and history taking, 4th ed. JB Lippincott, 1987.
  4. Bove et al. Subjective nature of lower limb radicular pain. J Manipulative Physiol Ther 2005; 28(1): 12-14.