This intensively researched paper is a study of nearly 3000 patients initially evaluated at primary care centers for low back pain.[ 1 ] Some were diagnosed with a component of neuropathic leg pain and another group had what the authors consider to be nociceptive referred leg pain. Such patients had non-neuropathic pain in a leg in association with low back pain. The authors conclude that there is “some evidence of higher levels of morbidity in low back leg pain patients with neuropathic pain.” This is hardly earthshattering. Primary care providers if they find evidence of neuropathic leg pain should be aware that this is more serious than if there is nociceptive leg pain. However, there is no overarching statistic that the authors of this paper present to confirm this conclusion. “More research is needed” is hardly helpful. They state that there is “some consistent evidence for worse back and leg pain related disability in LBLP (low back leg pain) patients with neuropathic pain.” Such conclusions are consistent with other published evidence, but the authors sought to confirm this by studying only those patients who presented to primary care centers. For a study that relied heavily on careful collation of scientific studies, there is a paucity of statistical inclusion in the results.

This study excludes patients who were diagnosed with lumbar spinal stenosis and “herniated discs,” as well as patients with diabetes, malignancy, fractures, cauda equina symptoms, multiple sclerosis, Guillain–Barre syndrome, HIV disease, rheumatoid conditions, and spinal cord injury. What does this mean? The authors are left with a group of patients with back pain of unknown origin, which is presumably the most common reason that one would consult a primary care physician.

To be diagnosed with neuropathic pain, the authors note that there must be evidence of somatosensory injury. It is unclear what the mechanism for this would be, given the exclusion of a vast list of known reasons for it to occur, including the most common – spinal stenosis and herniated discs. What is also unclear is the mechanism for nociceptive or referred leg pain with low back pain.

Certainly patients frequently experience a mixture of nociceptive and neuropathic pain symptoms, with one form dominant over the other, but it is unclear what the cause of non-neuropathic, nociceptive “referred” leg pain would be. The authors reference an open access paper that defines it as pain that “does not involve compression of nerve roots but is rather explained by a convergent afferent input on central neurons.” Such a phrase comes under the heading of “mumbo jumbo.” The term has an interesting origin, of which its essence is that “mumbo jumbo” can be exceedingly convincing. It is not, however, scientifically so.

It is important to note that this paper is, by the authors’ admission, not a meta-analysis. Clearly, a great deal of effort was made to filter down the available “wealth” of information to the twelve acceptable studies. In the end, this paper reads like the preamble to a future systematic evaluation of the full nature of the pain present in individuals who present to primary care providers under the umbrella of “low back pain.”

This is certainly a worthwhile goal.

References

1. Harrisson SA, Stynes S, Dunn KM, Foster NE, Konstantinou K. Neuropathic Pain in Low Back-Related Leg Pain Patients: What Is the Evidence of Prevalence, Characteristics, and Prognosis in Primary Care?. A Systematic Review of the Literature. J Pain. 2017. 18: 1295-312