There is nothing called a pain “nerve”, pain fibre, or pain signal

No-pain-fiber

There are however noxious stimulus, nociceptors, nociception, and nociceptive neurons. Nociceptors are specialized peripheral sensory neurons that alert us to potentially damaging stimuli by detecting extremes in temperature, pressure or injury-related chemicals. Nociception, however, a potent modulator of pain, but not the only one.

It is vital that we as clinicians and professionals do fall in the trap of doing this “unfortunate trivialization” as Dr. Wall called it. We must use “one set of words for a stimulus event and another for a perceived sensory event” (1). Nociception does not equal pain. 

“The labeling of nociceptors as pain fibers was not an admirable simplification but an unfortunate trivialization. The writers of textbooks will continue to purvey trivialization under the guise of simplification. The experimental results show that the final analysis that produces the perception of pain is not monopolized by the peripheral receptor properties of nociceptors. The response of nociceptors is one of the factors incorporated into the central analytic mechanisms that can generate many perceptual syndromes including pain.” Wall et al. 1986

Or as Prof. Wall stats more plainly in his book “Pain The Science of Suffering”:

“Tissue damage and pain are not so intimately linked that the two can be considered equivalent. We must therefore be very cautious and use one set of words for a stimulus event and another for a perceived sensory event.” 

A quick test I use to asses if a colleague, doctor, fellow health care provider, researcher or teacher has an informed and updated view and opinion about pain, is if they use erroneous taxonomies and words, like pain “nerve”, pain fiber, or pain signal. If they do that, with a high likelihood, they have dogmatic and outdated views about pain.

We must as professionals be aware that our client’s expectations (2) can influence their pain. So there is a real risk if we use this erroneous language that is can negatively affect and increase the pain of our clients. The same pain that we are trying to liberate them from, and that they come to us as professionals to be liberated from.

The current guidelines (3) go even a step further and say that clinicians should not utilize pathoanatomical explanations for the specific cause of the patient’s pain (low back), or any strategies that (directly or indirectly) increase the perceived threat or fear associated with the patient’s pain.

References:

1. Wall P, McMahon S. The relationship of perceived pain to afferent nerve impulses. Trends Neurosci. 9(6), 254–255 (1986).

2. Cormier S, Lavigne GL, Choinière M, Rainville P. Expectations predict chronic pain treatment outcomes. Pain. 2016 Feb;157(2):329-38.

3. Delitto A, George SZ, Van Dillen LR, Whitman JM, Sowa G, Shekelle P, Denninger TR, Godges JJ. Low back pain. J Orthop Sports Phys Ther. 2012 Apr;42(4):A1-57. Epub 2012 Mar 30.