Pain Threshold and Pain Tolerance in Fibromyalgia

Pain Threshold and Pain Tolerance in Fibromyalgia

By: Dr Alex Robber

Pain threshold

There is an overwhelming misunderstanding that still persists when it comes to understanding the degree of pain people feel with Fibromyalgia. The explanation for this misunderstanding is that in fact there are two distinct words used to describe pain levels.

The word ‘ pain threshold’ describes the level at which the body perceives a sensation as painful at first. The word “pain tolerance” has a completely different meaning, which simply describes how much pain an individual can actually take without breaking. We may think of tolerance as the “level of acceptance” of a current pain.

Fibromyalgia has a low threshold and most often very high pain tolerance

People who suffer from fibromyalgia have a low threshold and most often very high pain tolerance. This is partly true because the concentrations of substance P in the cerebral spinal fluid were found to have greatly increased. Substance P is a neuromodulator (a substance which changes the effectiveness of the neurotransmitter) which helps us to perceive a stimulus as painful.

Interestingly, there are some rare medical conditions in which substance P is very small or completely absent, and a person feels little or no pain. That may initially seem like a blessing, but it can actually be very dangerous because there is then no “trigger pain” when there is a critical condition in the body this requires treatment. Do you imagine how serious it would be if someone with acute appendicitis did not feel any pain and had a rupture in the appendix?

Pain Thresholds and Fibromyalgia

The pain levels vary from person to person and research suggests that fibromyalgia is abnormally low. That is why in those with this condition events that are not painful to most people will cause pain. Allodynia is the medical term for pain caused by things which do not usually hurt. In fibromyalgia the threshold of pressure pain (the point at which pressure is painful) is a common focus area for researchers.

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The explanation behind the tender-point test is a low-pressure pain tolerance which is a standard diagnostic procedure for the disorder. Two research investigated whether a blood pressure cuff can be used by physicians as a quick way to identify patients who should be treated for fibromyalgia. Each concluded that the definition of a low pressure-pain threshold is a reasonably accurate tool.

Effects of exposure to pain

“Daily exposure to painful stimuli is widely believed to improve pain tolerance–that is, increase the individual’s ability to tolerate pain by becoming more accustomed to it. This is not true though the increased exposure to pain will lead to more painful potential exposures. Repeated exposure bombards pain synapses with repeated feedback, increasing their responsivity to later stimuli through a learning-like method.

Therefore, although the person may learn to cope with pain through cognitive methods, these methods may not be sufficient to cope with the boosted response to potential painful stimuli. “The cells are potentiated by an intense bombardment of painful stimuli to respond to pain so that they will respond more vigorously to mild stimulus in future.

What contributes to central sensitization of pain perception where nociceptive neurons are sensitized by peripheral tissue damage or inflammation in the dorsal horns of the spinal cord, was this form of sensitization suggested as a potential causal mechanism for chronic pain conditions?

Role of normal levels of substance P

Obviously having a normal level of substance P is the ideal situation where the body tells you exactly what it should feel and at the appropriate level it perceives pain. Look at the diagram below and you’ll get a general idea of how Substance P works.

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You can see that nerve impulses and pain transmission is quite complex and requires many more chemicals, but substance P plays a very important role. Now with substance P elevation, as in fibromyalgia, a feeling which should be perceived as natural is experienced as painful.

The name for an enhanced perception of pain in this disorder is hyperemia. Sometimes even a light touch on the skin can feel like burning and I’ve seen a lot of patients who can’t even stand to have their legs covered by the bed sheets at night. For Fibro patients, a relatively small muscle strain due to over-exertion sometimes induces a totally inappropriate severe pain level and then causes unnecessary muscle splinting and spasm which then has a spiraling effect downwards.

The body overreacts due to an erroneous indication of pain caused by high P substance and begins what I call “symptom cascading.” A simple discomfort becomes a serious pain that can sometimes cause a major flare to the Fibro patient.

Pain tolerance in fibromyalgia patients

In 46 female patients with primary fibromyalgia and 50 healthy women of the same age, pressure pain thresholds and pressure pain tolerances on the non-trigger-point muscle and bone were assessed using a dolorimeter. For patients with fibromyalgia, the pressure pain levels and the pressure pain tolerances on both the muscle and bone were lower than in healthy controls.

All the variations were extremely statistically significant although there was some degree of overlap between the patients and the controls. It is concluded that patients with primary fibromyalgia have generalized pain response enhancement, a symptom that may be helpful in diagnosing fibromyalgia.

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So, does that mean the patients with Fibro are weak? Does that say we’re all crying with the pain and over-reacting? Yes, it’s typically the complete opposite actually. Here is where threshold meanings vs. tolerance are becoming very relevant. Patients with fibro do feel pain earlier and at unacceptable amounts but we have incredibly high pain tolerances for most of us. The explanation for this is that people with Fibro feel a certain amount of pain all the time.

References:

  • Chandran AB, et al. Nursing research. 2012 Sep-Oct;61(5):363-8. Sphygmomanometry-evoked allodynia in chronic pain patients with and without fibromyalgia.
  • Meeus M, et al. Journal of rehabilitation medicine. 2010 Oct;42(9):884-90. Reduced pressure pain thresholds in response to exercise in chronic fatigue syndrome but not in chronic low back pain: an experimental study.
  • Winger A, et al. BMJ open. 2014 Oct 6;4(9):e005920. Pain and pressure pain thresholds in adolescents with chronic fatigue syndrome and healthy controls: a cross-sectional study.
  • Zanette SA, et al. Molecular pain. 2014 Jul 8;10:46. Higher serum S100B and BDNF levels are correlated with a lower pressure-pain threshold in fibromyalgia.
  • Pain Threshold and Pain Tolerance in Fibromyalgia & ME/CFS by Adriene Dellwo via Verywell Health

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