Pain is a universal experience, something we all have felt it in our own ways. Whether the pain we felt was sharp and stabbing, a deep throbbing ache or maybe it also had some burning or electrical qualities. However we choose to describe it, pain knows no age limit as it affects us as infants all the way through old age.
Important Definitions and Concepts:
· What exactly is pain? Pain is defined by the International Association for the Study of Pain (IASP) as “a sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”
· Acute pain has 2 characteristics. First, it is a symptom of an underlying health condition and second it has a relatively short duration but can last up to 6 months.
· Chronic pain has 2 characteristics that are different from Acute pain. First, it lasts longer than 6 months and second, most importantly, it is pain that occurs in addition to the pain of the original health condition. It is pain that is independent of the underlying injury or illness that began the entire process. Chronic pain affects how a person lives their daily lives.
· Sensitization is the amplification of danger signaling in any part of the system (from peripheral and central nerves). It is a normal function of the pain system; it is considered dysfunctional when it is chronic or seriously disproportionate to the actual sensation. Sensitization can contribute to chronic pain conditions.
· Central sensitization is the end product of a highly reactive nervous system. It is only related to the central nerves (I.E. spinal column). It is a very complex topic that could be an entire blog of its own, but I will simplify it to the best of my ability here. In some individuals, the nervous system can stay in a constant state of reactivity even after the healing of the original injury or illness. When this occurs, the entire nervous system gets wound up becoming more and more reactive to the slightest stimulus and it maintains pain in a vicious cycle that is above and beyond the original condition’s pain.
o The main hallmarks of central sensitization are increasingly widespread pain and increasingly intense pain.
o There are 2 characteristics of central sensitization. Both involve a heightened sensitivity to the sense of touch. First, Allodynia occurs when a person experiences pain with things that are normally not painful. For example, pain me be felt with simple touch or even massage. The second characteristic is Hyperalgesia where a stimulus that typically is painful is perceived as more painful than it should be. An example of this is a simple bump that might be mildly painful under normal conditions, is felt to be extremely painful like a bone being broken in chronic pain patients.
o In certain individuals central sensitization can lead to heightened sensitivity across all senses with some noting sensitivity to sound, light and odor.
o There are byproducts of central sensitization related to cognitive deficits (I.E. poor concentration and poor short term memory) and others related to the nervous system’s increased reactivity. These are anxiety and irritability due to the emotional control of the nervous system, poor sleep, fatigue and eventually depression.
These additional problems cause stress and this additional stress adds to the reactivity of the nervous system whereby making the pain worse- creating another vicious cycle.
Looking at it a different way…. Chronic pain is actually pain causing pain by means of central sensitization.
Types and Categories of Pain:
There are 3 basic types of pain:
· Nociceptive pain- arises from various kinds of trouble in tissues and is reported to the brain by the nervous system.
· Neuropathic pain- arises from damage to the nervous system itself from either disease, injury or physical irritation.
· Other pain- pain that is not arising from neurological dysfunction, or damage. Some additional names often used include: Nocipathic pain, Nociplastic pain, Algopathic pain, Centralized pain, Primary pain.
One other way of categorizing pain is if it is somatic or visceral.
· Somatic pain is experienced in the skin, muscles, bones and joints.
· Visceral pain is pain of the organs in the thoracic or abdominal cavities.
This distinction here is not just about location or depth; there are also very different characteristics that reflect different priorities for the brain. The brain is very concerned with location of the somatic pain so it can avoid outside sources of danger, however it cannot tell where visceral pain is coming from so it often gives referred pain symptoms in distant areas of the body. Instead, with visceral pain the brain is more concerned with things that could go wrong with organs like overstretching, decreased oxygen to the organ, and inflammation of the organ. In these cases, the symptoms are excessive and stubborn to draw attention to the inner problem to prompt us taking action to get it corrected.
Now that we understand what pain is and how it is often categorized,
lets look at how we hurt-
An important point to understand about pain is that Nociception is not pain and there are no ‘pain nerves’ or ‘pain fibers’. Nociceptors are the nerves that detect potentially harmful or unpleasant stimuli and Nociception is what those nerves do for a living- they send reports about the state of the tissue, not pain. Pain is actually a brain generated experience that is based on many factors including nociception, but is not limited to nociception alone. Pain does not occur until the brain says so- there are a lot of routine and boring nociception that never become ‘pain’ because our brain will make us change positions or adapt to something before it becomes a problem where it then is perceived as pain. So we have come to understand that pain is independent of tissue state- we can hurt without having tissue problems and we can have tissue problems that don’t hurt- to an amazing degree.
The pain system generally works in three distinct stages:
· The first is when the injury or ailment causes damage. The long neurons at the site of injury in the body sense the damage and shoot a pain message toward your spine.
· The second stage is when those signals are handed-off to other neurons in your spinal cord.
· The final stage is where the spinal cord neurons carry the signal to a specific spot in your brain that corelates with where the injury occurred in the body- it is here that the sensation of pain is created.
It is now understood that in stage two above is where things can go amiss and chronic pain can be triggered. A certain type of nervous system cells, called glia, can accelerate the pain system into an endless inflammatory loop that creates continuous pain signals. Why this happens to some and not others is not yet understood.
Now we have covered the basics for understanding pain, we will continue our journey in Part 2 where we will dive deeper into why we hurt.
Resources:
Brice B.K. PhD and Harrison T.E. MD. (2013) Mayo Clinic Guide to Pain Relief, Second Edition. Mayo Clinic.
https://uspainfoundation.org/ GOOD RESOURCE TO LOOK AT FOR CAM
Next time:
Stay tuned for my next blog in 2 weeks with Pain Science Part 2: New Discovery into Why We Hurt.
Related Post Links:
Pain Science Part 2:
Pain Science Part 3:
Pain Science Part 4:
Pain Science Part 5:
Pain Science Part 6:
Author: Jen Hassaj | 7-12-23
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