What is chronic pain?
Chronic pain is a major biopsychosocial issue, with significant impact on the quality of life of individuals, their families, interpersonal relationships, occupation and society. In the United States for example, chronic pain accounts for over 100 billion dollars in directed an indirect expenses1.
Chronic pain is a major clinical challenge, with many cases accepting that a cure is unlikely, however the impact on quality of life, mood and function can be significantly reduced by appropriate measures2. It is often diagnosed as pain that has been present for more than 12 weeks2.
Chronic pain can be considered to be in one of four categories: (1) neuropathic pain, (2) musculoskeletal pain, (3) inflammatory pain and (4) mechanical/ compressive pain1. The majority of people with chronic pain will be managed in the community or primary care, with a proportion requiring access to Specialist secondary care or Tertiary Persistent Pain services.
Chronic primary pain is defined as pain in one or more anatomical regions that persists or recurs for longer than 3 months, as noted earlier, and is associated with significant emotional distress of functional disability that cannot be better accounted for by another chronic pain condition3. This is a new definition, which applies to chronic pain syndromes that are best conceived as health conditions in their own right3.
The International Association for the Study of Pain defines it as
“an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”4
It is widely acknowledged that the experience of persistent pain will be influenced by a range of factors including the physiological state, thoughts, emotions, behaviours and social influences of the individual living with the condition.5,6
Sounding the pain alarm
Not long ago neuroscientists debated whether pain was a separate sense, supplied with its own nerve cells and brain centres like the senses of hearing or taste or touch. Maybe you hurt, the scientists reasoned, because nerve endings sensitive to touch are pressed very hard. To some extent, that is true: some nerve fibres in your skin will be stimulated by a painful pinch as well as a gentle touch. However, neuroscientists now know that there are many small nerve cells with extremely fine nerve fibres that are excited exclusively by intense, potentially harmful stimulation. Scientists call the nerve cells nociceptors, from the word noxious, meaning physically harmful or destructive.
Some nociceptors sound off to several kinds of painful stimulation – a hammer blow that hits your thumb instead of a nail; a drop of acid; a flaming match. Other nociceptors are more selective. They are excited by a pinprick but ignore painful heat or chemical stimulation. It’s as though nature has sprinkled your skin and your insides with a variety of pain-sensitive cells, not only to report what kind of damage you’re experiencing, but to make sure the message gets through on at least one channel.
Broadcasting the news
That same dispersion of force continues once pain messages reach the central nervous system.
Suppose you touch a hot stove. Some incoming pain signals are immediately routed to nerve cells that signal muscles to contract, so you pull your hand back. That streamlined pathway is a reflex, one of many protective circuits wired into your nervous system at birth.
Meanwhile the message informing you that you’ve touched the stove travels along other pathways to higher centres in the brain. One path is an express route that reports the facts: where it hurts; how bad it is; whether the pain is sharp or burning. Other pain pathways plod along more slowly, the nerve fibres branching to make connections with many nerve cells (neurons) en route. Scientists think that these more meandering pathways act as warning systems alerting you of impending damage and in other ways filling out the pain picture. All the pathways combined contribute to the emotional impact of pain – whether you feel frightened, anxious, angry, annoyed. Experts called those feelings the “suffering” component of pain.
Still other branches of the pain news network are alerting another major division of the nervous system, the autonomic nervous system. That division handles the body’s vital functions like breathing, blood flow, pulse rate, digestion, and elimination. Pain can sound a general alarm in that system, causing you to sweat or stop digesting your food, increasing your pulse rate and blood pressure, dilating the pupils of your eye, and signalling the release of hormones like epinephrine (adrenaline). Epinephrine aids and abets all these response as well as triggering the release of sugar stored in the liver to provide an extra boost of energy in an emergency.
Censoring the news
Obviously not every source of pain creates a full-blown emergency with adrenalin-surging, sweat-pouring, pulse- racing responses.
Moreover, observers are well aware of times and places when excruciating pain is ignored. Think of the quarterback’s ability to finish a game oblivious of a torn ligament, or a fakir sitting on a bed of spikes. One of the foremost pioneers in pain research adds his personal tale too, of the time he landed a salmon after a long and hearty struggle, only then to discover the deep blood- dripping gash on his leg.
Acknowledging such events, neuroscientists have long suspected that there are built-in nervous system mechanisms that can block pain messages.
Now it seems that just as there is more than one way to spread the news of pain, there is more than one way to censor the news. These control systems involve pathways that come down from the brain to prevent pain signals from getting through.
The brain’s own opiates
Both groups of scientists found not just one pain- suppressing chemical in the brain, but a whole family of such proteins. The Aberdeen investigators called the smaller members of the family encephalins (meaning “in the head”). In time, the larger proteins were isolated and called endorphins, meaning the “morphine within.” The term endorphin is now often used to describe the group as a whole.
The discovery of the endorphins lent weight to the general concept of the gate theory. Endorphins released from brain nerve cells might inhibit spinal cord pain cells through pathways descending from the brain to the spinal cord. Endorphins might also be activated when you rub or scratch your itching skin or aching joints. Laboratory experiments subsequently confirmed that painful stimulation led to the release of endorphins from nerve cells. Some of these chemicals then turned up in cerebrospinal fluid, the liquid that circulates in the spinal cord and brain. Laced with endorphins, the fluid could bring a soothing balm to quiet nerve cells.
The NSW Agency for Clinical Innovation (ACI) guide to Pain Management programs5, reported that the available evidence indicated that individuals with chronic pain should not be treated as a “one size fits all” approach to pain management programs, but rather selected according to their particular characteristics.
The management of persistent pain can effectively adopt a biopsychosocial approach, with Psychologists supporting Primary and Secondary care Physicians alongside Allied Health Practitioners, to improve both physical and psychosocial wellbeing6. Interdisciplinary care promotes the understanding of the ‘whole person’ experience, and this care can occur in many formats, not all of which are directly tied to tertiary pain centres6.
The Australian and New Zealand College of Anaesthetists (ANZCA) Faculty of Pain Medicine (FPM) recommendations regarding the use of Opioid Analgesics for individuals with chronic Non-Cancer Pain highlighted the lack of definitive evidence supporting the long-term effectiveness of opioid analgesics in chronic Non-Cancer Pain (CNCP) and the substantial evidence of potential harm7. The media widely publicises the current “Opioid Crisis”, particularly in the United States but also in Australia. ANZCA FPM7 reported the accumulating evidence highlighting the adverse effects of opioid therapy, and that the use of high pain severity ratings is a poor basis for opioid prescription, given pain ratings are well known to also be influenced by psychological and contextual factors. Co-prescription of other medications alongside long term opioid therapy is associated with further risk of adverse events.
Chronic pain is never unidimensional. It is also never purely biological or solely psychological and treatment can be a lengthy process. Different people react differently to pain depending on their physiological, psychological, social, educational and cultural variables.
When providing medical care to a person with chronic pain it is important to get a sense of depth and breadth of their past and ongoing life experiences and current social situation. What the person believes about the cause, meaning, impact, expectation, perceptions and goals regarding their pain can make a difference to helping them manage and cope with their pain experiences. Quality medical care, education and information is very important.
Vocational support is particularly helpful in compensation cases. A focus on staying functional is best to assist the individual to manage their chronic pain condition.
- Rosenquist EWK. Evaluation of Chronic Pain in UpToDate online. Literature review Oct 2019.
- Scottish Intercollegiate Guidelines Network (SIGN). Management of chronic pain. Edinburgh: SIGN;
- Treede R-D, Rief W, et al. Chronic pain as a symptom or a disease: the IASP Classification of Chronic Pain for the International Classification of Diseases (ICD-11). Pain 160(2019)19-27.
- Merskey H, Bogduk N, (editors). Classification of chronic pain, second edition. Seattle: ISAP Press;
- Pain Management Programs – Which Patient for Which program? Agency for Clinical Innovation. April
- The Role of the Psychologist in the Management of Persistent Australian Pain Society Position Statement. March 2016. For Review: March 2019.
- Recommendations regarding the use of Opioid Analgesics in patients with chronic Non-Cancer pain. Faculty of Pain Medicine. Australian and New Zealand College of Anaesthetists. PM01.
*All views, opinions and conclusions expressed are those of the authors and/or speakers and do not necessarily reflect the view, opinion, conclusion and/or policy of ExamWorks and its affliates.