Why pain can become chronic and what we can do to manage it
TL;DR — Nerve and tissue damage lead to neuroinflammation. Persistent neuroinflammation and individual factors lead to persistent pain Reducing neuroinflammation is key to managing chronic pain
Today I am going to share with you the two articles which brought everything together for me concerning why pain becomes chronic and the principles by which we can manage it.
All pain starts with a trigger.
An incident, an accident, a surgical procedure, a series of micro-traumas over decades, physiological and iatrogenic triggers — this list is not exhaustive but I am sure you understand my point.
Acute pain transforms into chronic pain through the continued stimulation of the nervous system — this leads to neuroinflammation. Through the influence of several individual factors both external and internal, pain can become chronic.
Let me explain this to you using the diagram below from Ji et al’s brilliant paper — follow the numbers.
- Trauma, surgery, medications, disease, cancer, and infections are all implicated in damaging tissue -> acute pain.
- These insults lead to injury and damage to our nervous system, and the tissues (bone and muscle, organs) and lead to the activation of our immune system.
- Tissue damage causes neuroinflammation through a process called central sensitisation — ongoing stimulation of our nervous system through the creation of an inflammatory molecule soup!
- Neuroinflammation causes the activation of glial cells which are pivotal in pain becoming chronic. - The activation of glial cells leads to the production of more inflammatory soup and a vicious cycle ensues.
- Primed glial cells secrete more molecule soup which leads to more pain transmission and more glial cells being activated.
- Glial cells are important because medications like opioids (morphine, hydromorphone, fentanyl, oxycodone) stimulate them to produce inflammatory molecules which worsen pain - Neuroinflammation mixed with a person's psychological background, environmental and social factors, genetics and previous injury are the potent mix which leads to the transition from acute to chronic pain
- The final product of unremitting neuroinflammation is neurodegeneration which we see clinically as cognitive impairment, chronic pain and chronic neurological disease
As you can see, what happens on a molecular level, interacts with a person’s individual psychological, social, and genetic tendencies to result in chronic pain.
That is why the socio-psycho-bio model is important in managing pain as all these factors play a role in the development and persistence of chronic pain.
Listed below are the known factors that work together with neuroinflammation to cause the transition from acute to chronic pain — these correspond with the number (5) above.
Factors that can influence the transition from acute to chronic pain
Psychological factors
- Anxiety
- Depression
- Catastrophisation
- Post-traumatic stress disorder
Pain factors
- Severe unremitting acute pain
- Pain in multiple sites
Person factors
- Poor self-efficacy
- Catastrophisation
- Fear and avoidant behaviour
- Hopelessness
- Insomnia
Medication
- Chronic opioid use
- Chronic benzodiazepine use
- Alcohol misuse
- Smoking
Social factors
- Low health literacy
- Low socioeconomic status
- Low health engagement/participation
So what can we do?
- Address neuroinflammation
- Address complexity
Addressing neuroinflammation
The key to managing chronic pain is reducing neuroinflammation.
Procedures can help if there is a structural or physical disease that is producing continued sensitisation and medications can help to restore the body’s innate pain management system — descending inhibitory control.
Descending inhibitory control is the body’s innate system of managing pain and is the target of several medications. Importantly in chronic pain central sensitisation leads to a decrease in its influence.
Despite the popular focus on medications and procedures which can help, the most potent interventions in the ongoing reduction of neuroinflammation are non-procedural and non-pharmacological.
Exercise is one of the most important weapons we have in producing endorphins, enkephalins, and dynorphins — our body’s natural opioids which produce “exercise-induced hypoalgesia” through the activation of descending inhibitory control.
Furthermore, optimising sleep, reducing the use of opioids, and addressing anxiety, worry, depression and trauma all play a role in helping to manage neuroinflammation and thus chronic pain.
Medications that can help to restore descending inhibitory control are anti-neuropathic medications such as Gabapentin and Pregabalin or anti-depressants such as amitriptyline, duloxetine, venlafaxine or desvenlafaxine.
Medications such as Palmitoylethanolamide (PEA) have also been used as these are known glial cell modulators that help reduce the production of the inflammatory molecule soup.
But as I mentioned in my first article, there is no perfect medication and each person will present a unique picture that needs to be discussed and managed individually.
Address complexity
I came across this diagram from Linton and Nicholas during my study last year.
This was pivotal because it brought sense to the suffering that I had seen in my patients as a General Practitioner and now as a Pain Medicine Fellow.
Chronic pain doesn’t simply cause physical pain, it can lead to a loss of function, a loss of role in society, negative thoughts, an endless spiral of treatment failures and finally a dramatic change in life trajectory.
This diagram is brilliant as it helps us see a person with chronic pain not as a giant complex mess but as a person with treatable problems.
This is called formulation, the construction of a problem list and encompasses a person’s social life, cognitive and behavioural processes and any underlying medical and psychiatric issues that need to be addressed.
The key message in managing chronic pain
The key factors in reducing neuroinflammation and addressing complexity form the foundation of the socio-psycho-bio model of care.
This is something that can be addressed systematically by a GP Specialist or referral to a Tertiary Pain Medicine Service.
The bottom line is that the chronicity of pain can affect multiple dimensions of a person's life and therefore needs a multimodal and disciplinary approach.
I am sure that this article will be helpful.
Take care.
Dr. Jonathan Ramachenderan
Live intentionally.
Love relentlessly.
Enjoy your health.
