Chronic pain is one of the most cunning and formidable adversaries that one can have in life. Pain is not just a simple sense like vision – where what you see is what you get. Rather, chronic pain is a comprehensive experience that involves all levels of the nervous system. Our perception of persistent pain tends to increase with time, becoming more and more intrusive on the conscious mind. When severe, the experience of pain can act like a “psychological cancer” – invading into your consciousness and taking over your daily life.
One of the best ways to understand chronic pain is to consider how torture works. Torturers know that they don’t actually have to do anything too bad to people; rather they just need to keep doing it! If they can make the person feel powerless, and sleep deprive them, then they’re a good chance to break anyone.
Chinese water torture is a classic example. The subject is strapped down and a regular, slow drip of water applied to the forehead. At the start this is likely to feel just like a gentle tapping sensation – certainly not painful. However, if the process is allowed to continue for 24-48 hours, then each drop comes to feel like a sledgehammer blow. A number of things happen in the body to cause this transformation (“pain windup”):
- The nerve receptors in the skin of the forehead transform from feeling the gentle tap of a water drop (mechanoreceptors) to registering it as a painful stimulus (nociceptors). At the same time, their sensitivity is markedly increased, by 10-20 fold.
- Sensory nerves transmit the pain signal back to the spinal cord, where extra connections are made to form an “information superhighway” for the pain signal to be better transmitted up to the brain.
- The pain signal then enters the brain through the more primitive, lower parts of the brain (Limbic System). This is the emotional circuitry of the brain and the signal is therefore influenced by our emotional state. If we are calm, then the amplifier tends to be turned down. However, if we are anxious, depressed or stressed, the amplifier tends to turn up the volume of the pain signal. This can set up a vicious circle, whereby our (understandably) negative emotional response to the pain sets us up for worse pain.
- Finally the pain signal arrives out in the brain’s cortex - our thinking brain. This is probably where the experience of pain happens. If pain persists for any significant length of time, then the area of our brain that is focusing on the pain increases in size. This increased focus, (“hypervigilance”), means that for any given stimulus we are likely to feel more pain. If we start worrying excessively about the pain and its effect on our lives, (“catastrophisation”), this can set up a snowballing effect where the experience of pain starts taking over our lives. This may even contribute to increased muscle spasm in the painful areas, further worsening the pain.
Musculoskeletal Treatment of Chronic Pain
Musculoskeletal (MSK) medicine treatment aims to address the patient’s whole pain experience. First and foremost, it aims to restore normal function and turn off the primary cause of the pain signal from the body. This is commonly done using techniques that unload overloaded muscles, tendons, ligaments and joints. On other occasions, MSK will investigate and treat degenerative changes in the joints of the spine and limbs. MSK will also look for causes of direct nerve irritation. The psychological dimension of pain is addressed through education and the occasional prescription of medication. Long term improvement is aided by addressing predisposing factors and implementing practical maintenance strategies.
Although stress doesn’t directly cause pain, it acts like the wind that fans the flames of a bushfire. For any of us, our chronic pain experience will be much worse during a period of high stress, compared to a period of low stress. The stress response involves an increase in muscle activity, which increases the risk of muscle-generated pain signals. As seen above, it also increases pain amplification through the emotional centres of the brain. Finally, stress increases brain activity, potentially increasing the monitoring of pain in the thinking brain.
PSYCHOLOGICAL STRATEGIES IN CHRONIC PAIN
Whilst chronic pain is never just in our minds, it can be profoundly influenced, (positively or negatively), by what is going on in our heads. Strategies that improve our mental processing of pain, (including counseling, meditation and some medications), can be very helpful in lessening the pain experience.
General strategies to decrease stress are often essential to help gain positive momentum with chronic pain. Simple mindfulness-meditation techniques, which aim to calm the mind, have been shown to reduce chronic pain levels by decreasing its amplification. Specific counseling can also be helpful in challenging unhelpful thoughts about pain.
Some medications, e.g. Lyrica, can help by reducing the transmission of nerve signals in neuropathic pain. Other medications, including anti-depressants, can help to reduce the central amplification of pain and improve mood and sleep.
The neuro-circuitry of anxiety-depression, and the neuro-circuitry of chronic pain, are 95% the same. Furthermore, unrelieved chronic pain would increase most people’s risk of depression anyway. Clinically, most people with chronic pain will have some depressive symptoms. In practical terms, it is only if their depressive symptoms persist once their pain has been relieved, that we can confidently diagnose separate depression.
Sleep deprivation worsens pain! Actual experiments on medical students reveal that normal, healthy people will develop widespread body pain if they are sleep-deprived for a week! Many patients get into a vicious circle where their pain interrupts their sleep, which in turn worsens their pain. In addition to treating the primary cause of the pain, interventions can be helpful to try and reduce the impact of this vicious circle.
Dr. Chris Homan
MBBS FRACGP FACRRM DRANZCOG PGDipMSM(Otago)