Sensational sensitization in chronic pain

Auteur: Gepubliceerd op: 

AAAAAAAAAAA! A man in obvious and unrelenting pain arrives at the emergency department (ED); a large nail sticking through his shoe from sole to top. Horrendously, no pain medication reduces his pain. Weirder still, when they remove his shoe there’s no damage to his foot: the nail had gone right between his toes. Still, his pain had been very real, what’s going on here? This quirky and altogether interesting case was reported on in the British Medical Journal in 1995.


As a former philosophy student and PanEssay editor, cases like this excite me wildly. Having worked as a doctor for 4 years now (ED, neurology, pain care, and psychiatry), I have kept a keen interest in everything bordering neurology and psychiatry. I’d love to share some of the insights -I think to- have gained and please bear with me during two paragraphs of philosophy. 


I wholeheartedly believe our philosophical views on matters like the mind relate strongly to how we work in medicine. In fact, the philosophy of dualism is reflected in our strict division between somatic disciplines (like neurology) and psychiatry. Unsurprisingly then, dualism entails that there is a strict division between two substances: the material (the body) and the immaterial (the soul). Most philosophers nowadays think that this view is problematic. Its biggest flaw can be summarized by one question: How could these mutually exclusive substances interact?


Dualism’s counterpart, monism (or physicalism), does away with the concept of an immaterial substance. It entails all phenomena of the mind (like pain) can be directly reduced to physical processes. This reductionist view struggles to account for these phenomena, however. So a middle ground, albeit still a form of physicalism, emerged: functionalism. In essence, the same way the kidneys function to produce urine, the mind is a (very complex) function of the nervous system in a way that is analogous with a computer: the nervous system is the hardware, the mind is the software (mindware). However, this analogy is not perfect. Mindware is directly related to the way the nervous system is organized. Essentially, mind and body are two sides of the same coin. 


To me, the case above clearly demonstrates why we need a functional perspective on the mind to be able to explain the pain that the formerly mentioned patient was in. For if it was purely a matter of pain in the soul, how could a physical event like a nail puncturing a shoe give rise to that? And if it was purely a matter of the body, how could there be pain without any damage to it? Interestingly, we are learning that something in the function of the pain system can go awry, especially in chronic pain syndromes. 


Our pain system isn’t that different from a fire-alarm: a noxious stimulus signaling potential damage to the body (i.e. smoke) gets picked up by a nociceptor (the smoke sensor), is transmitted via neurons to the central nervous system where this signal is ultimately processed by the brain and the “alarm” goes off: pain! Such a system can become too sensitive or indiscriminate, giving rise to many  false alarms; fire alarms in student kitchens anyone? When this happens in the pain system, pain can arise with a small or even without a stimulus. This is called central sensitization pain: without damage to the central nervous system (spinal cord and brainstem) the pain system becomes dysfunctional. Often psychosocial factors play an important role alongside biomedical ones. Is sensitization pain real? Well, it might be a false alarm, but it is really going off keeping people awake and potentially ruining their lives. Fortunately, it can be managed, which starts with recognizing the problem. 


It’s very important to distinguish sensitization from nociceptive and neuropathic pain in which cases underlying damage should be treated first. However, these pain types are not necessarily mutually exclusive. There are no specific tests to diagnose sensitization-type pain, but some signs should make one consider it: 1. The pain has spread or varies wildly in anatomical distribution 2. Pain medication has a very limited effect. 3. Comorbid exceptional tiredness 4. Sensitization to other stimuli (like light, sounds or even smells) 5. Extreme hyperalgesia and allodynia (not fitting a neuroanatomical distribution).


So what can be done about it? Multidisciplinary management by physicians, specialized physical therapists and psychologists is recommended in severe cases. However, every medical professional can do the most important things: take symptoms seriously without doing further harm and educate patients about the possibility of sensitization-type pain. When the presentation of pain is so weird or extreme and it’s hard to not get frustrated or cynical, it helps to consider and express understanding of the effects the pain has on someone’s life. For instance, I met a young mother at the ED in tears because of her ongoing medication-resistant back pain. The simple question: “It must be hard not being able to care for your baby, do you feel like this makes you a bad mother?” opened her up and after a good conversation she left without additional medication. 


This last bit is important: avoid further harm by not prescribing unhelpful pain medications and avoiding surgery in patients with sensitization-type pain. This can be challenging, because it requires first and foremost that patients feel heard and understood, and ideally understand the cause of their pain. This includes explaining the possible factors that may contribute to their pain. The pain system being a functional system, these include not only biological factors but also psychological, behavioral and social factors as well (see table 1). 


So we need a biopsychosocial model to handle sensitization pain, as well as many other somatically insufficiently explained symptoms for that matter. In fact, we’d be remiss not taking psychosocial factors into account when treating diseases with a clear biological basis, because all subjective symptoms arise in a functional system: the mind. So of course they are influenced by factors other than biological ones. To make sense of this, both doctors and patients need to get rid of dualism, which is more insidious than you might think, and embrace a functionalists’ philosophy of mind. 


Table 1. Examples of biopsychosocial factors contributing to sensitisation type pain




  • Other (chronic) conditions

  • Movement patterns (ie tensed)

  • Medication (pain medication can paradoxically increase pain!)

  • Low quality of sleep

  • Hypertonia 

  • Decreased fitness and/or strength

  • Suboptimal lifestyle

  • Catastrophic thoughts

  • Anger

  • Conditions: anxiety, depression, PTSS, autism, ADHD, hypochondria

  • Overly avoiding activities, especially healthy exercise. 

  • Kinesiophobia (fear of moving) 

  • Limited in activities (exhaustion)

  • Support structure: relationships, friends, family and how they deal with the situation 

  • Cultural ideas on the meaning of pain and suffering (biomedical? spiritual? religious?)

  • Employment

  • Stressors 


Recommended other media:


Possible conflicting interests:

Transcare, a care provider for people with chronic pain and tiredness, was my former employer. Currently, I have no formal relationship with them other than working together on providing a seminar on chronic pain to bachelor students of m