Pain and Inflammation

Understanding the types of pain

The two main types of pain are known as nociceptive and neuropathic pain – each with distinct characteristics that may require different treatment approaches.

Nociceptive pain is the most common type of pain and occurs when the nociceptors in the body detect noxious stimuli that have the potential to cause harm. This includes mechanical pressure, chemical toxins and extreme temperatures. The receptors in turn send electrical signals via the nervous system to the brain, leading to the perception of pain.

Neuropathic pain, which can be referred to as a ‘complex chronic pain state’, is associated with damage to the neurons responsible for the pain signalling pathways. Regardless of noxious stimuli, messages of pain are sent to the central nervous system. This can develop from infections, health conditions such as diabetes, surgery or injury. Norman Doidge, psychiatrist, psychoanalyst and renowned author of ‘The Brain’s Way of Healing’, suggests that chronic pain may be defined as a ‘learned’ pain, indicating the body’s alarm system is stuck in the ‘on’ position after an acute pain episode has not been resolved, leading to damage of the central nervous system.

For nociceptive pain, the first-line of orthodox management tends to be pharmaceutical analgesic medications such as paracetamol, ibuprofen and aspirin. For more severe pain, prescription opioids may be offered. The mechanisms of action of the medications differ but have a common goal to help disrupt the transmission of pain signals. These options may be helpful for acute short-term pain relief but may not provide much benefit for chronic pain.

Extended use of pharmaceutical pain relief medications may lead to further damage such as stomach ulceration, increased risk of strokes and liver damage. Opioids can also be addictive. Our brain makes its own opioid-like substances to block pain; pharmaceutical opioids attach to our opioid receptors. According to psychiatrist-turned-pain-specialist Dr Michael Moskowitz, once we saturate all our natural opioid receptors the brain produces new ones. The brain becomes less responsive to long-term opioids, thus making one more sensitive to pain, in turn more dependent on drugs, which can worsen chronic pain.

Chronic injury makes cells in the pain system fire more easily and causes pain maps to enlarge their ‘receptive field’. This means that we begin to feel pain over a greater surface area. As pain maps enlarge, there is ‘spillage’ into adjacent pain maps leading to ‘referred pain’.

Research findings indicate there is on-going competition in the brain for how it is used. Activities the brain performs regularly take up increasing amounts of space, resulting in ‘theft’ of resources from other areas. The same areas in the brain that ‘fire’ in chronic pain also process thoughts, sensations, images, memories, movements, emotions and beliefs – when they are not processing pain. This could explain why we can’t concentrate, become irritable, have emotional outbursts, don’t move gracefully and can’t tolerate certain sounds and light when we are in pain. Our brain has been hijacked by the pain signal. This may be heightened when we are in chronic pain because when an area of the brain is processing acute pain, approximately 5% of neurons in that area are dedicated to processing pain; in chronic pain this can increase to 15–25%.