What is pain? You may be surprised - I know I was

What is pain? You may be surprised - I know I was

When I was in school science class, I was taught that nerves under the skin sensed pain, like touching a hot stove, and sent the signal to the brain, which then sent a signal back to respond, like pulling your hand away. But that's not how it happens.

“We don’t have pain receptors,” explains neuroscientific pain specialist Lorimer Moseley. Pain does not come from the region feeling it, but from the senses' assessment of the danger, expectations, previous exposure, cultural/social norms/beliefs, and how it makes us feel. Pain, as defined by the International Association for the Study of Pain, is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.” Pain is a localized emotion.

Does this mean it's all in our heads? No “danger detectors” distributed throughout the body tissues act as the eyes of the brain. So here's what happened.

Nociceptive pain (that is, in response to stimuli) is an early warning. The nerves have sensed temperature, vibration, stretch, lack of oxygen, or chemical changes from damaged cells and send an early warning to the brain, which in turn triggers the inflammatory response, protecting the area and sending in neutrophils to fight infection, which enlarge blood vessels to increase blood flow and volume (leading to swelling and redness).

However, there are two problems. First, the inflammatory response also increases pain sensitivity - yes, that means you feel pain more than before the injury, an overreaction. And second, the mitochondria (the organelle responsible for cell digestion and respiration) shed from damaged cells are attacked by the neutrophils as invaders, triggering an unnecessary second round of inflammatory response (and you guessed it – more pain sensitivity). In chronic pain, the true need for pain is distorted and the pain continues.

The cause of the signals can also be confusing. In somatic pain, the pain is sharp, localized, and painful to the touch. But visceral pain is a vague, deep pain that is difficult to pinpoint - like cramps or colic. Problems in the pelvis, abdomen, or chest can manifest as pain in the lower, middle, or upper back. It may also refer to pain, such as a heart attack, in the shoulders, back, or neck rather than the chest.

Turn off hazard alarms to treat pain from acute injuries. This may mean treating the underlying cause medically, such as antibiotics for an infection. When the brain feels safe, the pain stops. Analgesics can be used to block the signals and therefore the pain - but now we're back to the problems of taking these long-term. For example, codeine can even increase pain sensitivity. And all analgesics can cause analgesic rebound, in which the body's production of natural endorphins decreases in response to analgesic use and increases pain sensitivity again.

Non-nociceptive pain is a whole different world. There is no external stimulus here, since the signal comes from the nervous system itself, be it between the nerves between the tissue and the spinal cord (peripheral nervous system) or between the spinal cord and the brain (central nervous system). The cause can be nerve degeneration (as in stroke, multiple sclerosis, or lack of oxygen), a pinched nerve (under pressure or a disc problem), a nerve infection (like shingles), a nerve injury (due to a fracture or soft tissue injury) – all signals are misinterpreted as pain.

This sympathetic pain can be severe to prevent use, which in turn causes new problems such as muscle loss, osteoporosis and stiffness in the joints (the new collagen is stiffer than the collagen replaced). It can even be pathological pain, abnormal, increased, aberrant, dysfunctional pain, which includes fibromyalgia, irritable bowel syndrome and some headaches.

Neuropathic pain is responsible for both phantom limb pain, from mild “pins and needles” to a constant and intense burning sensation, and the extreme limb pain of complex regional pain syndrome following seemingly minor tissue damage such as an insect bite or small cut. But once the pain becomes chronic, in conditions such as back pain, rheumatoid arthritis, fibromyalgia or cancer pain, treatment becomes elusive.

Pain that is not associated with an acute injury can have various factors: immune system, endocrine system, movement problems, cognition, or the very mechanisms by which the brain represents the body. Sensitivity increases, the dark side of neuroplasticity. Negative emotions increase pain, such as sadness, fear, pain, or simply poor job satisfaction. Negative emotions are the result of chronic pain, as depression is common in chronic pain patients.

Muscle knots, awkward posture, vitamin D deficiency, bisphosphonates (for osteoporosis or Paget's disease) and statins (used to lower cholesterol) can cause pain. Even an easily identifiable complaint such as back pain can be due to poor posture, poor lifting, excess weight (including on the knees), curved spine, traumatic injury, high heels, poor mattress, poor shoes, aging/degeneration of the spine, disease (rheumatoid arthritis, osteoarthritis, fibromyalgia, gallbladder, Cancer, multiple sclerosis, stomach ulcers, AIDS), psychological factors after physical healing...it's complex.

So, after your doctor treats the acute injury and offers analgesics if necessary, imagine the immense and confusing task if the pain persists. So doctors and their patients try things: massage, TENS units, anticonvulsants, antidepressants, acupuncture, meditation, chiropractic, osteopaths, biofeedback, low-impact exercise, stretching, physical therapy, cognitive behavioral therapy - the fact is, they're doing their best, but they're guessing.

“We don’t have enough evidence from studies to know which approach is right for which patient,” confirms Dr. Russell Porteny, chair of pain medicine at Beth Israel Hospital and past president of the American Pain Society. "Despite decades of research," notes WebMD, "chronic pain remains poorly understood and notoriously difficult to control. A survey by the American Academy of Pain Medicine found that even comprehensive treatment...on average only helps about 58% of people." with chronic pain. And even that means dealing with pain, not healing it.

Pain and pain response vary from person to person and from moment to moment with the same person. “Any credible evidence that the body is in danger and protective behavior would be helpful increases the likelihood and intensity of pain,” explains Dr. Moseley. “Any credible evidence that the body is safe reduces the likelihood and intensity of pain.

“It’s so simple and so difficult.”

Inspired by Tim Emerson