What is Pain? How Do We Treat It?

What is pain?  How do we treat it? 

Increased Inflammation = Increased neurogenic excitation = Increased pain. 

What is pain? We talk about it all the time. Heck, I make a profession out of trying to fix it, yet it is amazing how relatively little we understand the mechanisms behind this universal phenomena.   I hope by providing some background knowledge of our current understanding of pain science it will help you recognize what information your pain is trying to tell you, so we can perhaps help resolve it. Getting out of pain is not a one size fits all equation. 

In the most basic sense, pain is an emotional response to either a real or perceived threat to the body.  We are going to talk a lot about what triggers the threat response but first let's briefly address the emotional component.  

Your brain is constantly evaluating the degree of threat pain signals represent and how it should react.  To some degree there is a learned experience to pain where your brain learns to decide how harmful the pain is and how far it should go to protect you.

 Think of the little kid that falls on the floor.  What happens first?  Do they immediately cry, or do they look around to see how the adults are reacting first? The child is learning what is potentially harmful or not.

 As a health professional, we need to be very careful of this learned response example and the consequences of negative language when describing painful conditions. Imagine, you go to the doctor for advice on your back pain.  That doctor orders an MRI and tells you have something called "degenerative disc disease (DDD)" and proceeds to tell you all the bad things about DDD.  Like the little kid who's parents panicked when they hit the floor  you are learning that your back pain is harmful and probably start to cry.  

Is every little kid fall harmful? No.

Are all cases of DDD harmful?  Absolutely NOT.    

Now, let's picture something a little more direct.  You get bit by a dog.  Next time you have a dog coming towards you are probably a little less likely to greet that dog with open arms, you've learned some dogs are not always cute and cuddly.

One last example on regards to emotion: 

Let’s pretend you use your hands for a living, and without having full use of your hands you wouldn’t be able to do your job and provide income to pay  your rent or mortgage.  With that in mind, consider these two imaginary scenarios:  

Scenario 1.  You’re walking down the sidewalk and you miss a curb, rolling your ankle and falling to the ground.  When you hit the ground you become immediately aware that your ankle is sore and swollen.  You aren’t sure if you broke it or not.  

Scenario 2.  You’re walking down the sidewalk and you miss a curb, rolling your ankle and falling to the ground.  When you hit the ground you become immediately aware of a sharp pain in your hand and wrist.  It is sore and swollen.  You aren’t sure if you broke it or not.

Which one hurts more? 

Most likely scenario 2.  Even if we assume the hand and ankle had the exact same level of pain input to the brain,  the hand scenario comes with some level of emotional panic.  Your hands are your living. So the need to protect them is emotionally higher, and the “pain” is amplified.  It’s a very real thing.

So what exactly is happening when pain is triggered.  

Throughout the body you have pain sensory receptors called nociceptors.  Their job is to send a signal to the brain when they perceive some sort of threat to the system. Threats can be in the form of stranger or danger signals.  Stranger signals are foreign substances to the body such as viruses, bacteria, or other pathogens.  Danger signals are things that can cause more physical damage like pressure, heat/cold stress, electrical stress etc.  

Pain receptors are always signaling a low level feedback signal to the brain.  When something triggers them they increase the rate of signaling.  The activation of these nociceptors lets the brain know there is a new level of threat to the system. We call this increased rate of firing neurogenic excitation. 

Inflammation is the trigger. 

The actual trigger that causes the pain receptors to increase their rate of firing is inflammation.  Inflammation is an umbrella term for a collective mix of immune system chemicals that respond to threats.  In general the roll of inflammation is to repair damaged cells, clear out foreign substances, and help clear out cell waste products.  

The release of inflammation is triggered by nerve endings spread throughout the body. We have sensory nerves responsible for detecting pressure, temperature, vibration, smell, light, chemical changes, and so on….   When these sensory nerves are affected by their respective thermal, mechanical, or chemical stressor they release inflammatory cytokines into the system.  These inflammatory mediators will have an effect on local blood vessels to change blood flow to the area, generate at local immune response we previously discussed, and also stimulate the pain receptors. 

To summarize the pain response: You have a mechanical, thermal, or chemical threat that activates the sensory nerve. The sensory nerve releases inflammatory cytokines into the surrounding area, this triggers neurogenic excitation of the nociceptors which is perceived as pain by the brain.  Increased Inflammation = Increased neurogenic excitation = Increased pain. 

The final pain response is determined by how your brain decides to interpret the pain signals.  This happens in many different emotional and pain processing centers of the brain. This is likely where some of the emotional and learned experience pieces tie in. 

Now that the brain is aware of the threat and it can respond appropriately to protect the system through whole body immune, autonomic, and endocrine systems.  It is a very elaborate chemical / electrical alarm system and repair process.

What does this mean in regards to getting out of pain? 

If you want to get rid of the pain, what you are really asking is to either reduce neurogenic excitation from the peripheral nerve or reduce the intensity of the reaction from the brain. This means your “pain treatment” needs to address either the local inflammatory response, systemic inflammatory generation, or central (brain and spinal cord) effects of pain. Certainly we could write an entire paper on each of these topics, but for now let’s provide a brief overview of each situation: 

Local Response 

Locally after an injury there is going to be inflammation due to damaged tissue.  The inflammation will be there to heal and repair.  The treatment goal is to make sure that there isn’t an over reactive immune response and make sure that as the local tissue heals the inflammatory response stops.  

Local Transition from Acute to Chronic. 

We have to be careful because in some situations, new injuries can transition to long term pain problems, even after apparent tissue healing has occurred.  There are many theories,  that will go beyond the scope of this article, but I suspect there is either a repetitive injury effect, another systemic immune factor, emotional exacerbation, or genetic component when dealing with the transition to chronic pain scenarios.  

Systemic Inflammatory Response. 

Some pain does not appear to be related to a specific pain event or mechanism of injury.  In autoimmune disease, fibromyalgia, and other systemic neuro-inflammatory conditions the pain seems to come and go, or bounce around.  We now have evidence that points to a systemic and chronic inflammatory component to these conditions.  I suspect that consistent neurogenic excitation from the inflammatory cytokines is responsible.  Imagine your brain just getting constant bombardment of threat signals.  This is simply my opinion, but I wonder if it just responds to the most pressing input of the day so that's where you feel it. I also wonder what that constant feedback does to the emotional parts of the brain.  We are certainly seeing that systemic inflammatory conditions relating to blood brain barrier permeability, anxiety, depression, and other neurodegenerative diseases like Alzheimers.  

The cause of systemic inflammatory conditions is of great interest and I don’t know that we have an exact cause pinned down just yet.  Areas of interest to me include diet; leaky gut; metabolic disorders like diabetes, pre-diabetes, metabolic syndrome, and insulin resistance; chronic stress; and sleep deprivation.

Central Sensitization and Effects on Pain Perception. 

Central sensitization refers to actual structural changes of the central nervous system (CNS) (brain and spinal cord) that effects the way the CNS interprets sensory signaling.  There again are many theories behind why central sensitization occurs but I again suspect repetitive trauma, emotional exacerbation, immune, or genetic contributions. The term for the changes in the structure of the CNS structures is called central plasticity.  It is significant to note that there does appear to be evidence that it is reversible in nature. 

With central sensitization, the brain senses pain to normal, non threatening, stimulus. Pain perception is less about the frequency of the nociceptive signal coming up, but now more about the way the brain interprets the signal.  

I like to use an example of an alarm system.  Central sensitization would be like having an alarm system with the sensitivity set so high that every time a gentle breeze blew it would set the alarm off.  Wind is a mechanical stimulus, that potentially could be threatening.  I want my alarm system to know when a tornado is coming, but I don’t necessarily need to know every time there is a strong breeze.  The strong breeze in this example is not the problem, but rather the sensitivity of the alarm reading. 

You would not try to fix the issue of the alarm going off all the time by stopping the wind, you would try to turn the sensitivity dial down.  Similarly, when treating someone with central sensitization (an alarm problem) treating the input (the wind) isn’t going to fix anything.  You would to choose treatment techniques that reduced the central processing. 

Conclusions. 

Pain is information to the body, I’m not sure we should attach such a demonizing label to it.  Certainly, it is a negative feedback system but it really is protective. It is at the core of how our body protects us from both real and perceived threats. We also should not treat all pain the same way.  When we are looking at the root cause of pain it is more than just some diagnosis label.   It is not a one size fits all equation.

Written By: 

Dr. Nicholas Sanders PT, DPT, CSCS, CIDN.

Nick is the founder of PHYT For Function a one on one specialty, physical therapy clinic in Northeast Ohio and Co-Creator of the Neuro-Release Treatment Course, a nervous system based cupping, percussion massage, and IASTM manual therapy course presented by Integrative Dry Needling.  Nick is both a doctor of physical therapy and certified strength and conditioning specialist. He is driven to find the best combination of manual therapy, exercise, and lifestyle habits to improve pain, aging, and performance.