While much of talk in rehab deals with tissue injury and tissue pain, realize that the brain always makes the final decision as to whether or not you should feel pain. No brain, no pain.
This sentiment does not mean that pain is not real. All pain is real. However, pain is a construct that the brain creates in order to ensure your survival.
Spinal Cord Alarms
When an injury occurs and the DRG receives impulses from peripheral structures or the brain, the spinal cord neurons must adapt to better uptake all these signals. In essence, the DRG becomes better at sending danger messages up to the brain. This change leads to short term increases in sensitivity to excitatory chemicals. Those stimuli that didn’t hurt before now do (allodynia) and those that used to hurt now hurt more (hyperalgesia).
In persistent pain, this change continues occurring to the point where neurons that do not carry danger messages start growing into space where danger messages are taking place. Now innocuous stimuli such as grazing the skin begin hurting. The pain may be normal, but the underlying processes become abnormal.
When these spinal cord alarm systems become unhealthy, the brain no longer receives an accurate message of what is going on. The alarms become magnified and distorted. The brain is told there is more damage in the tissues than is actually present.
What is good is that this increased sensitivity can change once damaged structures are under control and/or the underlying physiological processes are understood by the person in pain.
Another change that happens in the brain is termed smudging, in which brain areas devoted to body parts or functions begin overlapping. This process is why some body parts may become difficult to use or other areas become sensitive compared to the injured area.
Fortunately, since the brain homunculus frequently changes, these effects are reversible. The homunculus must be trained just like any other muscle or skill.
It is now understood that thoughts are powerful enough to maintain a pain state, known as thought viruses. These viruses are known to cause and enhance a low back pain experience, and likely have an effect at the whole body. Here are some examples of thought viruses.
Pain means something harmful is happening to my body.
Stopping social activity because of pain.
It is bad if no one can find out what is wrong with me.
Pain scares me.
Refusing to move until all pain is gone.
Central Sensitization is when the brain and spinal cord become overly sensitive to processes. This change occurs in chronic pain states. Diagnoses such as fibromyalgia, chronic fatigue syndrome, and non-specific low back pain are often given out. The diagnosis given often depends on where you live and which health professional you have seen. Here are the characteristics of central sensitization.
Pain persists past normal healing times.
Pain is worsening.
Lots of movements hurt. Even imagining movement can hurt.
Pain becomes unpredictable.
There are other past, present, and future problems in life.
The Autonomic Nervous System
The sympathetic nervous system helps us cope and stay protected from threat. It does so by sending adrenaline to all the tissues among many other processes.
In chronic pain states, there are increased levels of adrenaline, though in some cases adrenaline can become depleted. Adrenaline does not itself cause pain, but does increase alarm system sensitivity.
On the other hand, the parasympathetic nervous system is what slows us down and helps shift us out of a sympathetic state. This system is why relaxation and meditation can help with the healing process.
The Endocrine System
Chronic pain states are often associated with high levels are cortisol as well. Cortisol often gets a bad rap despite its role as a protector. What cortisol does is slow down unnecessary body processes which are not needed for immediate protection and enhances those which are.
The Immune System
The immune system has a major link to the autonomic and endocrine systems. The immune system works by releasing pro-inflammatory cytokines, which can create lethargy, loss of appetite, sensitive movements, etc. Even old pains can come back because of cytokines. Here are some fun immune system facts.
Immune system becomes more involved in serious or chronic states.
Immune system responses can become learnt.
Long-term stress and pain can lead to altered activity which leads to more cytokine production.
Immune stressors can be major or multiple minor events.
The immune system may underpin pain states such as mirror pain and loss of fine sensibility.
The immune system can be activated by the brain.
There are also several ways you can boost your immune system to counteract pain causing behaviors.
In threatening states, big mover muscles become primed. This change occurs evolutionarily so your body can escape potential threats. In injured states, prime movers can act as splints. If this state occurs for the long term, muscles can start to feel stiff and achy. Even if pain is gone, sometimes these muscles do not return to their normal activity levels.