This is a summary of section 4 of “Explain Pain” by David Butler and Lorimer Moseley. CNS Alarms 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
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