Definition of pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.¹
Whether it is acute or chronic, pain is a complex biopsychosocial phenomenon.
Pain is not simply experienced based on a switch that is activated in the body’s periphery, but involves circuits in the central nervous system (spinal cord and brain) that can either diminish or exaggerate pain depending on other factors such as mood and stress.
In conditions related to the spine or joints, for example, it is not uncommon to see a discrepancy between damage visible on imaging and a person’s self-reported level of pain. This is due to the complexities of the pain experience, which not only includes structural changes, but also peripheral and central pain mechanisms and subjective factors.
Acute pain is new-onset pain and is generally reflective of tissue damage. For the most part, the pain ends when the injury heals or the illness is resolved. However, when it lasts or recurs for more than 3 months it is defined as chronic pain.
Chronic pain can be linked to tissue damage but is also related to other factors such as chronic inflammation, emotions, and neuroplastic changes that occur in the brain. With chronic pain, pain itself can become the disease as the nervous system may stay in a state of reactivity after the initial injury has healed.
Chronic pain as a disease of the nervous system.
When exposed to repetitive stimulation and inflammation, peripheral pain terminals can become sensitized. Changes take place at the level of the pain receptors, the spinal cord, and brain, resulting in hyper-reactivity of the central nervous system, referred to as central sensitization. In other words, the brain and spinal cord “turn up the volume” in response to any unpleasant stimulus.
This leads to an increased experience of pain at lower thresholds, even without harmful stimuli. It is a phenomenon resulting in the progression of localized pain to a generalized pain disorder. Attention must therefore shift away from the symptoms of pain to the underlying neurophysiological process. Chronic pain from central sensitization can occur with all pain conditions, including acute spine injuries, whiplash injuries, failed back surgery syndrome, and disorders of the spine.
Given the many factors that impact pain, adequate treatment requires a comprehensive approach – one that considers the cortical, inflammatory, and psychosocial factors that impact it. We must consider the entire pain pathway – its molecules, cells, and circuits – and how seemingly unrelated behaviors such as poor sleep habits, can lower pain threshold and tolerance, and if left untreated, can be a barrier to pain management.
Lifestyle behaviors and choices we make every day, directly impact inflammation, immunity, the nervous system, and many other elements integral to the pain experience and healing.