What is Pain?

The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” (Merskey, 1994) This definition describes pain as a subjective experience; therefore, unlike hypertension or diabetes, there is no objective measurement for pain intensity.  Analysis of the objective data (history, psychosocial assessment, physical findings, imaging results, lab tests, etc.) is needed to evaluate the patient’s subjective report of pain.

Acute pain is characterized as being of recent onset, transient, and usually from an identifiable cause. 

Chronic or persistent pain can be described as ongoing or recurrent pain, lasting beyond the usual course of acute illness or injury healing, more than 3 to 6 months, and which adversely affects the individual’s well-being. Another definition for chronic or persistent pain is pain that continues when it should not. The International Association for the Study of Pain defines pain as a negative sensory and emotional experience. As such, the definition recognizes the important role of psychology in the experience of pain, and as therapeutic target. 

Chronic pain is classified by pathophysiology (the functional changes associated with or resulting from disease or injury) as nociceptive (due to ongoing tissue injury), neuropathic (resulting from damage to the brain, spinal cord, or peripheral nerves), or a mixture of these, combined with negative psychosocial effects. 

Central pain syndrome is a neurological condition caused by a process that specifically affects the central nervous system (CNS), which includes the brain, brainstem, and spinal cord. The disorder occurs in people who have or who have experienced strokes, multiple sclerosis, Parkinson's disease, brain tumors, limb amputations, brain injuries, or spinal cord injuries. It may develop months or years after injury or damage to the CNS. This also includes conditions such as chronic headaches, fibromyalgia, and Complex Regional Pain Syndrome (CRPS). 

Continuous pain is pain that is typically present for approximately half the day or more.

⚫ Science Daily Feb 6, 2008, Northwestern University

⚫ The frontal region of the cortex, “Never shuts up”

⚫ The brain does not keep an equilibrium