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By: Robert G. Bell

Robert G. BellIn a previous post, I discussed pain and the associated national epidemic with the misuse of pain medication. Everyone has pain, whether it be acute or chronic, and it is an individual struggle. The key is management of the pain through various regimens that may include combinations of physical, medical, and pharmaceutical therapies as well as nontraditional therapies. But what is pain and how is it described?

Although my mother said I invented the word, the word “pain” originally derives from Greek ποινή (poine) meaning the price paid, penalty, or punishment. Pain, as defined by the International Association for the Study of Pain (IASP), is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage,” and pain is usually described in terms of its severity, duration, and type. So pain generally can be described as a sensation that hurts. Pain is a symptom, a little (or big) reminder telling you something may be wrong in your system (the 5th vital sign). The underlying cause of the pain (e.g., compressed nerve) has to be diagnosed and properly treated to cure, alleviate, or lessen the associated pain. If the source of the pain cannot be treated or is unknown, pain management therapies are usually suggested.

The type of pain can be described as either acute or chronic. Acute pain is usually severe and short-lived, and it is often a signal that your body has been injured. When the injury heals, the acute pain usually goes away. Chronic pain is usually present for long periods of time that can range from mild to severe and is often the result of a disease or injury that may require ongoing treatment.

Pain pathophysiology generally comprises two categories: nociceptive (including viseral and somatic) and neuropathic (including peripheral and central) pain. Nociceptive pain stimulates specific pain receptors, which may be mechanical, chemical or thermal in nature, that are specifically designed to detect stimuli (such as a cut or a broken bone) that may cause harm to the body. It can be somatic where pain is felt on the skin, muscle, joints, bones, and ligaments.  It is visceral when the pain felt in the internal organs and main body cavities. Visceral pains are more difficult to localize than somatic pains.  For example, the sensations are more likely to be a vague deep ache in the lower back, abdominal pain to the mid-back, and thoracic pain to the upper back (referred pain).Skeleton pain

Neuropathic pain (nerve pain) is associated with nerve damage and is often described as a burning or heavy sensation, or numbness along the path of the affected nerve, possibly due to pinched or trapped nerve. The pain originates from the nerves between the tissues and the spinal cord (peripheral nervous system) and the nerves between the spinal cord and the brain (central nervous system). Neuropathic pain can be caused by nerve degeneration, as might be the case in an accident, stroke, multiple-sclerosis, or hypoxia. A torn or slipped disc will cause nerve inflammation which triggers neuropathic pain, and nerve infections, such as shingles, can also cause neuropathic pain.

Pain and pain tolerance is a very individual experience and only the person who is experiencing the pain can describe it accordingly. It can adversely affect the domains of the patients’ quality of life.  The patient’s emotional response to pain contributes significantly to the overall pain the patient experiences. There are large inter-individual differences in pain severity evoked by similar stimuli, and no valid objective measure has been found to compare the severity of one person’s pain with that of another. What may be painful to me might not be to you. It is almost impossible to measure a person’s pain objectively, but it is typically measured by a subjective pain assessment scale instruments. A reliable pain assessment instrument requires consistent results when performed under similar conditions and validity that the assessment instrument actually measures pain and not some other symptoms (such as anxiety). Unfortunately, there is no universal or ideal pain assessment tool. The best one is you and how you communicate with your physician to identify and address the root cause of the pain.

Most of us have pain, whether it be acute or chronic, nociceptive or neuropathic, and it can range from annoying to debilitating. So don’t complain—our next posts will describe some techniques to help you manage the pain.

Robert G. Bell, Ph.D., is president and owner of Drug and Biotechnology Development LLC, a consultancy to the pharmaceutical industry and academia for biological, drug, and device development.