THE EXPERIENCE OF PAIN

Pain is a warning mechanism protecting an individual by influencing them to withdraw from harmful stimuli and is primarily associated with injury or the threat of injury. Pain is subjective and difficult to quantify, as it has both affective and sensory components. The neuroanatomic basis of pain reception develops before birth, and individual pain responses are learned in early childhood. These responses are affected by social, cultural, psychological, cognitive, and genetic factors (Meldrum, 2021).

What Is Pain?

In 1979 the International Association for the Study of Pain defined pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” The newer 2020 definition (below) replaces terminology that relied upon a person’s ability to describe the experience to qualify as pain. Unlike the older definition, the newer definition no longer excludes infants, elderly people, and others—even animals—who cannot verbally articulate their pain.

  • Pain is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors.
  • Pain and the detection of painful stimuli are different phenomena. Pain cannot be inferred solely from activity in sensory neurons.
  • Through their life experiences, individuals learn the concept of pain.
  • A person’s report of an experience as pain should be respected.
  • Although pain usually serves an adaptive role, it may have adverse effects on function and social and psychological well-being.
  • Verbal description is only one of several behaviors to express pain; inability to communicate does not negate the possibility that a human or a nonhuman animal experiences pain.
    (IASP, 2021a)

Pain alters the quality of life more than any other health-related problem. It interferes with sleep, mobility, nutrition, thought, sexual activity, emotional well-being, creativity, and self-actualization. Surprisingly, even though pain is such an important obstacle to comfort, it is one of the least understood, most undertreated, and oft-discounted problems of healthcare providers and their patients.

PAIN-RELATED TERMINOLOGY
Term Definition
(IASP, 2021a)
Allodynia Pain due to a stimulus that does not normally provoke pain
Analgesia Absence of pain in response to stimulation that would normally be painful
Causalgia A syndrome of sustained burning pain, allodynia, and hyperpathia after a traumatic nerve lesion
Dysesthesia An unpleasant abnormal sensation, whether spontaneous or evoked
Hyperalgesia Increased pain from a stimulus that normally provokes pain
Hyperpathia A painful syndrome characterized by an abnormally painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold
Hypoalgesia Diminished pain in response to a normally painful stimulus
Neuralgia Pain in the distribution of a nerve or nerves
Neuropathic pain Pain caused by a lesion or disease of the somatosensory nervous system
Nociception pain Pain arising from actual or threatened damage to non-neural tissue due to the activation of nociceptors (high-threshold sensory receptors of the peripheral somatosensory nervous system)
Pain threshold Amount of pain required before individuals feel the pain; the lower the threshold, the less pain can be endured; the higher the threshold, the more pain can be endured
Pain tolerance level Maximum intensity of a pain-producing stimulus that a subject is willing to accept in a given situation; the subjective experience of the individual
Paresthesia An abnormal sensation whether spontaneous or evoked

Classification of Pain

The classification of pain is complicated, and there are several different classification systems, many of which overlap. Among other characteristics, pain can be classified by duration and source.

BY DURATION

Pain is classified by duration as acute or chronic.

Acute Pain

Acute pain is protective in that it motivates a person to take action immediately. Acute pain is caused by noxious stimulation due to injury, a disease process, or the abnormal function of muscle or viscera. Acute pain begins suddenly, is usually sharp in quality, and correlates with the amount of damage. It is temporary and subsides as healing takes place. In acute pain, the central nervous system is intact, and acute pain is a symptom. Examples of causes of acute pain include:

  • Surgery
  • Broken bones
  • Dental work
  • Burns or cuts
  • Labor and childbirth

There are two types of acute pain:

  • Somatic pain results from superficial injury to skin and subcutaneous tissue (e.g., burns, cut, abrasions) or deep injury to muscle, bone, joint, and connective tissues (e.g., fractures, arthritis, fibrositis, rupture of muscle belly).
  • Visceral pain results from injury to the internal organs (e.g., peptic ulcer, angina pectoris, renal colic).

In most instances, acute pain does not last longer than six months and disappears when the underlying cause of pain has been treated or has healed (Cleveland Clinic, 2022).

Chronic Pain

Chronic pain is ongoing and usually lasts longer than six months. This type of pain continues even after the injury or illness that caused it has healed. Chronic pain persists, recurs, or progresses over a long period of time and is often resistant to medical treatments. Pain signals remain active in the nervous system for weeks, months, or years. Some people suffer chronic pain even when there is no past injury or apparent body damage. Chronic pain is linked to such conditions as:

  • Headache
  • Arthritis and other musculoskeletal conditions
  • Cancer
  • Chemotherapy/radiation
  • Nerve pain
  • Back pain
  • Fibromyalgia
  • Surgical complications
    (Cleveland Clinic, 2022)

BY SOURCE

The sources (causes) of pain are divided into the categories of nociceptor, neuropathic, psychogenic, and idiopathic.

Nociceptor Pain

Nociceptor pain is acute pain that results when tissue damage produces a stimulus that sends an electrical impulse across a receptor (nociceptor) by way of a nerve fiber to the central nervous system. Receptors for this type of pain are located all around the body, particularly under the skin and the internal organs. Some body tissues, such as the brain and lung, have no nociceptors, and some tissues have many.

Nociplastic Pain

Nociplastic pain arises from altered nociception despite the absence of clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system. This type of pain may reflect changes in the way the nervous and immune systems function (Slater & Davies, 2021).

Neuropathic Pain

Neuropathic pain results from damage to or dysfunction of the peripheral or central nervous system rather than from stimulation of pain receptors. Mechanisms of neuropathic pain are complex and involve changes:

  • At the peripheral nociceptor and nerve level
  • At the dorsal root ganglion (DRG)
  • In the central nervous system, nociceptive pathways, and terminal structures

One example of neuropathic pain is phantom limb syndrome, which can occur following an amputation and when the brain continues to receive pain messages that originally carried impulses from the missing limb (Watson, 2022).

Radicular Pain

Radicular pain is a very specific type of pain that can occur when the spinal nerve becomes compressed or inflamed. It radiates from the back and hip to the leg(s) by way of the spine and spinal nerve root. People with radicular pain may experience tingling, numbness, and muscle weakness (Beaumont Health, 2022).

Psychogenic Pain

Psychogenic pain is believed to be sustained mainly by psychological factors. It does not refer to the common idea that pain experienced by some patients is exacerbated by psychological factors, or the finding of high pain-related distress or comorbid psychiatric disease. Instead, it implies that the pain is best understood as a result of psychological processes. It is classified as a somatic symptom disorder with prominent pain, which is diagnosed on the basis of excessive thoughts, feelings, or behaviors related to pain that are distressing, impair function, and appear out of proportion to physical findings.

It must be remembered that psychogenic pain is truly experienced and is not a deception. This distinguishes it from disorders that reflect a serious mental disorder in which reports of pain may not indicate a true experience of pain, and from malingering (Portenoy & Dhingra, 2020).

Idiopathic Pain

Idiopathic pain, also called pain of unknown origin, is chronic pain lasting six months or longer that has no identifiable cause. Although its origin is often unknown, idiopathic pain is very real. It is also possible for this type of pain to remain long after a medical condition has healed when pain normally should have ended (Jacques, 2021).

Factors That Influence the Experience of Pain

The experience of pain is influenced by both physiologic and psychosocial factors, all of which clinicians must consider in pain management. Physiologic factors include age, gender, genetic makeup, and stress response. Psychosocial factors include the person’s personality, the meaning ascribed to pain by an individual, fear and catastrophizing, and emotional distress (Ratka, 2020; Padgett, 2019).