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Chronic pain is medically defined as pain that has lasted 6 months or longer. This constant or intermittent pain has often outlived its purpose, as it does not help the body to prevent injury. It is often more difficult to treat than acute pain. Expert physician care is generally necessary to treat any pain that has become chronic. When opioids are used for prolonged periods drug tolerance, chemical dependency and even psychological addiction may occur. While drug tolerance and chemical dependency are common among opioid users, psychological addiction is rare.
Causes
Chronic pain is essentially caused by the bombardment of the central nervous system (CNS) with nociceptive impulses, which causes changes in the neural response. The pain subsequently provokes changes in the behaviour of the patient, and the development of fear-avoidance strategies. As a result, the patient may also become physically atrophied and deconditioned. However, it is important to remember that chronic pain is multifactorial, involving psychological, physical and social factors.
Types of pain
Acute pain is defined as short-term pain or pain with an easily identifiable cause. Acute pain is the body's warning of present damage to tissue or disease. It is often fast and sharp followed by aching pain. Acute pain is centralized in one area before becoming somewhat spread out. This type of pain responds well to medications.
Chronic pain is medically defined as pain that has lasted 6 months or longer. This constant or intermittent pain has often outlived its purpose, as it does not help the body to prevent injury. It is often more difficult to treat than acute pain. Expert care is generally necessary to treat any pain that has become chronic. When opioids are used for prolonged periods drug tolerance, chemical dependency and even psychological addiction may occur. While drug tolerance and chemical dependency are common among opioid users, psychological addiction is rare.
The experience of physiological pain can be grouped into four categories according to the source and related nociceptors (pain detecting nerves).
Cutaneous pain is caused by injury to the skin or superficial tissues. Cutaneous nociceptors terminate just below the skin, and due to the high concentration of nerve endings, produce a well-defined,
localized pain of short duration. Example injuries that produce cutaneous pain include paper cuts, minor (first degree) burns and lacerations.
Somatic pain originates from ligaments, tendons, bones, blood vessels, and even nerves themselves, and are detected with somatic nociceptors. The scarcity of pain receptors in these areas produces a dull, poorly-localized pain of longer duration than cutaneous pain; examples include sprained ankle and broken bones.
Visceral pain originates from body organs visceral nociceptors are located within body organs and internal cavities. The even greater scarcity of nociceptors in these areas produces a pain usually more aching and of a longer duration than somatic pain. Visceral pain is extremely difficult to
localize, and several injuries to visceral tissue exhibit "referred" pain, where the sensation is
localized to an area completely unrelated to the site of injury. Myocardial ischaemia (the loss of blood flow to a part of the heart muscle tissue) is possibly the best known example of referred pain; the sensation can occur in the upper chest as a restricted feeling, or as an ache in the left shoulder, arm or even hand.
Phantom limb pain is the sensation of pain from a limb that one no longer has or no longer gets physical signals from - an experience almost universally reported by amputees and quadriplegics.
Finally neuropathic pain ("neuralgia") can occur as a result of injury or disease to the nerve tissue itself. This can disrupt the ability of the sensory nerves to transmit correct information to the thalamus, and hence the brain interprets painful stimuli even though there is no obvious or documented physiologic cause for the pain.
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This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Chronic_pain"
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