Chronic pain pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

## Overview

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## Functional Anatomy

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The anatomy of the nociceptive system can be grossly divided into the peripheral and central nervous system. The peripheral nervous system consists of small myelinated and unmyelinated nerve fibers. These nerve fibers converge into a region of the spinal cord referred to as the dorsal horn. The dorsal horn is the first relay station in pain signal transmission. The next element of pain transmission includes nerve fibers that then travel to the thalamus. From the thalamus the next order of neurons ascend to the limbic system and sensory cortex. This accounts for the affective elements and discriminative of pain respectively.[1][2]

## Nociception

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The experience of pain biologically is referred to as nociception. Nociception occurs in any tissue or organ in which pain signals arise secondary to a disease process or trauma. The nociception can also occur if there is dysfunction or damage to nerves themselves.[3]

## The Pathophysiology of Chronic Pain

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Under persistent activation nociceptive transmission to the dorsal horn may induce a wind up phenomenon. This induces pathological changes that lower the threshold for pain signals to be transmitted. In addition, it may generate nonnociceptive nerve fibers to respond to pain signals. Nonnociceptive nerve fibers may also be able to generate and transmit pain signals. In chronic pain this process is difficult to reverse or eradicate once established.[4]

## References

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1. ↑ Romanelli P, Esposito V (2004). "The functional anatomy of neuropathic pain". Neurosurg. Clin. N. Am. 15 (3): 257–68. PMID 15246335.
2. ↑ Vanderah TW (2007). "Pathophysiology of pain". Med. Clin. North Am. 91 (1): 1–12. PMID 17164100.
3. ↑ Merskey H (1994). "Logic, truth and language in concepts of pain". Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation. 3 Suppl 1: S69–76. PMID 7866375.
4. ↑ Vadivelu N, Sinatra R (2005). "Recent advances in elucidating pain mechanisms". Current opinion in anaesthesiology. 18 (5): 540–7. PMID 16534290.

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