What are characteristics of nociceptive modulation in low back pain (LBP)?

Updated: Aug 22, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Answer

Answer

Nociceptive modulation first occurs in the dorsal horn, where nociceptive afferents converge to synapse on a single wide dynamic range (WDR) neuron. WDR neurons respond with equal intensity regardless of whether the neural signal is noxious or an exaggerated nonpainful stimuli (hyperalgesia). Hyperalgesia and allodynia initially develop at the injury site; however, when peripheral and central sensitization occur by means of WDR neural activity and central processing, the area of pain expands beyond the initial more-limited region of focal tissue pathology.

Finally, a phenomenon termed wind-up results from the repetitive activation of C-fibers sufficient to recruit second-order neurons that respond with progressively increasing magnitude; NMDA receptor antagonists can block this effect. Wind-up contributes to central sensitization, including hyperalgesia, allodynia, and persistent pain. These nociceptive mechanisms, which reinforce the pain signal, frequently recruit the sympathetic nervous system. Elevated norepinephrine levels in injured areas increase pain sensitivity by means of regional vasomotor and sudomotor changes. Also, higher acetylcholine levels can augment ongoing local and regional involuntary muscle contraction and spasm.


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