What is the neurophysiology of 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

Nociception is the neurochemical process whereby specific nociceptors convey pain signals through peripheral neural pathways to the central nervous system (CNS). Acute tissue damage to the spinal motion segment and associated soft tissues activates these pathways. When the peripheral source of pain persists, intrinsic mechanisms that reinforce nociception influence the pain. The nervous system can enhance a pain stimulus generated by tissue damage to levels far greater than any threat it signifies to the human organism; this is a common clinical scenario in cases of chronic spinal pain.

Noxious mechanical, thermal, and chemical stimuli activate peripheral nociceptors that transmit the pain message through lightly myelinated A-delta fibers and unmyelinated C-fibers. Nociceptors are present in the outer annular fibrosis, facet capsule, posterior longitudinal ligament, associated muscles, and other structures of the spinal motion segment. Peripheral transmission of pain stimuli leads to the release of excitatory amino acids, such as glutamine and asparagine, which then act on N -methyl-D-aspartic acid (NMDA) receptors, causing the release of the neuropeptide SP. Neuropeptides such as SP, CGRP, and VIP are transported to the endings of nociceptive afferents, which inflammation and other algogenic mechanisms sensitize. Thereafter, the affected nociceptors respond to mild or normal sensory stimuli, such as a light touch or temperature change (allodynia).


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