The complexity of the spinal structures and of pain mechanisms collectively make the problem of low back pain enigmatic. Pain is often severe and tends to persist. This paper reviews the abundant multisegmental innervation patterns of the spine, prior to a discussion of recent findings on the neurophysiological mechanisms of nociception and the consequences of injury. The activity profiles of nociceptors and wide dynamic range (WDR) neurones undergo change, following injury, or in the presence of inflammation. Thresholds decrease and spontaneous discharge activity occurs. WDR neurones develop a nociceptive function. They respond to activity in large diameter A-mechanoreceptors which leads to allodynia. In addition, Class IV joint receptors which only fire in the presence of inflammation may serve to intensify pain. A high density of NA+ channels in the dorsal root ganglion prevents a potential conduction block due to T-cell branching but facilitates spontaneous discharge activity especially following nerve injury. Finally, the degeneration of superficial dorsal horn neurones that occurs following nerve injury is more pronounced in the presence of persistent pain but a causal relationship has not been determined at this time.
|Original language||English (US)|
|Number of pages||14|
|State||Published - Jan 1 1992|
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