What is the pathophysiology of postherpetic neuralgia (PHN)?

Updated: Mar 06, 2018
  • Author: W Alvin McElveen, MD; Chief Editor: Robert A Egan, MD  more...
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Answer

Some patients with postherpetic neuralgia (PHN) appear to have abnormal function of unmyelinated nociceptors and sensory loss (usually minimal). Pain and temperature detection systems are hypersensitive to light mechanical stimulation, leading to severe pain (allodynia). Allodynia may be related to formation of new connections involving central pain transmission neurons. Other patients with PHN may have severe, spontaneous pain without allodynia, possibly secondary to increased spontaneous activity in deafferented central neurons or reorganization of central connections. An imbalance involving loss of large inhibitory fibers and an intact or increased number of small excitatory fibers has been suggested. This input on an abnormal dorsal horn containing deafferented hypersensitive neurons supports the clinical observation that both central and peripheral areas are involved in the production of pain.


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