What causes postherpetic neuralgia (PHN) of herpes zoster (shingles)?

Updated: Feb 11, 2021
  • Author: Camila K Janniger, MD; Chief Editor: Dirk M Elston, MD  more...
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The cause of PHN also remains a mystery. Rapid initiation of treatment decreases the incidence of PHN substantially, an effect that can be explained by the theory that incessant pain of active zoster sets up a positive feedback loop within the thalamus and the cortex, creating a central pain syndrome similar to phantom leg pain. According to this theory, prompt treatment breaks the loop by providing pain-free periods early in the disease course.

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