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Post-Herpetic Neuralgia is due to changes in the nervous system produced
by the varicella virus. Scientists do not understand the specifics of these
processes. It is known that nerve injury can change nerve cells such that
they discharge spontaneously, are activated more easily, and show exaggerated
responses to stimuli. Nerve regrowth after the injury produces new nerve endings
that are also prone to unprovoked discharge. The excessive activity is thought
to lead to hyperexcitability of the portion of the spinal cord that contains
the cell bodies of the sensory neurons. This results in altered central nervous
system signal processing and exaggerated central nervous system responses
to all input (Kost, 1996). In addition, the attack by the virus leads to the
release of chemical mediators of inflammation. Chronic inflammation can develop,
producing irritable sensory receptors as well (Rowbotham, 1999, 2001).
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