Definition
In the case of pain that occurs in the context of shingles, it is first necessary to distinguish the so-called post-zosteric neuralgia from the actual “zoster pain“. The “zosterschmerz” is the pain that occurs during a typical course of shingles infection. It is usually felt as burning and itching and is accompanied by a pustular rash restricted to a certain area of skin.
Thus, this pain usually disappears as the rash heals, although the duration and intensity of the pain can be influenced by appropriate measures. The so-called “post-zosteric neuralgia“, the most frequent complication of shingles, differs from this. It is referred to when the pain persists for more than two months after the external skin irritations have subsided, i.e. when it becomes chronic.
Cause
Both the actual “zoster pain” and the “post-zosteric neuralgia” occur in the context of shingles, in which varicella zoster viruses, which are already present in the organism due to a previous infection, are reactivated. During their migration to the skin along the nerve fibers, which are, among other things, responsible for the sensation of touch, the viruses trigger the typical skin changes and the associated “zoster pain” in the affected areas through inflammatory processes. In some cases, the pain occurs even before the manifestation of the actual rash.
However, it is not yet clear in detail why the pain persists after the healing of the skin changes and can develop into “post-zosteric neuralgia”. One possible explanation is permanent damage to the affected nerve fibers by the virus. This damage and subsequent improper healing leads to hypersensitivity, so that signals are constantly sent to the pain-conducting nerve fibers.
As a result, the nerve cells in the spinal cord, which are addressed by these nerve fibers, also become overexcitable. Thus, the nerve cells become active and report information about a pain sensation to the brain even when the actual cause of the pain has long since subsided. However, this constantly running signal cascade could also run the other way around towards the skin surface and meet pain receptors there, which in turn cause a local inflammatory reaction.
A further theory holds conversion processes, which are caused by shingles, responsible for the disturbed pain sensation. These conversion processes in both the peripheral and central nervous systems cause pain-conducting nerve fibers to be coupled to fibers that are responsible for normal touch and tactile sensation. In this way, the normal spinal cord inhibition of excessive pain sensation is circumvented.
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