Chronic nerve damage found in post-herpetic neuralgia
medwireNews: Pain and discomfort in people with post-herpetic neuralgia typically resolve within months of infection yet sensory function and innervation can remain abnormal for many years, an observational study indicates.
Karin Petersen (California Pacific Medical Center Research Institute, San Francisco, USA) and colleagues investigated the natural history of post-herpetic neuralgia in people with varicella zoster virus infection.
They identified 43 patients who had participated in an earlier study of herpes zoster, of whom 14 reported suffering pain at 6 months post-diagnosis. These individuals were comprehensively assessed at a median of 3.9 years after infection; 10 patients were subsequently assessed again at a median of 7.7 years.
Writing in Pain, Petersen et al reveal that all of the patients who were pain-free at 6 months remained pain-free throughout extended follow up. None were taking medication for zoster-associated pain.
Of the 14 patients who had pain at 6 months, just two were still experiencing pain at 3.9 years. One of these patients met the criteria for clinically meaningful post-herpetic neuralgia (defined as pain of more than 30 on a 100-mm visual analog scale over the past 48 hours).
One patient who was pain-free at 6 months reported very mild pain at the final follow up visit, while three patients had mild allodynia at this point.
"Sensory function continued on a path toward normalization, but was still abnormal in many subjects, especially those who met criteria for post-herpetic neuralgia at 6 months," remark Petersen et al.
Interestingly, analysis of cutaneous biopsies taken showed no clear evidence of re-innervation, and there was also a persistent asymmetry with regard to both hyperesthesia and hyperalgesia between post-herpetic skin and control "mirror" skin.
The researchers conclude that "there is only modest recovery of sensory function and no anatomical recovery despite pain resolution in the majority of subjects."
They add: "This supports our previous conclusion that the severity of the initial injury was the dominant factor and that recovery of sensory function and anatomical re-innervation of the skin was not a requirement for pain resolution."
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By Joanna Lyford, Senior medwireNews Reporter