Background: Herpes zoster causes acute pain and sometimes leads to postherpetic neuralgia (PHN). The previously reported risk factors of PHN such as old age, allodynia, paresthesia and so on are not based on evidence. Although nerve block is useful to relieve acute pain and recommended for prevention of PHN, evidence is scanty.
Methods: The patients with herpes zoster within 3 months after the onset were studied. The patient underwent nerve blocks and proper medical treatment, and were followed for up to one year. The risk factors of PHN were assessed. We evaluated whether nerve block prevented PHN.
Results: A total of 144 consecutive patients were studied. Twenty seven % of patients suffered PHN. Old age (> 65 y. o) and hypesthesia were confirmed to be the risk factors of PHN, whereas the intensity of acute pain was not. Patients who underwent nerve block within 1 month after the onset were less likely to suffer from PHN compared with patients of delayed nerve blocks.
Conclusions: Old age, hypesthesia and delayed nerve blocks were the risk factors of PHN. Nerve blocks in the early phase of herpes zoster may be useful to prevent PHN, particularly in the younger patients.