Pain and its Assessment in Herpes Zoster
Pain typically accompanies acute herpes zoster. In a proportion of patients, herpes zoster pain persists well beyond rash healing. This persisting pain is termed post-herpetic neuralgia (PHN). Because of the substantial personal and economic burdens caused by PHN, studies of the pathophysiology of herpes zoster pain and of the efficacy of antiviral treatment in reducing prolonged pain are of great importance. Different methods have been used to examine pain in research on herpes zoster and in clinical trials, making it difficult to compare across studies. There is substantial evidence, however, that demonstrates the importance of distinguishing acute pain from PHN. Several differences have been found between acute herpes zoster pain and PHN, including pathophysiological findings, risk factors and pain quality. Recommendations for the design and analysis of future trials of antiviral agents in herpes zoster have been recently proposed. These include a definition of PHN and recommended secondary end points for future trials. Adopting these recommendations in future research on herpes zoster pain, and in the design and analysis of future trials, will facilitate comparisons across studies of the pathophysiology and prevention of PHN.