Predictors of Postherpetic Neuralgia: A Prospective Study From Eastern Nepal

Herpes zoster (HZ) is a viral infection with severe acute and chronic pain. This study was aimed at determining the incidence rate of postherpetic neuralgia (PHN). The objectives of the study were to understand the epidemiology of HZ and to identify the risk factors for PHN at a referral hospital in eastern Nepal.

A total of 82 patients with HZ presenting within 72 h of skin eruption with a pain rating of 40 or above on a visual analog scale, with an age ≤ 75 years and those willing to participate were included in the study. However, those who had already started antiviral medicine or analgesics were excluded. All baseline details were noted and the participants were followed for 16 weeks at monthly intervals to assess the pain status and development of PHN. The epidemiological parameters and the predictors of PHN were predicted using the chi-square test and logistic regression analysis.

The mean age of the participants was 47 ± 18.77 years. The majority (32.9%) of the participants belonged to 61-70 years. Thoracic dermatome was most frequently (56.1%) involved. At the 16-week follow-up, of the 77 patients who completed the study, 14 had persistent pain; hence, the incidence of PHN was 18.2%. Advancing age (> 50 years) (adjusted odds ratio 2.95, 95% confidence interval (CI) 1.33-6.53); diabetes (OR 13.09, 95% CI 1.40-122.24); and prolonged prodromal pain (OR 12.01, 95% CI 1.40-102.77) were the most important risk factors for PHN.

In our study, the prevalence of PHN was quite high (18.2%) despite timely antiviral treatment and regular follow-up. An age of more than 50 years, prolonged prodromal pain, and diabetes were the most significant predictors of PHN. Hence, early intervention and frequent follow-up of those individuals are recommended.