Effects of applying nerve blocks to prevent postherpetic neuralgia in patients with acute herpes zoster: a systematic review and meta-analysis

Abstract

Background: Postherpetic neuralgia (PHN) is a common and painful complication of acute herpes zoster. In some cases, it is refractory to medical treatment. Preventing its occurrence is an important issue. We hypothesized that applying nerve blocks during the acute phase of herpes zoster could reduce PHN incidence by attenuating central sensitization and minimizing nerve damage and the anti-inflammatory effects of local anesthetics and steroids.

Methods: This systematic review and meta-analysis evaluates the efficacy of using nerve blocks to prevent PHN. We searched the MEDLINE, EMBASE, Cochrane Library, ClinicalTrials.gov and KoreaMed databases without language restrictions on April, 30 2014. We included all randomized controlled trials performed within 3 weeks after the onset of herpes zoster in order to compare nerve blocks vs active placebo and standard therapy.

Results: Nine trials were included in this systematic review and meta-analysis. Nerve blocks reduced the duration of herpes zoster-related pain and PHN incidence of at 3, 6, and 12 months after final intervention. Stellate ganglion block and single epidural injection did not achieve positive outcomes, but administering paravertebral blockage and continuous/repeated epidural blocks reduced PHN incidence at 3 months. None of the included trials reported clinically meaningful serious adverse events.

Conclusions: Applying nerve blocks during the acute phase of the herpes zoster shortens the duration of zoster-related pain, and somatic blocks (including paravertebral and repeated/continuous epidural blocks) are recommended to prevent PHN. In future studies, consensus-based PHN definitions, clinical cutoff points that define successful treatment outcomes and standardized outcome-assessment tools will be needed.

Keywords: Epidural block; Herpes zoster; Nerve block; Paravertebral block; Postherpetic neuralgia; Stellate ganglion block.

Fig. 1. Flow diagram demonstrating study search results.

Fig. 2. Risk of bias summary: review authors' judgements about each risk of bias item for each included study. Green = low risk of bias; yellow = unclear risk of bias, red = high risk of bias.

Fig. 3. Effects of nerve blocks on the incidence of postherpetic neuralgia. The incidence of postherpetic neuralgia was significantly lowered in nerve block treatment compared with control standard treatment at 3, 6 and 12 months after the onset of herpetic skin rash, but heterogeneity among trials was high.

Fig. 4. Effects of nerve blocks on the incidence of postherpetic neuralgia according to the types of nerve block. The incidence of postherpetic neuralgia was lowered by repeated/continuous epidural block, but not by stellate ganglion block and single epidural block.

Fig. 5. Comparison of single block versus repeated/continuous blocks on the incidence of postherpetic neuralgia. The incidence of postherpetic neuralgia was lowered by repeated/continuous blocks, but not single block.

Fig. 6. Effects of nerve blocks on the duration of acute pain caused by herpes zoster.