Neuraxial and sympathetic blocks in herpes zoster and postherpetic neuralgia: an appraisal of current evidence.

BACKGROUND AND OBJECTIVES: Epidural, intrathecal, and sympathetic blocks are used for the treatment of pain caused by herpes zoster (HZ) and postherpetic neuralgia (PHN). This study was undertaken to evaluate and synthesize existing evidence for using these nerve blocks with various injectates (local anesthetic [LA] alone, LA + steroids) in treating pain of HZ, PHN (>6 months), and its prevention.

METHODS: A computerized search of published trials in the English language from 1966 to 2001 was carried out on Medline, EMBASE, and Cochrane Clinical Trial databases. Levels of evidence and grades of recommendations were made based on criteria published by the Oxford Centre for Evidence-Based Medicine.

RESULTS: Among the studies meeting inclusion criteria, treatment was initiated during acute pain in 71% (15/21) and PHN in 29% (6/21). Randomized controlled trials (RCTs, level 1b evidence) constituted 19% (4/21), individual cohort (levels 2b, 3b) 29% (6/21), and case series (level 4) 43% (9/21). Overall, 80% (15/21) of trials showed a positive outcome with these blocks. The use of sympathetic (LA) and epidural blocks (LA + steroid) for pain of HZ was supported by 1 RCT each, and intrathecal block (LA + steroid) for PHN was supported by 2 RCTs.

CONCLUSIONS: Evidence for the beneficial effect of epidural LA + steroid in HZ, and intrathecal LA + steroid in PHN appears to be consistent (grade A). If given within 2 months of HZ, epidural LA + steroid may reduce the incidence of PHN after 1 year (grade A). Evidence for use of sympathetic blocks in HZ and PHN, although generally useful (Grade B), requires RCTs for validation.