The efficacy of selective nerve root block for the long-term outcome of postherpetic neuralgia

Background: Several nerve blocks can reduce the incidence of postherpetic neuralgia (PHN) as well as relieve acute zoster-related pain, but the long-term outcome of PHN has not been clearly determined. This study investigated the efficacy of selective nerve root block (SNRB) for herpes zoster (HZ) on the long-term outcome of PHN. Methods: We prospectively conducted an interview of patients who had undergone an SNRB for HZ from January 2006 to December 2016 to evaluate their long-term PHN status. The relationship between the time from HZ onset to the first SNRB and the long-term outcome of PHN was investigated. Results: The data of 67 patients were collected. The patients were allocated to acute (SNRB ≤ 14 days, n = 16) or subacute (SNRB > 14 days, n = 51) groups. The proportions of cured patients were 62.5% and 25.5% in the acute and subacute groups (P = 0.007), respectively. In logistic regression, an SNRB > 14 days was the significant predictor of PHN (adjusted odd ratio, 3.89; 95% confidence interval, 1.02-14.93; P = 0.047). Kaplan–Meier analysis revealed that time from the SNRB to the cure of PHN was significantly shorter in the acute group (2.4 ± 0.7 yr) than in the subacute group (5.0 ± 0.4 yr; P = 0.003). Conclusions: An early SNRB during the acute stage of HZ (within 14 days) appears to decrease the incidence and shorten the duration of PHN, with a median of 5.0 years of follow-up.