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

Abstract

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.

Keywords: Follow-Up Studies; Ganglia; Herpes Zoster; Incidence; Logistic Models; Nerve Block; Neuralgia; Pain.; Postherpetic; Spinal.

Fig. 1

Subjects flow diagram. ZRP: zoster-related pain, SNRB: selective nerve root block, HZ: herpes zoster.

Fig. 2

Receiver operating characteristic curve. The areas under the curve (AUC) is 0.658 (95% confidence interval, 0.514–0.802; P = 0.035).

Fig. 3

Patient-reported long-term severity of postherpetic neuralgia (PHN). Acute group: selective nerve root block (SNRB) ≤ 14 days, subacute group; SNRB >14 days from herpes zoster onset. Details of patients-reported 4-step severity grading of PHN: “relieved”, no pain; “improved”, pain is reduced but remained; “sustained”, painful and no change in pain after treatment; “aggravated”, more painful after treatment. ^aThe proportions of cured (relieved) patients were 62.5% and 25.5% in acute and subacute groups, respectively, which was significantly different by Mann–Whitney rank-sum test (P = 0.007).

Fig. 4

Kaplan–Meier curve. Time from selective nerve root block (SNRB) to complete cure of postherpetic neuralgia (PHN) was significantly shorter in the acute group than in the subacute group (2.4 ± 0.7 years vs. 5.0 ± 0.4 years; P = 0.003 by log-rank test). Acute group: SNRB ≤ 14 days; subacute group: SNRB >14 days from herpes zoster onset.