Comparison of the efficacy of continuous epidural block with epidural electrical stimulation and conventional continuous epidural block for management of zoster-associated pain beyond the acute phase: A retrospective study

Continuous epidural block (CEB) is a popular clinical method for controlling postherpetic neuralgia (PHN). However, the long-term effects of CEB on PHN have not yet been established. This study aimed to confirm the clinical efficacy of epidural electrical stimulation catheters in CEB to manage PHN. Patients were classified into 2 groups: those with subacute PHN, between 30 and 180 days after the onset of the rash; and those with chronic PHN, over 180 days after the onset of the rash. On the basis of the type of catheter used, the patients were further divided into the following 2 groups: the esopocan group, in which the site of herpes zoster infection was confirmed using a contrast medium alone; and the epistim group, in which an additional method of electrical stimulation through a guide-wire in the catheter was used for detecting the site affected by herpes. Clinical efficacy was assessed with a numerical rating scale immediately 1, 3, and 6 months after the procedure. We also investigated whether additional interventional treatment was necessitated because of insufficient pain control during the 6-month follow-up. We examined 88 patients. In the subacute PHN period, the numerical rating scale score was significantly lower in the epistim group than in the esopocan group until 6 months. In the chronic PHN period, no significant differences in the numerical rating scale scores were observed between the 2 groups until 6 months. In the subacute PHN period, the adjusted odds ratio for other interventional procedures within 6 months in the esopocan group versus the epistim group was 2.59 (95% confidence interval [CI] 0.83–8.09, P = .10), and in the chronic PHN period, it was 1.31 (95% CI 0.11–5.46, P = .79). Epidural drug administration to specific segments using electrical stimulation catheters may be more useful in mitigating zoster-associated pain in subacute PHN.