Background and Objectives. The goal of this study was to evaluate the analgesic effects of intrathecal versus epidural methylprednisolone acetate (MPA) in patients with intractable postherpetic neuralgia (PHN).

Methods. We studied 25 patients with a duration of PHN of more than 1 year. The patients were randomly allocated to one of two groups: an intrathecal group (n = 13) and an epidural group (n = 12). Sixty milligrams of MPA was administered either into the intrathecal or the epidural space four times at 1-week intervals depending on the treatment group. Continuous and lancinating pain and allodynia were evaluated by a physician unaware of group assignment with a 10-cm visual analogue scale before treatment, at the end of treatment, and 1 and 24 weeks after treatment. In addition, cerebrospinal fluid (CSF) was obtained for measurement of interleukin (IL)-1β, -6, and -8 and tumor necrosis factor-alpha before and 1 week after treatment.

Results. We found marked alleviation of continuous and lancinating pain and allodynia in the intrathecal group (P <.001). The improvements were much greater in the intrathecal group than in the epidural group at all time points after the end of treatment (P < .005). IL-8 in the CSF decreased significantly in the intrathecal group as compared to the epidural group at the 1-week time point (P <.01), whereas the other cytokines were undetectable.

Conclusions. Our results suggest the effectiveness of intrathecal as compared to epidural MPA for relieving the pain and allodynia associated with PHN. Also, our findings, together with the decrease in IL-8, may indicate that intrathecal MPA improves analgesia by decreasing an ongoing inflammatory reaction in the CSF.