In Reply:—
I would like to thank Dr. Kabbara for his further information and clarification of the ease of the transsacrococcygeal approach to the ganglion impar. It was not my intent to impugn the utility of this approach, but to highlight the ease of the paramedial approach to the ganglion impar as a useful alternative. It is my hope that this potentially useful sympathetic block will find favor with clinicians, by either approach, and that many patients will benefit from it.
The interest and comments of Michalek et al. are appreciated. They note that the duration of efficacy of sympathetic block of the ganglion impar with local anesthetics and steroids in my case report does not match the duration of relief that they have seen in treating patients with perineal pain of noncancer etiology (chronic postoperative perineal pain, vulvodynia, and vulvar pruritus). However, the mechanism of pain in postherpetic neuralgic (PHN), although not completely understood, seems to be quite different from that in the patient population treated by Michalek et al.
Treatment of PHN with sympathetic blocks, with or without steroids, is controversial but has been described in several studies with favorable results far outlasting the normal duration of action of the local anesthetic or steroid. Forrest1injected 1–2 ml bupivacaine, 0.5%, with 60–120 mg methylprednisolone once a week for 3 weeks. At 1 month, 57% of patients were pain free, and 6 months later, 86% of these patients continued to be pain free. Forrest also reported on 37 patients with longstanding PHN who were treated with three epidural steroid injections given at 1-week intervals. Significant reductions in visual analog scale ratings were noted at 1 month, and 89% of the patients were pain free at 1 yr.2Milligan and Nash3also reported favorable long-lasting relief of PHN after stellate ganglion blocks. The mechanism of the prolonged effect is unclear. Hetherington4advocated consideration of sympathetic blocks as a major adjunctive therapy for all PHN patients, although it is recognized that there are no guidelines as to how many to perform or how often to perform them.
Therefore, the experience of Michalek et al. with duration of efficacy may not necessarily apply to PHN due to complex and differing mechanisms of pain. I agree that further investigation is warranted. However, because PHN in the sacral dermatomes is uncommon, it will be difficult to conduct a well-controlled study to find more definitive answers.
Scott &White Memorial Hospital and Clinic; Scott, Sherwood, and Brindley Foundation; the Texas A&M University Health Science Center College of Medicine; Temple, Texas. rmcallister@swmail.sw.org
