We read with great interest the recently published case report by McAllister et al.  1describing the successful management of postherpetic neuralgia in the perineal area using repeated ganglion impar blockade by a local anesthetic solution. This is one of the first case reports describing the efficacy of blockade of the terminal part of the sympathetic chain in non-cancer-related pain. We congratulate the authors on their therapeutic success, but several questions remain to be answered.

Ganglion impar blockade is not a routinely used analgesic procedure. Initial articles have reported chemical neurolysis of the ganglion impar as adjuvant therapy of cancer-related pain in the perineal region. In their overview, De Medicis and de Leon-Casasola provide a summary of studies evaluating the efficacy and complication rate of ganglion impar blockade.2They conclude there have been only two studies reporting good efficacy of neurolytic blockade using 6% phenol for visceral perineal pain of cancer origin in a total of 36 patients. There is only one study addressing the efficacy of ganglion impar inhibition in noncancer pain. The procedure was found to be ineffective in 20 patients with coccygodynia.3In addition to this study, there have been only a couple of case reports on the successful management of perineal pain of noncancer etiology using this technique of blockade.1,4 

In their patient with postherpetic neuralgia, McAllister et al.  used a corticosteroid as an additive to a local anesthetic, administering it to the presacral area. The analgesic efficacy of corticosteroids to sacral sympathetic structures has not been demonstrated to date, and the mechanism of its analgesic activity remains unclear.

Another thing we found surprising was the long-term analgesic effect of local anesthetic solution (3–5 months). The common duration of the analgesic effect of local anesthetics administered to that area in diagnostic/prognostic blockade is 2–7 days.2 

In our experience with the management of noncancer perineal pain in 26 patients with chronic pain after perineal surgery, vulvodynia, and vulvar pruritus to date, we are able to make a preliminary outcome determination using the ganglion impar procedure: A testing blockade with a local anesthetic has an analgesic efficacy of 2–5 days. Multiple blockade was accomplished in these patients using a mixture of a local anesthetic with clonidine (10 ml bupivacaine, 0.375%, plus 75 μg clonidine). In this pilot study, clonidine extended the analgesic effect to as long as 14 days. Clonidine administered to the sympathetic nervous system presumably prolongs the duration of blockade, as demonstrated by Kimura et al .5Still, to achieve long-term analgesic effect in this cohort, most patients required chemical ganglion impar neurolysis or radiofrequency thermolesion.†

Further larger and randomized clinical studies are needed to confirm the acceptability of ganglion impar blockade and destruction in noncancer perineal pain.

* Na Homolce Hospital, Prague, Czech Republic. pafkam@seznam.cz

McAllister RK, Carpentier BW, Malkuch G: Sacral postherpetic neuralgia and successful treatment using a paramedial approach to the ganglion impar. Anesthesiology 2004; 101:1472–4
DeMedicis E, de Leon-Casasola O: Ganglion impar block: Critical evaluation. Tech Reg Anesth Pain Manage 2001; 5:120–2
Vranken JH, Bannink IMJ, Zuurmond WWA, Sassen AM, de Lange JJ: Invasive procedures in patients with coccygodynia: Caudal epidural infiltration, pudendal nerve block and blockade of the ganglion impar (abstract). Reg Anesth Pain Med 2002; 25:S25
Kamalam DR, Freedman GM, Kreitzer JM: Radiofrequency ablation of ganglion impar for intractable coccydynia (abstract). Anesth Analg 2002; 94:S228
Kimura Y, Hamaguchi S, Okuda Y, Kitajima T: Addition of clonidine increases duration and magnitude of vasodilative effect induced by sympathetic block with mepivacaine in dogs. Reg Anesth Pain Med 2001; 26:329–32