Cancer pain arising from the pelvic viscera can be a devastating manifestation of advanced malignancy. When conservative therapies are inadequate or associated with intolerable side effects, interventional neurolytic therapy should be considered. We describe an alternative technique to blockade of the ganglion impar using computed tomography (CT) guidance through a lateral approach.

A 76-yr-old woman with recurrent squamous cell carcinoma of the vulva was referred to the pain management service. Diagnosis was first made in 2004, and she had undergone radiation therapy and chemotherapy in the same year. This was followed by a modified left hemivulvectomy and a modified radical vulvectomy in July and December 2005, respectively, for recurrent disease. She presented 4 months later with worsening rectal and vaginal pain. Perineal pain was aggravated by defecation and micturition. Physical examination revealed a fungating lesion involving the perineum and biopsy was consistent with recurrent cancer. Pain was not adequately controlled with high doses of opioid medication. CT pelvis demonstrated soft tissue thickening and irregularity extending from the vulva to the anus. The patient consented to a neurolytic block of the ganglion impar under CT guidance.

With the patient positioned prone on the CT scanner, preliminary axial scout images were obtained to identify the sacrococcygeal junction. Two entry points approximately 10.5 cm lateral to the midline on the left and right were marked on the skin. After preparing a sterile field, local infiltration with 1% lidocaine was given. Under intermittent CT fluoroscopic guidance, a 22-gauge 5-inch spinal needle was introduced via  a lateral approach such that the tip of the needle approached the region of the ganglion impar. A second 22-gauge 5-inch spinal needle was then introduced from the contralateral side to bring the needle tip near the location of the ganglion impar. Iodinated contrast, 0.2 ml, was injected, and CT images were obtained to confirm correct needle placement (fig. 1). A prognostic block using 2 ml bupivacaine, 0.5%, was injected through each needle. Ten minutes later, the patient reported a significant reduction in pain intensity from 8 on the numeric rating scale (0 being “no pain” and 10 being the “worst imaginable pain”) to 2. Gentle palpation over the sacral region did not elicit any pain. A 4-ml mixture containing 1 ml bupivacaine, 0.5%, and 3 ml alcohol, 100%, was then injected through each needle. Both needles were cleared with 1 ml lidocaine, 1%. The patient tolerated the procedure well, with no complications. After the procedure, she continued to have good pain relief and also reported a decrease in pain on defecation and micturition.

Fig. 1. Injection of contrast dye to confirm correct placement of the needle tip anterior to the sacrococcygeal junction. 

Fig. 1. Injection of contrast dye to confirm correct placement of the needle tip anterior to the sacrococcygeal junction. 

Close modal

The ganglion impar is the terminal portion of the sympathetic chain located anterior to the sacrococcygeal junction. It is a solitary ganglion that is formed by merging of the left and right sympathetic chains inferiorly. Ganglion impar blocks are effective for treating visceral pain originating from the perineum.1Different techniques to block the ganglion impar have been reported. Plancarte et al.  2first described the anococcygeal approach to the ganglion impar using a bent needle. This was later modified to a curved needle technique by Nebab et al.  3The ganglion impar can also be reached by passing a needle through the sacrococcygeal junction.4,5 

Computed tomography–guided neurolysis of the ganglion impar is an alternative to performing the procedure under fluoroscopy. Using a bilateral approach, two needles were advanced from the lateral side of the sacrum horizontally until the needle tips were positioned anterior to the sacrococcygeal junction. This avoided the risk of rectal perforation in the anococcygeal approach and the risks of infection, bleeding, and needle breakage in the sacrococcygeal approach. The needles pass through skin, subcutaneous tissues, and muscles only, and it can be almost pain free with adequate local anesthesia. This technique is relatively easy and safe to perform.

*Duke University Medical Center, Durham, North Carolina.

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