Blocking the Ganglion Impar is often used to treat perineal, tailbone, pelvic, or rectal pain. The cause of perineal pain may range from prostatitis, proctitis, cancer, radiation treatment of prostate cancer, sacral postherpetic neuralgia, failed back surgery syndrome, spinal cord malformations, and/or maybe idiopathic (uncertain etiology).
The Ganglion Impar (also called the Ganglion of Walther) is the last ganglion of the sympathetic trunk and represents the distal or final termination of the two paravertebral sympathetic chains. The Ganglion Impar lives anterior or in front of the sacrococcygeal junction; in front of the tailbone. The Ganglion Impar receives its pain fibers from the perineum, distal rectum, anus, distal urethra, vulva, and distal one-third of the vagina. Pain from any of these regions may benefit from block of the Ganglion Impar.
The procedure is done as an outpatient with the patient lying comfortably on their stomach. A local anesthetic or numbing agent is first applied. A small needle is then placed with x-ray guidance between the sacrum and coccyx to the Ganglion Impar. Following dye injection to confirm proper position, a mixture of local anesthetic and steroid is placed and the needle removed.
For pain due to cancer and also some of the above benign chronic pain problems, a neurolytic procedure to destroy the Ganglion Impar may be considered. This may be done by radiofrequency ablation, or sometimes with a neurolytic solution such as alcohol.