The ganglion impar is a cluster of nerves located in front of the coccyx (tailbone), where it comes together with the sacrum (a triangular bone located at the base of the spine). It is part of the sympathetic nervous system and is responsible for supplying innervation to the perineal structures. This includes the perineum, distal rectum, anus, distal urethra, scrotum, vulva, and distal vagina. Over-activity of these nerve cells can cause chronic pain.
A Ganglion impar block can be used to diagnose chronic pelvic or rectal pain or to treat pain symptoms once the ganglion impar has been identified as a cause. The injection works by blocking nerve impulses that send pain signals to the brain.


A ganglion impar block is an outpatient procedure that takes about 10 minutes. It may be performed under IV sedation.
For the procedure, the patient will be asked to lie down on the stomach. A pillow may be placed under the pelvis to flatten out your lower back. The skin on your lower back will be cleaned and prepped, and a local anesthetic will be injected to numb the area. Then, the doctor will use fluoroscopy (real-time X-ray guidance) to guide the block needle into the right spot. Contrast dye may be injected to ensure the needle’s placement is correct. When the needle is in the right place, local anesthetic and steroid medication will be injected. Afterwards, the needle will be removed and a small adhesive bandage may be applied.


After the Ganglion impar block procedure there may be a temporary pain relief as a result of the local anesthetic. When the anesthetic starts to wear off, the pain will likely return, but it may be less severe than before.
If the ganglion impar nerves are the cause of the pain, the patient will start to notice more long-term relief once the steroid medication starts to work (typically within three to five days). The amount of time the pain symptoms are alleviated can vary from a few weeks to several months, or even years. 
Subsequent injections may be necessary for long term pain control.