Overview of Ganglion Impar Block 

The ganglion impar is a mass of nerve cells that are near the coccyx (tailbone). Also called the ganglion of Walther, these nerves are responsible for sending pain signals to the brain. A ganglion impar block is an injection that gives pain relief to patients who have sympathetically mediated pain that arises from disorders of the somatic structures and viscera in the pelvis and perineum.

The conditions treated with the ganglion impar block are chronic perineal pain, abdominal pain, perianal cancer, disorders of the colon, rectum, and genitals, postherpectic pain, failed back surgery syndrome, and postherpetic neuralgia of the sacral region.

The ganglion impar block is used as a diagnostic test to assist the physician in determining the specific source of pain in the perineal area. Pain in this area is hard to pinpoint due to the diverse anatomic structures and innervations. The autonomic nervous system sends messaged from the internal organs to the brain. The ganglion impar innervates the rectum, vagina, anus, perineum, and coccyx. Ablating or numbing this region halts painful stimuli transmission so the brain does not allow the pain sensation.

The Procedure

The ganglion impar block involves the injection of phenol, botox, an anesthetic, and other medication with a fine needle into the low back area. During the procedure, these areas are prepped with a local numbing agent, and fluoroscopic guidance is used to advance the needle into the ganglion impar. Contrast dye is injected and a therapeutic block is performed to give immediate relief of discomfort.

Once the patient receives pain relief from the block, there may be additional blocks given in the future. The patient is eligible for other procedures such as neurolysis with alcohol, radiofrequency ablation, and surgical section. This block is a safe and effective treatment measure for a variety of conditions.

Risks and Side Effects

The CT-guided ganglion impar block results in significant reduction of pain and has very few risks and side effects. This block is a safe treatment modality when performed by a competent practitioner. Thousands of ganglion impar blocks have been performed with no risks and side effects. The risks include a misplaced needle that causes bleeding into the retroperitoneal space, nerve injury, nerve paralysis, punctured organs, vessel puncture, drug allergy, seizures, and infection. Also, since the size, location, and shape of the ganglion impar varies from person to person, there is a risk that the block will not be effective.

After the Procedure

Once the procedure is over, the pain will go away and the area will be numb. However, the pain will return after a day or two. Due to the mechanical process of needle insertion, there is a chance you will experience some stiffness in the insertion area. Be sure to have someone to drive you home following the procedure, and apply ice to the affected area to alleviate the discomfort. It is safe to perform normal activities as tolerated.

Resources

Foye PM. Finding the causes of coccydynia (coccygeal pain). J Bone Joint Surg Br. Jan 18 2007.

Foye PM. Ganglion impar blocks for chronic pelvic and coccyx pain. Pain Physician. Nov 2007;10 (6):780-781.

Foye PM. Safe ganglion Impar blocks for visceral and coccyx pain. Techniques in Regional Anesthesia and Pain Management. April 2008; 12(2):122-123.

Nathan ST, Fisher BE, Roberts CS. Coccydynia: a review of pathoanatomy, aetiology, treatment and outcome. J Bone Joint Surg Br. Dec 2010; 92(12):1622-7.

Reig E, Abejón D, Del Pozo C, et al. Thermocoagulation of the ganglion impar or ganglion of walther: description of a modified approach. Preliminary results in chronic, nononcological pain. Pain Pract. Jun 2005;5 (2):103-10.