by Elizabeth Cudilo M.D., Paul Lynch M.D., and Tory McJunkin M.D.
If you have vague, poorly localized perineal pain that is frequently accompanied by sensations of burning or urgency, you may benefit from this block. However, since the symptoms of burning and urgency, especially if they’re associated with urination or defecation, may be secondary to a medical condition (i.e. urinary tract infection, sexually transmitted infection, prostate inflammation, etc.) it is important to first consult your primary care doctor to make sure you are not experiencing perineal area pain from one of these causes.
Since the ganglion impar receives afferent pain fibers from the perineum, distal rectum, anus, distal urethra, vulva, and distal third of the vagina, this block can potentially alleviate pain originating from the above-mentioned regions. The most recent literature highlights that the ganglion impar block has also been used successfully to treat nonmalignancy-associated perineal pain from various etiologies, including sacral postherpetic neuralgia, spinal cord malformations, and failed back surgery syndrome, to name a few. Emerging evidence also suggests that due to its sympathetic innervations, a ganglion impar block may provide relief to patients with perineal hyperhidrosis (excessive sweating).
Perineal pain originating from:
- Distal rectum
- Distal urethra
- Distal third of the vagina
Perineal pain secondary to:
- Cancer that metastasized to perineum (cervical, prostate, testicular, colorectal etc.)
- Sacral postherpetic neuralgia
- Post-surgical thrombosis of perineal veins
- Spinal cord malformations
- Vaginal protrusion
- Failed back surgery syndrome
- Testicular ablation
- Perineal hyperhidrosis
AnatomyThe ganglion impar is the only unpaired autonomic ganglion in the body and marks the end of the two sympathetic chains. It is usually described as being located anterior to the sacrococcygeal joint in the retroperitoneum. However, Oh et al. (2004) found that the location, shape, and size of the ganglion impar are variable. After performing anatomical dissections on 50 sacra and coccyges, the authors found that the location of the ganglion impar can range from the sacrococcygeal junction to approximately 10mm anterior to the tip of the coccyx, with the majority of the ganglia impar being located approximately 25-30mm anterior from the tip of the coccyx . This anatomical variation may contribute to the possible inefficacy of this nerve block in some patients.
The ganglion impar receives afferent pain fibers from the perineum, distal rectum, anus, distal urethra, vulva, and distal third of the vagina. This block can potentially alleviate pain originating from the above-mentioned regions. The impar ganglion’s postganglionic fibers then pass along to the sacral and coccygeal spinal nerves.
Ever since Plancarte et al. (1990) introduced and described their approach to performing the impar ganglion block via the horizontal approach through the anococcygeal ligament, researchers to date continue to introduce modified techniques that attempt to maximize the ease of performing this block, while maintaining patient safety and increasing the chance of maximal pain alleviation for their patients.
One modified techniques is using different visualization techniques, such as fluoroscopic guidance or ultrasound guidance. Another technique is using different approaches to get to the ganglion impar, such as using the transsacrococcygeal ligament approach, the transcoccygeal joint approach, the paramedial approach, or the paracoccygeal corkscrew approach. Lastly, the doctor can also use different needles, such as using a curved needle or needle-inside-needle technique.
Of these approaches, the transsacrococcygeal approach remains the most popular due to its simplicity and effectiveness.2,3,16With this technique, you will be asked to lie down on your abdomen, face-down with a pillow under your pelvis to help flatten out the lower lumbar spine’s natural curvature. Your lower back and intergluteal cleft will be prepped and draped in a sterile manner before local anesthesia is administered at the point of entry of the needle into your skin. When your skin is adequately anesthetized, the needle will be advanced under fluoroscopy guidance until correct needle placement is obtained. Its correct placement will also be confirmed by administration of contrast dye. Once position is confirmed either a diagnostic block (to determine if your perineal pain is visceral or somatic) or a therapeutic block will be performed.
A successful block is marked by profound pain relief.
Local anesthetic is usually administered for diagnostic ganglion impar blocks or for patients with non-cancer-related pain. For patients who have a documented response to the administration of local anesthetic onto the ganglion impar, a therapeutic block is performed with administration of the neurolytic agent like phenol. Radioablation of the ganglion impar is also another treatment modality for longer-lasting pain relief.
The procedure usually takes less than 15 minutes. Sometimes your physician will recommend intravenous sedation to make the procedure more comfortable. Your physician will monitor your pain and vital signs (pulse, blood pressure, temperature) after the procedure.
Benefits of Ganglion Impar Blocks
Ganglion impar blocks are a short, minimally-invasive procedure that can treat chronic, neuropathic perineal pain from visceral and sympathetic pain syndromes, especially if they are secondary to malignancy. Published literature also highlights that significant pain relief can also be achieved if the pain is of nonmalignant origin and originates from one of the organs that sends its afferent fibers to the ganglion impar.
Risks of Ganglion Impar Blocks
The risks for this procedure is very low. In fact in current published literature, there are no major complications reported from this block. Plancarte, et al. (1993) did describe one case where they observed epidural spread of contrast within the caudal canal; however, needle repositioning quickly resolved the problem without any harm to the patient.
Despite these published statistics, the theoretical risks of this procedure exist and includes: if the needle is misplaced, you can experience bleeding, especially into your retroperitoneal space; nerve injury or paralysis; puncture of surrounding organs (including rectum); and puncture of adjacent vessels. Risks secondary to the spread of the anesthetic include drug allergy and seizure (if the medication is injected into a blood vessel). Also with any penetration of skin and soft tissues, the risk of infection always exists.
Lastly, due to the anatomical variation of where the impar ganglion is situated, another risk of this procedure is an ineffective block in some patients. If no relief is obtained after your physician has placed the block through the transsacrococcygeal approach, he or she may elect to try another approach to best accommodate your anatomy (transcoccygeal joint approach, paramedial approach, etc.).
Nonetheless, the most common side effect related to this procedure is the lack thereof.
Ganglion impar block is a well-established treatment modality for chronic, neuropathic perineal pain from visceral and sympathetic pain syndromes secondary to malignancy.
In 1990, Plancarte et al. not only described the ganglion impar technique but also demonstrated its efficacy in cancer patients. Sixteen patients with advanced cancer (cervical, endometrial, bladder, colon, and rectal) with perineal involvement (localized perineal pain with burning and a sensation of urgency) with a minimal response to pharmacotherapy received a neurolytic ganglion impar block. After the block, eight patients obtained complete pain relief with the remaining patients reporting a 60-90% reduction in their pain.
These initial favorable results in malignancy-associated perineal pain prompted researchers to investigate if similar results could be obtained for patients with non-malignant perineal pain or pain from the various afferent innervations that the ganglion impar receives. Agarwal-Kozlowski et al. (2009) evaluated the efficacy of the ganglion impar block on perineal pain of various etiologies (including malignancy, postsurgerical of thrombosis of perineal veins, postherpetic neuralgia, spinal cord malformations, vaginal protrusion, failed back surgery syndrome, testicular ablation, and what was deemed as perineal pain of unknown origin) in 43 patients. In this study, the authors reported a reduction of patients’ pain scores from 8.2+/-1.6 to 2.2+/-1.6 (P<0.0001, 95% confidence interval 0.5) immediately after neuroablation of the ganglion impar and maintained this pain relief through the four-month follow up. In 2005, Reig et al. was also able to reduce visual analog scale (VAS) pain scores in 13 patients with chronic, non-malignancy-associated perineal pain with radiofrequency ablation. Before the ganglion impar block, the VAS pain scores were equal to or greater than seven in all the patients; after the block, VAS pain scores were reduced by an average of 50%. Toshniwal et al. (2007) had similar success in their 16 patients with chronic perineal pain. All of the ganglion impar blocks performed reduced VAS pain scores by 50% and the authors highlight that all the patients had significant pain relief at the two-month follow-up (p <0.05 compared to baseline) with the mean VAS pain scores being ~2.22 Besides pain alleviation, the impar ganglion block shows promise as a treatment modality for perineal hyperhidrosis (excessive sweating).11
The benefits of a ganglion impar block can be temporary for some people and the amount and duration of pain relief varies from person to person. Some tend to have relief for weeks where others can benefit from the block for years. Fortunately, the procedure is a low-risk, non-surgical treatment that if successful the first time will most likely continue to provide pain relief with repeat treatments.
If you are suffering with chronic perineal pain or pain that you or physician believe is originating from the perineum, distal rectum, anus, distal urethra, vulva, and distal third of the vagina, the ganglion impar block may be of great benefit for you. Contact Arizona Pain Specialists today to see if you’re a good candidate for a ganglion impar block. We are happy to offer this exciting treatment option to patients in Scottsdale, Glendale, and the Phoenix metro area. Call today.
- Agarwal-Kozlowski K, Lorke DE, Habermann CR, Am Esch JS, Beck H. CT-guided blocks and neuroablation of the ganglion impar (Walther) in perineal pain: anatomy, technique, safety, and efficacy. Clin J Pain. 2009 Sep;25(7):570-6.
- Başağan Moğol E, Türker G, Kelebek Girgin N, Uçkunkaya N, Sahin S.