Ganglion Impar Block

Key facts

Who it is for

The ganglion impar and the transsacrococcygeal approach

The sympathetic chains that run down each side of the spine meet at the very bottom in a single ganglion, the ganglion impar (also called the ganglion of Walther). It lies directly in front of the joint between the sacrum and the coccyx, behind the rectum. It carries pain signals from the coccyx and its ligaments, the perineum, the anus and lower rectum, the distal urethra and vagina, and the scrotum or vulva. Because so much of the lower pelvis reports through this one small target, one well-placed injection can quiet a wide area.

Transsacrococcygeal approach. The original technique bent a needle and threaded it up from below the tailbone, which was awkward and hard to control. Today the standard is to pass a thin needle straight through the disc between the sacrum and the coccyx under fluoroscopy, so the tip comes to rest exactly in front of the joint where the ganglion sits. Contrast dye then spreads in a characteristic curved pattern along the front of the sacrum and coccyx, confirming the position and showing that the tip is not in the rectum or a vessel. This approach is quick, needs only 3–5 mL of medication, and keeps the needle away from the rectum by staying in bone until the last few millimeters. If the sacrococcygeal joint is fused, we go through the joint between the first and second coccygeal segments instead.

Test or treatment. Anesthetic alone is a test: sit, stand and press on the tailbone for the next few hours and rate the pain. If it drops by 50% or more, the ganglion is the pathway. Most first blocks include a steroid so the test doubles as a treatment; relief then typically lasts weeks to a few months, sometimes much longer. Coccydynia is usually caused by a hypermobile or dislocating coccyx, a bone spicule, or ligament strain, so the block treats the pain signal while a cushion, pelvic floor therapy and time treat the cause.

Progression to impar radiofrequency. When a block gives good relief that wears off, radiofrequency ablation (conventional or pulsed) of the ganglion impar through the same approach typically extends relief to 6 months or longer in reported series. For pelvic cancer pain, a positive test block is followed by a neurolytic block with alcohol or phenol, which lasts months.

What happens on procedure day

1. Check-in and a review of your pain score, what makes it worse, your blood-thinner list and, if diabetic, your morning glucose. Tell us if you have had any rectal bleeding, fever or recent bowel surgery.
2. You lie face down on the fluoroscopy table with a pillow under your hips and your legs slightly apart; a folded sheet protects your privacy. Light sedation is given if you want it. Blood pressure and pulse are monitored.
3. The skin over the tailbone is cleaned with chlorhexidine; the area is small and no shaving is needed. Under fluoroscopy we locate the sacrococcygeal joint and numb the skin and the joint capsule with lidocaine.
4. A thin needle passes through the sacrococcygeal disc until the tip sits just in front of the joint. You feel firm pressure and sometimes a brief deep ache; you should not feel pain in the rectum, and we ask you to tell us if you do.
5. A small amount of contrast dye is injected and must show the curved spread in front of the sacrum and coccyx. Then 3–5 mL of anesthetic, with steroid for a treatment block, goes in slowly. Total needle time is under 10 minutes.
6. You rest for 15–20 minutes, then sit on a firm chair and press on the tailbone to test the block. Rate your pain before you leave and hourly for the rest of the day.
7. You go home with a pain diary. A driver is needed if you were sedated; otherwise many patients drive themselves, sitting on a cushion.

After the procedure

Day 0. The tailbone and perineum feel numb or heavy for 2–8 hours; some people notice numbness around the anus or a strange sensation with the first bowel movement, which passes. Sitting should be easier while the anesthetic lasts, and the diary should capture that. Keep the bandage dry for the day; shower normally the next day. No tub baths, swimming or intercourse for 48 hours.

Days 1–3. Soreness where the needle passed through the joint is common and can briefly make sitting worse before the steroid works. Use a wedge or ring cushion, stand and walk often, and keep stools soft with fluids and fiber so bowel movements do not strain the area. A short pain flare for 1–3 days is normal after steroid.

Week 1–2. Steroid benefit is usually clear by day 7. This is the time to start or restart pelvic floor physical therapy and to correct sitting posture; relief lasts longer when the mechanical cause is addressed.

When we judge the response. The diagnostic answer comes from the first day's diary; the steroid response is judged at 2–3 weeks. Call the same day for fever over 100.4°F, increasing pain or swelling at the tailbone, rectal bleeding, pus or drainage, new numbness that lasts beyond 24 hours, or trouble controlling your bowel or bladder.

What the evidence shows

Ganglion impar block was first described for pelvic cancer pain and has since become the standard injection for coccydynia. The evidence is honest but modest: it comes mainly from case series and a few small comparative trials rather than large randomized studies. In series of patients with chronic coccydynia that had not responded to cushions, medication and therapy, a transsacrococcygeal block with local anesthetic and steroid gave meaningful relief in a majority of patients, with benefit often lasting weeks to months and some patients needing two or three blocks. Small studies of radiofrequency ablation of the ganglion impar after a positive block report relief lasting 6 months or longer in most responders. For cancer-related perineal pain, series of neurolytic impar blocks report substantial reductions in pain and opioid use. Systematic reviews of coccydynia treatment place the block after conservative care (cushions, anti-inflammatories, manual therapy) and before coccygectomy, which is reserved for the small group with a clearly unstable coccyx who fail injections. The transsacrococcygeal approach has a low complication rate in published series when done under fluoroscopy. Gulf Coast Pain & Spine performs ganglion impar blocks in Houston and Webster, and in Pearland when that office opens in November 2026.

Alternatives and what comes next

Before a block: a wedge or coccyx cut-out cushion, 4–6 weeks of anti-inflammatory medication, pelvic floor physical therapy with manual treatment of the coccyx, and attention to sitting habits resolve most coccydynia within a few months. A local steroid injection around the coccyx or the sacrococcygeal joint, or a caudal steroid injection, is an alternative when the pain is from the joint or ligaments rather than the nerve pathway. Pudendal nerve block is the better-matched injection when perineal pain follows the pudendal nerve (worse sitting, better standing, one-sided burning).

After a block that helps but wears off: radiofrequency ablation of the ganglion impar through the same approach, typically 6 months or longer of relief and repeatable; for cancer pain, chemical neurolysis. For pelvic pain that also involves the bladder, uterus or prostate, a superior hypogastric plexus block reaches the next level up. For persistent, well-localized coccygeal or perineal pain that responds to blocks but keeps returning, peripheral nerve stimulation or dorsal root ganglion stimulation of the sacral roots is an option. Coccygectomy is a last resort for a proven unstable coccyx. If a well-placed block gives no relief, the pain is not passing through the ganglion impar, and we re-examine the sacroiliac joints, the lumbosacral spine and the pelvic floor.

Safety and preparation

• Blood thinners: this is a spine-adjacent block near the caudal canal, so under ASRA guidance warfarin, DOACs (apixaban, rivaroxaban, dabigatran), clopidogrel, prasugrel and ticagrelor are usually held for 2–7 days depending on the drug; aspirin can often continue. We arrange the hold with the prescriber. Never stop a blood thinner on your own.
• Diabetes: a steroid block raises blood sugar for 1–7 days; we postpone the steroid, or do the block with anesthetic only, if your morning glucose is above roughly 200–250 mg/dL.
• Infection or fever: fever above 100.4°F, a perianal abscess, fistula, pilonidal cyst, or any skin infection near the tailbone postpones the block because the needle path is close to the rectum. Tell us about any recent rectal or gynecologic procedure.
• Allergies (contrast, steroid, local anesthetic): contrast dye is used to confirm safe placement. Tell us about a contrast allergy so we can pre-treat.
• Pregnancy: the block requires fluoroscopy and is deferred; tell us if you are or could be pregnant. Tailbone pain after childbirth is common and is treated with cushions and therapy first.
• Sedation and driving: sedation is optional and light. With sedation you need a driver and no driving for 24 hours; without it you may drive yourself, sitting on a cushion.
• Bowel preparation: none is needed, but avoid constipation in the days before; straining after the block increases soreness. Empty your bowel and bladder before the procedure if you can.

Risks and side effects

Frequently asked questions

Related care

Related treatments

Related conditions