Overview
What to know about Lumbar Sympathetic Block
The lumbar sympathetic chain is a string of nerve clusters running along the front and sides of the lower spine. These nerves help regulate blood vessel tone, sweating and pain signaling in the legs and feet, and in some conditions they help drive pain[1][2].
A lumbar sympathetic block — also called a lumbar sympathetic nerve block — places local anesthetic next to this chain to switch those signals off for a while. It is used mainly for complex regional pain syndrome (CRPS) of the leg or foot, and sometimes for circulation-related (ischemic) leg pain, phantom limb pain and other nerve pain in the legs[1]. Our board-certified physicians perform it in our office or at an affiliated ambulatory surgery center.
How it works
How the procedure works
Blocking the sympathetic nerves relaxes the blood vessels in the leg, so the foot often turns pink and warm within minutes. That warming is how your physician confirms the block reached its target. Medicare, for example, looks for a foot temperature rise of at least 2°C, or a difference of at least 1.5°C between the feet, 20 minutes after the block[7].
If your pain drops while the sympathetic nerves are blocked, the pain is likely sympathetically maintained, and a short series of blocks combined with physical therapy may help you move and rehabilitate more comfortably[5]. Results vary, and people treated within the first 12 months of CRPS appear more likely to benefit[1].
Candidacy
Who it helps
Often a good fit if you have
- CRPS of the leg, ankle or foot — burning pain out of proportion to the original injury, with swelling, color or temperature changes, or sensitivity to light touch[3]
- Early CRPS or a flare-up that is not improving with therapy and medicines[6]
- Leg or foot pain from poor circulation when other treatments are limited[2]
- Phantom limb pain or other leg nerve pain that may be sympathetically maintained[1]
- You are ready to pair the blocks with an active rehabilitation program
May not be right if
- An infection at the injection site or an allergy to local anesthetics[7]
- A bleeding disorder or an unreviewed blood thinner — sympathetic blocks are intermediate bleeding-risk procedures[8]
- Pregnancy, because the block uses X-ray
- Leg pain from a pinched nerve in the spine (sciatica) — an epidural steroid injection is usually a better fit
Your visit
What to expect
Step 1
Before
Evaluation
We confirm the diagnosis, record your baseline pain, function and skin temperature, and review prior treatments. A clear CRPS diagnosis and a rehabilitation plan are required for most insurance coverage[7].
Medication review
Tell us about every blood thinner and supplement you take. Some may need to be paused, but only after your doctor and the prescribing doctor agree[8].
Arrangements
Bring a driver, wear comfortable clothes, and follow our eating and drinking instructions if light sedation is planned.
Step 2
During
Positioning
You lie face down on a padded table. Your blood pressure and heart rate are monitored, and an IV may be placed for light sedation.
X-ray-guided placement
After numbing the skin of your lower back, your physician uses live X-ray to guide a thin needle alongside a vertebra, usually at the L2 or L3 level, to the front edge of the spine. Contrast dye confirms the medicine will spread along the sympathetic chain[1].
Injection and temperature check
Local anesthetic is injected, and the temperature of both feet is measured to confirm the warming that signals a successful block[7].
Step 3
After
Observation
You rest while we check your blood pressure — it can dip as the leg vessels relax — and recheck your foot temperature.
Use the window
Your leg may feel warm, and sometimes numb or heavy, for several hours. Plan therapy and gentle movement for the following days, and keep a pain diary[5].
Follow-up
If the block helped, a short series may be scheduled; if it did not, your physician will discuss other options.
Performed at Pain Physicians NY, Gramercy / Kips Bay, East 23rd Street, or at an affiliated ambulatory surgery center.
Types & approaches
Lumbar Sympathetic Block: types and approaches
Lumbar sympathetic block for CRPS of the leg or foot
CRPS often starts after a sprain, fracture or surgery and causes pain far greater than the original injury, with swelling and changes in skin color, temperature and sweating[3]. The New York Workers’ Compensation Board recommends sympathetic ganglion blocks for acute CRPS or a flare-up as an add-on to functional restoration, noting that benefit is nearly always seen within one to three blocks[6].
Medicare in New York covers lumbar sympathetic blocks for CRPS when strict diagnostic criteria are met, standard treatment has not helped and you are treated by an interdisciplinary team. Each repeat block requires at least 50% pain relief right after the previous one plus measured foot warming[7].
Circulation-related and other leg nerve pain
Because a sympathetic block relaxes blood vessels, it can indirectly ease pain from poor blood flow (ischemic pain) in the legs[2]. Lumbar sympathetic blocks have also been used for phantom limb pain and painful diabetic neuropathy, though the evidence for these uses is mostly observational[1].
These uses are less established than CRPS, and Medicare’s New York policy considers sympathetic blocks for indications other than CRPS investigational[7]. They are considered case by case, together with a vascular specialist when circulation is the main problem.
How we know the block reached its target
A good sympathetic block warms the foot on the treated side. Medicare uses a rise of at least 2°C, or a difference of at least 1.5°C between the feet, measured 20 minutes after the block[7]; New York workers’ compensation looks for at least 1°C before a second block[6].
Warming without pain relief suggests the pain is not sympathetically maintained. That is still useful information, because it points your care toward other treatments[5].
Treatment pathway
What often comes next
You are here
Lumbar Sympathetic Block
Safety
Risks and side effects
- Soreness, bruising or swelling at the injection site, usually gone within hours to days[1]
- A warm, and sometimes temporarily numb or heavy, leg
- Light-headedness from a drop in blood pressure
- Uncommon: groin or front-of-thigh pain from irritation of a nearby nerve
- Rare: bleeding, infection, or medicine entering a blood vessel; in the clinical trials reviewed by Cochrane, reported side effects were minor[4]
Evidence
What the research shows
High-quality evidence for sympathetic blocks in CRPS is scarce. A 2016 Cochrane review of 12 small trials (461 people) found low to very low certainty evidence and could not support or refute their use; the limited data did not show a clear pain benefit, and reported side effects were minor[4].
CRPS treatment guidelines note that there is surprisingly little good evidence for lumbar sympathetic blocks specifically, but that a subset of patients does respond, and experts support a short series alongside active physiotherapy[5]. Prospective studies suggest better relief when CRPS has been present for less than 12 months[1].
Conditions
Conditions this can help
FAQs
Lumbar Sympathetic Block: frequently asked questions
What is the procedure for a lumbar sympathetic nerve block?
You lie face down, the skin of your lower back is numbed, and your physician uses live X-ray to guide a thin needle beside the spine to the sympathetic chain, usually at the L2 or L3 level. Contrast dye confirms the position, then local anesthetic is injected[1]. The temperature of your feet is checked to confirm the warming that signals success[7]. You go home the same day.
Who is a good candidate for a lumbar sympathetic block?
The best candidates have CRPS of the leg or foot — burning pain, swelling, and color or temperature changes after an injury or surgery — that is not improving with therapy and medicines[6]. It may also be considered for circulation-related leg pain or other leg nerve pain thought to be driven by the sympathetic nerves[1]. It works best as part of a rehabilitation program and appears more effective earlier in CRPS[1].
How painful is a lumbar nerve block?
Most people feel a sting from the skin numbing and then deep pressure in the lower back as the needle is positioned. Light sedation is available if you are anxious. Many people notice their foot getting warm, and sometimes tingly, within minutes. Your back may feel sore or bruised for a day or two afterward, which ice and over-the-counter pain relievers usually manage.
How long does it take for a sympathetic nerve block to work?
Foot warming and pain relief usually begin within minutes to about half an hour[5]. The anesthetic itself wears off within hours, but relief sometimes outlasts it: in a very small study of local anesthetic sympathetic blocks for CRPS, relief averaged more than three days, compared with 19 hours after a saltwater injection[5]. Responses vary widely, so we track your pain over several days.
How many lumbar sympathetic blocks will I need?
Usually a short series. New York workers’ compensation guidelines note that benefit is nearly always seen within one to three blocks, with more only if function keeps improving[6]. Medicare in New York requires at least 50% immediate relief and measured foot warming before each repeat block, and documented lasting improvement beyond five blocks[7]. If the first well-performed blocks do not help, more are unlikely to.
What should I not do after a lumbar sympathetic block?
For the rest of the day, do not drive, avoid strenuous activity, hot tubs and alcohol, and get up slowly, because your leg may feel numb or heavy and your blood pressure may dip. Keep the bandage dry until the next day. Do not skip therapy in the days after the block — that is when the pain-relief window is most useful[5]. Call us for fever, severe back pain or weakness that does not fade.
What happens when a sympathetic nerve block doesn’t work?
A block that warms the foot but does not ease your pain suggests your pain is not sympathetically maintained, which helps steer treatment[5]. Rehabilitation, medicines and psychological support continue. For CRPS that is not progressing, your physician may discuss spinal cord stimulation, which CRPS guidelines support for some patients[5], peripheral nerve stimulation or Scrambler therapy.
Can a nerve block help with knee pain?
Yes, but usually not this one. Knee arthritis pain travels through the genicular nerves around the knee, so a genicular nerve block is the usual test for chronic knee pain[9]. A lumbar sympathetic block is reserved for CRPS or other sympathetically maintained pain, which can affect the knee, leg or foot[1]. Your physician will match the block to the source of your pain.
What are the risks of a lumbar sympathetic block?
Most side effects are minor: soreness or bruising in the back[1], a warm or temporarily numb leg, and light-headedness from lower blood pressure. Uncommon risks include groin or thigh pain from a nearby nerve, bleeding, infection and medicine entering a blood vessel. In the clinical trials reviewed by Cochrane, reported side effects were minor[4]. Tell us if you might be pregnant, because X-ray is used.
Does insurance cover a lumbar sympathetic block?
Medicare’s local policy for New York, effective October 25, 2026, covers lumbar sympathetic blocks for CRPS when strict diagnostic criteria are met, standard treatments have not helped and you are cared for by an interdisciplinary team; other uses are considered investigational[7]. New York workers’ compensation recommends these blocks for acute CRPS or flare-ups[6]. Commercial plans often need prior authorization, and no-fault claims follow their own rules. We verify your benefits before scheduling.
Do I need to stop my blood thinner before the block?
Possibly. Sympathetic blocks are classed as intermediate bleeding-risk procedures in interventional pain guidelines, so some blood thinners may need to be paused for a set time beforehand[8]. The decision depends on which medicine you take and why you take it. Never stop a blood thinner on your own — we will coordinate with the doctor who prescribed it.
Related
Related treatments
Stellate Ganglion Block
An image-guided injection at the base of the neck that calms overactive sympathetic nerves feeding arm and hand pain.
Spinal Cord Stimulation
A small implanted device that sends mild electrical pulses to the spinal cord to quiet chronic nerve pain — always tested first with a short trial.
Peripheral Nerve Stimulation
A thin lead placed beside a painful nerve delivers mild electrical pulses — often for just 60 days — to calm chronic pain without a spinal implant.
Scrambler Therapy
A non-invasive treatment that uses electrodes on the skin to send “non-pain” signals along your nerves, given as a series of daily sessions.
Epidural Steroid Injections
An X-ray-guided injection that calms an irritated spinal nerve to ease sciatica, arm pain and pain from spinal stenosis.
Sources
Last updated November 3, 2026. This page is educational and does not replace a consultation with your physician.
- 1.Lumbar Sympathetic Block — StatPearls, NCBI Bookshelf · Medical reference
- 2.Sympathetic Nerve Block — StatPearls, NCBI Bookshelf · Medical reference
- 3.Complex Regional Pain Syndrome — StatPearls, NCBI Bookshelf · Medical reference
- 4.Local anaesthetic sympathetic blockade for complex regional pain syndrome — Cochrane Database of Systematic Reviews (O’Connell NE et al.), 2016 · Review
- 5.Complex Regional Pain Syndrome: Practical Diagnostic and Treatment Guidelines, 5th Edition — Pain Medicine (Harden RN et al.), 2022 · Guideline
- 6.New York State Medical Treatment Guidelines: Complex Regional Pain Syndrome — New York State Workers’ Compensation Board, 2022 · Regulatory
- 7.LCD L40267: Peripheral Nerve Injections and Procedures for Chronic Pain — Centers for Medicare & Medicaid Services / Wellpoint Federal (formerly National Government Services), 2026 · Regulatory
- 8.Interventional spine and pain procedures in patients on antiplatelet and anticoagulant medications (second edition) — Regional Anesthesia & Pain Medicine (Narouze S et al.), 2018 · Guideline
- 9.Nerve Blocks — Cleveland Clinic · Patient education