A medial branch block is a short-acting numbing injection used to prove whether the facet joints are the source of your pain.
What is a medial branch block?
This is mainly a diagnostic test. Local anesthetic is placed on the medial branch nerves that supply one facet joint (a small joint at the back of the spine). If your pain mostly goes away for the duration of the anesthetic, that joint is confirmed as the source. Then radiofrequency ablation becomes an option.
What is a medial branch block used for?
- Suspected facet joint pain in the neck or low back
- Lasting post-whiplash neck pain
- Before considering radiofrequency ablation
What happens during a medial branch block?
- Quick. It usually takes under 15 minutes, under X-ray guidance.
- You will keep a pain diary for the next few hours. This is the real result of the test, so it matters.
- The relief is meant to be short. When the pain comes back, that is expected. It is not a failure.
- Two positive blocks are normally required before ablation, because a single block has a real chance of giving a false positive (a result that looks good but is wrong).
What are the risks of a medial branch block?
This is a small-volume diagnostic injection, so the risk is low. Temporary numbness or weakness in nearby muscles is possible for a few hours. The most common problem is not a complication at all. It is a result we cannot read. This is usually because the pain diary was not kept. Or the patient took extra pain medicine during the test window, so the effects could not be told apart.
To talk about whether this is right for you, call us or request an appointment.
How do you know if a medial branch block worked?
The result is the pain diary, not the procedure. What matters is the degree of relief during the anesthetic’s active window, and how the pain returns after. Write it down as it happens.
Two positive blocks are required before ablation because a single one has a real chance of giving a false positive. Checking twice before you commit to a procedure that lasts months is sensible. It is not red tape.
Before and after your procedure
You may drive yourself unless told otherwise, since no sedation is used. Do not take extra painkillers on the day; they make the result unreadable. Keep the pain diary hour by hour for six hours afterward. This is the real result of the test. Without it the block has to be repeated. Return to normal activity immediately; the relief is deliberately short.
How the procedure is actually done
Each facet joint gets its feeling from two medial branch nerves. So blocking one joint means numbing two nerves, and a row of joints means more. The nerves lie at known points on the bone. Under live X-ray (fluoroscopic) guidance, a very small volume is placed at each. We keep it small on purpose, because if it spreads into the joint or nearby muscle, the relief does not answer the question.
Who it suits, and who it does not
It suits neck or back pain with a facet pattern. It is the required step before radiofrequency ablation. Two blocks on separate days are standard, because a single block carries a real false-positive rate from placebo response and anesthetic spread. It is not a therapeutic injection. Any relief beyond the anesthetic duration is a by-product, not the goal.
The role of imaging
Imaging is used to rule out serious disease and to plan a procedure. It does not find the source of pain by itself. Degenerative findings (signs of the spine breaking down) show up in nearly everyone past middle age. They also show up in huge numbers of people with no symptoms. So a report listing several problems rarely settles which one hurts. That is what the examination and targeted blocks are for.
Common questions
Why do the pain diary?
The diary is the test result. Without it we cannot tell whether the block was positive. Then the procedure has to be repeated.
There is more on this in Diagnostic Nerve Block.
Why two nerves for one joint?
Each facet joint gets its supply from two medial branches. So a joint is only fully tested when both are blocked.
Facet Joint Pain covers how facet pain shows up and how it is diagnosed.
Why do I need the block twice?
One block has a real chance of giving a false positive. Two results that agree make it far more likely the joints are truly to blame before committing to ablation.
What if relief lasts a week?
That is a steroid or irritation effect rather than a positive anesthetic block. It is read differently.
How long will a medial branch block last?
The relief is short on purpose. It lasts only as long as the local anesthetic is active. That is why we ask you to keep a pain diary hour by hour for six hours afterward. When the pain comes back, that is expected. It is not a failure. Relief that lasts about a week is a different effect and is read differently.
What happens next if a medial branch block doesn’t work?
First, we check that the result can be read. The most common problem is a result we cannot read. This is usually because the pain diary was not kept or extra painkillers were taken. Then the block has to be repeated. Say a properly kept diary shows your pain did not mostly go away. Then that joint is not confirmed as the source, and ablation of those nerves is not the next step.
Is it worth getting a medial branch block?
If radiofrequency ablation is being considered, it is the required step: two positive blocks come before ablation. The block is quick, usually under 15 minutes under X-ray guidance, and its risk is low. Its value is the answer it gives. It proves whether a specific facet joint is the source of your pain before you commit to a procedure whose effect lasts months.
Sources
- Cohen SP et al. Consensus practice guidelines on interventions for lumbar facet joint pain from a multispecialty, international working group. Regional anesthesia and pain medicine, 2020. PubMed 32245841
- Manchikanti L et al. Comprehensive Evidence-Based Guidelines for Facet Joint Interventions in the Management of Chronic Spinal Pain: American Society of Interventional Pain Physicians (ASIPP) Guidelines Facet Joint Interventions 2020 Guidelines. Pain physician, 2020. PubMed 32503359
- Wahezi SE et al. Lumbar Medial Branch Block Volume-Dependent Dispersion Patterns as a Predictor for Ablation Success: A Cadaveric Study. PM & R : the journal of injury, function, and rehabilitation, 2018. PubMed 29174073
- Roy C et al. Correlation of lumbar medial branch neurotomy results with diagnostic medial branch block cut off values: a letter to the editor. Pain medicine (Malden, Mass.), 2013. PubMed 23565823
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