Understanding the Diagnostic Block
What is a medial branch block?
A medial branch block (MBB) is a diagnostic injection used to determine whether one or more facet joints are causing your spine pain. Facet joints are small joints at the back of the spine. Tiny medial branch nerves carry pain signals from these joints.
Using live X-ray guidance (fluoroscopy), the clinician places a small amount of local anesthetic near selected medial branch nerves. Contrast dye may be used to confirm needle position. The numbing medicine temporarily interrupts the pain signal; it does not permanently treat the nerve.
Which area is being tested?
| Region | Typical area assessed |
|---|---|
| Cervical | Mostly axial neck pain; it may extend toward the base of the skull, shoulders, or upper back. |
| Thoracic | Mostly axial mid-back pain, sometimes wrapping toward the ribs or chest wall. |
| Lumbar | Mostly axial low-back pain; it may extend into the buttocks or upper thighs. |
What results should I expect?
- Pain relief usually begins within minutes and lasts only as long as the local anesthetic—often several hours, although timing varies.
- A positive response means meaningful relief of your typical pain while doing activities that normally provoke it. It does not guarantee the outcome of future treatment.
- Little or no relief is still useful information and may suggest that another structure is contributing to your pain.
- Some insurers or clinical protocols require a second diagnostic block before radiofrequency ablation.
Risks and possible side effects
Most effects are mild and temporary. Serious complications are uncommon but may occur.
- Common/temporary: soreness or bruising, temporary pain flare, dizziness, fainting, headache, or temporary numbness or weakness.
- Uncommon/rare: bleeding or hematoma, infection, allergic or medication reaction, unintended spread of anesthetic, blood-vessel injection, nerve injury, seizure, or persistent worsening of pain. A collapsed lung is a very rare risk of thoracic procedures. Severe neurological injury, paralysis, or death is exceedingly rare.
Preparing for Procedure Day
Follow the individualized instructions from Renova Pain and the procedure facility.
Blood thinners and anti-inflammatory medications
- Do not stop NSAIDs. This includes ibuprofen, naproxen, meloxicam, diclofenac, ketorolac, and celecoxib.
- Do not stop aspirin or prescribed anticoagulant or antiplatelet medication. Examples include Plavix/clopidogrel, warfarin, Eliquis/apixaban, Xarelto/rivaroxaban, Pradaxa/dabigatran, and Lovenox/enoxaparin.
- Tell us about every medication and supplement you take. Continue taking them as prescribed unless your Renova Pain clinician personally contacts you with different instructions.
GLP-1 medications for diabetes or weight loss
Examples include Ozempic®, Wegovy®, Mounjaro®, Zepbound®, Trulicity®, Victoza®, Saxenda®, Rybelsus® and similar drugs. Tell us the medication, dosing schedule, last dose, current dose, recent dose changes, and any nausea, vomiting, abdominal pain, bloating, or constipation.
Most low-risk patients may continue a GLP-1 medication under current multisociety guidance, but the procedural and anesthesia teams must decide. Higher-risk patients may need a 24-hour liquid-only diet, medication withholding, or rescheduling.
If the anesthesia team tells you to HOLD it: skip a daily GLP-1 on procedure day; hold a weekly GLP-1 for 7 days. Do not stop diabetes medication without a glucose-management plan from the prescriber.
General preparation
- Tell us about allergies, pregnancy or possible pregnancy, infection, fever, antibiotics, recent hospitalization, bleeding problems, and all medications or supplements.
- Unless sedation is planned, follow the facility’s eating and drinking instructions. Take approved routine medications with a small sip of water.
- Arrange transportation if instructed. A driver is required when sedation is used.
- Wear loose clothing. Bring your photo ID, medication list, required paperwork, and this guide/pain diary.
What to Expect
The block is brief; careful pain testing afterward is essential.
During the procedure
- You will lie face down or, for some cervical procedures, in another position selected for safety.
- The skin is cleaned and numbed. The clinician uses fluoroscopy to guide thin needles to the target nerves, then injects a small amount of local anesthetic.
- You may feel pressure or brief discomfort. Tell the team immediately about unusual pain, tingling, weakness, ringing in the ears, metallic taste, dizziness, or other concerning symptoms.
Sedation checklist — only if sedation is planned
Medial branch blocks are commonly performed with local anesthetic only because sedation may change pain reporting. If sedation is medically necessary or planned, follow these instructions:
No solid food for at least 8 hours before arrival. Stop clear liquids 2 hours before arrival unless the facility gives stricter instructions.
Clear liquids include water, clear apple juice, and black coffee or tea without milk or creamer. No alcohol, gum, tobacco, or candy after fasting begins.
Take approved morning medications with a small sip of water. Ask specifically about insulin and other diabetes medications.
Arrange for a responsible adult to drive you home and remain available. Do not use a rideshare or taxi alone.
Immediately afterward: test your usual pain
- Record pain before the block and at the scheduled times in the pain diary. Estimate your percentage of relief and write what you can do more easily.
- Do not rely on soreness at the needle sites when judging the result. Focus on the familiar pain the block was intended to test.
- Temporary numbness or weakness can occur. Ask for help before standing and do not test activities until you feel steady.
Bandage, bathing, activity, and sedation safety
Record Your Response
Bring this completed page to your follow-up visit.
Use 0–10, where 0 = no pain and 10 = worst pain imaginable. Percentage relief = how much your typical pain improved compared with before the block. Record the activities you tested and any functional change.
My usual pain before the block
Pain and activity log
| Time | Pain 0–10 | Relief 0–100% | Activity tested / what changed | Side effects |
|---|---|---|---|---|
| 30 minutes | ||||
| 1 hour | ||||
| 2 hours | ||||
| 4 hours | ||||
| 6 hours | ||||
| 8 hours | ||||
| Bedtime |
Overall response
What could you do more easily? _______________________________________________________________
Did your typical pain return? □ Yes □ No Approximate time it returned: ________________________
Warning signs
Call promptly for fever, increasing redness or drainage, severe or rapidly worsening pain, new numbness or weakness, difficulty walking, severe headache, chest pain, shortness of breath, or an allergic reaction.
Call 911 for new paralysis, loss of bowel or bladder control, trouble breathing, facial or throat swelling, stroke-like symptoms, or loss of consciousness.