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What is a Medial Branch Block?

The medial branch nerve block (the nerves carrying pain signals from the facet joint to the spinal cord) temporarily stops the nerve’s ability to carry pain signals to the brain, which in turn will determine if the facet joint(s) is the source of pain. Medial branch nerves are the small nerves that carry pain signal to the brain from the facet joint in the spine. These nerves do not control any major muscles or carry any sensation to the arms or legs, so there is no danger of negatively affecting other pain sensing processes with this injection.

This injection is a procedure in which a long-acting numbing agent is injected near small medial nerves connected to a specific facet joint (also called a zygapophysial joint or Z-joint) under live X-ray, known as fluoroscopy. Live X-ray helps in placing the needle and avoiding injury.


What Conditions Can Be Treated with Medial Branch Block

Sometimes the Z-joints can become inflamed. This pain can range from a simple tight feeling in the low back to more severe pain. You may have facet-mediated pain if the pain has lasted longer than a few months. The MBB is used to determine if the zygapophysial (facet) joint is the source of pain.

medial branch block


Once you have decided to have the injection, the following events take place:

  • Do not eat or drink anything after midnight before your injection.
  • You can take your regular heart and blood pressure medications on the morning of the injection with a sip of water.
  • You will lie on a table in a procedure room.
  • The skin in the area where the injection will be made will be cleaned.
  • The skin is numbed with lidocaine.
  • Using fluoroscopy (live X-ray) for guidance, the physician directs a needle toward the medial branch nerve near the facet joint.
  • The chemicals are injected.
  • The injection procedure will take about 30 minutes.
  • You will be in a recovery room for about 30 minutes.
  • It is important that you have someone to drive you home.
  • It is common to experience an increase in pain once the numbing medicine wears off.
  • You will need to make an appointment with your doctor to discuss your level of pain relief after the injection.
    • If the facet joint is the source of pain, you will experience pain relief over the next few hours. It is encouraged to do activities that will cause the usual pain after the injection.
    • If no pain relief, the joint is not the source of pain. You should keep a pain log that records the level of pain relief over the next 12-24 hours after the injection. This will be important information to convey to your physician or PA on the follow up visit. If you experience relief, it will be temporary and means you will be a candidate for radiofrequency nerve ablation (or RFA) of the medial nerves.