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.
Sometimes the facet 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.