A medial branch block (MBB) is a diagnostic injection that temporarily numbs the small medial branch nerves carrying pain signals from your spinal facet joints, helping our physicians confirm whether those joints are the true source of your neck or back pain.
OVERVIEW
What a medial branch block is and how it works
The facet joints are the paired joints at the back of the spine that link each vertebra to the one above and below it. Each facet joint is supplied by tiny sensory nerves called the medial branches, which relay pain signals from the joint toward the brain. When arthritis, injury, or age-related degeneration irritates a facet joint, these nerves can become a steady source of neck or back pain.
During a medial branch block, your physician places a small amount of local anesthetic right next to these medial branch nerves under live imaging guidance. By briefly switching off the nerves that serve specific joints, the block helps reveal whether those joints are driving your pain. If your usual pain drops substantially during the hours the anesthetic is working, the facet joints are the likely source.
CONDITIONS
What a medial branch block helps evaluate
Our physicians use medial branch blocks at the Columbia Pain & Spine Institute offices in Gresham and Portland, Oregon to evaluate facet-related pain in the neck, mid-back, and lower back, including:
Commonly treats
A medial branch block is most useful for axial pain that stays close to the spine. It is not used to diagnose pain that radiates down an arm or leg, which usually points to a different source such as a nerve root.
YOUR VISIT
What to expect
Before
The procedure is performed on an outpatient basis. Let us know in advance about blood thinners, diabetes medications, or any chance you may be pregnant. Because the block is a diagnostic test, it helps to arrive with a clear sense of your usual pain so you can compare it afterward. Plan to have someone available to drive you home.
During
You lie face down while the skin is cleaned and numbed. Using live X-ray guidance (fluoroscopy) for precise needle placement, your physician positions a thin needle next to each target medial branch nerve and injects a small amount of local anesthetic. The injection itself usually takes only about 10 to 20 minutes.
After
Because this is a diagnostic block, the most important part happens after you leave. You record how your pain responds over the next several hours while the anesthetic is active, often using a simple pain diary. A meaningful drop in your usual pain points to the facet joints as the source. Any numbness or soreness near the injection site typically settles quickly, and most patients return to their normal routine the following day.
QUESTIONS
Frequently asked questions
Will a medial branch block make my pain go away for good?
Not by itself. The anesthetic lasts only a few hours, so any relief is temporary by design. The block is a diagnostic test that helps confirm which joints are driving your pain. When the response is positive, lasting relief typically comes from a follow-up procedure such as radiofrequency ablation.
How is an MBB different from a facet joint injection?
A medial branch block targets the nerves that supply the facet joint, placing anesthetic next to those nerves rather than inside the joint itself, as a facet joint injection does. Because the medial branches are the same nerves treated during ablation, a positive block is a standard way to help predict whether ablation is likely to help.
What happens if my block is positive?
A clearly positive response suggests the targeted facet joints are a meaningful source of your pain. The next step is usually a conversation about radiofrequency ablation, which uses controlled heat to interrupt those same nerves for longer-lasting relief. Our team will discuss whether you are a candidate.
RELATED CARE
Explore related procedures
Facet Joint Nerve Ablation
The category hub for diagnosing and treating facet-related spine pain. Learn about the program.
Radiofrequency Ablation
The therapeutic next step after a positive block, for longer-lasting facet pain relief. Read more.
Sacroiliac Joint Nerve Block
A related diagnostic block when low-back or buttock pain may come from the SI joint. Read more.
Not sure which evaluation is right for you? Browse our full list of interventional pain services, or contact our Gresham and Portland offices to learn more. New patients are welcome by physician referral; records may be faxed to (503) 382-8120.
Contact Columbia Pain & Spine Institute