A Medial Branch Block (MBB) is a common medical procedure used to diagnose the source of chronic back or neck pain. This diagnostic injection targets specific nerves associated with the small joints of the spine, known as facet joints. By temporarily numbing these nerves, the procedure helps identify if inflamed or arthritic facet joints are the cause of a patient’s discomfort. It can also offer temporary pain relief, which further aids in confirming the pain’s origin.
Understanding Medial Branch Nerves
The spine consists of small bones, called vertebrae, connected by pairs of small facet joints. These joints provide stability while allowing for movement such as bending, flexing, and twisting. Each facet joint receives nerve signals from small medial branch nerves, which transmit pain signals to the brain. Conditions like inflammation, arthritis, or trauma to these facet joints can cause irritation, leading to pain.
The Procedure Steps
The medial branch block procedure is performed on an outpatient basis and is relatively quick, often taking around 15 minutes. The patient is positioned, usually lying face down, and the skin over the injection site is cleansed with an antiseptic solution. A local anesthetic is then administered to numb the skin and superficial tissues, which is often described as a brief stinging or burning sensation.
A physician uses X-ray guidance, known as fluoroscopy, to precisely direct a thin needle toward the medial branch nerves. This imaging technique allows for accurate needle placement, which is crucial for the procedure’s diagnostic value. Sometimes, contrast dye is injected to confirm the correct needle position and ensure the medication will cover the targeted nerves. Once the needle is accurately placed, an anesthetic is slowly injected near the medial branch nerves. In some cases, a small amount of steroid medication may also be included to reduce inflammation, though the goal remains diagnostic.
What to Expect During and After
During the medial branch block procedure, patients experience minimal discomfort beyond the initial local anesthetic injection. Some individuals might feel pressure as the needle is advanced, but significant pain is uncommon. Sedation is not recommended for this procedure, as it can interfere with accurately assessing the patient’s pain response. The medical team monitors the patient throughout the process.
Immediately after the injection, the treated area may feel numb, and some patients might experience mild soreness or bruising at the injection site. This numbness typically lasts several hours. Patients are advised to take it easy for the remainder of the day and avoid strenuous activities. Applying an ice pack to the injection site can help alleviate any discomfort. It is important to monitor the injection site for any signs of infection, such as increased redness, swelling, or drainage, and to contact a doctor if these symptoms appear. Patients should also contact their doctor if they experience severe headaches, significant pain, or weakness.
Interpreting the Results
Patients are asked to keep a pain diary for several hours or up to 24 hours following the procedure, noting their pain levels and how they respond to activities that usually cause discomfort. Significant pain relief after the injection suggests that the facet joint is the source of the pain.
If the initial block provides substantial, temporary pain relief, a second diagnostic block may be performed to confirm the results, sometimes using a different anesthetic. This two-block protocol helps reduce the chance of a false-positive diagnosis. A positive response to the MBB indicates that further, longer-lasting treatments, such as radiofrequency ablation (RFA), may be effective. RFA targets the same medial branch nerves to provide more prolonged pain relief by using heat to disrupt the nerves’ ability to send pain signals. If the MBB does not provide pain relief, it suggests that the pain is likely originating from a different source, guiding the physician to explore other diagnostic avenues.