A Medial Branch Block (MBB) is a diagnostic tool used by pain specialists to pinpoint the source of chronic back or neck pain. The procedure involves injecting a local anesthetic near the medial branch nerves that transmit pain signals from the facet joints in the spine. These joints, which link the vertebrae, can become painful due to conditions like arthritis or injury. The MBB temporarily blocks the nerve signals, confirming whether the facet joint is the generator of the patient’s discomfort and determining the next step in a personalized pain management plan.
Immediate Post-Procedure Care and Expectations
Following an MBB, patients are observed in a recovery area to monitor the temporary effects of the anesthetic. Temporary numbness or mild soreness at the injection site is normal. Patients are advised not to drive for the remainder of the day, and clinics often recommend having someone stay with them for the first night. The immediate pain relief experienced is temporary and due solely to the local anesthetic numbing the nerve.
Patients should maintain a pain diary, tracking the degree of relief and how long it lasts. This documentation is essential because the true diagnostic window occurs after the initial numbness wears off. Patients should avoid strenuous activities for the first 24 hours, focusing instead on gentle movement to assess the block’s effect on routine activities.
Interpreting the Diagnostic Results
The interpretation relies on the patient’s reported pain reduction after the anesthetic wears off. A “positive block” means the patient experiences a significant reduction in typical pain symptoms, commonly defined as 50% to 80% relief.
A positive outcome confirms the facet joint is the primary source of chronic pain. To increase accuracy and minimize false positives, the diagnostic process often involves performing two separate MBBs on different occasions. If both blocks provide substantial, temporary relief, the diagnosis of facet joint pain is confirmed, justifying progression to durable treatment.
If the patient reports little to no change in pain after the anesthetic wears off, the block is “negative.” This rules out the facet joint as the major pain generator, allowing the physician to redirect the diagnostic focus elsewhere.
Progression to Radiofrequency Neurotomy
A confirmed positive diagnosis leads to the most common next step: Radiofrequency Neurotomy (RFN), also called Radiofrequency Ablation (RFA). RFN is a therapeutic procedure targeting the same medial branch nerves identified by the diagnostic block, aiming for much longer pain relief.
The mechanism uses an electrode to deliver an electrical current that creates heat, disrupting the nerve’s ability to transmit pain signals. This controlled thermal lesioning temporarily halts the nerve’s function without destroying it permanently. The procedure is performed under fluoroscopic guidance to ensure precise application of heat to the target nerve tissue.
RFN typically provides substantial pain reduction lasting between 6 to 18 months, sometimes up to two years. This extended duration allows patients to engage in physical therapy and other restorative activities without pain while the nerve slowly regenerates.
Next Steps Following a Negative Block
If the MBB provides no significant pain relief, it indicates the facet joints are likely not the primary source of discomfort. This negative result is valuable information that helps narrow the search for the true cause of the pain.
Physicians may order further diagnostic tests, such as an MRI or bone scan, to look for issues like a herniated disc, spinal stenosis, or nerve compression. The focus may also shift to other joints, such as the sacroiliac (SI) joint, which can mimic facet joint pain. A targeted diagnostic injection into the SI joint may be the subsequent procedure.
The management plan will emphasize conservative treatments, including physical therapy and medication management, while the diagnostic process continues. The negative MBB prevents unnecessary treatment of the facet joints and ensures the next steps target the true source of chronic pain.