Chronic neck or back pain casts a wide shadow over your life, especially when it’s hard to pin down the cause. When imaging can’t prove the underlying causes of this type of pain, a medial branch block is sometimes used. It’s a diagnostic injection that directly tests the suspected source. The nerves carrying signals from a facet joint are temporarily blocked, and the patient compares how they feel with the nerves blocked vs. without the nerves blocked.
Practices like SPSC Spine Care, NJ Spine Specialists and more use medial branch block procedures to help patients narrow down their diagnoses before committing to long-term treatment. It sounds complicated, but it’s simple in practice. Numb the (suspected) offending nerve and see if the patient feels better. If they do, they know that’s the nerve causing problems. If they don’t, there’s a different underlying cause.
What Is a Medial Branch Block?
Facet joints sit on both sides of each vertebra and connect one section of the spine to the next. They guide spinal movement and take on more load when the back extends or rotates. Small medial branch nerves carry pain signals away from these joints.
A medial branch block places a local anesthetic beside one or more of those nerves. The medication does not go inside the facet joint. If the patient experiences less pain while the nerve is numbed, that’s serious evidence that the nerve is involved in the issue.
This usually isn’t the first thing a physician will try. It’s usually only considered after three months of pain persisting through other forms of treatment like physical therapy and anti-inflammatory medication.
Justifying a medial branch block is also difficult if the problem doesn’t seem to be related to facet joints. Different diagnostic approaches may be used for symptoms pointing more toward a herniated disc or nerve-root compression.
Why Facet Joints Start Hurting
The cartilage covering a facet joint can thin with age, which exposes the joint surfaces underneath to more wear and tear. Extension and rotation may become painful as the joint loses some of its smooth motion.
An old whiplash injury, for example, can accelerate those changes by altering how one part of the neck carries load. Arthritis and years of repeated strain can also contribute.
Degenerative disc disease is another common cause. As a disc loses height, it transfers more of the spine’s load to the facet joints above and below it. Facet arthrosis refers to deterioration within the joint itself, similar to the cartilage breakdown that can affect a hip or knee.
Why Two Nerves May Be Blocked for One Joint
Each facet joint receives two nerve signals. One from the medial branch at the same level as the joint and one from the branch immediately above it. So a physician testing one joint will block both nerves feeding said joint.
If they only block one, the test can deliver misleading results. The unblocked branch can still be carrying part of the pain signal.
What Happens During a Medial Branch Block Procedure
The patient lies face down while the treatment area is cleaned and prepared. Using fluoroscopy, a form of live x-ray, the physician guides a thin needle toward the medial branch nerve at each level being tested. A small amount of contrast dye helps confirm the needle position before the anesthetic is injected.
Most patients notice temporary soreness or discomfort at the injection site. Infection, bleeding, and short-lived numbness outside the intended area are possible but uncommon. Imaging guidance helps the physician place the medication beside the intended nerve while avoiding nearby structures.
Why One Medial Branch Block May Not Be Enough
A singular diagnostic block doesn’t always provide a dependable answer on its own. Research reviewed by Lawson and colleagues reported false-positive rates of approximately 27% to 45% for single diagnostic blocks. They found that relief after just one injection may be a placebo response or some other kind of temporary effect. This finding creates a huge margin of error that makes it difficult to support a long-term treatment decision without external confirmation.
A physician may repeat the block at a separate visit using an anesthetic with a different duration of action. When both procedures produce a similar reduction in the patient’s familiar pain during the expected anesthetic window, physicians can be more confident in the findings.
What a Positive or Negative Result Means
The result physicians look for is a clear reduction in the pain the patient normally experiences. That relief may last only a few hours, and the pain returning afterward does not mean the test failed. Temporary change is exactly what they’re looking for, and it’s existence at all is the test result.
Patients may be asked to repeat movements that usually provoke their symptoms and record their pain on a simple scale while the anesthetic is active. The timing and degree of relief help the physician judge whether the targeted joint is involved.
When the block produces little or no change, the tested nerve and facet joint can be ruled out as sources. The physician may then reassess other structures, such as a disc or the sacroiliac joint, instead of moving directly toward radiofrequency ablation at the wrong target.
Medial Branch Block vs. Facet Joint Injection
Some people confuse these two procedures, but they are different. A facet joint injection delivers medication directly into the joint capsule. A medial branch block places anesthetic beside the nerve outside the joint.
A 2023 randomized study by Malhotra and colleagues compared the two approaches in patients with low back pain. Both groups improved on the study’s pain and disability measures, while the medial branch block was reported as easier to administer.
The difference is important because a medial branch block is generally used to test the nerve pathway before treatment. A facet injection places medication at the joint itself and may be used for a different diagnostic or therapeutic purpose.
Does the Location Change the Procedure?
The same type of medial branch nerve runs along the cervical, thoracic, and lumbar spine, but the surrounding anatomy and pain patterns change by region.
A cervical medial branch block targets nerves in the neck. These blocks may be considered when pain is aggravated by turning or extending the neck and may spread toward the shoulder or back of the head.
A thoracic block targets the mid-back, where the physician works around the rib-bearing vertebrae. Lumbar blocks target the lower spine and are commonly used when extension or rotation reproduces lower-back pain.
But the diagnostic principle is the same regardless of the location. Numb the suspected problem nerve temporarily, and see if that decreases the patient’s pain.
What Happens After the Block
Patients are usually advised to take it easy for the rest of the day and follow the practice’s instructions about driving, especially if they were sedated. The physician may ask the patient to track pain and test a few ordinary movements that normally trigger symptoms.
Once the soreness from the injection settles, easing back into gentle movement, similar to the exercises used for facet arthrosis, can help maintain mobility without provoking the joint again.
When two blocks consistently point to the same facet joint, physicians might suggest treatments like radiofrequency ablation. The procedure uses heat to interrupt the medial branch nerve’s ability to transmit pain for longer than the temporary anesthetic used during the diagnostic block.
At SPSC Pain Care, Dr. Edward Shen, a board-certified pain management specialist and Division Chief at Trinitas Regional Medical Center, works with patients managing chronic back and neck pain through this diagnostic and treatment process.
Frequently Asked Questions
Does a medial branch block hurt?
Most patients feel a brief sting from the numbing medication and some pressure as the needle is positioned. Sedation may be available, but whether it is used depends on the patient, the treatment plan, and the physician’s instructions.
How long does relief from a medial branch block last?
The anesthetic effect usually lasts for a limited period, often several hours, depending on which medication is used. Patients are commonly asked to track pain during that window because the entire result hinges on the timing and amount of relief.
What happens if the block does not help?
A block that produces no meaningful change makes the targeted facet joint less likely to be the primary source. The physician may evaluate another spinal level or consider structures such as a disc or sacroiliac joint. The result can also prevent the patient from proceeding to radiofrequency ablation at a target that was never properly confirmed.
What the Injection Adds When an MRI Is Inconclusive
An MRI can identify a worn or arthritic facet joint without proving that the joint is responsible for the patient’s symptoms. A medial branch block adds the missing functional test by showing whether temporarily silencing one nerve changes the pain the patient recognizes.
When imaging is inconclusive and the clinical pattern still points toward the facet joints, that short-lived response can guide whether radiofrequency ablation or another treatment should be considered.
Sources
A, Malhotra N, Kumar A, et al. (November 22, 2023) Comparative Evaluation of Intraarticular Facet Joint Injection Versus Medial Branch Block in Patients With Low Back Pain: A Randomised Controlled Study. Cureus 15(11): e49232. doi:10.7759/cureus.49232
Lawson GE, Nolet PS, Little AR, Bhattacharyya A, Wang V, Lawson CA, Ko GD. Medial Branch Blocks for Diagnosis of Facet Joint Pain Etiology and Use in Chronic Pain Litigation. International Journal of Environmental Research and Public Health. 2020; 17(21):7932. https://doi.org/10.3390/ijerph17217932
