Jenny L. F. Andrus, MD
Nerve blocks are commonly used by many types of physicians to prevent or treat pain. An anesthetic medication is injected near the nerve that affects a specific area of the body to provide effective, short-term pain relief to the patient. For example, nerve blocks may be administered by Anesthesiologists before surgeries, like a knee replacement or a tendon repair. Dentists and Oral Surgeons commonly use nerve blocks for root canals and wisdom tooth removal. As an Interventional Pain Management Specialist, I use them primarily as a diagnostic tool for my chronic pain patients, although they do often offer welcomed pain relief.
Medial Branch Nerves supply feeling to the facet joints in the spine. Each facet joint is enervated by two medial branch nerves, one at the level above the joint and one at the same level as the joint. These nerves carry signals to and from the brain. The facet joints are small joints which allow the spine to twist and bend fluidly while providing support and stability to the spine. The facet joints can become diseased or damaged by age, arthritis, or other conditions and the cartilage inside the joint can begin to wear away. Bone spurs may or may not develop and the joint may become less lubricated with synovial fluid. They may also become swollen and inflamed as other joints can with arthritis. As a result, the medial branch nerves can become irritated, inflamed or compressed.
Symptoms of facet joint arthritis and medial nerve irritation/compression are pain and stiffness. This pain and stiffness is typically at the level of the affected joint and may radiate into the limbs. Advanced arthritis can cause pronounced stiffness and reduced ability to twist or bend sideways.
Most of the time, the patient has seen a spine specialist and has had a physical exam, x-rays of their spine and usually an MR scan, which revealed arthritis of the facet joint(s). The patient may have tried conservative treatment with Physical Therapy, oral steroids, NSAIDS and activity modification, but they may not have seen a desired reduction in their pain. At that point, they would be referred to me for interventional procedures that hopefully address their pain without surgery.
The medial branch block is performed as an outpatient procedure and is done under live x-ray or fluoroscopy guidance. Anesthetic medication is injected at both sites of nerve enervation. If the patient experiences pain relief, I know that the facet joint is the root cause of their pain. The pain relief is temporary which gives us information on next steps for longer term pain relief. If there is no pain relief whatsoever, I will look elsewhere than the facet joints for the cause of the pain.
Occasionally, the patient will have significant pain relief for a long time after their medial branch block. However, the typical result is a short period of pain relief followed by a return of the pain. This indicates further treatment will be necessary to address the issue. I usually recommend radio frequency ablation of the nerves feeding the facet joints unless there is a definitive structural issue that will only be resolved through spinal surgery. In some cases, injection of steroid into the joint is preferred and can also provide significant pain relief.