What is Diagnostic Medial Branch Nerve Block Injection?
Back pain is one of the most common medical problems in the U.S. According to the National Institutes of Health, 80% of adults will experience back pain at some point in their lives. Chronic back pain, or pain that continues for weeks or months, affects up to 8% of adults. Lower back pain is the most common, affecting the five vertebrae in the lumbar area of the spine. Treatment usually includes medication, exercise, and physical therapy. If you experience chronic back pain, your doctor may recommend a diagnostic medical procedure called a medial branch nerve block to determine the source of pain.
Structure of the Spine
Coccyx, sacral and thoracic vertebrae have limited or no motion. In contrast, cervical and lumbar vertebrae have a wide range of motion. Lumbar vertebrae are the largest, providing the ability to lift heavy objects and to twist, turn, bend and stretch. The spine is made of 33 vertebrae total:
- Seven cervical vertebrae in the neck support the head
- Twelve thoracic vertebrae in the mid-back support the rib cage
- Five lumbar vertebrae in the lower back support your body’s weight
- Five sacral vertebrae connect the spine to the pelvic bones
- Four coccyx vertebrae support ligaments that connect to the pelvic floor
Although each type of vertebra performs a specific function, they all have a similar structure. The drum-shaped vertebral body absorbs weight. The bony projections on the vertebral arch, called articular processes, attach muscles and ligaments to the spine. The spinal cord, blood vessels and nerves run through a tunnel in the center of each vertebra. Discs between vertebrae act as shock absorbers and cushions.
Facet joints connect each vertebra to the one above and below it. They allow a wide range of movement of the spine and provide additional protection to the vertebrae and spinal cord. Facet joints are faced with cartilage and contain synovial fluid to reduce friction between the bones. They can become inflamed or damaged from injury, arthritis or other conditions, causing pain.
Medial Branch Nerve Blocks
Medial branch nerves go from the spinal canal to the facet joints and carry sensory information between the joints and brain. When facet joints degenerate or are inflamed, these nerves transmit the sensation of pain. Medial branch nerve blocks are both diagnostic and therapeutic. The doctor uses a small needle to inject a local anesthetic outside the joint near the nerve. A steroid may also be given.
Ultrasound or fluoroscopy allows the doctor to see the joints and nerves to precisely place the needle. A contrast dye enhances visualization. All the nerves on a joint are treated at the same time. The patient is awake during the procedure, which usually lasts between 15 and 30 minutes. There are several possible outcomes:
- If the pain continues, the procedure is diagnostic, indicating that the facet joint is not the source.
- If the pain subsides for a short time, the procedure has both diagnostic and therapeutic value, showing that the pain comes from this area, but the steroid has limited effect.
- If the pain goes away or diminishes over several days, the treatment is therapeutic, showing that the steroid affected the pain.
Even temporary pain relief can help healing and allow time for other treatments, including physiotherapy to strengthen muscles and enhance flexibility. When the procedure confirms that the joint is the source of pain, your doctor may recommend additional medial nerve blocks, or a procedure called radiofrequency ablation that interrupts the transmission of pain signals to the brain.Make an Appointment
Diagnostic Medial Branch Nerve Block Injection Risks & Complications
There are few risks and complications associated with medial nerve block injections. Complications include bleeding, increased pain, allergic reaction to the dye or medication or infection. Severe infection is rare, occurring in less than 0.1% of all injections. Very rarely, the procedure can damage the nerve or spinal cord. Your doctor will evaluate your condition to determine whether this procedure is appropriate. Medication, exercise, targeted physical therapy, and other modalities may also be recommended to help alleviate pain and heal the spine.