What is a Selective Nerve Block?
The selective nerve root block (SNRB) is a minimally invasive procedure that involves injecting a small amount of steroid and numbing medication around a very specific nerve root/spinal nerve that exits out of the spinal cord. It can be done in the cervical (neck), thoracic (chest) and lumbar (low back) areas.
Why Are Selective Nerve Blocks Used?
When a nerve root becomes compressed and inflamed, it can produce back and/or leg pain. Occasionally, an imaging study (e.g. MRI) may not clearly show which nerve is causing the pain and an SNRB injection is performed to assist in isolating the source of pain. In addition to its diagnostic function, this type of injection for pain management can also be used as a treatment for a far lateral disc herniation (a disc that ruptures outside the spinal canal).
The SNRB injection allows Dr. Moradian to determine exactly what nerve root or roots are being affected. The selective nerve root block procedure can be a diagnostic test (finding out which nerve is involved) or therapeutic test (providing pain relief for low back and/or leg pain) depending on the medications that are injected.
How Are Selective Nerve Root Blocks Performed?
A selective nerve root block procedure is a minimally invasive technique that is performed in an outpatient setting. Typically, the procedure takes between 30 and 60 minutes to complete.
A selective nerve root block procedure is usually performed with the patient lying in a prone position under a fluoroscopic X-ray. The skin of the affected area is cleaned with an antiseptic solution and is then numbed with a local anesthetic. A needle is then inserted, using fluoroscopic guidance, into the proper position within the spine. A small amount of contrast dye is injected to confirm proper needle placement.
The final needle position for a selective nerve root block is just superior to the targeted nerve root through the foramen (which is the space between the vertebral bodies). The injection, which usually consists of a local anesthetic such as lidocaine and a steroid such as dexamethasone, is injected into the affected area. Once the injection is complete, the patient is monitored for adverse reactions. If the patient’s pain subsides after the injection, it is presumed that the pain-generating nerve root has been identified.
What are the Expected Results?
Most patients resume normal activities the day after the injection procedure. Many patients may report an immediate relief of symptoms that is due to the injection of the local anesthetic, which may be followed by a slight increase in pain until the cortisone begins to exert its effects.
The relief of symptoms from a selective nerve root block varies among patients and can last from several days to several months.
Following a selective nerve root block, patients may experience increased pain at the injection site, increased radicular pain, lightheadedness, increased spinal pain, nausea, headache, and vomiting.
What are the Risks of SNRB?
Although uncommon, selective nerve root block procedure risks may include bleeding, infection, and allergic reaction to the medications. Additionally, serious rare complications include: membrane perforation of the dura, nerve damage, and paralysis.