Selective nerve root block (SNRB) is an injection procedure used either to reduce or diagnose neck or back pain.
Therapeutic SNRB uses targeted injections of a numbing agent and a steroidal anti-inflammatory in an effort to cut off pain signals traveling from a particular nerve root to the brain. Diagnostic SNRB uses a numbing agent, usually lidocaine, to produce temporary pain relief – thereby confirming a particular nerve root is the source of pain or other symptoms, such as tingling, numbness or muscle weakness.
Blocks are often used to help physicians figure out exactly where damaged nerves are located. If the pain is relieved after a particular nerve site is injected, it’s safe to assume that nerve was the one causing the problem. A nerve root block is not an epidural steroid injection, which is injected into the epidural space surrounding the spinal cord. Instead, an SNRB is injected outside the epidural space, at the root of the nerve as it exits the spinal canal through the intervertebral foramen (the natural passageway created by two stacked vertebrae). The use of a live X-ray, or fluoroscopy, allows the physician performing the procedure to see the exact site of injection in real time.
Conditions treated or diagnosed by SNRB
Spinal nerve compression due to a bulging or herniated disc, spinal stenosis or other condition can cause pain and inflammation of the nerve, as well as numbness, weakness, muscle spasms, pain and tingling in the extremities. Traditional open neck or back surgery for the treatment of a spinal condition may require large incisions, a hospital stay and an extended recovery period. A nerve root block, which requires only an injection, may be an attractive alternative to surgery.
An injection procedure such as SNRB usually is attempted only after other conservative treatment methods, such as physical therapy and oral pain medication, have proven ineffective for conditions such as:
- Spinal stenosis – narrowing of the spinal canal
- Bone spurs – bony growths that are the body’s response to diminished skeletal stability
- Herniated disc – extrusion of nucleus material through a tear in the outer wall of an intervertebral disc
- Bulging disc – loss of structural integrity of a disc’s outer wall, forcing the wall out of its normal boundary
- Arthritis of the spine – degeneration of cartilage associated with spinal joints
- Spondylolisthesis – slippage of one vertebra over another
There are some rare but possible risks to be aware of before receiving a nerve root block injection. Slight internal bleeding, infection at the site of injection and allergic reaction to the drugs administered are all possibilities. In unusual cases, more damage to the nerve may occur as a result of the needle injection. It is recommended that a nerve root block treatment is limited to several injections per year.
A few side effects may be felt following a block injection, including numbness along the path of the nerve, muscle weakness and some pain at the injection site. The use of an ice pack for a few days often will help this localized irritation. Symptomatic pain might improve immediately, although it may take a few days for the steroids to take effect.