What is a Nerve Root Block?
The spinal nerves of the body pass down the spine, within the central canal. At each level of the spine, a pair of nerves branch off through the sides of the spine, known as the intervertebral foramina. Normally, these openings are sufficient to allow enough space for the nerve root to pass without being affected. In some cases, though the nerves may become constricted due to elements pressing into it, such as displaced vertebra, herniated discs, and osteoarthritis of the facet joints. A nerve root block is substance that is injected into the sheath surrounding the nerve root to the pain block pain signals caused by one or more of the conditions mentioned above. Let's take a look at one of these types of treatments - the Selective Nerve Root Block (SNRB).
The Selective Nerve Root Block (SNRB) is a back pain management procedure that can be used as both a diagnostic and treatment tool. This procedure can answer the question, "Is that person's back pain caused by compression of a specific nerve root?" Imaging tests such as X-Rays and MRIs may indicate lesions and other forms of pathology in the regions of the spine where the patient feels pain. On the other hand, doctors cannot be sure that the pathology indicated on the medical images is the main pain generator. The fact is, most people with and without back pain have degenerative changes in their spines that would become apparent if they had MRIs. When the nerve block delivered to the spinal nerve roots produce pain relief in the patient, that is confirmation that compression of that structure is the cause of the patient's back pain.
The Procedure: With this procedure, the spine surgeon or anesthesiologist will target the nerve where it exits the foramen. This is the section of the nerve that is often affected by conditions such as lateral disc herniation. The substance that is injected into the sheath surrounding the nerve root includes lidocaine (a numbing agent) and a steroid (anti-inflammatory medication). In order for the doctor to guide the needle into the specific location, Fluoroscopy (live X-Ray) is used. The patient will be awake and will provide feedback to the doctor in the minutes following the injection. If the patient reports pain relief, this response will confirm irritation or compression of that nerve root to be the main pain generator (source of pain). After the injection, the steroid also helps to reduce inflammation around the nerve root.
Success rates vary for this procedure, though they will have value to the patient's treatment program as a diagnostic tool, regardless of the results. This procedure is considered to be very safe, provided that the patient is not treated with these medications more than three times per year. Too frequent abuse of steroids to a given area is associated with tissue destruction.
Selective Nerve Root Block procedures are thought to be more difficult to perform than epidural steroid injections. For this reason, patients who receive this therapy should be under the care of an experienced spine surgeon, who is very comfortable using Fluoroscopy guidance. Because the injected substance is so close to the nerve itself, patient's with sciatic related leg pain may initially feel an increase in symptoms shortly following the procedure. Because the injection site is outside the spine, there is there is no risk of cerebrospinal fluid leak (wet tap) associated with other pain management injections, such is epidural injections.
Facet Joint Block: A facet joint block involves the injection of this same substance around areas of inflammation caused by facet joint arthritis. A facet joint block may be used when the facet joint itself is the primary pain generator. Like SNRBs, these injections may be used for both diagnostic purposed and as a pain management treatment. The injected substance may block the pain signal and reduce inflammation around the facet joints.
Each vertebra has 4 bony processes: two that rise backwards and upwards to connect with the vertebra above it, and two processes that go backwards and downwards to connect with the vertebra below them. There is a single facet at the ends of these processes where they connect to the other vertebra. The facet joint includes the two facets, a layer of cartilage between the facets, and connective tissue surrounding the joint to hold it together.
In the facet block procedure, the doctor also used Live Fluoroscopy to guide the needle into the correct position before the injection is made.