Selective Nerve Root Block

A Selective Nerve Root Block uses a very specific injection of local anesthetic along one of the nerves that exit between each vertebral body. Each of these nerves is responsible for sensation in a localized region of the arms or legs. The injection can be done in the lumbar spine and is specific to one side of body. If the patient’s pain is relieved by the injection for the duration of the local anesthetic, the spinal surgeon can have increased confidence that surgery at this level will help relieve the patient’s pain.

A diagnostic injection should be done on a day in which the patient is having actual pain symptoms so that a definite determination can be made as to whether the patient’s pain has been modified or relieved by the injection. The injection is not 100% specific as there may be multiple levels contributing to the symptoms or the injection may slightly affect an adjacent level. The procedure may also be done with a therapeutic injection of steroid medication to further reduce nerve irritation.

What to Expect

The patient does not need to be without food or water(NPO) prior to the test. The scheduling nurse will inquire if the patient is taking blood thinning medication and ask about the patient’s history of allergies.

The procedure is done in a radiology room and usually takes 15-30 minutes. Local anesthetic is used from the skin down to the spine. A longer-lasting local anesthetic is used for the actual injection along the nerve which can last up to 6 or more hours.

A driver should come with the patient as there is expected numbness in the arm or leg for several hours. Usually, this does not affect walking though patients are advised to be careful about going up or down steps until the local anesthetic has worn off.

Specific Blocks Types

Zygoapophyseal Joint Blocks (Facet Joints)

Each spinal vertebra rests on and transmits the supported weight of the body through three points to the adjacent vertebra. These three points are the intervertebral disc in front and two zygoapophyseal or facet joints towards the back of the spine.The facet joints are prone to arthritis. Inflamation in the joint may irritate and inflame adjacent nerves causing back and sometimes radicular pain. Local anesthetic can be injected into the joint or along the nerves that supply the joint (Medial Branch Block). If the patient’s pain is relieved by the injections, the procedure helps determine that the pain is arising from the joints rather than from another source of back pain.

Medial branch blocks involve multiple injections as nerves from above and below supply the joint.

This procedure requires approximately 30 minutes per level. Patients need not be NPO (without food or water) and may drive themselves home soon after the procedure. These blocks are often combined with an injection of steroid medication into the joint for a longer, more therapeutic effect.

Orthopedic Hardware Block

Following fusion procedures or other implantation of orthopedic hardware, pain can sometimes develop from the hardware. To determine if this is the source of pain, an injection of local anesthetic can be made along the hardware insertion points. Pain relief over the duration of the local anesthetic is a good indicator that the hardware is a source of pain.The procedure is done in a special fluoroscopic room that allows multiple angles of visualization of the hardware. There is no special patient preparation and the injection usually takes less than 20 minutes.

Spondylolysis Block

A spondylolysis defect is a crack in a portion of the neural arch that surrounds the spinal canal. This defect lies between the vertebral body and the two zygoapophyseal joints which are the three weight bearing points of each vertebra. The defects are thought to be caused from previous injury. If they occur on both sides of the neural arch, they can allow a slippage (spondylolithesis) of one vertebra forward upon another.

A precise injection of local anesthetic can be made into the defect to determine if it is a source of pain. This is usually done with fluoroscopic or computed tomography guidance. The procedure requires no special preparation and usually takes less than 30 minutes.

Pseudoarthrosis Block

The lowest lumbar or first sacral vertebra may develop a variation called a transitional vertebra. In this variant, a portion of the vertebra above is enlarged and curves down to meet the vertebra below. If these do not fuse together, they can form a false joint or pseudoarthrosis. If the two parts rub against each other during spinal motion, a painful arthritis can develop. This false joint can also be injected with local anesthetic to determine how much it contributes to the patient’s pain symptoms. The injection is done using either fluoroscopic or computed tomographic guidance and takes about 30 minutes. There is no special patient preparation.