Selective Nerve Root Block
What is a Selective Nerve Root Block?
A selective nerve root block (SNRB) injection or just nerve block injection is used to both diagnose and treat an inflamed spinal nerve. A medication, typically, an anesthetic or anesthetic with steroid is administered near the spinal nerve as it exits the intervertebral foramen (bony opening between adjacent vertebrae). The medication reduces inflammation and numbs the pain transmitted by the nerve.
What to expect during selective nerve root injections
UPMC neurosurgeons perform this procedure with the patient lying on the stomach on an x-ray table. The surgeon uses fluoroscopy (x-ray) to help locate the specific nerve root.
A needle is inserted into the area and the medication and an anesthetic are injected. The injection takes just several minutes. After the injection, the patient is monitored for 15-20 minutes and then released. Most patients start noticing pain relief after the third to seventh day, which can last weeks or months. If the first injection fails to relieve pain symptoms in one to two weeks, the doctor may recommend another injection. In a 12-month period, doctors usually limit injections to three.
How Selective Nerve Block Injections Work
When used for treatment purposes, steroids are usually mixed with anesthetics or used alone in selective nerve root block injections. Steroids in nerve blocks work by a combination of the following mechanisms1:
Inhibits the action of certain enzymes such as phospholipase A that causes neural irritation and pain
Block specific fibers (C fibers) within the nerve that results in lesser pain transmitted to the brain
Decreases the permeability of nerve fibers to receive blood, decreasing pain transmission
Through these mechanisms, the pain signals transmitted by the target nerve may be reduced.
Before administering the injection, the skin over the treatment site is cleaned to prevent infection. Usually, a small amount of contrast dye is injected first in order to identify if the needle is in the proper location near the target nerve and to avoid injecting into a blood vessel1
Due to anatomic variations in every patient, fluoroscopy or ultrasound guidance is almost always used to locate the nerve. The injection may recreate the usual pain that has been experienced by the patient.
When Root Block Injections Are Used
Selective nerve root block injections are used to treat an inflamed nerve root caused by a herniated disc, degenerative changes in the vertebrae such as bone spurs causing nerve compression, and/or conditions such as scoliosis. In any of these conditions, there may be a chemical irritation or pinching of the nerve due to mechanical compression.
Multiple nerve blocks may be performed if more than one nerve is suspected of causing pain.
Risks and Complications of Nerve Block Injections
Although rare, a few risks are possible with selective nerve root block injections, including:
- Allergic reactions
- Spinal cord damage
- Pneumothorax (or collapsed lung with thoracic injections)