What is a Selective Nerve Root Injection (SNRI)?
A Selective Nerve Root Injection is a more precise injection done under fluoroscopic guidance (X-Ray) using anesthetic with a long lasting steroid (“cortisone”) around the nerve root as it exits the spinal column. This injection is sometimes referred to as a transforaminal injection.
What is the purpose of it?
This injection is used as a diagnostic as well as a therapeutic injection. It helps us determine if the nerve is irritated by “numbing” the nerve. The steroid will therapeutically reduce the inflammation and pain caused by pressure on the nerve.
How long does the injection take?
The actual injection takes only approximately 10 minutes.
What is actually injected?
The injection consists of a mixture of local anesthetic (like lidocaine) and the steroid medication. Prior to injecting the medicine, a small volume of contrast dye is used to confirm proper needle placement.
Will the injection hurt?
This procedure is done under local anesthesia. You may feel a “bee sting” when the local anesthetic is injected. After you are numb, you may feel a slight pressure when we inject the medication.
How is the injection performed?
It is done with the patient lying on the stomach with fluoroscopic (x-ray) guidance. The skin in the back is cleaned with antiseptic solution and then the injection is carried out. After the injection, you are returned to your room and monitored for 15-20 minutes before you are released with someone to drive you home.
What should I expect after the injection?
Immediately after the injection, you may feel that your pain may be gone or quite less. This is due to the local anesthetic injected. This will last for a few hours. Your pain may return and you may have a sore back for a day or two. Icing will reduce this. This is due to the mechanical process of needle insertion as well as initial irritation from the steroid itself. You should start noticing pain relief starting the 3rd to 7th day.
What should I do after the procedure?
You must have a ride home. We advise patients to take it easy for the day of the procedure. You should apply ice to the injection site 20 minutes every hour on the day of your injection. After the first day, you can perform activity as tolerated.
Can I go to work the next day?
Yes. Unless there are complications, you should be able to return to your work the next day. The most common thing you may feel is soreness in your back.
How long will the effects of the medication last?
The immediate effect is usually from the local anesthetic injected. This wears off in a few hours. The cortisone starts working in about 3 to 7 days and its effect can last for several days to many months.
How many injections do I need to have?
If the first injection does not relieve your symptoms in one to two weeks, you may be recommended to have one more injection. If you respond to the injections and still have residual pain, you may be recommended for a third injection, or a different procedure.
Can I have more than three injections?
In a twelve-month period, we generally do not perform more than three injections. Giving more than three injections will increase the likelihood of side effects from cortisone. Also, if three injections with fluoroscopic guidance have not helped you much, it is very unlikely that you will get any further benefit from additional injections.
What are the risks and side effects?
This procedure is safe when performed in a controlled setting (surgical center sterile equipment, and the use of x-ray.) However, with any procedure there are risks, side effects, and possibility of complications. The most common side effect is local tenderness – which is temporary. The other risks involve, infection, bleeding, worsening of symptoms. As with other types of injections, you should not have the procedure if you are currently taking blood-thinning medicine (Aspirin or Coumadin.) Side effects related to cortisone include: fluid retention, weight gain, increased blood sugar (mainly in diabetics,) elevated blood pressure, mood swings, irritability, insomnia, and suppression of body’s own natural production of cortisone. Fortunately, the serious side effects and complications are uncommon, but include nerve damage, coma, and death. You should discuss any specific concerns with your physician.