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A nerve root block can help if you have pain in your back or leg that doesn’t improve with other pain relief methods.

For a nerve root block, a doctor injects medication that coats a nerve root, near the spine. If the procedure works, pain signals that start anywhere below the nerve root, including in the leg, don’t travel up to the brain.

Here’s what you should know about nerve blocks, including what happens during the procedure and how long its pain relief lasts.

What Is a Lumbar Nerve Root Injection?

During a selective nerve root block (SNRB), you’ll lie down on your stomach on a cushioned exam table. A health care provider will clean your back with antiseptic.

A surgeon usually uses x-ray imaging to inject the medication around the nerve. This ensures the doctor injects the medication in the right spot.

If the nerve is difficult to target, the surgeon may first inject a dye that shows up on the x-ray. This way, the surgeon can adjust the needle if the dye doesn’t go to the correct nerve. When the dye test shows the needle is in the right position, the doctor will inject the medication.

After the SNRB injection, you’ll stay at the hospital for about 20 minutes. A health care provider will monitor you to make sure you don’t experience unexpected side effects or an allergic reaction.

How painful is a selective nerve root block?

You may feel a pinching or stinging sensation when the doctor inserts the needle and delivers the medication, but this should only last a moment.

Feeling some weakness or numbness for a few hours after the procedure is normal. However, your care team will want to make sure the weakness isn’t so severe that it affects your ability to stand or walk.

You’ll need someone to drive you home from your appointment, and you’ll need to refrain from driving for 24 hours after the procedure. This is because you may develop numbness or weakness in your leg, or you may feel drowsy from the medication.

How do I prepare for a nerve root injection?

There are usually no special instructions to follow before a nerve root injection. However, you may need to stop taking certain medications in the hours or days before a procedure. For example, your doctor may ask you to temporarily stop a blood-thinning medication that could increase the risk of bleeding during the SNRB injection.

The procedure itself only takes a few minutes. You may need to change into a hospital gown.

Why Would I Need a Root Nerve Block?

You may need a nerve root injection to:

• Diagnose the cause of pain in the back or leg.
• Treat chronic pain in the back or leg.

If doctors aren’t sure which nerve is causing pain, they may try blocking a nerve root they suspect is sending pain signals. If the pain goes away, the doctors know the blocked nerve is the source of the pain. If it doesn’t go away, the pain is likely coming from somewhere else.

Usually, people have nerve blocks when oral pain medications, physical therapy, and other pain treatments don’t work.

One common reason for a nerve block infection is a herniated disc, or a slipped disc. This is when the inner part of a disc between two vertebrae protrudes out of place. The slipped disc can then put pressure on a nerve root.

By helping to relieve pain, a nerve root injection can allow people to engage in physical activities they couldn’t engage in otherwise. It can also help relieve the emotional and social effects of back and leg pain.

How Long Does a Nerve Root Block Injection Last?

A nerve root injection usually provides pain relief for several weeks to many months. For some people, nerve blocks give an irritated nerve a chance to heal. Therefore, even though they provide temporary relief, a series of nerve blocks is sometimes enough to treat pain long-term.

If pain continues after many nerve block procedures, your doctor may recommend back surgery or other pain treatments.

Will I Feel Relief Right After a Nerve Root Block?

The steroid medication usually takes a few days to start working. If you don’t feel any pain relief within a week or two, your doctor may recommend another injection.

In some cases, doctors inject a pain-relieving medication and a steroid into the space beside the nerve. The pain-relieving medication may work right away and then wear off. But the steroid may take time to work.

For this reason, you may feel immediate pain relief right after the procedure. However, the pain may return hours or days later when the pain medication wears off. Then, the pain will go away again when the longer-lasting steroid starts working.

What Are the Risks of a Nerve Root Block?

Risks of the procedure include bleeding and infection. The medication also may damage the nerve or affect the wrong nerve, causing long-lasting numbness or weakness.

These risks are rare, however. You can reduce them by choosing a center experienced in performing various types of nerve blocks.

You should also ask your surgeon about the risks to you personally. A nerve block procedure is riskier or less risky depending on your age, anatomy, and other health problems.

You should also tell your doctor if you’re pregnant or may have gotten pregnant because the x-ray technology used in a nerve root block isn’t always safe for a fetus. The doctor can choose imaging tools that use less radiation for a pregnant person.

Most hospitals and insurers will only allow people to have three to four nerve blocks a year. This is because the risks of nerve blocks increase if you exceed this number.