Overview
A selective nerve root block (SNRB) places a small amount of numbing medicine, often with a steroid, next to a single spinal nerve root where it exits the spine.
GSMC is led by Dr. Dharam Mann, who completed fellowships in pain management, cardiac anesthesia and critical care at Massachusetts General Hospital/Harvard.
It can help confirm which nerve is causing arm or leg symptoms and may relieve pain from an inflamed nerve. The results can also help with surgical planning.
How it works
Using X-ray guidance and contrast dye, the physician places a needle at the opening where the target nerve exits the spine (the foramen) and injects medication.
Who it may be for
- Arm or leg pain thought to come from a specific nerve root
- Patients whose imaging shows more than one possible source
- Candidates for surgery who need diagnostic clarity
Your exam and imaging decide whether this treatment is appropriate for you.
What to expect
- Before: we review your medications (especially blood thinners), allergies and imaging. You may need a driver.
- During: you lie on a procedure table, the skin is cleaned and numbed, and the physician uses X-ray (fluoroscopy) or ultrasound guidance to place the needle.
- After: you are monitored briefly and usually go home the same day. Keep a pain diary so we can judge the response.
Recovery
The arm or leg may feel numb or weak for a few hours. Arrange a driver. Your instructions may differ.
Risks and side effects
Every procedure has risks. Your physician will review them with you, including:
- Temporary soreness at the injection site
- Temporary increase in pain
- Bleeding or bruising
- Infection (uncommon)
- Allergic reaction (rare)
- Temporary rise in blood sugar if a steroid is used
- Temporary numbness or weakness in the limb
- Nerve injury (rare)
Insurance and cost
Many plans, including Medicare, may cover this treatment when criteria are met. We verify benefits before scheduling. See accepted insurance.
Frequently asked questions
How is a nerve root block different from an epidural?
A nerve root block targets one specific nerve. An epidural spreads medication more widely in the epidural space.
Why is it used before surgery?
It can help confirm which nerve level is responsible for symptoms.
How long does a nerve block last?
It depends on the medicine and the reason for the block. The numbing medicine wears off in a few hours. If a steroid is included, relief often starts in 2 to 7 days and may last weeks to months. Some people get longer relief than others. Your doctor will follow up to see how you responded.
Why does my pain come back after the numbing wears off?
That's normal. The numbing medicine works for a few hours. The steroid needs a few days to calm the inflamed nerve. Some soreness at the injection site during that gap is common.
What are the side effects of a nerve block?
Common, short-lived effects:
- Soreness where the needle went in
- Temporary numbness or weakness in the arm or leg
- A flushed face
- Trouble sleeping
- Higher blood sugar for a day or two if you have diabetes
Less common risks:
- Infection
- Bleeding
- Headache
- Nerve irritation
Your doctor will go over the risks with you before the procedure.
Can I drive home after a nerve block?
Plan to have someone drive you. Your arm or leg may feel numb or weak for a few hours.
How many nerve blocks can I have?
There's no single number for everyone. Steroid doses are usually limited over a year. Your doctor will plan your doses based on your health and how well each block works.
Is a nerve block also a test?
Often, yes. If a block numbs a specific nerve and your pain goes away for a while, that helps confirm where your pain is coming from. That guides your next step.
When should I call the office?
Call if you have:
- Fever
- Redness or drainage at the site
- A severe headache
- New weakness that doesn't go away
- Any loss of bladder or bowel control
This page is general patient education and does not replace advice from your own clinician. Individual results vary.