Selective Nerve Root Block (SNRB)

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A selective nerve root block is a diagnostic test performed to determine if a specific spinal nerve is the source of pain.  A SNRB is performed to diagnose cervical (neck) or lumbar (low back) radiculopathy (irritation and inflammation of a nerve root).

Using fluoroscopic guidance, steroid medication (a strong anti-inflammatory) is injected at a specific nerve root   If the injection reduces symptoms, the pain source is identified.  The test takes 15- to 30-minutes per spinal level.

Patient Preparation: At Home

Below is a short list of common instructions. Your physician provides instructions specifically for you.

• Stop blood-thinning medication 2 days prior to the test
• Do not take any aspirin product 5 days prior to the test
• Stop anti-inflammatory medication 5 days prior to the test
• Stop pain medication 8 hours prior to the test
• Do not eat or drink 6 hours prior to the test
• Arrange for someone to drive you home

Patient Preparation: At the Medical Facility

The patient checks in, completes paperwork, and staff members review the patient’s medical history and asks questions about current medications and known allergies. After the check-in, the patient is instructed to change into a hospital gown and lie down on a hospital bed.

Before the test begins, a nurse monitors the patient’s heart (EKG), checks blood pressure, measures blood oxygen levels (finger oximeter), and checks vital signs. This is routine.

Medication to relax the patient is administered through an intravenous line.  However, the patient is awake during the procedure so they can respond to the physician's questions.

What to Expect During the Procedure

The procedure is performed in an operating room or other sterile setting. The patient is draped in such a way that the physician and medical team can clearly see and access the injection site. The draping usually restricts what the patient can see. The injection site is cleaned. The injection site area is numbed.

The medical team observse the procedure using fluoroscopy, a type of video x-ray. A large fluoroscopic device (called a C-arm for its characteristic C-shape) is positioned to obtain the proper images. Fluoroscopic images are displayed on monitors in the operating room.  Fluoroscopy ensures needle placement is precise.

Diagnostic injections may include an anesthetic agent, steroid, or antibiotic.  During the injection procedure, physician asks the patient when (and if) discomfort is felt.  This provides valuable feedback to the physician.

After the Procedure

The patient stays on their hospital bed while in the recovery area. A nurse monitors vital signs and answers questions. Typically, a patient is discharged home after 30- to 60-minutes with written instructions. Although the patient may feel well after this procedure, he or she should not attempt to drive. Someone should drive the patient home.

Side effects may occur after the procedure; some are normal and expected:

• The area around the injection site will feel numb. Relief from typical symptoms may last for 6-hours following the injection. 
• Side effects of steroid medication include blurred vision, frequent urination, increased thirs,t and change in blood sugar levels, especially in diabetic patients. If these side effects become bothersome or worsen, contact the physician.
• If fever, chills, increased pain, weakness or loss of bowel or bladder function occurs, seek immediate medical attention. Call 911.

A follow up visit with the physician is arranged to discuss test results.

Possible Complications

A selective nerve root block, like other medical procedures, has certain inherent risks  Potential complications include infection, low blood pressure, headache, and injury to nerve tissue. The physician discusses potential risks and benefits of a SNRB in advance of the procedure.

Patient Restrictions

Some patients should not undergo a SNRB, such as those with:
 

• An allergy to the contrast medium and/or drugs to be injected
• Are anemic
• Significant asthma
• Bleeding problems
• An infection
• Kidney disease
• Are pregnant or breast-feeding
• Severe spinal abnormality

Conclusion

Selective nerve root blocks can help identify the cause of back pain. The procedure can be performed safely and is effective in carefully selected patients.