Selective Nerve Root Block (SNRB)

A Selective Nerve Root Block (SNRB) diagnostic test helps determine if a specific spinal nerve root is the pain source. A SNRB helps your doctor diagnose cervical (neck) or lumbar (lower back) radiculopathy (irritation and inflammation of a nerve root).

Under 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 15-30 minutes per spinal level.


Possible Complications

Like other medical procedures, a selective nerve root block may present risks. Complications include risk of infection, low blood pressure, headache, and injury to nerve tissue.


Patient Restrictions

Some patients should not undergo SNRB.  Contraindications (precautions) include:

  • Allergy to the contrast medium and/or drugs to be injected
  • Anemia
  • Significant asthma
  • Bleeding problems
  • Infection
  • Kidney disease
  • Pregnant or breast-feeding
  • Severe spinal abnormality


Patient Preparation: At Home

Tell your doctor about all medication you take, including over-the-counter drugs/herbs. Below is a short list of common instructions. Your doctor will provide a more specific list for you.

  • Stop blood-thinning medication two days prior to the test
  • Do not take any aspirin products five days prior to the test
  • Stop anti-inflammatory medication five days prior to the test
  • Stop pain medication eight hours prior to the test
  • Do not eat or drink six hours prior to the test
  • Arrange for someone to drive you home


Patient Preparation: At the Medical Facility

  • The medical staff will review your history, condition, medications, allergies and other pertinent information.
  • You change into a gown.
  • A nurse monitors your blood pressure, blood oxygen levels (pulse oximeter on finger) and other vital signs before, during and after the procedure.
  • Medication may be administered to help you relax. Diagnostic spinal injections require that you be awake so that you can answer questions during the procedure.  


What to Expect During the Procedure

  • A selective nerve root block is performed in a sterile setting under fluoroscopic guidance.
  • The skin at the injection site is cleaned and prepared. A local anesthetic numbs the skin around the injection site. Although local anesthetic stings, it helps make the SNRB more comfortable. 
  • Fluoroscopic guidance (real-time X-ray) is used to guide the needle into the proper position during the procedure. 
  • Diagnostic injections may include an anesthetic, steroid and/or antibiotics. 
  • A diagnostic injection aims to replicate your typical discomfort (symptoms). Your feedback helps to identify the cause of the pain.


After the Procedure

  • You are moved to the recovery area, where the medical staff continues to monitor your vital signs. 
  • You may be discharged home in 30-60 minutes with written instructions.
  • The area around the injection site will feel numb. Relief from typical symptoms may last for 6 hours following the injection. 
  • Steroids may cause side effects, including blurred vision, frequent urination, increased thirst and change in blood sugar levels, especially in diabetic patients. If these side effects become bothersome or worsen, please call your doctor.
  • If fever, chills, increased pain, weakness or loss of bowel/bladder function occurs, seek immediate medical attention.
  • Please follow up with your doctor for the test results.
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