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Selective Nerve Root Block (SNRB)

A Selective Nerve Root Block (SNRB) is a diagnostic test performed to 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

A selective nerve root block, like other medical procedures, 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 2 days prior to the test
  • Do not take any aspirin products 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 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 respond to 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 during the procedure to guide the needle into the proper position. 
  • Diagnostic injections may include an anesthetic, steroid, and/or antibiotic. 
  • The goal of a diagnostic injection is to replicate your typical discomfort (symptoms).  Your feedback helps to identify the cause of 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 that include 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 test results.
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