Lumbar Selective Nerve Root Block (SNRB)

A Straightforward Guide for Patients


What is a Lumbar Selective Nerve Root Block?

A lumbar SNRB is a minimally invasive diagnostic procedure used to evaluate low back and leg pain. While the physical technique is identical to a transforaminal injection, it serves as a tool to determine if a specific nerve is the true “culprit” behind your symptoms. This is a critical step when imaging doesn’t clearly match your symptoms.

Purpose of the Injection

  • Diagnostic Confirmation: The primary goal is to identify or confirm which exact nerve or spinal level is causing the pain.
  • Duration: Because the focus is diagnostic, relief is typically temporary, lasting only a few hours to a day.

What to Expect During the Procedure

The injection is performed in a sterile procedure room using real-time X-ray guidance for accuracy and safety.

  • The skin is cleaned and numbed with a local anesthetic.
  • Most patients do not need sedation, although it may be offered for certain approaches.
  • Occasionally, you may feel a brief “electric” sensation down the leg or arm, depending on the area treated—this is normal and not harmful.
  • The procedure typically takes about 10-15 minutes.

Aftercare Instructions

General Care

  • If you received sedation, do not drive or operate machinery for 24 hours.
  • You may return to normal daily activities as tolerated.
  • Showering is allowed, but avoid soaking in a tub, pool, or lake for 24 hours.
  • Pain relief may take 7–10 days as the steroid begins working.
  • The care team will call you the next day to check on your recovery.

If Sedation Was Used

  • No solid food for 8 hours before the procedure.
  • Clear liquids only up to 2 hours before your appointment
    (water, broth, clear juice without pulp, black coffee or tea).
  • No carbonated drinks, gum, candy, mints, or throat lozenges in the 2 hours prior.
  • The care team will review your medications and tell you which ones to take beforehand.
  • Not following these instructions may require the procedure to be rescheduled.

Possible Risks and Side Effects

Risks are similar to those of other spinal injections:

  • Injection site soreness or allergic reactions to medication.
  • Infection, bleeding, or dural puncture.
  • Temporary nerve irritation or increased pain.
  • Note: Risks may be slightly lower for a pure diagnostic block if steroids are omitted.

When Will I Feel Relief?

  • Immediate: You should feel numbing relief shortly after the injection.
  • Diagnostic Value: Your provider will ask you to monitor your pain levels closely for the first few hours to see if your typical “pain” disappeared while the nerve was numbed.

Insurance Requirements

Insurance providers typically authorize lumbar SNRB procedures under these conditions:

  • Diagnostic Necessity: Used to confirm a diagnosis when symptoms are severe enough to interfere with daily activities.
  • Failed Initial Treatment: Documentation of failure to respond to at least 4 to 6 weeks of non-invasive care.
  • Plan Specifics: Many plans will only cover a single-level nerve block per visit to ensure diagnostic accuracy.