What Is a Diagnostic Nerve Block?

A diagnostic nerve block is a test procedure used to identify the specific nerve responsible for a patient’s pain. During the procedure, a local anesthetic is injected near the suspected nerve. If the pain in the area innervated by that nerve is reduced or eliminated, it confirms the nerve as the source of pain.

Please note: this is a diagnostic test, not a long-term treatment.

Since the anesthetic effect is temporary, the patient must monitor and record pain levels in the hours following the procedure. Numbness or tingling sensations should be disregarded—we are solely interested in whether pain is reduced.

How Does the Procedure Work?

  1. The skin at the injection site is numbed with a local anesthetic.
  2. Under ultrasound or fluoroscopic (X-ray) guidance, a needle is advanced toward the target nerve.
  3. Upon nearing the nerve, the patient may feel tingling, pressure, or even a sharp pain—this helps confirm correct needle placement.
  4. Once the correct location is reached, the anesthetic is injected directly near the nerve.
  5. Discomfort, pressure, or a brief increase in symptoms can occur during injection.

During the procedure, the physician will ask questions to help evaluate the effect of the block. Mild sedation may be given to help the patient relax, but full anesthesia is not used, as patient cooperation is required.

Duration of the Procedure

  • The procedure typically takes about 15 minutes.
  • However, patients should plan to spend a few hours at the clinic, particularly if multiple nerves need to be tested or post-procedure assessments are required.

After the injections, patients may be asked to perform specific movements or activities that usually trigger pain to assess the effectiveness of the block.

Possible Complications

As with any medical procedure, complications may occur, though they are uncommon:

  • Pain at the injection site
  • Bleeding
  • Infection
  • Nerve injury
  • Allergic reaction to the anesthetic

Discuss these risks with your doctor before the procedure.

Pre-procedure Instructions

Medications:

  • Blood thinners such as Coumadin, Warfarin, Plavix, Lovenox must typically be stopped prior to the procedure. Please inform your doctor if you are taking any of these.
  • Low-dose aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) may usually be continued unless advised otherwise.

On the Day of the Procedure:

  • Eat and drink normally, unless sedation is planned (see below).
  • Wear loose, comfortable clothing.
  • Arrive at the clinic about 30 minutes early.
  • Bring someone to accompany you and drive you home.

If you are taking short- or long-acting pain medications, your doctor may adjust your dose before the procedure.

Do not take any short-acting pain medications (e.g. Percocet, Tylenol, Ibuprofen) on the day of the procedure.

If You Will Be Sedated:

  • Arrive with an adult companion to drive you home.
  • Do not drive for 24 hours after sedation.
  • Do not eat for 6 hours before the procedure.
  • You may drink clear fluids until 2 hours before the procedure.
  • If you must take medications, use small sips of water only.
  • If you do not follow these guidelines, sedation will not be possible.

Diabetic Patients:

Please consult your physician about how to adjust medications on the day of the procedure, especially if fasting is required.

Important Note:

To ensure the test is accurate, you must arrive with your usual pain level—typically 5 out of 10 or higher on the pain scale. If you are not experiencing pain on the day of the procedure, please notify the clinic, as the appointment may need to be rescheduled.

Let me know if you’d like a simplified patient version, infographic layout, or to add this into a pre-op booklet.