What is the step by step procedure for a selective nerve root block?

Step-by-Step Procedure for Selective Nerve Root Block

Selective nerve root blocks are effective diagnostic and therapeutic procedures for radicular pain, providing targeted relief when properly performed with appropriate technique and safety measures.

Pre-Procedure Assessment and Preparation

1. Patient Selection:

   • Identify patients with radicular pain correlating with imaging findings showing nerve root compression
   • Confirm the specific nerve root to be targeted based on clinical symptoms and imaging
   • Review contraindications: infection, coagulopathy, patient refusal, or allergy to medications

2. Equipment Preparation:

   • Fluoroscopy or CT guidance equipment
   • Sterile tray with antiseptic solution
   • Local anesthetic (lidocaine 1-2%)
   • Corticosteroid (typically methylprednisolone 40mg)
   • Appropriate needles (22-25 gauge, length dependent on patient anatomy)
   • Contrast medium for confirmation of needle placement

3. Patient Preparation:

   • Obtain informed consent
   • Position patient based on target level:
     • Cervical: Supine with slight neck extension
     • Thoracic: Prone
     • Lumbar: Prone with pillow under abdomen to reduce lumbar lordosis
   • Apply monitoring equipment (pulse oximetry, blood pressure)
   • Establish IV access for emergency medications if needed
   • Have patient wear surgical mask during the procedure to minimize droplet spread

Procedure Execution

1. Skin Preparation:

   • Perform thorough antiseptic preparation of the skin
   • Drape the area to create a sterile field

2. Localization and Approach:

   • Cervical Spine:

     • Posterior approach with curved blunt needle is recommended for safety to minimize risk of arterial injection 1
     • Identify target foramen under fluoroscopic guidance
     • Avoid anterior approach due to risk of vertebral artery injury

   • Lumbar Spine:

     • Identify the target nerve root under fluoroscopic guidance
     • Align fluoroscope to visualize the "Scotty dog" appearance (oblique view)
     • Target the "eye" of the Scotty dog (pedicle)

3. Needle Insertion and Advancement:

   • Infiltrate skin and subcutaneous tissue with local anesthetic
   • Insert needle under fluoroscopic guidance
   • Advance needle in small increments with frequent fluoroscopic checks
   • Aim for the superior and posterior aspect of the intervertebral foramen
   • Stop advancement if patient reports paresthesia (indicates proximity to nerve)

4. Position Verification:

   • Inject small amount of contrast medium (0.5-1.0 mL)
   • Confirm proper needle placement with contrast spread along nerve root
   • Avoid intravascular injection pattern (rapid washout of contrast)
   • Aspiration should be negative for blood or CSF before injection

5. Medication Administration:

   • Inject test dose of local anesthetic (0.5-1.0 mL) to assess for immediate adverse reactions
   • If no adverse reaction, inject the therapeutic mixture:
     • Local anesthetic (1-3 mL of 1-2% lidocaine)
     • Corticosteroid (typically 40 mg methylprednisolone)
   • Inject slowly to minimize pressure and discomfort

6. Post-Injection Assessment:

   • Document immediate pain relief (diagnostic value)
   • Monitor for 15-30 minutes for adverse reactions
   • Assess motor and sensory function before discharge

Post-Procedure Care

1. Immediate Care:

   • Monitor vital signs for 15-30 minutes
   • Assess pain level using standardized scale
   • Document any sensory or motor changes

2. Discharge Instructions:

   • Provide written instructions for post-procedure care
   • Advise patient to rest for 24 hours and avoid strenuous activity
   • Inform about potential temporary numbness or weakness in the affected limb
   • Instruct to report severe headache, fever, or worsening neurological symptoms

3. Follow-up Assessment:

   • Schedule follow-up evaluation to assess efficacy
   • Document duration of pain relief (typically varies from 2.5-4.3 months depending on severity of pathology) 2

Safety Considerations and Complications

1. Potential Complications:

   • Vasovagal reaction
   • Dural puncture and post-dural puncture headache
   • Infection (rare with proper technique)
   • Bleeding/hematoma (more common in patients on anticoagulants)
   • Nerve injury
   • Intravascular injection (particularly concerning in cervical procedures)

2. Special Precautions:

   • For cervical procedures, use posterior approach with curved blunt needle to minimize risk of arterial injection 1
   • Use real-time fluoroscopy during contrast injection to detect intravascular spread
   • Calculate safe dose of local anesthetic to avoid systemic toxicity
   • Have resuscitation equipment readily available

Clinical Efficacy

• Approximately 69% of patients experience some pain relief by day 7 post-procedure 3
• Efficacy varies based on pathology severity:
  • Mild disc prolapse: ~4.3 months relief
  • Moderate disc prolapse: ~2.5 months relief
  • Severe disc prolapse: minimal sustained relief beyond immediate post-procedural period 2
• Cervical, lumbar, and sacral procedures show similar efficacy when properly performed 3

This detailed protocol emphasizes safety while maximizing therapeutic benefit for patients with radicular pain. The technique should be performed by trained specialists with appropriate imaging guidance to ensure accurate needle placement and minimize complications.