What is the purpose of a Lumbar Selective Nerve Root Block (LSNRB)?

From the Guidelines

Lumbar selective nerve root blocks (SNRBs) are a recommended diagnostic and therapeutic procedure for patients with radiculopathy, particularly those with sciatica or neurogenic claudication, as they can provide significant pain relief and improve quality of life. The procedure involves injecting a combination of local anesthetic and corticosteroid directly around a specific spinal nerve root under fluoroscopic guidance, as described in the guideline from the American College of Physicians and the American Pain Society 1.

Key Points to Consider

• The diagnosis of radiculopathy is based on symptoms such as pain, sensory impairment, weakness, or diminished deep tendon reflexes in a nerve root distribution, and can be supported by a positive straight-leg-raise test 1.
• SNRBs are particularly effective for patients with radicular pain from herniated discs, foraminal stenosis, or other conditions causing nerve compression in the lumbar spine.
• The procedure is minimally invasive and can be performed on an outpatient basis, with patients typically remaining awake but may receive mild sedation.
• Potential complications include temporary numbness, infection, bleeding, or nerve damage, though these are rare.

Procedure Details

• The procedure involves injecting a combination of local anesthetic (typically 1-2 ml of 0.5% bupivacaine or 1-2% lidocaine) and corticosteroid (such as 40-80 mg methylprednisolone or 10-40 mg triamcinolone) directly around a specific spinal nerve root under fluoroscopic guidance.
• Patients should arrange for someone to drive them home afterward and should avoid strenuous activities for 24 hours.
• Pain relief may be immediate from the anesthetic and can last for weeks to months from the steroid's anti-inflammatory effects.

Clinical Considerations

• The goal of the procedure is to reduce inflammation around compressed nerve roots, which helps decrease pain signals and improve function, as outlined in the guideline from the American College of Physicians and the American Pain Society 1.
• SNRBs can be an effective treatment option for patients who have not responded to conservative management, such as physical therapy, medication, or lifestyle modifications.

From the Research

Lumbar Selective Nerve Root Block Efficacy

• The therapeutic efficacy of selective nerve root blocks in treating lumbar radicular leg pain has been investigated in several studies 2, 3, with results showing that these blocks can be effective in providing rapid and substantial regression of pain.
• In one study, 87% of patients experienced rapid pain relief, and 60% of patients with disc herniation or foraminal stenosis had permanent resolution of pain, avoiding the need for surgery 2.
• Similar results were found in another study, where 87% of patients had substantial regression of pain, and 60% of patients with disc herniation or foraminal stenosis had permanent resolution of pain 3.

Diagnostic Accuracy

• The diagnostic accuracy of lumbar selective nerve root blocks has been evaluated in a prospective controlled study 4, which found that these blocks have a sensitivity of 57%, a specificity of 86%, and an accuracy of 73%.
• The study also identified potential causes of false results, including insufficient infiltration, insufficient passage of the injectate, and intraepineural injections, as well as overflow of the injectate into the epidural space or symptomatic level 4.

Comparative Studies

• A comparative study was conducted to evaluate the effectiveness of two different pharmacological formulae in selective nerve root injections 5, with results showing no significant difference in the type of steroid or local anesthetic used.
• The study found that both formulae were effective in relieving pain, with similar rates of surgical intervention required in both groups 5.

Procedure Techniques and Safety

• The use of CT fluoroscopic guidance for selective lumbar nerve root blocks has been investigated 6, with results showing that this technique can result in minimal radiation dose levels and procedure times comparable to fluoroscopic guidance.
• The average external radiation dose was found to be 0.73 mrem per procedure, with an average of 2 seconds of CT-fluoroscopy time and four images per procedure 6.