Is a right sural and superficial peroneal nerve block with ultrasound guidance a suitable treatment option for a 58-year-old female patient with chronic regional pain syndrome (CRPS) affecting her right lower extremity, primarily the right ankle, who has a history of falls and worsening symptoms despite physical therapy?

Peripheral Nerve Blocks for CRPS of the Lower Extremity: Not Supported by Evidence

Superficial peroneal and sural nerve blocks are not appropriate for treating CRPS affecting the right ankle, as peripheral somatic nerve blocks should not be used for long-term treatment of chronic pain, and the evidence-based approach for CRPS specifically recommends sympathetic blocks (lumbar sympathetic blocks for lower extremity CRPS), not peripheral nerve blocks. 1, 2

Why Peripheral Nerve Blocks Are Not Indicated for CRPS

The American Society of Anesthesiologists (ASA) explicitly states that peripheral somatic nerve blocks should not be used for long-term treatment of chronic pain, which includes CRPS. 1, 2 This is a critical distinction that separates appropriate from inappropriate interventional approaches for this condition.

The Evidence-Based Interventional Approach for Lower Extremity CRPS

For lower extremity CRPS requiring interventional pain management, the guidelines are clear:

• Lumbar sympathetic blocks (not peripheral nerve blocks) may be used as components of multimodal treatment when there is consistent improvement and increasing duration of pain relief with each successive block. 1, 2
• Sympathetic blocks target the underlying pathophysiology of CRPS, which involves autonomic dysfunction and sympathetically maintained pain. 1, 3
• The ASA and American Society of Regional Anesthesia and Pain Medicine (ASRA) provide strong consensus that sympathetic blocks (stellate ganglion for upper extremity, lumbar sympathetic for lower extremity) are appropriate when integrated into comprehensive rehabilitation. 1

Why This Patient's Insurance Denial Is Justified

The insurance company's classification of superficial peroneal nerve block as "experimental and investigational" for chronic pain related to CRPS is consistent with current evidence-based guidelines:

• There is no guideline support for using peripheral somatic nerve blocks (such as sural or superficial peroneal blocks) for CRPS treatment. 1, 2
• The single case report describing sphenopalatine ganglion blocks (a different type of sympathetic block) for lower extremity CRPS from 2005 does not provide sufficient evidence to support peripheral nerve blocks, and notably, that intervention was a sympathetic block, not a peripheral somatic nerve block. 4
• Current treatment algorithms for CRPS do not include peripheral nerve blocks as part of the evidence-based approach. 1, 2, 3, 5, 6

What Should Be Done Instead: Evidence-Based Treatment Algorithm

First-Line Treatment (Should Be Maximized First)

• Physical therapy with gentle mobilization and progressive exercises is the cornerstone of CRPS treatment and must be initiated immediately. 1, 2, 3, 5, 6
• Active range of motion exercises that gradually increase while restoring alignment and strengthening weak muscles. 1, 2
• Sensorimotor integration training to normalize movement patterns. 2
• NSAIDs or acetaminophen for pain control to enable participation in physical therapy. 1, 2

Second-Line Pharmacologic Options

• Gabapentin or tricyclic antidepressants (amitriptyline, nortriptyline) for the neuropathic pain component. 2, 3, 5, 6
• Short course of oral corticosteroids (30-50 mg daily for 3-5 days, then taper over 1-2 weeks) to reduce inflammation and edema. 1, 2
• Topical lidocaine for localized neuropathic pain. 2

Appropriate Interventional Options (If Conservative Treatment Fails)

If pain severity prevents participation in rehabilitation despite maximal medical management:

• Lumbar sympathetic blocks (not peripheral nerve blocks) may be considered for lower extremity CRPS, with the critical requirement that each successive block demonstrates consistent improvement and increasing duration of relief. 1, 2
• Documentation must include objective functional outcomes beyond pain scores, including improvements in activities of daily living, autonomic stability, and temperature dysregulation. 1

Advanced Treatment for Refractory Cases

• Spinal cord stimulation is recommended for persistent CRPS that has failed multimodal conservative treatment, requiring a mandatory trial period before permanent implantation. 1, 2, 3, 5, 6

Critical Clinical Pitfalls to Avoid

• Do not delay physical therapy while waiting for pain to resolve—this worsens outcomes through disuse and pain upregulation. 2
• Do not use peripheral somatic nerve blocks for CRPS, as this contradicts evidence-based guidelines and may be considered experimental. 1, 2
• Do not continue sympathetic blocks indefinitely without documented progressive improvement and increasing duration of relief with each block. 1, 2
• Ensure the patient is engaged in active rehabilitation—interventional procedures serve only to facilitate participation in physical therapy, not as standalone treatments. 1, 2

Documentation Considerations for Any Future Interventional Request

If considering appropriate interventional procedures (lumbar sympathetic blocks, not peripheral nerve blocks):

• Document failure of maximal conservative treatment including physical therapy, NSAIDs, gabapentinoids or tricyclics, and consideration of oral corticosteroids. 1, 2, 3
• Document objective functional impairments and how pain prevents participation in rehabilitation. 1
• Ensure the procedure is part of a comprehensive multimodal treatment plan with ongoing physical therapy. 1, 2