Peripheral Nerve Blocks for CRPS: Not Recommended
Peripheral somatic nerve blocks (including sural and superficial peroneal nerve blocks) should NOT be used for long-term treatment of chronic pain, including CRPS. 1
Guideline-Based Contraindication
The American Society of Anesthesiologists (ASA) and American Society of Regional Anesthesia and Pain Medicine (ASRA) explicitly state that peripheral somatic nerve blocks should not be used for long-term treatment of chronic pain. 1 This is a clear, direct recommendation that applies to the proposed sural and superficial peroneal nerve blocks for this patient's chronic CRPS.
The Aetna policy correctly classifies superficial peroneal nerve block for chronic pain related to ankle/foot conditions as experimental and investigational because effectiveness has not been established. [@User Question Context@]
Recommended Treatment Alternatives for CRPS
First-Line Approach
- Physical therapy with gentle stretching and active range of motion exercises should be the cornerstone treatment, which this patient is already receiving with documented progress. 2
- Analgesics (acetaminophen or ibuprofen) for pain relief if no contraindications exist. 2
Second-Line Interventional Options
- Sympathetic blocks (lumbar sympathetic or stellate ganglion blocks) may be used as components of multimodal CRPS treatment when there is consistent improvement and increasing duration of pain relief with each successive block. 1, 2 This is the appropriate nerve block approach for CRPS, not peripheral somatic blocks.
- The key distinction: sympathetic blocks target the autonomic nervous system component of CRPS, while peripheral somatic blocks do not address the underlying pathophysiology. 1
Advanced Treatments for Refractory Cases
- Spinal cord stimulation should be considered for CRPS patients who have not responded to other therapies, with a trial performed before permanent implantation. 1, 2
- TENS (transcutaneous electrical nerve stimulation) as part of a multimodal approach. 1, 2
Evidence Quality Assessment
The 2023 Cochrane overview found no high-certainty evidence for any therapy for CRPS, with most studies being small and at high risk of bias. 3 However, the ASA/ASRA guidelines (most recently summarized in 2025) provide the clearest directive: peripheral somatic nerve blocks are contraindicated for chronic pain management. 1, 2
A 2019 survey revealed wide practice variation in sympathetic blocks for CRPS, highlighting the need for evidence-based guidelines—but notably, this discussion centered on sympathetic blocks, not peripheral somatic blocks. 4
Critical Clinical Pitfalls
- Do not confuse sympathetic blocks with peripheral somatic blocks. Sympathetic blocks (stellate ganglion, lumbar sympathetic) target the autonomic component and may be appropriate for CRPS; peripheral nerve blocks targeting sensory nerves are not recommended. 1
- Fall risk consideration: This patient has already experienced a fall due to foot numbness. Peripheral nerve blocks would worsen sensory deficits and increase fall risk, directly compromising safety and quality of life. [@User Question Context@]
- Insurance denial is appropriate: The payer's classification as experimental/investigational aligns with ASA/ASRA guidelines stating these blocks should not be used for chronic pain. [1, @User Question Context@]
Recommended Clinical Pathway
- Continue current physical therapy with documented ROM and strength improvements. 2
- Optimize pharmacologic management (NSAIDs, gabapentin, or bisphosphonates if not already tried). 3, 5
- Consider sympathetic blocks (NOT peripheral somatic blocks) if sympathetically maintained pain is suspected, with documentation of progressive improvement. 1, 2
- Evaluate for spinal cord stimulation trial if refractory to conservative and sympathetic block approaches. 1, 2
The proposed procedure contradicts established guidelines and should be denied on both medical necessity and safety grounds. 1