What is CRPS?
Complex Regional Pain Syndrome (CRPS) is a regional, post‑traumatic, chronic and often disabling neuropathic pain condition—most commonly affecting a limb—associated with sensory, motor, and autonomic disturbances.
Why CRPS matters to pain physicians
CRPS is a diagnosis that is primarily clinical and time‑sensitive: early recognition, psychological screening, and rapid initiation of functional restoration can prevent progression to irreversible disability. For refractory disease, a staged escalation—neuropathics → sympathetic modulation → IV desensitization → neuromodulation—helps maintain ethical proportionality while targeting the dominant pain mechanisms.
Pain mechanisms: nociceptive vs neuropathic
Nociceptive pain
Nociceptors in tissues send pain signals to the CNS. Pain is often aching/throbbing and well localized. It is often time‑limited (resolves with tissue healing), though it can become chronic, and generally responds to conventional analgesics.
Neuropathic pain
Damage to the nerve itself produces typical symptoms: tingling, shock‑like or burning pain, commonly with numbness. It is usually chronic and often responds poorly to conventional analgesics.
Definitions and historical context
The International Association for the Study of Pain (IASP) describes CRPS as a collection of locally appearing painful conditions following a trauma, typically distal, exceeding the expected intensity and duration of the original trauma and often resulting in considerable motor restriction.
Historical milestones include early descriptions of causalgia (Mitchell, 1864), post‑traumatic osteo‑atrophic changes (Sudeck, 1900), the term Reflex Sympathetic Dystrophy (Evans, 1947), and later the IASP adoption of the term CRPS (1994).
Clinical classification
CRPS Type 1
Also referred to historically as Sudeck’s atrophy, shoulder‑hand syndrome, painful post‑traumatic osteoporosis, post‑traumatic pain syndrome/dystrophy, or minor causalgia.
CRPS Type 2
Historically aligned with major causalgia.
CRPS‑NOS
Patients who do not fully meet the newer clinical criteria, but whose signs and symptoms cannot be better explained by another diagnosis.
Epidemiology (high‑yield)
Reported features include genetic predisposition (HLA‑DQ1), incidence ~5.46 per 100,000 persons/year, female predominance (~4:1), median onset around 46 years, and fractures as a common precipitant (~46%).
Pathophysiology: what we are really treating
CRPS is mechanistically heterogeneous. Postulated mechanisms include abnormal somatosensory/sensory processing, sympathetically mediated pain, and immune dysfunction.
Sympathetically maintained pain (SMP)
A clinically important subgroup shows overlap of pain with autonomic dysfunction. Features may include constant burning pain, touch‑evoked allodynia, cold allodynia, dysesthesia and numbness. In SMP, symptoms may improve with sympathetic blockade (and historically, regional guanethidine or IV phentolamine).
Diagnosis in practice
CRPS remains a clinical diagnosis—history and examination are primary. Investigations are adjunctive and are used mainly to rule out mimics.
IASP diagnostic criteria (and what they miss)
1. Presence of an inciting noxious event or a cause of immobilization.
2. Continuing pain, allodynia (pain from a normally non‑painful stimulus) or hyperalgesia (increased pain from a painful stimulus) disproportionate to the inciting event.
3. Evidence (at some point) of edema, skin blood‑flow changes, or abnormal sudomotor activity (sweating/edema) in the region of pain.
4. Exclusion of other conditions that would otherwise account for the degree of pain and dysfunction.
Practical limitation: the IASP criteria are sensitive but less specific because vasomotor, sudomotor, and edema changes are grouped rather than treated as distinct elements; and motor/trophic signs were not included.
Differential diagnosis checklist (don’t miss these)
• Diabetic neuropathy
• Small fiber neuropathies
• Entrapment syndromes
• Discogenic disease
• Thoracic outlet syndrome
• Other vascular conditions (e.g., Raynaud’s phenomenon, DVT)
Imaging / tests used as adjuncts
Triple‑phase bone scintigraphy may support the diagnosis in selected contexts; calcitonin is described as a therapeutic option in association with this work‑up.
Doppler ultrasound is useful when vascular causes (e.g., DVT) are suspected; MRI may identify coexisting structural injury but does not “prove” CRPS.
Management: staged, multimodal, function‑first care
Core principles: functional restoration with a structured algorithm to normalize function; individualized plans; comprehensive diagnostic evaluation; early and aggressive interventions; prevention of progression to irreversible late stages; assessment of psychological status; consistent support; and combining pharmacologic therapy, sympathetic blocks, and rehabilitation. Sympathetic efferent blockade is emphasized as a key interventional pillar.
Stepwise escalation pathway (clinic‑ready)
• Early recognition and diagnosis (use modern clinical criteria such as Budapest criteria in routine practice).
• Education + graded functional restoration: desensitization, mirror therapy, and structured physiotherapy as tolerated.
• Pharmacologic optimization: neuropathic agents ± adjuncts; avoid polypharmacy without goals.
• Sympathetic modulation when clinically indicated (blocks → neurolysis in selected refractory cases).
• Intravenous desensitization / infusion protocols (e.g., lignocaine infusions) where appropriate.
• Neuromodulation for refractory, long‑duration disease with central sensitization features (e.g., Spinal Cord Stimulation).
Pharmacologic options used in real‑world CRPS care
Examples used in the attached case include:
• Gabapentinoids: pregabalin (e.g., 75 mg HS escalated to 150 mg BD in the case)
• Tricyclics/antidepressants: nortriptyline, amitriptyline; SNRIs such as duloxetine
• Adjuncts used in the case: mirtazapine, olanzapine (context‑specific, not routine)
• Anti‑inflammatory / disease‑modifying: sulfasalazine (case‑based)
• Calcitonin (intranasal 200 IU in the case)
• Analgesics/NSAIDs: paracetamol; etoricoxib ± muscle relaxant (case‑based)
Interventional therapies (menu)
• Intravenous regional anesthesia / continuous plexus block / continuous epidural (selected cases)
• Sympathetic nerve blocks like the Stellate ganglion block
• Intrathecal baclofen (selected cases)
• Spinal cord stimulation (SCS)
• Functional restoration programs
• CBT / psychotherapy
Sympathetic procedures: safety anatomy & complications
Lumbar sympathetic block / neurolysis: structures to respect
• Exiting nerve roots (nerve injury)
• Intraspinal/epidural spread
• Genitofemoral nerve injury
• Intervertebral disc injury → discitis
• Kidney/ureter injury
• Inferior vena cava injury (especially right side) → bleeding
• Local anesthetic systemic toxicity
• Segmental arteries → bleeding
• Infection, post‑procedure pain, vasovagal reaction, allergic reaction
Thoracic sympathetic block: structures to respect
• Intercostal artery/vein/nerve (bleeding/nerve damage)
• Lung (pneumothorax)
• Exiting nerve roots; intraspinal/epidural injection
• Azygos vein (bleeding)
• Thoracic duct (left) → chylothorax
• Esophagus/trachea/vagus nerve (discomfort, infection)
• Infection, bleeding, post‑procedure pain, vasovagal reaction, allergic reaction
When to consider SCS in CRPS
SCS is typically considered for refractory CRPS after failure of conservative rehabilitation, pharmacologic optimization, and sympathetic interventions—especially in long‑duration disease with central sensitization features (allodynia, trophic changes, temperature asymmetry).
Case‑based technical summary: trial with octopolar leads via L1 entry advanced to ~T7 with fluoroscopic confirmation, followed by permanent IPG implantation and programming.
Case vignettes (teaching pearls)
Case A: Young female with post‑traumatic lower limb CRPS / CRPS‑NOS
Key features included burning pain, hyperalgesia, allodynia, swelling, redness, shiny skin, trophic nail changes, temperature asymmetry, and marked functional limitation. Despite multimodal care over >2 years, symptoms persisted, prompting stepwise escalation culminating in SCS.
Case B: Adolescent boy with severe hand pain and glove‑like distribution
A 15‑year‑old boy developed severe resting right‑hand pain with allodynia following chronic scar friction while writing; examination showed glove‑like distribution with autonomic/trophic changes. Multiple alternative diagnoses were suggested elsewhere and investigations were largely normal; physiotherapy was limited by pain. The diagnosis remained clinical after ruling out key differentials.
FAQ
What is the single most important principle in CRPS management?
Function‑first care: early recognition, consistent support, psychological screening, and structured functional restoration combined with mechanism‑based pharmacology and interventions.
When should I suspect sympathetically maintained pain?
When pain overlaps with autonomic dysfunction (temperature/sweating changes) and there is meaningful, reproducible relief with sympathetic blockade.
When do I escalate to neuromodulation?
After failure of optimized rehab and medications, and after appropriately selected sympathetic interventions, particularly in long‑duration disease with central sensitization.
