Complex Regional Pain Syndrome

The Budapest diagnostic criteria (IASP-adopted) are the diagnostic standard. All four must be met:

• •Continuing pain disproportionate to the inciting event.
• •At least 1 SYMPTOM (patient-reported) in 3 or more of the 4 categories.
• •At least 1 SIGN (clinician-observed) in 2 or more of the 4 categories at the time of evaluation.
• •No other diagnosis better explains the signs and symptoms.

The four categories:

• •Sensory: hyperaesthesia, allodynia.
• •Vasomotor: temperature asymmetry (over 1 degree C difference), skin colour changes or asymmetry.
• •Sudomotor/oedema: oedema, sweating asymmetry.
• •Motor/trophic: decreased ROM, weakness, tremor, dystonia; hair, nail, or skin changes.

CRPS-NOS (not otherwise specified) covers a clinical picture consistent with CRPS that does not fully meet the Budapest criteria at the time of assessment but is not better explained by another diagnosis (recognised by RCP 2018).

Key clinical features:

• •Sensory: burning, throbbing, deep pain disproportionate to the inciting event; extends beyond a single nerve territory (Type I) or beyond the expected nerve injury (Type II); regional, not dermatomal; allodynia (clothing or light touch causes pain); hyperalgesia.
• •Vasomotor: temperature asymmetry (>1 degree C); red, blue, mottled, or pale skin changes that may fluctuate.
• •Sudomotor/oedema: distal limb oedema (often prominent early); hyperhidrosis or hypohidrosis.
• •Motor/trophic: reduced ROM, weakness with 'give-way', tremor; dystonia may develop in chronic CRPS and is severely disabling; warm and oedematous early, with thin, shiny, atrophic skin and altered hair and nail growth later.

Typical scenario: a patient not recovering as expected after a distal radius fracture, with disproportionate pain, swelling, stiffness, and colour or temperature changes; onset after cast removal is classic. In children CRPS is more common in girls, often lower limb, often without an identifiable precipitant, and generally has a better prognosis with early management.

Diagnosing CRPS does NOT mean stopping investigation for ongoing pathology - non-union, hardware complications, infection, and nerve damage must continue to be considered when clinically indicated.

CRPS is a clinical diagnosis based on the Budapest criteria; there is no confirmatory test. Investigations exclude differentials and support the clinical picture.

Blood tests:

• •FBC, CRP, ESR: should be normal in CRPS. Raised markers suggest infection or inflammatory disease.
• •Blood glucose and HbA1c (exclude diabetic neuropathy).
• •TFTs, calcium, vitamin D (metabolic mimics).
• •DVT assessment per local VTE pathway when the limb is swollen.
• •RF and anti-CCP if inflammatory arthritis is suspected; blood cultures if infection is suspected.

Imaging:

• •Plain X-ray (affected and contralateral limb): may show patchy periarticular osteoporosis (Sudeck''s atrophy) - a classic but LATE radiographic finding. X-rays are often normal in the first 3-6 months. Also useful to exclude fracture complications.
• •MRI: bone marrow oedema in early disease, soft tissue oedema, joint effusion, and skin thickening; useful to exclude AVN, infection, and stress fracture. Not diagnostic of CRPS in isolation.
• •Triple-phase bone scan: historically used and exam-relevant. Shows increased uptake in all three phases; used less in current UK practice.

Nerve conduction studies and EMG: use when a definable nerve lesion is suspected (confirms Type II CRPS). Not required routinely.

Early diagnosis and early active graded rehabilitation are the single biggest modifiable factor in outcome. Treatment delay drives poor prognosis. RCP (2018), the Faculty of Pain Medicine, NICE NG193, and NICE CG173 frame UK practice.

Four pillars:

1. Education and psychological support:

• •Validate CRPS as a real, recognised condition - NOT psychological.
• •Set realistic expectations: recovery is possible but may take months to years.
• •CBT is the most evidence-based psychological approach (targets catastrophising and fear-avoidance); ACT may also help. Screen for and treat comorbid depression and anxiety; address sleep.

2. Physical rehabilitation (the cornerstone):

• •Physiotherapy is the single most important intervention. Goal: restore function, desensitise the limb, and promote normal sensorimotor processing.
• •Graded exposure to movement and loading - progressive, patient-paced, within tolerance. 'Hurt does not equal harm'. Immobilisation worsens CRPS.
• •Desensitisation: graded texture exposure (soft fabric, then rougher, then firmer pressure) to normalise sensory processing in allodynic areas.
• •Mirror therapy: visual illusion of normal pain-free movement targeting altered body representation and sensorimotor processing.
• •Graded motor imagery (GMI) - three stages: laterality recognition, then imagined movements, then mirror therapy.
• •Active and active-assisted ROM (avoid forced passive ROM, which can worsen pain).
• •Aquatic therapy: warm water reduces oedema (hydrostatic pressure), reduces stiffness, and facilitates movement.
• •Oedema management: elevation, compression garments, contrast baths (with caution given temperature sensitivity), lymphatic drainage.
• •Occupational therapy for functional hand or foot rehabilitation and workplace adaptation.

3. Pharmacological management (adjunctive - supports rehabilitation, not curative):

• •Neuropathic pain agents by analogy with NICE CG173: amitriptyline (also helps sleep), duloxetine (SNRI), gabapentin, or pregabalin.
• •Short-course oral corticosteroids (e.g. tapering prednisolone over 2-4 weeks) may be considered as a specialist-led option for early (<3 months) warm CRPS with prominent inflammatory features. Not effective in established or chronic disease.
• •Bisphosphonates (IV pamidronate, neridronate) have some evidence in early CRPS but are specialist use.
• •Topical lidocaine 5% patches may help localised allodynia (specialist advice). Topical capsaicin 8% patch is specialist-only.
• •AVOID long-term opioids: poor evidence, significant risk, opioid-induced hyperalgesia.

4. Specialist and interventional approaches when first-line fails:

• •Spinal cord stimulation (NICE TA159) for chronic refractory CRPS - MDT decision.
• •Sympathetic nerve blocks (limited evidence).
• •Intrathecal drug delivery and ketamine infusion in specialist settings.

Refer early - within 6-8 weeks if not improving with active rehabilitation - to confirm the diagnosis, exclude ongoing pathology, optimise symptom control, and access multidisciplinary rehabilitation.

Prevention: the RCP guideline does not currently recommend any specific prophylaxis for CRPS because of insufficient evidence. Vitamin C 500 mg daily for 50 days after distal radius fracture is historically tested in UK exams but recent evidence has questioned its efficacy and it is not an established UK prophylaxis recommendation. Early high-vigilance pathways and early rehabilitation after trauma remain the best preventive strategies.

Rehabilitation is the primary treatment. Early, active, graded rehabilitation produces the best outcomes; the goal is functional restoration, not pain elimination.

Key principles:

• •'Use it or lose it' - the limb must be used functionally; immobilisation and disuse worsen CRPS.
• •'Hurt does not equal harm' - essential patient education before starting rehabilitation.
• •Patient-paced, graded progression - start within tolerance and build gradually.
• •Functional goals framed around valued activities (dressing, cooking, writing, walking, returning to work).

The programme combines desensitisation, mirror therapy and GMI, active ROM and progressive strengthening, weight-bearing progression, aerobic fitness, oedema management (elevation, compression, lymphatic drainage), and falls prevention for lower-limb CRPS. CBT or ACT is integrated alongside physical rehabilitation; sleep hygiene and low-dose amitriptyline are options for sleep.

Prognosis: early-treated CRPS (within 6-12 months) often improves significantly; chronic CRPS (over 12 months) carries a more guarded prognosis but improvement remains possible. Poor prognostic indicators: diagnostic delay, cold presentation, dystonia or motor features, psychological distress, ongoing litigation, lower-limb involvement.

• •Budapest diagnostic criteria (IASP-adopted) - the diagnostic standard for CRPS: pain disproportionate to the event PLUS 1 or more symptoms in 3 of 4 categories PLUS 1 or more signs in 2 of 4 categories PLUS no better diagnosis.
• •RCP CRPS guidelines (2018) - the UK reference; emphasises early diagnosis, multidisciplinary rehabilitation, and early specialist referral; recognises CRPS-NOS.
• •NICE NG193 - general chronic pain principles apply.
• •NICE CG173 - neuropathic pain management used by analogy for the neuropathic component (amitriptyline, duloxetine, gabapentin, pregabalin first-line).
• •NICE TA159 - spinal cord stimulation for chronic refractory CRPS.

• •Budapest criteria: pain disproportionate to event + 1 symptom in 3 of 4 + 1 sign in 2 of 4.
• •Four categories: sensory, vasomotor, sudomotor/oedema, motor/trophic.
• •Type I (no nerve lesion) is around 90%; Type II is a documented nerve lesion.
• •Distal radius fracture is the commonest precipitant; onset after cast removal is classic.
• •Physiotherapy is the cornerstone; immobilisation worsens CRPS.
• •Patchy periarticular osteoporosis (Sudeck''s atrophy) is a LATE X-ray finding.