creation date: 2026-06-11 13:03
tags: Pathologies

Complex Regional Pain Syndrome

Background

Definitions

Complex regional pain syndrome (CRPS) describes a group of painful conditions characterized by:

Continuing (spontaneous and/or evoked) regional pain (regional = not specific dermatome/nerve)
Disproportionate in time or degree to usual course of any known trauma or lesion

Type I: no evidence of peripheral nerve injury (90% of cases)
Type II: evidence of peripheral nerve injury

Pathogenesis

Common inciting events include fractures, rash injuries, sprains, and surgery. However, in 10% of cases, no precipitating factor can be identified.

The pathogenesis is unknown. Proposed mechanisms involve:

Peripheral inflammation/autoimmunity of autonomic neurons
Catecholamine hypersensitivity and formation of reflex arc
Central sensitization
Genetics

Clinical Presentation

Signs & Symptoms

CRPS manifests within 4-6 weeks of an inciting event, more commonly in the upper limbs and head/trunk sparing.

Initial symptoms usually include pain, erythema, and swelling. The limb may be warm initially before evolving to cold.

Pain:

Burning, stinging, tearing
Deep in limb (may be superficial in some cases)
Continuous and undulating (can be paroxysmal)
Worse at night
Exacerbated by limb movement, contact, temperature variation, stress

Sensory abnormalities:

Hyperalgesia, allodynia, or hypesthesia
Often on distal limb, sometimes stocking/glove pattern

Motor symptoms:

Reduction of complex muscle strength (hand grip, tip toe standing)
ROM limitations due to edema, pain, contractures
CNS related (tremor, myoclonus, dystonic postures, impaired movement initiation)

Skin changes:

Autonomic changes: skin temperature, colour, sweat, edema differences (compared to unaffected side)
Trophic changes: increased hair growth, nail growth changes, contraction and fibrosis of joints/fascia, skin atrophy

History & Physical Exam

History should include:

Timeline of onset, including inciting event if any
Degree of symptoms
Distribution of symptoms

Diagnosis

Criteria

Clinical diagnosis criteria is as follows:

Continuing pain disproportionate to any inciting event
Report at least one symptom in three of the following categories:
- Sensory (hyperesthesia and/or allodynia)
- Vasomotor (temperature asymmetry and/or skin colour changes/asymmetry)
- Sudomotor/edema (edema and/or sweating changes/asymmetry)
- Motor/trophic (decreased ROM and/or motor dysfunction and/or trophic changes)
Display at least one sign at time of evaluation in two out of four of above categories
No alternative diagnosis better explains the findings

Work-up

Additional testing can be performed if clinical features are atypical and to rule out alternative diagnoses.

Bone scintigraphy (supports diagnosis if increased radiotracer update compared to contralateral)
Plain film radiograph (may find patchy osteoporosis)
Autonomic testing (not routine)

Differential

Alternative diagnoses include:

Infections (erythema, edema, warmth, pain)
Compartment syndrome (pain out of proportion)
Peripheral vascular disease (discolouration, pain with activity)
Deep vein thrombosis
Peripheral neuropathy
Vascular thoracic outlet syndrome
Rheumatoid arthritis
Raynaud phenomenon
Erythromelalgia
Functional neurologic symptom disorder (conversion disorder)
Factitious disorder (Munchausen syndrome)

Red Flags / Complications

Major complication is prolonged disability and risk of recurrence.

Management

Goals of therapy is to restore function, decrease pain and disability, and improve quality of life. Recovery is typically expected within 6 months.

Non-pharmacological

Initial therapy consist of:

Patient education, including addressing kinesiophobia
Physical and occupational therapy
Psychosocial and behavioural therapy if needed

Pharmacological

Initial pharmacological therapy choices are:

NSAIDs
Adjunctive neuropathic pain medication (gabapentinoid or TCA)
Bisphosphonate if evidence of abnormal uptake on bone scan
Topical lidocaine or topical capsaicin (d/c if irritating or no benefit after 3-5 days)

MD Notes

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