Complex Regional Pain Syndrome (CRPS) 

Definition of CRPS

According to the International Association for the Study of Pain (IASP), CRPS is defined as:

“A syndrome characterized by continuing pain, allodynia, or hyperalgesia in a limb, disproportionate to any known trauma or pathology, and associated with sensory, autonomic, motor, or trophic disturbances.”

Classification of CRPS

Type

Cause

Nerve Injury Present?

Examples

CRPS Type I (Reflex Sympathetic Dystrophy – RSD)

Follows trauma, surgery, or fracture

No identifiable nerve injury

Wrist fracture, ankle sprain

CRPS Type II (Causalgia)

Follows direct peripheral nerve injury

Yes (documented nerve damage)

Gunshot wound, nerve compression

 

Pathophysiology of CRPS

CRPS involves peripheral and central sensitization, leading to chronic pain. Key mechanisms include:

1. Neurogenic Inflammation

• Increased release of substance P, bradykinin, cytokines → pain hypersensitivity.

2. Sympathetic Nervous System Dysfunction

• Increased catecholamine release → vasoconstriction, ischemia, trophic changes.

3. Central Sensitization

• Persistent pain input → hyperexcitability of spinal cord neurons → allodynia, hyperalgesia.

4. Neuroplasticity & Cortical Reorganization

  • Functional changes in the somatosensory cortex → motor dysfunction, neglect-like symptoms. 

Clinical Features of CRPS

1. Pain Characteristics

• Severe, burning, deep aching pain

• Allodynia (pain from non-painful stimuli)

• Hyperalgesia (exaggerated pain response)

• Pain worsens with movement, stress, or temperature changes

2. Sensory Symptoms

• Abnormal temperature perception

• Paresthesia, dysesthesia

3. Autonomic Dysfunction

• Skin changes: Redness, mottling, cool or warm extremity

• Edema: Due to vascular leakage

• Sweating abnormalities: Hyperhidrosis or anhidrosis

4. Motor Dysfunction

• Weakness, tremors, dystonia

• Joint stiffness and contractures

5. Trophic Changes

• Hair growth changes: Excessive or absent hair

• Nail changes: Brittle or ridged nails

• Skin changes: Atrophy, shiny skin

Budapest Diagnostic Criteria for CRPS

To diagnose CRPS, all the following must be met:

1. Continuing pain, disproportionate to injury

2. At least one symptom in ≥3 categories:

• Sensory: Hyperalgesia, allodynia

• Vasomotor: Skin color/temperature asymmetry

• Sudomotor/Edema: Edema, sweating asymmetry

• Motor/Trophic: Weakness, tremors, dystonia, hair/nail changes

3. At least one sign in ≥2 categories

4. No other explanation for symptoms

Investigations

Test

Findings in CRPS

X-ray

Osteopenia (late stage)

Bone Scintigraphy (3-phase bone scan)

Increased uptake in early stage

MRI

Edema, soft tissue changes

Thermography

Temperature asymmetry

Quantitative Sensory Testing (QST)

Increased pain perception

 

Management of CRPS

1. Pharmacological Management

Drug Class

Examples

Indications

NSAIDs

Ibuprofen, Naproxen

Mild pain

Neuropathic Pain Modulators

Gabapentin, Pregabalin

First-line for neuropathic pain

Tricyclic Antidepressants (TCAs)

Amitriptyline

Chronic pain relief

SNRIs

Duloxetine, Venlafaxine

Neuropathic pain

Bisphosphonates

Pamidronate, Alendronate

Osteopenia, bone pain

Corticosteroids

Prednisolone

Acute inflammation

Opioids (only if severe pain)

Tramadol, Morphine

Refractory cases

IV Ketamine Infusion

Low-dose ketamine

NMDA receptor blockade

Clonidine (α2 agonist)

Transdermal patch

Sympathetic dysfunction

2. Interventional Procedures

• Sympathetic Nerve Blocks (Stellate ganglion block, Lumbar sympathetic block)

• Spinal Cord Stimulation (SCS) – If refractory to medical therapy

• Intrathecal Drug Delivery (Morphine, Baclofen pump)

• Peripheral Nerve Blocks – For focal pain relief

 

3. Non-Pharmacological Therapies

• Physical Therapy – Prevents joint stiffness, improves function

• Mirror Therapy – Reduces cortical reorganization-related pain

• Cognitive Behavioral Therapy (CBT) – Addresses psychological distress

• Desensitization Techniques – Helps reduce allodynia

Prognosis

• Early diagnosis and intervention improve outcomes.

• Poor prognosis if untreated → Chronic disability, psychological impact.

MCQs for Postgraduate Exam

1. Which of the following is NOT a feature of CRPS?

a) Pain disproportionate to injury

b) Trophic changes in affected limb

c) Progressive muscle hypertrophy

d) Autonomic dysfunction

Answer: c) Progressive muscle hypertrophy

2. Which investigation is most sensitive in the early stages of CRPS?

a) X-ray

b) Bone scintigraphy

c) MRI

d) Thermography

Answer: b) Bone scintigraphy

3. Which drug is the first-line treatment for neuropathic pain in CRPS?

a) Morphine

b) Gabapentin

c) NSAIDs

d) Paracetamol

Answer: b) Gabapentin

4. Which of the following interventional techniques is most commonly used for CRPS?

a) Stellate ganglion block

b) Radiofrequency ablation

c) Facet joint injection

d) Cryoneurolysis

Answer: a) Stellate ganglion block

5. Which therapy helps in cortical reorganization-related pain in CRPS?

a) Transcutaneous electrical nerve stimulation (TENS)

b) Mirror therapy

c) Ultrasound therapy

d) Acupuncture

Answer: b) Mirror therapy

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