What causes Complex Regional Pain Syndrome (CRPS) in stroke patients?

Why Complex Regional Pain Syndrome Develops in Stroke Patients

Complex Regional Pain Syndrome (CRPS) in stroke patients develops as an exaggerated inflammatory and neurogenic response triggered by the combination of central nervous system injury from the stroke itself and secondary peripheral changes in the paretic limb, including sensorimotor dysfunction, trauma to the hemiplegic shoulder, and altered sympathetic regulation. 1, 2

Primary Pathophysiological Mechanisms

Central Nervous System Injury

• Specific brain lesions are directly associated with CRPS development: The head of the caudate nucleus, putamen, and white matter complexes in the corona radiata show the strongest correlation with poststroke CRPS when damaged 3
• The stroke creates maladaptive central neuronal plasticity, including reorganization of the primary somatosensory cortex 1
• Central sensitization occurs through repeated C-fiber discharge, causing increased spinal cord excitability 1

Secondary Peripheral Changes

• After the primary central lesion (stroke), secondary peripheral changes in the paretic extremity initiate CRPS 2
• An exaggerated inflammatory response develops with chemical mediators creating an "inflammatory soup" around primary afferent nerve fibers 1
• This localized neurogenic inflammation causes the edema, vasodilation, and hyperhidrosis characteristic of early CRPS 1
• Peripheral sensitization develops through hyper-excitability of afferent nerve fibers 1

Key Risk Factors That Trigger CRPS

Motor and Sensory Deficits

• The incidence of shoulder-hand syndrome reaches 67% in stroke patients with combined motor, sensory, and visuoperceptual deficits 4, 5, 6
• Severity of motor deficit and its recovery pattern directly correlate with CRPS onset 1
• Spasticity contributes to CRPS genesis, though a definitive causal relationship remains unconfirmed 4

Mechanical Trauma to the Hemiplegic Limb

• Glenohumeral subluxation is an important aetiological factor 1
• Trauma and injuries to the hemiplegic limb increase CRPS frequency 6
• Improper handling during rehabilitation, particularly overhead pulley exercises, increases risk 4, 6
• About one-third of acute stroke patients show shoulder tissue injury on ultrasound (effusion, tendinopathy, rotator cuff tears) that may contribute 4

Sympathetic Nervous System Dysregulation

• Sympathetic dysregulation plays a proposed role, though its central importance is debated 4
• A subgroup of CRPS patients exists with predominant sympathetic nervous system hyperactivity who respond to sympathetic blocks 1
• The sympathetic system maintains pain and autonomic dysfunction in the affected extremity 2

Clinical Pitfalls to Avoid

Prevention Failures

• Failure to protect the hemiplegic limb from trauma is a critical error 6
• Using overhead pulleys encourages uncontrolled abduction and dramatically increases hemiplegic shoulder pain incidence 4, 6
• Inadequate staff education about proper handling of the hemiplegic shoulder allows preventable trauma 4

Diagnostic Delays

• CRPS typically develops within weeks following stroke, making early recognition essential 7
• The diagnosis is primarily clinical, focusing on pain and tenderness of metacarpophalangeal and proximal interphalangeal joints, edema over the dorsum of fingers, trophic skin changes, hyperesthesia, and limited range of motion 5, 6
• Triple-phase bone scan showing increased periarticular uptake in distal upper extremity joints assists diagnosis when clinical presentation is unclear 5, 6

Distinguishing CRPS from Other Poststroke Shoulder Pain

The paretic upper limb frequently appears painful, edematous, with altered sensations within a non-use syndrome, making CRPS diagnosis more complex than in other pathological situations 1. However, CRPS specifically involves the hand with characteristic metacarpophalangeal and proximal interphalangeal joint involvement, distinguishing it from isolated shoulder pathology like adhesive capsulitis, rotator cuff tears, or bursitis 4.