Complex Regional Pain Syndrome (CRPS)/Reflex Sympathetic Dystrophy (RSD)
Debilitating syndrome characterised by severe pain out of proportion to initial injury that is associated with local autonomic dysregulation that usually occurs after trauma or surgery.
Many different diagnostic names given to this condition – causalgia; Sudeck’s atrophy; post-traumatic dystrophy; shoulder-hand syndrome; algodystrophy; post-traumatic pain syndrome; traumatic vasospasm; acute atrophy of bone; sympathetically maintained pain (the different and confusing terminology probably arose from the emphasis placed on the different and variable clinical manifestations of the syndrome).
Currently accepted terminology/nomenclature is that of the International Association for the Study of Pain:
1) Complex regional pain syndrome, Type 1 (reflex sympathetic dystrophy; not associated with a nerve injury)
2) Complex regional pain syndrome, Type 2 (causalgia; similar clinical picture to RSD, but are associated with injury to a peripheral nerve)
Appears to be a sympathetic nervous system disorder – pain is disproportionate to injury.
Aetiology:
Often follows trauma (fractures, lacerations, crush injuries, contusions, sprains); surgery; cast immobilisations; chemical and electrical burns; subcutaneous injections; malignancies; peripheral nerve disorders; strokes; myocardial infarction
Predisposing factors – smoking; diabetes mellitus; alcohol abuse; multiple sclerosis; hyperparathyroidism; hyperthyroidism
Pathogenesis:
Several hypotheses/mechanisms have been proposed:
• May be related to early release of a sympathotropic factor following injury
• a vicious pain cycle is set up by abnormal firing of sympathetic neurons
• peripheral mechanoreceptors or central neurones may be more sensitive
Clinical Features:
Characteristically a burning superficial pain and a deep aching pain; occurs from days to 6 months after initial injury; localised to site of injury initially, but later spreads; pain out of proportion to injury; swelling; worse on movement; muscle spasm; hyperaesthesia; oedema; decreased motor function; trophic skin changes; vasodilation; colour changes (mottling of skin, purple discolouration from venous stasis); hyperhidrosis; feet feel cold; F>M; ABI may be increased relative to unaffected side.
Bone scan will show increased uptake; x-rays will show periarticular soft tissue swelling, regional and patchy demineralisation/osteoporosis; nerve conduction studies will show abnormalities (may not show changes in early stages). Thermograms can document subtle temperature differences
Diagnostic sympathetic nerve blocks will be effective if pain is ‘sympathetically mediated pain’ but not if it is ‘sympathetically independent pain’.
Differential diagnosis – high index of suspicion is needed; pain is regional and not in dermatome distribution; other painful polyneuropathies; lumbar radiculopathy; sciatica; tarsal tunnel syndrome;
Early diagnosis is important as the condition is much more treatable if detected early, but diagnosis is often missed early due to :
1) General lack of awareness of the existence of the condition
2) Difficulty in differentiating between the pain, swelling and colour changes associated with the condition from those of the precipitating injury
3) Limited understanding that the c0ndition may develop early after an injury, with features of pain that are put of proportion to the injury sustained
4) Limited acceptance of the regional rather than the nerve root or peripheral nerve distribution of the pain
5) Overstatement of the psychologic factors (eg reactive depression) as a cause of the condition/complaint rather than an effect of the condition.
6) A sense that the patients are non-compliant when they fail to continue with movement therapy because the pain is worsened with movement
7) Lack of a definitive diagnostic test for the condition – need to rely on ‘vague’ clinical criteria.
Clinical Stages:
Often difficult to place individuals in overlapping stages – can fluctuate between stages 1 and 2 or can progress through stages rapidly or over many years.
Stage 1 – Acute Hyperaemic Stage:
Occurs immediately or up to a few days post injury; usually lasts 1-3 months; localised severe burning pain that is out of proportion to the original injury; hyperaesthesia, allodynia, hyperalgesia, hyperpathia; localised oedema/swelling; pain on movement; muscle spasm; decreased joint range of motion; vasospasm – skin is initially warm, red and dry then becomes cyanotic, cold, and sweaty; hyperhidrosis
Stage 2 – Dystrophic Ischaemic Phase
Lasts 3-6+ months; brawny appearing oedema spreads; pain is more severe and not as localised (spreads); skin is moist, cold and cyanotic; subcutaneous tissue and muscle wasting and atrophy; patchy osteoporosis;
Stage 3 – Atrophic Phase
Often irreversible; pain can be intractable, but may diminish; significant trophic changes; skin is smooth, shiny and tight; brittle nails; joint stiffness; muscle atrophy; generalised osteoporosis risk for pathological fractures; pain exacerbated by cold.
Stage 4 – Psychological Phase
Untreated or poorly treated depression and other psychopathology
International Association of the Study of Pain diagnostic criteria:
1) The presence of an initiating noxious event or cause of immobilisation
2) Continuing pain, allodynia or hyperalgesia with which the pain in disproportionate to any inciting event
3) Evidence at some time of oedema, changes in skin blood flow, or abnormal sudomotor activity in the region of the pain
4) This diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction
However, these criteria are not very sensitive .
Treatment:
Early mobilisation following initial injury – may be painful as even slight movement may trigger spasm. Condition seems to progress if kept immobilised.
Avoidance of alcohol and stop smoking
Stimulation of inhibitory neurons (massage, counterirritants, TENS, spinal cord stimulator)
NSAID’s; analgesics; tricyclic antidepressants; gabapentin
In an uncontrolled study, pamidronate (bisposphonate) appeared to be effective in treatment of 29 refractory cases
Sympathetic blocks
Counselling in pain management techniques; emotional support; biofeedback; relaxation training
Physiotherapy – movement; aqua therapy (movement in water) especially prevention of disuse atrophy
Later – chemical or surgical sympathectomy; morphine pump
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