Introduction

Complex regional pain syndrome (previously known as reflex sympathetic dystrophy (RSD) or Sudeck atrophy) is a poorly understood condition which typically affects the extremities (arms and legs), causing severe pain, disability and sometimes swelling. It most commonly occurs after trauma, such as a fracture or sprain, but the trauma can be fairly trivial and in some cases no trauma at all is identified.

It is caused by sustained sympathetic activity, and characterised by symptoms that are out of proportion to any original injury.

It usually affects a single limb, but in 5-10% of cases it may spread to another limb.

Although very poorly understood, it is not a psychological disorder, although sometimes misinterpreted as such – especially as it is often associated with depression.

It can be divided into two types, although the type present does not affect the management:

  • CRPS I – without an identified underlying nerve injury
  • CPRS II – with an underlying identified nerve injury

It typically settles after time, but it can last for several years. Activity and mobility should be encouraged, and patients often require referral to the pain clinic.

Epidemiology

  • Incidence of 25 per 100 000 per year
  • Incidence increases with age
  • 4x more common in women
  • Arm: 60% of cases
  • Leg: 40% of cases
  • In children
    • Very rare before the age of 6
    • Tends to affect the lower limb
    • Even more common in females than in adults

Aetiology

  • Fracture – 45% of cases
  • Sprain – 20% of cases
  • Elective surgery – 10% of cases
  • Spontaneous – 10% of cases
  • Other risk factors:
    • ACE-inhibitor use at the time of trauma
    • Limb immobilisation >4 weeks
    • Hx of migraine
    • Hx of asthma
    • Sibling of an affected child (genetic predisposition)
    • Smoking
    • Pre-existing anxiety or depression
    • Fibromyalgia

Pathology

  • Not well understood
  • An abnormal inflammatory response is thought to result in vasomotor dysfunction and alterations in neuroplasticity in the peripheral nerves
  • There is some evidence that prophylactic vitamin C 500mg daily for 50 days reduces the incidence – in distal radius fractures, and foot and ankle surgery

Presentation

Typically presents within one month of traumatic event or immobilisation. In the early stages, there may be very few identifiable physical signs, which can make diagnosis difficult.

  • Throbbing, burning pain which is usually worse at night
    • Out of proportion to the original injury
    • Pain often worsened by light touch or other sensations that do not usually cause pain (allodynia)
  • Parasthesia (“pins and needles”)
  • Spontaneous sweating
  • Spontaneous formation of goosebumps
  • Change in appearance of hand and skin
    • At first: red, warm, swollen hand or foot with dry skin
    • Later: cold, often cyanosed and mottled, moist skin
    • These changes are often demarcated by an obvious boundary line (very specific for complex regional pain syndrome)
  • Muscle wasting
  • Reduced strength and ROM of the hand – typically secondary to pain and swelling. Joint are also often described as being painful
  • Loss of hair and nails in very advanced cases
Complex regional pain syndrome

Complex regional pain syndrome – an image showing the swelling and redness sen in CPRS. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Diagnosis

Diagnosis is made using the Budapest Criteria. These require:

  • Pain that is out of proportion to any initial causative event PLUS
  • At least ONE symptom from each of the THREE following categories AND at least ONE sign from at least TWO of the categories:
    • Sensory – hyperalgesia or allodynia
    • Vasomotor – temperature difference, skin colour changes / asymmetry
    • Oedema / abnormal sweating
    • Motor – reduced ROM, weakness, tremor, dystonia
  • PLUS
  • No other diagnosis is more suitable

The problem with these diagnostic criteria, is that signs must be present at the time the patient is seen, which often causes a delay in diagnosis.

Imaging studies are often completely normal.

  • Occasionally patchy decalcification of bone may be seen on x-ray.
  • Bone scan may show increased uptake and can assist diagnosis in some cases
  • EMG / nerve conduction studies – may show changes in nerve conduction but are often too painful tome tolerated by the patient and not routinely adivised

Differential Diagnosis

Management

  • Prompt diagnosis is associated with a better prognosis. 
  • The most important factor is to keep using the affected limb. Prolonged periods of disuse are associated with a longer duration of illness and worse prognosis.
  • Involve a multidisciplinary team – typically the GP, pain specialist and perhaps orthopaedics or rheumatology.
  • Aim to improve function, and reduce fear about pain, particularly use-related pain.
  • Multiple analgesics are often required. Consider use of the analgesia ladder, for example:
    • Paracetamol, plus
    • NSAID, plus
    • Neuropathic agent – e.g. amitriptyline, gabapentin plus
    • Opiates
  • Consider the use of bisphosphonates in those with evidence of bone resorption. Has bene proven to improve pain in these patents.
  • Avoid the use of capsaicin – which is often severely painful.
  • Considering screening for and treating depression and anxiety which are associated with CRPS.
  • Occasionally surgery may be indicated:
    • Surgical decompression – in cases where local nerve compression is implicated (most commonly if there is carpal tunnel involvement)
    • Surgical or surgical sympathectomy – stellate ganglion (upper limb) or lumbar spinal (lower limb)

Prognosis

  • Pain will typically flare up and down during the duration of the illness. These are NOT a sign that the condition is progressing
  • Rates of resolution vary widely from study to study
    • 75% at one year in one study
    • 35% at 6 years in another
  • Good prognostic features
    • Upper limb
    • CRPS after fracture seems to have a better prognosis than other causes
    • Warm type CRPS (usually indicates an early diagnosis)
    • Children
  • In severe cases CRPS can spread to all extremities and be completely disabling
  • Be wary that many patients may develop opiate dependency after long periods of opiate treatment

Complications

  • Mental health complications – such as anxiety and depression
  • Immobilisation often makes the condition worse
  • Skin infections are common

References

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