Complex Regional Pain Syndrome

Complex Regional Pain Syndrome (CRPS Type 1 and Type 2) is a severe form of chronic pain that persists beyond the expected recovery time following a physical trauma. The two types, CRPS Type 1 and CRPS Type 2, share the same symptoms, but Type 2 is associated with a nerve injury.

Signs and Symptoms

CRPS usually starts in a limb and manifests as pain, swelling, limited range of motion, and changes to the skin and bones. The pain is often extreme and disproportionate to the severity of the initial injury. Symptoms can include burning, stabbing, grinding, and throbbing pain.

Moving or touching the limb is disproportionately painful (allodynia). Other findings include swelling, stiffness, and changes to the skin (temperature, colour, sweating, texture) and bones (disuse osteoporosis).

Clinical features include inflammation, hypersensitisation of pain receptors, dysfunction of vasoconstriction and vasodilation, and maladaptive neuroplasticity.

Diagnosis

Diagnosis is primarily based on clinical findings and follows the "Budapest Criteria," which require the presence of pain and a history of sensory, vasomotor, sudomotor, and motor or trophic changes. The criteria include:

1. Continuing pain, disproportionate to any inciting event.
2. At least one symptom in three of the following categories: sensory, vasomotor, sudomotor/oedema, motor/trophic.
3. At least one sign in two or more of the following categories: sensory, vasomotor, sudomotor/oedema, motor/trophic.
4. No other diagnosis better explains the signs and symptoms.

Diagnostic Adjuncts

No specific test is available for CRPS, but thermography, sweat testing, X-rays, electrodiagnostics, and sympathetic blocks can help build a picture of the disorder.

Thermography: Although CRPS may lead to altered blood flow, many factors can affect thermographic readings. Thus, thermography alone is not conclusive for diagnosing CRPS.

Radiography: Scintigraphy, plain radiographs, and MRI can be useful. Patchy osteoporosis may be detectable via X-ray or bone scan.

Electrodiagnostic Testing: Electromyography (EMG) and nerve conduction studies (NCS) are reliable for detecting nerve injury and distinguishing between CRPS types I and II.

Pathophysiology

CRPS is a multifactorial disorder involving inflammation, nociceptive sensitisation, vasomotor dysfunction, and maladaptive neuroplasticity. The persistent pain is thought to be caused by inflammatory molecules and neuropeptides released from peripheral nerves.

CRPS is not a psychological illness but can lead to psychological problems such as anxiety and depression.

Treatment

Treatment often involves multiple modalities including physical therapy, medications, and sometimes surgical interventions.

Therapy

Physical and occupational therapy can include transcutaneous electrical nerve stimulation, progressive weight-bearing, graded tactile desensitisation, massage, and contrast bath therapy. Mirror box therapy and graded motor imagery are also used, particularly in early CRPS.

Transcutaneous Electrical Nerve Stimulation (TENS): This therapy uses low-voltage electrical signals for pain relief. It is effective in treating pain and oedema but does not increase functional ability.

Medications

Medications for CRPS include anticonvulsants like gabapentin, muscle relaxers like baclofen, and infusions of ketamine or lidocaine. Bisphosphonates, calcitonin, and ketamine have shown tentative evidence of efficacy. Opioids are controversial and should be considered only after other treatments have been tried.

Surgery

Spinal Cord Stimulators: These appear to be effective for managing CRPS pain and improving quality of life. Dorsal root ganglion stimulation is another neurostimulation option that has shown promise.

Sympathectomy: This intervention is a last resort due to its risks and limited evidence of efficacy.

Amputation: About half of the patients show resolution of pain, while others may develop phantom limb pain.

Epidemiology

CRPS can occur at any age but is most frequently diagnosed at an average age of 42. It affects both men and women, with a higher prevalence in females. CRPS affects both adults and children, with increasing incidence among adolescents and young adults.

History

CRPS was originally described by Ambroise Paré and later termed "causalgia" during the American Civil War. The term "reflex sympathetic dystrophy" was introduced in the 1940s. In 1993, the term "complex regional pain syndrome" was adopted to encompass both causalgia and RSD.

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Self-assessment MCQs (single best answer)

What is the primary difference between CRPS Type 1 and CRPS Type 2?

Which of the following is NOT a symptom of CRPS?

What criteria must be met according to the "Budapest Criteria" for a diagnosis of CRPS?

Which diagnostic adjunct is NOT specifically used for CRPS?

What is the primary cause of the persistent pain in CRPS?

Which of the following therapies is specifically used for early-stage CRPS?

Which medication is NOT typically used in the treatment of CRPS?

Which surgical option is considered a last resort due to its risks and limited efficacy?

At what average age is CRPS most frequently diagnosed?

Who originally described the condition now known as CRPS?