Complex regional pain syndrome overview

# Overview
Complex Regional Pain Syndrome (CRPS) is a chronic progressive disease characterized by severe pain, swelling, and changes in the skin. Complex regional pain syndrome (CRPS) is a chronic pain condition that can affect any area of the body, but it often affects an arm or a leg.
It is important to understand that not all complex regional pain syndromes are the same. It is quite possible to have a post-phlebitic syndrome involving the leg that may present with skin color changes, excess pain, and swelling, but has nothing to do with RSD.
The cause of complex regional pain syndrome is currently unknown. Precipitating factors include underlying illnesses (especially vascular disease, an underlying rheumatic condition, a hidden infection or a coagulopathy in RSD cases), orthopedic injury, and surgery.  Although there are documented cases that have no identifiable injury to the original site in almost all cases of RSD, there was an underlying event or injury.

# Historical Perspective
The condition currently known as Complex regional pain syndrome was originally described by Silas Weir Mitchell during the American Civil War, who named the condition causalgia. In the 1940s, the term reflex sympathetic dystrophy came into use to describe this condition.

# Classification
Complex regional pain syndrome has been classified as type I (reflex sympathetic dystrophy with no nerve lesions) and type II (causalgia with obvious nerve damage).

# Pathophysiology
Recent research has suggested that oxidative damage (e.g. by free radicals) may play a role in pathophysiology of complex regional pain syndrome. The sympathetic nervous system may also play an important role in the pain. Another theory is that CRPS is caused by a triggering of the immune response

# Causes
The cause of complex regional pain syndrome is currently unknown. Precipitating factors include underlying illness (especially vascular disease, an underlying rheumatic condition, a hidden infection or a coagulopathy in RSD cases), orthopedic injury and surgery.

# Differentiating Complex Regional Pain Syndrome from other Diseases
Complex regional pain syndrome must be differentiated from shoulder-hand syndrome, Sudeck syndrome, Steinbrocker syndrome and Erythromelalgia.

# Epidemiology and Demographics
Complex regional pain syndrome is more common between ages 40- 60, affects women more frequently.

# Risk Factors
Precipitating factors for developing complex regional pain syndrome include underlying illness (especially vascular disease, an underlying rheumatic condition, a hidden infection or a coagulopathy in RSD cases), orthopedic injury and surgery.

# Natural History, Complications and Prognosis
Good progress can be made in treating complex regional pain syndrome if treatment is begun early which may even result in remission. If treatment is delayed, however, the disorder can quickly spread to the entire limb and changes in bone and muscle may become irreversible.

# Diagnosis

## Diagnostic Criteria
Both type I and type II varieties of complex regional pain syndrome share common diagnostic criteria of having spontaneous onset of pain not limited to the distribution of a single nerve, a history of edema or abnormal sweating. The only difference lies in the nature of the inciting event.

## History and Symptoms
The key symptom of complex regional pain syndrome is intense and burning pain which is much stronger than would be expected for the type of injury that occurred and it gets worse over time. Other symptoms include changes in skin, hair or nails. As disease progresses, there is more edema and there occur irreversible changes in skin and bones.

## Laboratory Findings
No specific test is available for complex regional pain syndrome, which is diagnosed primarily through observation of the symptoms. However, thermography, sweat testing, x-rays, electrodiagnostics, and sympathetic blocks can be used to build up a picture of the disorder. Three phase bones scans have been thought of as one of the most specific diagnostic studies for RSD, but they are not very sensitive and therefor delay recognition of cases. A delay in diagnosis and/or treatment for this syndrome can result in severe physical and psychological problems.  Early recognition and prompt treatment provide the greatest opportunity for recovery.

## X Ray
Patchy osteoporosis can be detected through X-ray as early as two weeks after the onset of CRPS.

## Other Imaging Findings
Bone scan can be used to detect osteoporosis sooner than X ray. Bone densitometry is also used to detect changes in bone density and monitor results of treatment.

## Other Diagnostic Studies
Thermography is the only test that allows for vasomotor mapping and therefore also provides information as to both the distribution of that patient's complex regional pain syndrome and its underlying generator. It is a diagnostic technique for measuring blood flow by determining the variations in heat emitted from the body. The nerve injury that characterizes type II CRPS can be detected by electromyography.

# Treatment

## Medical Therapy
The medical therapy of complex regional pain syndrome involves use of a variety of drugs including antidepressants, anti-inflammatories such as corticosteroids and COX-inhibitors such as piroxicam, vasodilators, GABA analogs such gabapentin and pregabalin, and alpha- or beta-adrenergic-blocking compounds. Local anaesthetic like lidocaine is often the first step in treatment. Physical therapy is the most important part of treatment. Implantation of spinal cord stimulators, sympathectomy, EEG feedback, psychotherapy and ketamine are amongst the newer forms of treatment. Surgical, chemical, or radiofrequency sympathectomy can be used as a last resort in patients with impending tissue loss, edema, recurrent infection, or ischemic necrosis suffering from complex regional pain syndrome. There is no prevention at this time for complex regional pain syndrome. Vitamin C has been shown to reduce the prevalence.