Reflex Sympathetic Dystrophy 

Complex Regional Pain Syndrome

The symptoms of CRPS usually manifest near the site of an injury, either major or minor, and usually spread beyond the original area. Symptoms may spread to involve the entire limb and, commonly, the opposite limb, and or other appendages. Furthermore, in some cases the optic nerves and muscles of one or both eyes can become involved, with the patient exhibiting double-vision, a decreased field of view, swelling around the eye(s) and most commonly the undesired closure of the eyelids with severe pain. 

The most common symptoms overall are burning and electrical like shooting pains. The patient may also experience muscle spasms, local swelling, increased sweating, changes in skin temperature and color, softening and thinning of bones, joint tenderness or stiffness, restricted or painful movement, and changes in the nails, dry skin over the complete body, and finally rapid shedding of skin. 

The pain of CRPS is continuous and may be heightened by emotional stress. Moving or touching the limb is often intolerable. Eventually the joints become stiff from disuse, and the skin, muscles and bone atrophy. The symptoms of CRPS vary in severity and duration. There are three variants of CRPS, previously thought of as stages. It is now believed that patients with CRPS do not progress through these stages sequentially and/or that these stages are not time-limited. 

Instead, patients are likely to have one of the three following types of disease progression: 

1.            Type one is characterized by severe, burning pain at the site of the injury. Muscle spasm, joint stiffness, restricted mobility, rapid hair and nail growth, and vasospasm (a constriction of the blood vessels) that affects color and temperature of the skin can also occur. 

2.            Type two is characterized by more intense pain. Swelling spreads, hair growth diminishes, nails become cracked, brittle, grooved, and spotty, osteoporosis becomes severe and diffuse, joints thicken, and muscles atrophy. 

3.            Type three is characterized by irreversible changes in the skin and bones, while the pain becomes unyielding and may involve the entire limb. There is marked muscle atrophy, severely limited mobility of the affected area, and flexor tendon contractions (contractions of the muscles and tendons that flex the joints). Occasionally the limb is displaced from its normal position, and marked bone softening and thinning is more dispersed. 

Diagnosis 

CRPS types I and II share the common diagnostic criteria shown below. Spontaneous pain or allodynia is not limited to the territory of a single peripheral nerve, and is disproportionate to the inciting event. 

1.            There is a history of edema, skin blood flow abnormality, or abnormal sweating in the region of the pain since the inciting event. 

2.            No other conditions can account for the degree of pain and dysfunction. 

The two types differ only in the nature of the inciting event. Type I CRPS develops following an initiating noxious event that may or may not have been traumatic, while type II CRPS develops after a nerve injury.

No specific test is available for CRPS, 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. Diagnosis is complicated by the fact that some patients improve without treatment. 

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. 

The International Association for the Study of Pain (IASP) lists the diagnostic criteria for complex regional pain syndrome I (CRPS I) (RSDS) as follows: 

1. The presence of an initiating noxious event or a cause of immobilization
2. Continuing pain, allodynia (perception of pain from a nonpainful stimulus), or hyperalgesia disproportionate to the inciting event
3. Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the area of pain
4. The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction. 

According to the IASP, CRPS II (causalgia) is diagnosed as follows: 

1.              The presence of continuing pain, allodynia, or hyperalgesia after a nerve injury, not necessarily limited to the distribution of the injured nerve 

2.              Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain 

3.              The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction. 

The IASP criteria for CRPS I diagnosis has shown a sensitivity ranging from 98-100% and a specificity ranging from 36%-55%. Per the IASP guidelines, interobserver reliability for CRPS I diagnosis is poor. Two other criteria used for CRPS I diagnosis are Bruehl's criteria and Veldman's criteria which have moderate to good interobserver reliability. In the absence of clear evidence supporting 1 set of criteria over the others, clinicians may use IASP, Bruehl’s, or Veldman’s clinical criteria for diagnosis. While the IASP criteria are nonspecific and possibly not as reproducible as Bruehl’s or Veldman’s criteria, they are cited more widely the literature including treatment trials. 

Thermography 

Thermography is a diagnostic technique for measuring blood flow by determining the variations in heat emitted from the body. A color-coded "thermogram" of a person in pain often shows an altered blood supply to the painful area, appearing as a different shade (abnormally pale or violet) than the surrounding areas of the corresponding part on the other side of the body. A difference of 1.0°C between two symmetrical body parts is considered significant, especially if a large number of asymmetrical skin temperature sites are present. The affected limb may be warmer or cooler than the unaffected limb. 

Sweat testing 

Abnormal sweating can be detected by several tests. A powder that changes color when exposed to sweat can be applied to the limbs; however, this method does not allow for quantification of sweating. Two quantitative tests that may be used are the resting sweat output test and the quantitative sudomotor axon reflex test. These quantitative sweat tests have been shown to correlate with clinical signs of CRPS. 

Radiography 

Patchy osteoporosis, which may be due to disuse of the affected extremity, can be detected through X-ray imagery as early as two weeks after the onset of CRPS. A bone scan of the affected limb may detect these changes even sooner. Bone densitometry can also be used to detect changes in bone mineral density. It can also be used to monitor the results of treatment, as bone densitometry parameters improve with treatment. 

Electrodiagnostic testing 

The nerve injury that characterizes type II CRPS can be detected by electromyography. In contrast to peripheral mononeuropathy, the symptoms of type 2 CRPS extend beyond the distribution of the affected peripheral nerve. 

Prevention 

Vitamin C has been shown to reduce the prevalence of complex regional pain syndrome after wrist fractures. A daily dose of 500 mg for fifty days is recommended. These studies are difficult to interpret because the incidence of CRPS in those who took the Vitamin C in this study are similar to the incidence without taking anything in other studies [(the most comprehensive incidence study)]. 

Treatment 

The general strategy in CRPS treatment is often multi-disciplinary, with the use of different types of medications combined with distinct physical therapies. 

·        DRUGS  Physicians use a variety of drugs to treat CRPS, including antidepressants, anti-inflammatories such as corticosteroids and COX-inhibitors such as piroxicam, bisphosphonates, vasodilators, GABA analogs such gabapentin and pregabalin, and alpha- or beta-adrenergic-blocking compounds, and the entire pharmacy of opioids. 

·       PHYSICAL AND OCCPUATIONAL THERAPY  Physical and occupational therapy are important components of the management of CRPS primarily by desensitizing the affected body part, restoring motion, and improving function. Though it should be noted some people at certain stages of the disease are incapable of participating in physical therapy due to touch intolerance. Physical therapy works best for most patients, especially goal-directed therapy, where the patient begins from an initial point, regardless of how minimal, and then endeavors to increase activity each week. Therapy is directed at facilitating the patient to engage in physical therapy, movement and stimulation of the affected areas.  

·       Physical therapy has been used under light general anesthesia in an attempt to remobilize the extremity. Such remobilization is used cautiously to avoid damage to atrophied tissue and bones which have become osteodystrophic. 

·       MIRROR THERAPY  Recent research has utilized mirror therapy to significantly reduce pain levels in CRPS patients, where the affected limb is placed within a mirror box, such that the unaffected limb is reflected in such a way as to make the patient think they are looking at the affected limb. Movement of this reflected normal limb is then performed such that it looks to the patient as though they are performing movement with the affected limb (although it will be pain free due to the fact it is a normal limb being reflected).

Following this movement of the normal limb, when the affected limb is moved, levels of pain are reduced and over a longer period significant changes between controls and intervention groups have been shown. Concepts of neural plasticity with in the brain have been hypothesized as to why this effect occurs, and similar mirror therapy has been used successfully to treat phantom limb pain. 

·      GRADED MOTOR IMAGERY  Because many studies have shown problems with the central nervous system and brain in people with CRPS, recently, treatments have been developed that target these problems.

TACTILE DISCRIMINATION TRAINING  Another approach to CRPS is based on a treatment called sensory discrimination training, which was used for phantom limb pain. 

·       GRADED EXPOSURE TO FEARFUL ACTIVITIES  Preliminary evidence from a replicated case series suggests that graded exposure to fearful activities is helpful for CRPS patients with a high fear of activity. 

·       LOCAL ANAESTHETIC BLOCKS/INJECTIONS  Injection of a local anesthetic such as lidocaine is often the first step in treatment. Injections are repeated as needed. However, early intervention with non-invasive management may be preferred to repeated nerve blockade. The use of topical lidocaine patches has been shown to be of use in the treatment of CRPS-1 and -2. 

·       SPINAL CORD STIMULATORS  Neurostimulation (spinal cord stimulator) may also be surgically implanted to reduce the pain by directly stimulating the spinal cord. These devices place electrodes either in the epidural space (space above the spinal cord) or directly over nerves located outside the central nervous system. Implantable drug pumps may also be used to deliver pain medication directly to the cerebrospinal fluid which allows powerful opioids to be used in a much smaller dose than when taken orally. 

·       SYMPATHECTOMY  Surgical, chemical, or radiofrequency sympathectomy — interruption of the affected portion of the sympathetic nervous system — can be used as a last resort in patients with impending tissue loss, edema, recurrent infection, or ischemic necrosis. 

Prognosis 

Good progress can be made in treating CRPS if treatment is begun early, ideally within 3 months of the first symptoms. If treatment is delayed, however, the disorder can quickly spread to the entire limb and changes in bone, nerve and muscle may become irreversible. The prognosis is not always good. The limb, or limbs, can experience muscle atrophy, loss of use and functionally useless parameters that require amputation. RSD/CRPS will not "burn itself out" but, if treated early, it is likely to go into remission.