The classification of abnormal, posttraumatic pain is complicated and encompassed in the term complex regional pain syndrome (CRPS). The term reflex sympathetic dystrophy (RSD), a descriptor of posttraumatic pain, is established in the lay, medical, and legal literature despite the absence of defined pathophysiologic findings and consistent clinical symptoms and signs. RSD is a condition considered to be present in a subset of patients contained within the broader category of CRPS. Even with introduction of the name CRPS, much of the contemporary literature uses RSD, algodystrophy, and other descriptors. The purpose of this chapter is to present diagnostic criteria that define clinical subtypes of CRPS and to provide a practical approach for treatment in the acute and chronic stages of this dynamic process.
General Considerations in Complex Regional Pain Syndrome
Clinical Definitions
The diagnosis of CRPS is contingent on the presence of regional pain combined with autonomic dysfunction, atrophy, and functional impairment ( Figure 53.1 and Box 53.1 ) affecting musculoskeletal, neural, and vascular structures. Type 1, or “classic,” RSD is not associated with an identifiable peripheral nerve injury. Type 1 CRPS is initiated by trauma and is often associated with swelling as a result of dependency, extensive trauma, or a cast or bandage that was quite tight. Type 2 is associated with an identifiable peripheral nerve injury (causalgia). Type 3 includes nontraumatic causes producing extremity pain such as myofascial syndrome ( Table 53.1 ). The type 3 category of CRPS is controversial; however, its use expands the concept to include all extremity pain pathologic conditions. This chapter discusses only CRPS type 1 and type 2.
Acute atrophy of bone
Algodystrophy
Algoneurodystrophy
Causalgia state/syndrome
Chronic traumatic edema
Major causalgia
Major traumatic dystrophy
Mimocausalgia
Minor causalgia
Minor traumatic dystrophy
Neurodystrophy
Neurovascular dystrophy
Osteoneurodystrophy
Pain dysfunction syndrome
Painful posttraumatic osteoporosis
Peripheral trophoneurosis
Postinfarctional sclerodactyly
Posttraumatic pain syndrome
Posttraumatic sympathetic dystrophy
Posttraumatic vasomotor abnormality
Posttraumatic vasomotor instability
Reflex nervous dystrophy
Reflex neurovascular dystrophy
Reflex sympathetic dystrophy
Shoulder-hand-finger syndrome
Shoulder-hand syndrome
Sudeck atrophy
Sympathalgia
Sympathetic algodystrophy
Sympathetic-mediated pain
Sympathetic neurovascular dystrophy
Sympathetic overdrive syndrome
Transient osteoporosis
Traumatic angiospasm
| Type | Description |
|---|---|
| Type 1 | Reflex sympathetic dystrophy (pain, functional impairment, autonomic dysfunction, dystrophic changes without clinical peripheral nerve lesion/injury) |
| Type 2 | Causalgia (pain, functional impairment, autonomic dysfunction, dystrophic changes with a diagnosable peripheral nerve injury) |
| Type 3 * | Other pain dysfunction problems (e.g., myofascial pain) |
Budapest Criteria
The International Association for the Study of Pain (ISAP) recommended and endorsed specific diagnostic criteria based upon a consensus process conducted through a “by invitation only” workshop held in the fall of 2003 ( Box 53.2 ). Subsequent internal and external validation studies and modifications of decision rules support a sensitivity of 0.70 and a specificity of 0.94. While not perfect, with a tendency toward overdiagnosis, these criteria are clinically superior to previous criteria but subject to observer variability ( Box 53.3 ).
* If seen without “major nerve damage,” diagnose CRPS I; if seen in the presence of “major nerve damage,” diagnose CRPS II.
- 1.
The presence of an initiating noxious event, or a cause if immobilization †
† Not required for diagnosis; 5% to 10% of patients will not have this.
- 2.
Continuing pain, allodynia, or hyperalgesia in which the pain is disproportionate to any known inciting event
- 3.
Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain (can be a sign or symptom)
- 4.
This diagnosis is excluded by the existence of other conditions that would otherwise account for the degree of pain and dysfunction
- 1.
Continuing pain that is disproportionate to any inciting event
- 2.
Must report at least one symptom in three of the four following categories:
- •
Sensory: report of hyperesthesia and/or allodynia
- •
Vasomotor: reports of temperature asymmetry and/or skin color changes and/or skin color asymmetry
- •
Sudomotor/edema: reports of edema and/or sweating changes and/or sweating asymmetry
- •
Motor/trophic: reports of decreased range of motion and/or motor dysfunction (weaknesses, tremor, dystonia) and/or trophic changes (hair, nails, skin)
- •
- 3.
Must display at least one sign at time of evaluation in two or more of the following categories:
- •
Sensory: evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or deep somatic pressure and/or joint movement)
- •
Vasomotor: evidence of temperature asymmetry and/or skin color changes and/or asymmetry
- •
Sudomotor/edema: evidence of edema and/or sweating changes and/or sweating asymmetry
- •
Motor/trophic: evidence of decreased range of motion and/or motor dysfunction (weakness, tremor, systonia) and/or trophic changes (hair, nails, skin)
- •
- 4.
There is no other diagnosis that better explains the signs and symptoms
The distinction “major nerve damage” is confusing as a discriminator for type 2 versus type 1 CRPS, and injury to an identifiable named nerve is appropriate to designate a diagnosis as type 2. Historically, causalgia was associated with an injury to a “major” mixed motor and sensory nerve (e.g., the median or sciatic nerve).
Neuropathic pain is defined as pain initiated or caused by a primary lesion or lesions or dysfunction of the peripheral nervous system or central nervous system (CNS). Nociceptive pain results from damage to tissues as a result of thermal, mechanical, chemical, or other irritants. Neuropathic pain may be associated with CRPS type 2, or it may be considered a distinct entity, depending on its source ( Table 53.2 ). Mononeuropathy, if symptoms and signs extend beyond the nerve distribution, may constitute CRPS type 2.
| Term | Definition |
|---|---|
| Pain | Unpleasant perception associated with actual or potential cellular damage |
| Analgesia | Absence of pain in response to an insult that should produce pain |
| Neuropathic pain | Pain initiated or produced by a primary lesion or lesions or dysfunction of the peripheral or central nervous system |
| Nociception | Response to an unpleasant (noxious) stimulus that produces pain in humans under normal circumstances because of thermal, mechanical, chemical, or other irritants of nonneural tissues |
| Allodynia | Pain in a specific dermatomal or autonomous distribution associated with light touch to the skin; a stimulus that is not normally painful |
| Hyperalgesia | Increased sensitivity to stimulation (includes allodynia and hyperesthesia) |
| Hyperesthesia | Increased sensitivity to simulation (pain on response to a mild nonnoxious stimulus) |
| Sympathetic pain | Pain in the presence of or associated with overaction of sympathetic fibers; by definition, the pain is relieved by sympatholytic interventions |
| Hypoesthesia | Decreased sensitivity to stimulation |
| Hyperpathia | Abnormally painful reaction to a stimulus |
| Dysesthesia | An unpleasant abnormal sensation |
| Paresthesia | An abnormal sensation |
The diagnosis of CRPS is based on the patient’s history and physical examination and relies on the intuition, experience, and clinical judgment of the physician.
Diagnostic criteria based upon consensus recommendations are a valuable but not an infallible tool that aids the diagnosis.
Although attempts have been made to establish these diagnostic tools, serum biomarkers or laboratory findings cannot be used to make the diagnosis of CRPS. Early recognition along with prompt treatment of CRPS is important to minimize permanent loss of function. However, despite prompt recognition and treatment, patients with CRPS may experience permanent impairment and disability. Many patients also face loss or suspension of work, changes in occupation, and psychological disorders.
CRPS may include sympathetically maintained pain (SMP) or sympathetically independent pain (SIP). These terms recognize the dynamic nature of dystrophic responses and stress the value of reliable and consistent clinical observations and descriptions. The diagnosis of SMP is based on pain relief with sympatholytic medications or sympathetic blocks ; however, SMP may become SIP over time. Objective and reproducible methods to assess pain, quantify trophic changes, define autonomic dysfunction, and measure functional impairment are important to provide consistent treatment regimens and reliably assess outcomes.
Historical Review
- •
Ambrose Paré, 16th century: Charles IX experienced burning pain after phlebotomy
- •
Percivall Pott, 1771: described pain after nerve injury
- •
Silas Weir Mitchell, 1864: description of causalgia
- •
Sudek, 1900: bone demineralization associated with posttraumatic pain
- •
Leriche, 1916: posttraumatic “burning” pain
- •
Evan, 1947, and Bonica, 1973; term reflex sympathetic dystrophy
- •
Proceedings of the VI Congress on Pain, 1991: introduced the term complex regional pain syndrome
- •
Budapest criteria, 2007: diagnostic criteria based on symptoms and signs with improved specificity
Physiology of Pain
Normally, pain is perceived only in the presence of actual or impending cellular tissue damage; persistent pain is pathologic in the absence of continued trauma. Painful peripheral nociceptive experiences that include cellular damage produce secondary inflammation by activating and sensitizing polymodal low-threshold mechanoreceptors and nociceptor afferent neurons, which produce, in theory, ectopic chemosensitivity to α-adrenergic agonists. This information is relayed via the process of transduction through small myelinated (Aδ), large myelinated (Aβ), and small unmyelinated (C) afferent fibers to the dorsal horn of the spinal cord, where sensitization of wide–dynamic range (WDR) neurons contributes to central nociceptive discharge ( Figure 53.2, A ). Within the dorsal horn, excitatory amino acids serve as the principal neurotransmitters. Transmitters include N -glutamate, aspartate, α-amino-3-hydroxy-5-methyl-4-isoxazopropionic acid (AMPA), N -methyl- d -aspartate (NMDA), and substance P. Of these, the NMDA receptor-transmitter interaction produces long-lasting potentials, is refractory to stimulation, and is theorized to play an important role in CRPS types 1 and 2. Nociceptive input is modulated via descending pathways, and both peripheral and central factors are required for the perception of pain (see Figure 53.2, B ). Pain intensity is determined by the magnitude and extent of the initiating/ongoing event, afferent input, efferent modulation, and CNS interpretation. Conscious appreciation of nociceptive (painful) experiences is dependent on a complex interplay of afferent and efferent information modulated and balanced by physiologic adaptations. Vasomotor disturbances may result from a variety of mechanisms, including antidromic vasodilation, vasoparalytic dilation, normal somatosensory reflexes, and denervation super sensitivity. Responses to nociceptive stimuli can vary significantly among individuals. The presence of nociceptive-induced inappropriate transmitter-receptor activity can affect peripheral microcirculatory control and, thereby, result in impaired nutritive blood flow and may sensitize CNS pathways.
Perception of Pain
By definition, CRPS does not exist in the absence of pain. Peripheral injury stimulates endogenous inflammatory mediators via nociceptive pathways. Repetitive trauma/injury may alter protective responses by producing earlier activation through sensitization. In addition to providing central input, local nociceptors initiate the direct release of peptides and neurotransmitters, control the inflammatory process, and promote tissue repair. Pain requires cognitive recognition.
Pain Mediators and Receptor Control
A variety of nonneurogenic and neurogenic mediators participate in the transmission of information interpreted as pain. Nonneurogenic mediators include bradykinin, serotonin, histamine, acetylcholine, prostaglandins E 1 and E 2 , and leukotrienes. Neurogenic mediators, which are biologically active peptides produced by primary afferent neurons, potentiate or inhibit nociceptive information. These mediators include substance P, vasoactive intestinal peptide, calcitonin gene–related peptide, gastrin-releasing peptide, dynorphin, enkephalin, galanin, somatostatin, cholecystokinin, γ-aminobutyric acid, dopamine, and glycine.
The role of α-adrenergic receptors and local blood flow in sympathetically maintained complex regional pain states is well documented, and relief of pain after intravenous phentolamine, a mixed α 1 – and α 2 -antagonist, is considered pathognomonic for SMP (CRPS type 1). Abnormal regulation of adrenoreceptor function or modulation (or both) in neural and vascular structures is the major common control pathway supporting the concept that RSD (SMP) is a receptor disease . Presynaptic and postsynaptic receptors are involved and affect nociceptive foci, blood flow, nutritional perfusion, and peripheral nerve excitability. The pathologic mechanisms involved in the compromise of extremity blood flow and neural control include: (1) abnormal neurotransmitter release secondary to nociceptive foci, (2) abnormal receptor distribution, and (3) alterations in receptor sensitivity (e.g., upregulation or downregulation).
Gate Theory of Pain
The “gate theory” is an appropriate aid in the conceptualization of pain. The theory assumes that a finite amount of information can be received at the spinal cord or cortical level. The “gate” is the dorsal horn of the spinal cord. Thus, painful information displaced or modified by less noxious input cannot be processed through the gate. Although as yet unproven, certain general principles relating to pain processing can be conceptualized by using this theory.
Acute Versus Chronic Pain
Acute pain is initiated during tissue injury or destruction, and the presence of acute pain may be beneficial or harmful. Beneficial effects include physiologic responses for maintenance of blood pressure, cardiac output, intravascular volume, and appropriate homeostasis. Acute pain warns the host of danger, prevents inappropriate motion of an injured extremity, and may diminish additional harm from repetitive injury. Persistence of pain beyond the need for protective action is unpleasant and may induce hypertension, tachycardia, coagulopathy, hyperglycemia, anxiety, fear, and chronic pain. Chronic pain that occurs in the absence of ongoing tissue destruction or that provides an inappropriate reflection of the intensity, magnitude, or duration of the tissue damage/compromise is pathologic. Although the pathophysiology of chronic pain is incompletely understood, the following processes can contribute to its establishment: persistent mechanical irritation of peripheral neural structures, incomplete regeneration of peripheral nerves, abnormal neurotransmitter activity, nutritional deprivation secondary to abnormal arteriovenous shunting, and central imprinting.
After trauma or surgery, a transient period of dystrophic extremity function is normal. However, it is abnormal for hyperpathia (heightened pain for a given stimulus), allodynia (painful responses to normally nonpainful stimuli), vasomotor disturbances, and functional deficiencies to persist. If untreated, these conditions may progress to permanent compromise of the extremity. Posttraumatic alterations in extremity physiology follow a variable time course. Consequently, abnormal prolongation of these otherwise normal responses is pathologic, and over time, irreversible changes in anatomic structures or physiologic processes may occur ( Figure 53.3 ). Therefore, CRPS may be considered an abnormally severe or prolonged manifestation of a normal postinjury response. Abnormally prolonged dystrophic events may damage or compromise the arteriovenous shunt mechanism, produce arthrofibrosis, cause excessive osteopenia, alter neuroreceptor function, or result in central pain imprinting or any combination of these sequelae.
Demographics of Complex Regional Pain Syndrome
In 2003, the incidence of CRPS in Olmsted County, Minnesota, was 5.46 per 100,000 person-years, with four times as many female as male patients. From the electronic medical records of more than 600,000 patients listed in the Dutch Health Care System, the overall incidence rate of CRPS in the Netherlands was higher at 26.2 per 100,000 person-years, with females affected three times more often than males. The mean age at onset was 46 years in the Minnesota study and 53 years in the Dutch study. However, CRPS can also develop in children and adolescents. The upper extremity is involved more frequently than the lower extremity, and fracture was the most common precipitating event. The incidence of cigarette smoking is higher in RSD patients, and cigarette smoking is statistically linked to RSD. Data suggesting a possible familial or genetic predisposition to RSD have also been presented but have not been confirmed. A predisposition to CRPS type 1 has been suggested on the involved side of hemiplegic patients. Eighty percent of patients in whom RSD was diagnosed within 1 year of injury will improve significantly, and it is reported that 50% of patients with untreated symptoms lasting longer than 1 year will have profound residual impairment.
Fracture of the distal end of the radius and ulna is one of the most common injuries associated with CRPS, and it complicates postinjury recovery in a measurable percentage of patients. The natural history of CRPS after distal radius fractures includes finger stiffness or “poor function” at 3 months after injury and correlates with residual RSD at 10 years. CRPS is more likely to occur after distal radius fractures in patients with tight casts or after a nociceptive or neuropathic event such as compression of the median nerve, overdistraction, instability of the distal radioulnar joint, or ulnar fracture. Dystrophic pain after surgical release of the carpal tunnel is commonly encountered in referral centers.
Common nerve injuries occurring during operative procedures that may precipitate CRPS include (1) injury to the palmar cutaneous branch of the median nerve during carpal tunnel surgery, (2) damage to the superficial branch of the radial nerve during surgical approaches to the first and second dorsal compartments for tenosynovitis, and (3) trauma to the dorsal branch of the ulnar nerve during a surgical approach to the distal ulna. The reports that CRPS may produce devastating consequences in association with simultaneous median nerve decompression at the wrist and partial palmar fasciectomy for Dupuytren contracture are not correct, and it may be performed safely.
Psychological Factors and Effects
CRPS is not a psychogenic condition. Extensive reviews of the existing literature do not support a psychological causation or an associated personality disorder. However, chronic pain is known to play a role in psychological well-being, with 58% of 283 consecutive patients admitted to pain centers, regardless of cause, fulfilling the criteria for personality disorders. Dependent, passive-aggressive, and histrionic personality disorders are common in those with chronic pain and are seen in patients with CRPS. Behavioral responses that reduce extremity use exacerbate edema and atrophy.
Psychological Problems Mimicking Complex Regional Pain Syndrome
The differential diagnosis of CRPS includes some psychological conditions, including conversion disorders and clenched fist syndromes. A patient with SHAFT (sad, hostile, anxious, frustrated, and tenacious) syndrome is difficult to discern from a patient with CRPS without active suspicion. A history of multiple operations, absence of consistent clinical findings, multiple treating physicians, a myriad of medications, psychiatric treatment, absence from work, disproportionate self-characterization and verbalization of symptoms, crying from pain, and a family history of disability are common factors. Misdiagnosis associated with abnormal postures is documented. Dysfunctional postures are defined, such as holding an upper extremity in a fixed posture. The typical posture of the hand of a patient with CRPS includes metacarpophalangeal (MP) and proximal interphalangeal (PIP) joint extension. MP and PIP joint flexion (clenched) is uncharacteristic of CRPS, and in such cases an alternative diagnosis is probable. Similarly, mild to moderate swelling is common; massive swelling or edema is rare, and alternative explanations (e.g., factitious symptoms) should be ruled out. Lack of objective findings (e.g., trophic changes, edema, osteopenia, radiographic or fixed contractures) suggests that other conditions are responsible for the symptoms.
Symptoms and Signs
The pain associated with CRPS is seen in a variety of clinical manifestations (see Table 53.3 ). The pain may be described as burning, throbbing, pressing, cutting, searing, shooting, or aching (or any combination of these descriptors). Hyperalgesia , or the perception of pain greater than would be expected, may be primary and affect the area of injury or secondary and affect nontraumatized surrounding areas or the entire limb. Identification of the zone of primary pain may aid in the localization of a nociceptive focus; however, diagnosis of the etiologic trigger event may not be possible until successful sympatholytic management of the secondary hyperalgesia is complete. Allodynia , or perception of pain initiated by normally innocuous stimuli, is a characteristic of sympathetically maintained CRPS. Hyperpathia , or pain produced by painful stimuli that appears with a delay, outlasts the initiating stimulus, and spreads beyond the normal neural distribution, is encountered frequently. It is important to differentiate spontaneous pain from stimulus-evoked pain. Difficulty sleeping because of burning pain is common and may be an early portent of progressive symptoms and signs.
Quantifying subjective complaints of pain with the use of standardized and validated instruments or questionnaires allows an objective analysis of symptoms. Useful instruments to evaluate symptoms and health status include the visual analog scale (VAS) for pain, the 36-item health status questionnaire (SF-36), the McGill Short Form Pain Questionnaire, and self-administered questionnaires designed to assess upper extremity symptoms/function. The self-administered questionnaire used for assessment of the severity of symptoms and functional status for patients with carpal tunnel syndrome is applicable to dystrophic states caused by carpal tunnel surgery or injury to the median nerve at the wrist and allows the examiner to graphically follow the patient’s health-related quality of life ( Figure 53.4 ). Cold intolerance, or pain on exposure to cold, may be analyzed by the McCabe Cold Sensitivity Severity Scale. The importance of standardized physiologic testing and instruments is supported by the lack of reproducibility of isolated clinical evaluations. However, the use of published criteria and scoring systems for CRPS may be helpful. The Budapest criteria facilitate the process.
Trophic changes— stiffness; edema; osteopenia; atrophy of the hair, nails, or skin; hypertrophy of the skin (or hyperkeratosis); or any combination of these changes—may be present in patients with CRPS (see Figure 53.1 ). Changes in the skin, hair, or nails are seen within 10 days of onset in 30% of extremities with CRPS type 1 (RSD). Despite treatment that reduces pain, cold intolerance, pain after use of the affected extremity, joint stiffness, nail and hair growth abnormalities, sensory disturbances, loss of finger extension/flexion, decreased grip strength, and shoulder stiffness are frequent and may persist. Osteopenia is common, involves both cortical and cancellous (trabecular) bone, and requires significant demineralization for visualization on plain radiographs ( Figure 53.5 ). Objective analysis of bone demineralization requires dual-photon absorptiometry or quantitative scintigraphy. Stiffness and atrophy of joints, muscles, and tendons may become apparent during endurance testing. Movement disorders and dystonic posturing may also occur.
Autonomic Function
The autonomic nervous system controls microvascular perfusion and sweat gland activity. Abnormalities in autonomic or vasomotor control, or in both, are seen during the course of CRPS in most patients, and loss of thermoregulatory control is common. Affected extremities (hands) may be either “ hot ” or “ cold ,” and significant differences in digital temperatures occur between the affected and unaffected extremities in 80% of patients. Abnormalities in thermoregulation/vasomotion usually occur and may vary depending on progression in the clinical stages of CRPS. Autonomic control may be evaluated by assessment of total digital blood flow, which consists of both thermoregulatory and nutritional components, and by analysis of sudomotor activity—sweating and piloerection. A detailed history will reveal symptoms of autonomic dysfunction in 80% of patients. Symptoms include abnormal sweating (excessive sweating or anhidrosis), vasomotor alterations, and heat or cold sensitivity (or both) (heat or cold intolerance). Vasomotor changes may be described as a reddish or bluish discoloration of the extremity either at rest or, more commonly, with the limb dependent. Evidence of autonomic dysfunction can be detected in 98% or more of patients by using sophisticated technology during the painful stages of CRPS. Digital perfusion and its components can be analyzed by digital temperature measurements, laser Doppler fluxmetry, plethysmography, and vital capillaroscopy. Sweating may be analyzed by resting sweat output, the quantitative sudomotor axon reflex test (QSART), changes in galvanic skin response, or asymmetry of somatosensory evoked potentials in the affected and contralateral extremities.
Sympathetic nervous system function, as reflected in laser Doppler fingertip blood flow and the vasoconstriction response to deep inspiration, varies by stage. Stage 1 patients exhibit increased blood flow but an unchanged vasoconstriction response, whereas stage 2 patients demonstrate decreased blood flow and stronger vasoconstriction.
Functional impairment may be analyzed by using standardized assessments of hand function, such as the Moberg pickup test. In addition, quantitative evaluation of extremity function before, during, and after stress with computerized equipment may detect subtle functional changes reflecting stiffness or atrophy. Thus, the use of standardized tests and various computerized systems can document functional impairment that may be difficult to quantify by traditional methods. The use of grip meters may be problematic. The utilization of standardized templates facilitates evaluation and documentation ( Tables 53.3 and 53.4 ).
| Budapest Criterion | 0, None | 1, Mild | 2, Moderate | 3, Severe | 4, Very Severe |
|---|---|---|---|---|---|
| Symptoms | |||||
| Pain | |||||
| Swelling | |||||
| Weakness | |||||
| Deformity | |||||
| Discoloration | |||||
| Cold sensitivity | |||||
| Radiculopathy | |||||
| Dystonia (movement) | |||||
| Pain | |||||
| Pain “out of proportion” | |||||
| Sensory: hyperesthesia | |||||
| Sensory: hyperpathia | |||||
| Sensory: allodynia | |||||
| Vasomotor Function | |||||
| Temperature asymmetry | |||||
| Skin color changes | |||||
| Skin color asymmetry | |||||
| Pseudomotor Function | |||||
| Edema | |||||
| Sweating changes | |||||
| Sweating asymmetry | |||||
| Other | |||||
| Motor or Trophic Abnormality | |||||
| Stiffness | |||||
| Decreased range of motion | |||||
| Trophic changes | |||||
| Weakness | |||||
| Tremor | |||||
| Dystonia | |||||
| Functional impairment | |||||
| Signs | 0, None | 1, Mild | 2, Moderate | 3, Severe | 4, Very Severe | |
|---|---|---|---|---|---|---|
| Clinical Signs | ||||||
| Skin | Mottled | |||||
| Cyanotic | ||||||
| Skin temperature | Cool | |||||
| Warm | ||||||
| Dry | ||||||
| Overly moist | ||||||
| Skin texture | Smooth | |||||
| Nonelastic | ||||||
| Atrophy | Pulp | |||||
| Skin | ||||||
| Joint | Stiffness | |||||
| Decreased passive range of motion | ||||||
| Nail changes | ||||||
| Hair growth | Decreased | |||||
| Increased | ||||||
| Contracture joints | ||||||
| Radiographic Signs | ||||||
| Trophic bone changes | ||||||
| Bone scan | ||||||
| Sensory | Allodynia | |||||
| Dexterity | ||||||
| Strength | Grip | |||||
| Dynamometer | ||||||
Physical Examination
The clinical characteristics of CRPS are related to altered extremity physiology. The magnitude of symptoms and signs is a reflection of the initiating event, postinjury response, inherent patient adaptability, interventional modalities, and time. The classic dystrophic progression from acute (<3 months) to dystrophic (3 to 6 months) to chronic (>6 months) occurs infrequently because of individual variability and the effects of partial treatment. Patients with CRPS who are evaluated for a painful, hot, swollen, stiff hand are easily recognizable; however, the precipitating nociceptive trigger (e.g., contusion of the superficial radial nerve) may not be identified until the SMP is managed and the dystrophic manifestations are treated. Once allodynia and hyperpathia are alleviated, careful examination may delineate an underlying disorder that may be amenable to treatment. Partially treated CRPS or variants of CRPS may be subtly manifested and can be labeled “poor results” or “noncompliant patients.” In the postoperative or posttraumatic period, unusual swelling, stiffness, pain, and restlessness may represent a dystrophic response.
The physical examination of suspected CRPS patients should include a neurologic assessment and evaluation of the cervical and thoracic spine. The presence of cervical disease (either diskogenic or degenerative) may exacerbate CRPS, a form of “double-crush syndrome.” Preexisting or acquired thoracic outlet or distant compression neuropathies may represent a “triple or more” crush syndrome. Cervical spine and shoulder range of motion should be recorded, and the brachial plexus should be evaluated. The arm should be assessed to rule out evidence of vascular or neurologic compression within the thoracic outlet. An adhesive capsulitis, or “shoulder-hand syndrome,” is a frequent sequela that may be overlooked unless the shoulder is examined. Hypersensitivity, vascular adequacy, edema, sensibility, joint range of motion, motor function, grip, pinch, fibrosis, sweating, and vasomotor tone of the entire extremity must be evaluated. Grip is frequently abnormal and should be assessed carefully. Currently, there are no objective laboratory tests to aid in the diagnosis of CRPS.
Mechanical Nociceptive Focus
Identification of nociceptive foci, which include peripheral nerve lesions and mechanical derangements, is important. Evaluation before and after sympatholytic intervention may delineate “trigger events” that might have initiated or propagated the dystrophic symptoms. Nociceptor input may be associated with SMP or SIP. However, early diagnosis plus prompt surgical correction of SMP associated with peripheral nerve injury is an effective management approach.
Diagnostic Testing
Pain Threshold Evaluation
Standardized evaluations and tests provide reproducible and objective information with regard to pain-pressure thresholds. Rubber-tipped algometers, dolorimetry, monofilaments, computer-controlled stimuli, or evaluations of thermal pain thresholds may be used to provide a quantitative measure of hyperpathia or allodynia. For example, perception of pain from a 2.83 Von Frey monofilament (normally not painful) in a specified area or dermatomal distribution defines the extent of allodynia. Success or failure of treatment can be assessed by repeated pain threshold evaluations. Monofilaments provide the most practical method for assessing and monitoring allodynia and hyperesthesia. Von Frey monofilaments are available in pocket kits, are inexpensive, and provide useful bedside sensibility and pain threshold data. Decreased pain after the use of a same-size or larger monofilament documents improvement, whereas persistent pain from the same-size or a smaller-diameter monofilament suggests ineffective management.
Radiography
Regional osteopenia can be seen on plain radiographs in approximately 80% of extremities affected by CRPS. Significantly decreased mineralization is necessary for changes to be visualized on standard anteroposterior and lateral radiographs (see Figure 53.5 ). Classic Sudeck atrophy includes diffuse osteopenia with juxtacortical demineralization and subchondral erosions or cysts. Five radiographic patterns of resorption have been described: (1) irregular resorption of trabecular bone in the metaphysis creating a patchy appearance, (2) subperiosteal bone resorption, (3) intracortical bone resorption, (4) endosteal bone resorption, and (5) surface erosions in subchondral and juxtachondral bone. Although osteopenia is easily visualized in metaphyseal areas, recent data confirm that the density of cortical and cancellous bone is affected equally in patients with CRPS.
Functional Magnetic Resonance Imaging
In the future, functional magnetic resonance imaging may be valuable in evaluating the pathophysiology associated with CRPS and in monitoring patients’ responses to interventions. Abnormalities in the size of the cortical representations of the affected hand on the primary and secondary somatosensory cortices have been reported, and “patterns of cortical reorganization in the primary somatosensory cortex seem to parallel impaired tactile discrimination.”
Bone Scan (Scintigraphy)
Three-phase technetium 99m bone scanning (TPBS) is performed commonly and has assumed a significant role in the diagnosis of RSD. With TPBS, the first, or “dynamic,” phase lasts 2 to 3 minutes and provides an assessment of digital perfusion; the second phase, or “blood pool image” or “tissue phase,” allows an assessment of total perfusion over a 3- to 5-minute period; and the third phase, a standard bone scan, evaluates uptake of radiotracer in bony structures ( Figure 53.6 ). In patients with CRPS, the use of a forearm or arm tourniquet or blood pressure cuff may affect accumulation of radiotracer in the hands or digits during phases I and II. Traditionally, scans have been considered “positive” if asymmetric flow is noted in phases I, II, or III. However, more recent reports suggest that the diagnostic yield of phase III alone equals the diagnostic yield of the three-phase scan ( Figure 53.7 ). Mackinnon and Holder have stated that a “strictly interpreted” phase III scan with “diffuse increased tracer uptake in the delayed image is diagnostic for RSD.” Although a positive phase III scan provides specific corroboration of the clinical diagnosis of CRPS, the sensitivity of scintigraphy is insufficient to provide stand-alone criteria, and, therefore, it should be used to corroborate clinical suspicion. In the majority of studies, a “positive” scan has high specificity but poor sensitivity. Quantitative scintigraphy provides useful physiologic data, allows quantitative assessment of regional bone loss associated with complex regional pain, and adds useful diagnostic information. However, bone scan data do not correlate with symptoms, do not provide prognostic information, and are unable to aid in the prediction of which interventional approaches might be successful.
