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26 Complex Regional Pain Syndromes

26 Complex Regional Pain Syndromes
The Massachusetts General Hospital Handbook of Pain Management

Complex Regional Pain Syndromes

Katharine H. Fleischmann and Edward Lubin

Pain, whose unchecked and familiar speed
Is howling, and keen shrieks day after day.
—Percy Bysshe Shelley (1792–1822)

I. History
II. Basic mechanisms
III. Clinical presentation

1. Acute stage

2. Dystrophic stage

3. Atrophic stage
IV. Diagnosis
V. Treatment

1. Physical therapy

2. Drug treatments

3. Regional anesthesia

4. Neuromodulation
VI. Conclusion
Selected Readings

The term complex regional pain syndrome (CRPS) was coined to describe pain syndromes that are often characterized by evidence of sympathetic nervous system dysfunction. This new terminology was suggested in order to break away from traditional concepts of the pain being mediated by the sympathetic nervous system, especially in view of the likely primary neuropathic cause of the pain and in view of the complexity of its cause, which is probably not simply related to the sympathetic nervous system. CRPS I and CRPS II are the two classic neuropathic pain syndromes previously known as reflex sympathetic dystrophy and causalgia.
CRPS I has been recognized as a clinical entity for many years. It is most often initiated by trauma, which can be mild or severe, chronic and repetitive, or a single event. The inciting event may be a minor or major fracture, a crush or amputation injury, or merely a sprain of the affected limb. Other examples stem from chronic repetitive movement trauma ranging from the use of computer or piano keyboards to heavy drilling equipment. Iatrogenic causes include surgery and poorly fitted casts. Up to one quarter of all cases of CRPS I have no clear cause.
The International Association for the Study of Pain (IASP) defines CRPS I as “a syndrome that usually develops after an initiating noxious event, is not limited to the distribution of a single peripheral nerve, and is apparently disproportional to the inciting event. It is associated at some point with evidence of edema, changes in skin blood flow, abnormal sudomotor activity in the region of the pain, or allodynia or hyperalgesia.” The patient generally complains of diffuse limb pain associated with a burning or stabbing sensation.
CRPS II involves a similar pattern of symptoms. The IASP definition is “burning pain, allodynia, and hyperpathia usually in the hand or foot after partial injury of a nerve or one of its major branches in the region of the limb innervated by the damaged nerve.” The symptoms of CRPS II may not occur immediately after nerve injury. As with CRPS I, they may be more insidious in their onset, occurring days, weeks, or even months after the injury. Concomitant vascular injury is common and exacerbates the sympathetic hyperactivity that often occurs in this syndrome. Essential elements of this syndrome are nerve injury, burning pain, and cutaneous hypersensitivity.
The clinical course of CRPS is divided into three stages. The first stage is the acute or hyperemic stage. The second is the dystrophic or ischemic stage. The third stage is atrophic. Radiography, scintigraphy, thermography, electromyography, and nerve conduction studies provide useful information, but the diagnosis of CRPS remains a clinical one.
The clinical syndrome we refer to as CRPS was scarcely mentioned in medical literature prior to 1864. In that year, Silas Weir Mitchell and his colleagues published “Gunshot Wounds and Other Injuries of Nerves.” This paper was reissued in its entirety in the orthopedic literature in 1982. Mitchell was a physician during the Civil War and frequently saw nerve injuries caused by low-velocity gunshot wounds. In this context, he described a syndrome in which severe burning pain was seen following peripheral nerve injury. He later introduced the term causalgia, meaning burning pain, to describe the syndrome we now call CRPS II.
Similar pain states were later documented in postsurgical patients, as well as in those with no clear inciting cause. In the 1920s, René Leriche, a French surgeon, was the first to establish a common link between the sympathetic nervous system and causalgia by demonstrating that sympathetic blockade or sympathectomy could relieve the symptoms of many of his patients. Patients with no clear-cut peripheral nerve injury or those with pain in more than one peripheral nerve distribution had what became known as reflex sympathetic dystrophy, now called CRPS I.
Numerous theories have been offered to explain the pathophysiology of CRPS I and CRPS II, but the exact mechanisms remain unknown. Most theories, however, postulate that sympathetic dysfunction plays a significant role in the development and maintenance of the syndromes. Indeed, the concepts of CRPS and sympathetically maintained pain are integrally related to one another. However, we now know that there are syndromes in which part or all of the pain appears to be sympathetically independent pain. CRPS most likely involves both peripheral and central mechanisms.
Peripherally, events after nerve injury herald long-term changes in neural processing. In animal models, persistent afferent small-fiber activity begins days to weeks after peripheral nerve ligation or section, and it can be measured at the site of a developing neuroma as well as in the dorsal root ganglia. The neural sprouts at these sites have growth cones that have mechanical and chemical sensitivities not possessed by the original neurons. These neural sprouts may also have increased numbers of sodium channels, leading to increased ionic conductance and hence increased spontaneous activity. There is also evidence of increased innervation by sympathetic terminals on the cell bodies of A-d and, to a lesser extent, C nociceptor fibers within the dorsal root ganglia, following injury to their axons. It is also hypothesized that a partial nerve lesion induces an up-regulation of functional alpha-2 adrenoceptors at the plasma membrane of intact nociceptive fibers.
Centrally, changes in the morphology of the spinal dorsal horn ipsilateral to a peripheral nerve injury may be secondary to intrinsic mechanisms arising in response to a chronic barrage of impulses, or in response to retrograde transport of chemical factors from the area of the lesion. The role of glutamate release in the spinal cord after peripheral nerve injury is being evaluated with increased interest. Increased spontaneous activity in the primary afferent neuron may be a factor leading to spinal cord glutamate release.
Although some studies suggest alternative neural and excitatory amino acid mechanisms of CRPS, the majority of animal studies point to a key role for the sympathetic nervous system in the maintenance of pain. Many models of sympathetically maintained pain in animals have been developed. Pretreatment with chemical or surgical sympathectomy blunts or abolishes the persistent tactile allodynia that arises in neuropathic pain models after experimental ligation or damage to nerves at sites adjacent to the spinal cord. Subsequent electrophysiologic studies demonstrate that some A-d and C fibers acquire sensitivity to norepinephrine applied to the nerve injury site. Clinical evidence in patients with CRPS also suggests that the pain is maintained by sympathetic activity, either through the sympathetic nervous system itself or by other mechanisms. Chemical or surgical sympathectomy may transiently alleviate or eliminate the pain, whereas peripherally administered norepinephrine rekindles the pain.
CRPSs are characterized by pain, changes in cutaneous sensitivity, vasomotor and sudomotor disturbances, and increased muscular tone. These are often followed by weakness, atrophy, and ultimately irreversible trophic changes involving the skin and underlying muscles, bone, and joints. CRPS I and II are divided into grades, which characterize the severity, and into stages, which chart the course over a period of days to several months. In addition, it is now widely accepted that in CRPS there is a component of pain attributable to sympathetic efferent function referred to as sympathetically maintained pain. Interruption of sympathetic pathways early in the disease often provides significant pain relief. Generally, there is also a component of pain that is not influenced by sympathetic activity and is therefore referred to as sympathetically independent pain.
1. Acute stage
The initial signs and symptoms of CRPS may appear at the time of injury or may be delayed for weeks. The acute stage is characterized by constant pain, usually of a burning quality, localized to a specific area of injury but not necessarily following a specific dermatomal or nerve distribution. This pain is aggravated by movement and is associated with abnormal cutaneous sensitivity, including hyperesthesia, hyperpathia, allodynia, and changes in sympathetic tone. The result is often a tender, edematous limb, reduced in functional capacity, with overlying skin that is warm, red, dry, and tense. Later in the acute stage, increasing sympathetic tone is manifested as increasing edema, hyperhidrosis, and decreased limb temperature. Nails become thickened. Hair growth increases and the hair becomes coarser. During the acute phase, the symptoms of CRPS can often be reversed to a significant degree by treatment.
2. Dystrophic stage
CRPS often proceeds to a second stage, which is the dystrophic or ischemic phase, especially if the acute phase is left untreated. This can occur in a couple of months or longer. During this stage, the pain may radiate proximally or distally from the site of injury to involve the entire limb. Burning remains the principal symptom. Joint stiffness may appear along with decreased hair growth, thinning hair, and brittle and ridged nails. The skin over the limb becomes moist, cyanotic, and cold. The muscles may still exhibit spasm, but atrophy is more prominent at this time. Bony changes may start to appear on radiographs, reflecting diffuse bony reabsorption and erosion. Most cases of CRPS are diagnosed at this stage. A sympathetic blockade may still be helpful in treating the disease. However, the response is likely to be less than complete.
3. Atrophic stage
If untreated or unresponsive to treatment, CRPS progresses to the third or atrophic phase, which is characterized by trophic changes that are essentially irreversible. Pain, although quite severe, is not always the most prominent feature of this stage. The entire limb is involved and the process may even extend proximally to the torso or even to the contralateral limb. The skin is smooth, glossy, tight, and cool, the overlying hair has often fallen out, and the nails are severely brittle. The digits become thin and tapered (Fig. 1). Muscle wasting becomes more pronounced. Flexion contractures are likely to be present and the joints are usually ankylosed (Fig. 2). Radiography reveals more diffuse osteoporosis, with marked medullary space widening and cortical thinning.

Figure 1. The appearance of the hand in CRPS. The skin is smooth, glossy, tight and cool, the overlying hair has fallen out, and the nails are severely brittle. The digits are thin and tapered. The joints are ankylosed.

Figure 2. Woman with severely affected right arm. Muscle wasting is pronounced and there are flexion contractures.

Treatment is largely palliative, and somatic and sympathetic blockade are likely to provide only transient relief. Physical therapy is aimed principally at increasing range of motion and providing some pain relief. Functional restoration cannot generally be expected. Psychological counseling is an integral part of therapy in treating CRPS, particularly at this stage.
CRPS includes a number of features that may or may not coexist: sympathetically maintained pain, autonomic dysfunction, and neuropathy resistant to traditional pharmacologic agents. Pain is the cardinal feature of CRPS, but there are also sensory changes, autonomic dysfunction, trophic changes, motor impairment, and psychological changes.
The diagnosis is based on the whole clinical picture, with additional information provided by carefully performed and interpreted confirmatory tests to ascertain the presence or absence of sympathetically maintained pain and autonomic dysfunction. These include sympathetic blockade (i.e., stellate ganglion block, lumbar sympathetic block) performed using local anesthetic and tests such as the quantitative pseudomotor axon reflex test, which allows a continuous hygrometric assessment of pseudomotor activity, felt to be a good indicator of C-fiber function. Clinical experience suggests that early intervention with sympatholytic procedures (pharmacologic or nerve block techniques) may be helpful therapeutically as well. Further data are required to confirm the appropriate timing and relative efficacy of different procedures and medications. Nevertheless, the importance of early diagnosis cannot be overemphasized. Table 1 lists the common clinical features of CRPS that may be useful in its differential diagnosis. Diagnostic criteria are listed in Table 2.

Table 1. Common clinical features of complex regional pain syndrome

Table 2. Diagnostic criteria of complex regional pain syndrome

The diagnosis of CRPS is purely clinical and requires the exclusion of confounding medical problems, as well as the evaluation of diagnostic criteria. The IASP continues to clarify and refine the diagnostic criteria for CRPS in an attempt to eliminate the diagnostic and therapeutic dilemmas.
Progress has been slow in refining treatment for CRPS. Because the condition is complex and incompletely understood, the treatment has been varied and formulated to address presumed pathophysiologic causes and to ameliorate specific symptoms. The common goal in the treatment of CRPS is functional restoration. Pharmacologic therapy as well as regional anesthetics and surgical interventions should be seen principally as adjuncts to physical therapy.
1. Physical therapy
Physical therapy should be started as soon as a diagnosis is made, even if the diagnosis is presumptive. Indeed, when physical therapy has already been started (e.g., after surgery on the hand or foot, or after casting for a fracture), the pain may worsen with the development of CRPS. Discontinuing therapy under these circumstances will only make matters worse. Physical therapy should continue, but the approach most likely will be altered. Mobilization of the affected limb is of paramount importance, and often the pain must be aggressively treated to accomplish this, using the regional anesthetic techniques and/or pharmacologic agents discussed later. A gentle approach using heat, massage, vibration, and other mild stimuli helps restore more normal sensory processing. Isometric strengthening should be followed by progressive stress loading, as tolerated. One must be careful when using medication or, in particular, regional anesthesia in conjunction with physical therapy to avoid aggressive range-of-motion exercises and heavy loading of the affected limb. (Chapter 16 contains a full description of physical therapy for patients with CRPS.)
2. Drug treatments
(i) Neuropathic pain medications
Tricyclic antidepressants
Tricyclic antidepressants (TCAs) block the reuptake of norepinephrine and serotonin into the presynaptic terminal from the synaptic cleft. They are effective in treating neuropathic pain syndromes, including postherpetic neuralgia, diabetic neuropathy, and CRPS. The exact mechanism of action of the analgesic effect of these medications is unknown, but it is thought to be multifactorial. Spontaneous pain, shooting pain, and allodynia may all be improved. The effect of TCAs on pain is thought to be separate from that on mood, as the doses required for pain reduction are generally smaller than those required for mood elevation. These agents can, however, facilitate the treatment of pain by improving mood, sleep, and anxiety states. The most commonly prescribed TCAs are amitriptyline, nortriptyline, desipramine, and doxepin. They have somewhat different effects on norepinephrine and serotonin reuptake and therefore somewhat different side-effect profiles (see Chapter 11, Table 1). This should be considered when prescribing these drugs, particularly in the elderly. Refer to Chapter 11 and Appendix VIII for a full description of these drugs.
The anticonvulsants are a heterogeneous group of drugs, some of which have known efficacy for the treatment of neuropathic pain. Several anticonvulsants have been used successfully for CRPS, including phenytoin, carbamazepine, valproic acid, and gabapentin.
The most popular of these is gabapentin because of its favorable side effect profile. The use of gabapentin for diabetic neuropathy, postherpetic neuralgia, and migraine headaches has been validated in multicenter randomized trials. Although such validation for the use of gabapentin for CRPS has not yet been achieved, recent reports suggest it has considerable efficacy in CRPS patients. Side effects are a significant drawback of the other anticonvulsants, but these may be used if gabapentin does not prove effective. The anticonvulsants are described in Chapter 11.
The mechanism of action of gabapentin is unknown. Because the drug’s structure resembles that of the neurotransmitter gamma-aminobutyric acid (GABA), it was originally thought that it acted via GABA receptors. However, it does not in fact interact with these receptors. The drug binds to a calcium channel subunit, but the significance of this action is also uncertain. The most common adverse effects of gabapentin are somnolence, dizziness, ataxia, fatigue, inability to concentrate, gastrointestinal (GI) disturbances, and nystagmus. These side effects can largely be prevented by careful upward titration of dosage to therapeutic levels (see Chapter 11 and Appendix VII).
Local Anesthetics
Mexiletine was developed as an anticonvulsant, but it has been used almost solely until recently as a class Ib antiarrhythmic. It is structurally similar to lidocaine and has been demonstrated to be useful in treating neuropathic pain states. Although few studies exist, it is generally felt that mexiletine may be useful in the treatment of CRPS. At the MGH, a trial of mexiletine is generally preceded by an intravenous (IV) lidocaine trial. If a patient has a good response to a lidocaine infusion, and because of their structural similarity, a trial of oral mexiletine is warranted. Recently, transdermal lidocaine patches have been used successfully in areas of localized neuropathic pain with allodynia and hyperalgesia in postherpetic neuralgia. EMLA (eutectic mixture of local anesthetic) cream is a topical preparation containing both lidocaine and prilocaine. They may both prove to be useful in the treatment of localized areas of hyperesthesia associated with CRPS, but this has not yet been demonstrated.
(ii) Nonsteroidal anti-inflammatory drugs
Nonsteroidal anti-inflammatory drugs (NSAIDs) are not useful as a sole pharmacologic therapy in CRPS because pain relief is generally inadequate, although they may be helpful during the early stages of the disease. However, they may be useful as adjunctive therapy, especially when there is joint and tendon involvement. The decision to use an NSAID is often based on the ability of the patient to tolerate the drug’s side effects. GI irritation, sometimes leading to catastrophic GI bleeding, is the most feared NSAID side effect. Other relatively common side effects are renal damage and platelet dysfunction. NSAIDs are therefore contraindicated in patients with a history of peptic ulceration, renal dysfunction, coagulopathy, and known sensitivity to NSAID. They are relatively contraindicated in patients with asthma, cardiac failure, and the elderly. The newer cyclooxygenase (COX)-2 inhibitors are less likely to cause GI irritation and bleeding. A detailed description of the NSAIDs can be found in Chapter 8.
(iii) Opioids
The use of opioids in neuropathic pain states is controversial. Formerly, neuropathic pain was considered to be unresponsive to opioids, although currently opioid responsiveness with a rightward shift of the dose–response curve (indicating efficacy but at higher doses) is accepted. Although there have been no well-controlled trials of opioid therapy in patients with CRPS, it appears that in a significant number of patients the addition of an opioid can improve pain scores markedly. Therefore, if patients have not responded adequately to other treatments, a trial of opioids may be warranted. Opioids should be used only as adjuncts to other treatments, and great care should be taken when prescribing them for patients with a history of substance abuse (see Chapter 30). A full description of opioid drugs can be found in Chapter 9 and in Appendix V.
(iv) Others
Baclofen has been reported to be useful in neurologic diseases involving painful muscle spasm and other neuropathic pain states, thus raising hopes for its utility in the treatment of CRPS. However, further studies are necessary.
Phentolamine, an alpha-adrenergic blocker, is used by IV infusion to test the susceptibility of CRPS to sympathetic blockade. It is reported that approximately 30% of patients with sympathetically mediated pain respond positively to an IV infusion test. In these patients, IV regional blocks that include sympatholytic agents may subsequently prove useful. Oral alpha-blockers have not been found useful in the treatment of neuropathic pain. Side effects, most importantly hypotension and tachycardia, preclude patients from taking any but the smallest doses and severely limit their utility as analgesics.
Clonidine, an alpha-2 agonist, has been shown to have significant analgesic properties. It can be administered systemically or neuraxially, and it has been proven effective for both nociceptive and neuropathic pain. IV regional blockade using 1 µg/kg clonidine can provide marked pain relief in patients with sympathetically mediated pain. Likewise, transdermal clonidine is believed to be useful, particularly when applied to discreet areas of hyperalgesia. Oral clonidine, now rarely used as an antihypertensive, is being evaluated for its role in the treatment of various pain states. Clonidine has both central and peripheral actions and may be a useful adjunct in the treatment of CRPS. Sedation is a significant side effect of clonidine, but patients are unlikely to become somnolent or unrousable. In addition, clonidine may cause hypotension and bradycardia.
Corticosteroids are known to markedly decrease inflammation and have been advocated for use in the early stages of CRPS. Although there are no well-controlled trials, there is recent evidence to suggest a marked inflammatory component to the early stages of CRPS. Thus, if a patient has pain secondary to joint movement and trophic changes, a trial of corticosteroids with a reasonably rapid taper is recommended. Using this approach, one may avoid many of the undesirable side effects of steroids while evaluating and treating the inflammatory component of CRPS early in the disease.
Capsaicin interferes with cutaneous nociceptive C-fiber function by depleting peptides such as substance P and calcitonin generelated peptide at the nerve terminals. Capsaicin cream should be applied directly to areas of hypersensitivity and, with time, may lead to decreased sensitivity. Unfortunately, it is often difficult to get patients to comply with a trial of capsaicin cream because of the significant pain with the initial applications.
Calcitonin bisphosphonates are sometimes given to patients with CRPS in an effort to bolster their bone density. The additional benefit of decreasing spontaneous pain is sometimes seen. Calcitonin is given by subcutaneous injections days to weeks apart; if there is a positive effect on pain, it is seen early.
3. Regional anesthesia
A number of regional anesthetic modalities have been used in the treatment of CRPS. The primary goal remains alleviation of pain as an adjunct to physical therapy in the process of functional restoration. Regional sympatholysis in patients with sympathetically maintained pain can be both diagnostic and therapeutic (in conjunction with physical therapy).
(i) Sympathetic blockade
Temporary sympatholysis of the upper extremity can be accomplished by a stellate ganglion block or a cervical sympathetic block. A lumbar sympathetic block provides sympathetic blockade in the lower extremities. An increase in temperature of the limb (upper or lower) is always a reassuring sign that the sympathectomy has been achieved (Horner’s syndrome by itself is not an indication of limb sympathectomy). The accuracy of these blocks has been greatly increased by fluoroscopic guidance of needle positioning. In addition to providing temporary pain relief, sympathetic blocks can help determine the extent of the sympathetic component of a patient’s pain, thereby predicting potential benefit from pharmacologic therapy. However, some degree of somatic blockade is almost certain to occur in conjunction with these blocks, so the test is not entirely clean.
The aim of temporary sympatholysis in CRPS is to achieve sufficient pain relief to allow functional restoration during a course of physical therapy. The endpoint for the combined therapy is either adequate functional restoration, or the point at which the patient is no longer able to increase endurance and workload after sympathetic blockade. A series of blocks may be necessary, in conjunction with the physical therapy sessions.
Sympathetic neurolysis has been advocated for patients with CRPS whose pain has been nearly or completely abolished by temporary sympathetic blockade. It can be accomplished by injecting phenol or absolute alcohol under fluoroscopic guidance. Chemical neurolysis lasts only 3 to 6 months, and patients may then suffer a recurrence, or even worsening, of their original pain. There is also a risk of spread of the neurolytic agent to the sensorimotor fibers in close proximity to the targeted nerves (e.g., phrenic nerve, lumbar plexus). This approach is recommended only for patients who have proved refractory to all other treatments.
More recently, percutaneous radiofrequency lesioning of the sympathetic trunk and endoscopic sympathectomy have been used in patients with clearly demonstrable sympathetically maintained pain. Long-term evaluation of the efficacy of these treatments has not yet been completed.
(ii) Intravenous regional blockade
Intravenous regional blockade has been attempted with numerous medications with varying reports of success. If a patient has failed other, more conservative therapies, a trial of IV regional medication is warranted. Local anesthetic and clonidine are often used in combination for this purpose. Some have advocated the addition of ketorolac if the patient is in the acute stage of CRPS when there is a significant inflammatory component. In the past, guanethidine, reserpine, bretylium, and other drugs have been used in IV regional blockade. None of these have clearly been shown to be helpful in the treatment of CRPS, and a number are no longer available in the United States. Many patients are unable to tolerate the procedure because of severe pain with limb exsanguination and tourniquet placement.
(iii) Epidural blockade
Lumbar epidural blockade and, less frequently, cervical epidural blockade have been used for extended periods of time to treat cases of CRPS that have been unresponsive to less invasive therapies. Lumbar epidural catheters can be used to provide continuous lumbar plexus blockade for patients who have inadequate pain relief and have been unable to participate in physical therapy. A low concentration of local anesthetic is used, high concentrations tending to produce sensory and motor blockade, which hampers functional restoration. Often, an opioid or clonidine is used in combination with the local anesthetic to augment pain relief. Temporary epidural catheters have been left in place for up to 6 weeks, allowing successful functional restoration. Clearly, there are risks associated with long-term epidural catheters, and sometimes the external infusion system can interfere with the exercise regimen. Implanted epidural infusion systems are more secure and less intrusive, but the risks of the surgical procedure are probably not warranted other than in the most refractory cases.
(iv) Brachial plexus blockade
Continuous brachial plexus blockade for patients with CRPS of the upper extremity has been advocated and can be accomplished with an axillary, infraclavicular, or supraclavicular catheter. The advantage, as with epidural catheters, is that the prolongation of neural blockade enables patients to make relatively rapid progress in physical therapy. Under neural blockade, care should be taken to avoid overextending the passive and active range of motion exercises. As with any catheter treatment, there are risks of dislodgement and infection. A fairly high infusion rate of local anesthetic is needed for successful brachial plexus catheter treatment, which limits the utility of these treatments in outpatients. The treatment is best suited to patients who have been unresponsive to pharmacologic therapy but are likely to have a good and rapid response to physical therapy with adequate sensorimotor blockade.
4. Neuromodulation
(i) Spinal cord stimulation
Spinal cord stimulation has proven useful in patients with refractory CRPS, and in those who have had intolerable side effects from other therapies. Patients must have met government guidelines and specific insurance company stipulations prior to approval of a trial of spinal cord stimulation. Stimulation is conducted at the C5-7 level for the upper extremities, and the T8-10 level for the lower extremities. Approximately 50% of preselected patients with CRPS have a positive response to a trial of stimulation therapy. Approximately 70% of these patients have good to excellent longerterm benefit. A goal of pain relief, rather than full functional restoration, is reasonable in view of the refractory nature of the pain in patients selected for this expensive therapy.
(ii) Peripheral nerve stimulation
Peripheral nerve stimulation has been advocated for use in patients with CRPS II, with symptoms entirely or mainly in the distribution of a single major peripheral nerve, who have been unresponsive to other therapeutic modalities. It is not considered an option for patients with CRPS involving an entire limb or further extension to the trunk or other extremities. Peripheral nerve stimulators present a special problem in that they generally cross several mobile joints and therefore may be dislodged with movement. In select patients, however, early small studies suggest this might be a successful treatment for patients with CRPS II who have been unresponsive to other therapies.
(iii) Psychotherapy
Many patients with CRPS become depressed at some time in the course of their illness. There has been a great deal of discussion regarding whether a premorbid tendency to depression predisposes patients to CRPS, or whether CRPS causes depression or uncovers a preexisting condition, and no consensus has been reached. Early in the illness, only about 10% to 15% of patients with CRPS report being depressed, which is an incidence similar to that of depression in the general population. Furthermore, when psychological tests are conducted at this stage, the results are similar to those in the general population. As CRPS progresses, anxiety and depression play a greater role, as is confirmed by psychological testing. Many patients are already on a TCA for their pain, but the dose may need to be increased. A psychiatrist, psychologist, or social worker familiar with CRPS should be involved in caring for patients at this juncture. Also, a biofeedback program for relaxation and reduction of muscle tension is a useful adjunct to pharmacologic therapy, physical therapy, and psychotherapy.
The vast majority of CRPS patients are best managed with a combination of skilled physical therapy with drug or interventional pain therapy. The aim is always to restore functionality as much as possible. A simple drug regimen, or a simple nerve block (usually sympathetic) or series of blocks, is sufficient in all but the most refractory cases. More complicated procedures, including implanted catheters and stimulators, are rarely needed in these patients. With a team approach to the treatment of patients with CRPS, a successful outcome is most likely.

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