Keywords

Introduction

Complex Regional Pain Syndrome (CRPS) is outlined as a painful and disabling condition accompanied by physical changes within the affected extremity, characterized by allodynia, edema, baldness, and sudomotor and dilatation dysfunction. The CRPS is a life-altering condition that generally affects the extremities after a trauma or nerve injury. The physiologic changes that follow as a result of the inciting injury are complex. In CRPS type I (reflex sympathetic dystrophy), small injuries or fractures initiate the onset of symptoms without evidence of nerve damage in the affected limb while CRPS type II (causalgia) develops once an injury to a large supplemental nerve happened with evidence of nerve damage in the affected limb. CRPS type 1 accounts for about 90% of CRPS [1]. However, some research has identified evidence of nerve damage in CRPS-I which puts into question as to whether the disorder is always divided into two types. Nevertheless, the treatment is similar [2].

Unfortunately, pain and disability related to CRPS frequently result in co-morbidities that produce a vicious cycle of pain and depression. It is distinct from other pain syndromes due to the presence of autonomic dysfunction, inflammatory changes, and a scarcity of dermatomal distribution. This condition is ambiguous in nature. It has been historically challenging to diagnose, laborious to treat, and the pathophysiology behind it has not been fully defined.

History

Ambroise Paré (1510–1590), the father of modern surgery, was the first to describe a disorder that could be related to the current concept of CRPS. He successfully treated a severe and persistent pain syndrome that occurred to King Charles IX of France after a phlebotomy [3]. The first written description of CRPS was made by Denmark who published a case report of a soldier wounded by a bullet that passed over his arm during the siege of Badajuz (1812) [4].

In 1864, Silas Weir Mitchell, in collaboration with George Morehouse and William Keen, published a monograph entitled “Bullet Wounds and Other Injuries,” which soon became the benchmark for diagnosing and treating nerve damage until World War I. A syndrome characterized by a typical chronic burning pain that is located at the end of the peripheral nerve injury site and is associated with skin disorders was described by the author and was highly suggestive of this disease and now became the hallmarks of what we now call CRPS. This clinical condition was later named “causalgia” in “Nerve Injuries and Their Consequences”, which is the second book published by Mitchell in 1872. It was later coined by Ruble Danglison in the first edition of the Medical Dictionary in 1874 [5, 6].

Another milestone in the history of the CRPS is made by Paul Sudek. In 1900, at the 29th Congress of the German Surgical Association, Sudeck presented an article entitled “Acute Inflammatory Bone Atrophy” which describes the results of his experiments on patients undergoing X-ray examinations which he was called “Sudeck atrophy” and is still a common term to define algodystrophy [7].

Another turning point in the history of CRPS was the hypothesis that the sympathetic nervous system plays a major role in the signs and symptoms of the disease. This hypothesis was accepted by Rene Leriche (1917) who described a patient with chronic hand pain and numbness after a bullet wound to the right arm. He performed the first sympathectomy on the patient and noted complete resolution of the pain syndrome within 2 weeks [8]. James E. Evans, then emphasized the term “sympathetic reflex dystrophy” (RSD) [9]. Philip S. Foisie, also described a persistent but low-grade arterial spasm after a soft tissue injury, which can lead to severe pain syndrome characterized by allodynia, edema, muscle atrophy, osteoporosis, joint stiffness, and decreased mobility. He argued that RSD might be better defined as a “traumatic arterial vasospasm” [10].

In the 1950s, Algology, a new field of medicine, was born as a branch of anesthesia. John Bonica (1953) was the first to propose the stages for RSD with three types of clinical imaginations [11] and these stages were used as the basis for the next diagnostic criteria (Table 9.1).

Table 9.1 Bonica three stages of the RSD
Full size table

John Bonica also found the first scientific association dedicated to the study of pain in 1973: The International Association for the Study of Pain (IASP). One of the several goals of the society was to standardize the classification of chronic pain. The first IASP conference was held in 1988 and the second one was in 1993 where they formulated and described the distinct characteristics of CRPS type I and CRPS type II [12]. Other diagnostic criteria for CRPS have been proposed by Peter Veldmann (1993) who criticized the subset in the steps suggested by IASP experts, and identified less common cold forms, and the more common hot forms [13]. Norman Harden and Stephen Bruehlc conducted two papers in 1999 in a multicenter study to test the internal validity and external validity of IASP criteria [14, 15]. A new classification system was proposed during the Consensus Conference in Budapest in 2003. This study supports the validity of the Budapest diagnostic criteria for CRPS and demonstrates their superiority over current IASP criteria. The results of this study support suggestions for accepting the Budapest criteria as a standard for diagnosing clinical CRPS [16].

Epidemiology

Many epidemiological studies have been performed, and there appears to be regional variations in terms of presentation. The diversity in these studies highlights the challenges of diagnosing CRPS. Because this is a clinical diagnosis, physicians will often have different results using different criteria.

An epidemiological study in USA by Sandroni et al. (2003) showed an incidence rate of 5.46 per 100,000 and a prevalence of 20.57 per 100,000. The female to male ratio was 4:1 with a mean age of 46 years and the upper/lower limb ratio was 2:1. All cases reported an inciting event and fracture was the most common stimulus (46%). An excellent correlation was observed between signs and symptoms, with vasomotor symptoms being the most common. Three-phase bone scan and autonomic testing diagnosed the disease in more than 80% of cases. Seventy-four percent of patients treated spontaneously recovered. These results suggest that invasive treatment of CRPS may not be necessary in most cases [17].

Another study in Netherlands by De Mos et al. (2007) estimated the overall incidence of CRPS at 26.2 per 100,000. Women were affected at least three times more often than men. The highest incidence occurred in women between 61 to 70 years old. The upper limb was more affected than the lower limb and fracture was the most common cause (44%). Menopausal women appear to be at the highest risk for CRPS [18].

The German epidemiological study by Ott and Maihofner (2018) reported an incidence of 71% and 29% between men and women, respectively. They also showed that the upper limb was more prone to CRPS (70% of patients), with CRPS I occuring more frequently than CRPS II (88% and 12%, respectively) [19].

Korean epidemiological study by Kim et al. (2018) showed that the difference between men and women was much narrower and the age with the highest incidence was much higher than the previous report. They also found that the pelvis, thighs, and lower limbs were more likely to be affected than the upper limbs in their patient population [20].

Denmark epidemiological study by Petersen et al. (2018), risk factors for CRPS were determined and the following ratios were found: women: men was 4:1, initial diagnosis of upper extremity: lower extremity was 2.5:, and surgical treatment: non-surgical was 3:1. The mean age was 47.5 ± 13.7 years and no gender differences were observed. Antebrachial fractures (23%) and CTS (9%) were the most common initial conditions [21].

According to UK study, CRPS is not a common disease. It has an incidence rate of 6.28 per 100,000 people per year for both types 1 and 2. According to the National Institute of Neurological Disorders and Stroke, the disease can occur at any age, is rare in the elderly and children under 10, and peaks at the age of 40 [22].

Pathophysiology

It is unlikely that a unique linear mechanism will be discovered behind the development of CRPS. According to the most common pathology model, CRPS is a detailed combination of various factors.

For example, peripheral mechanisms explain how hypoxia due to vasoconstriction and endothelial dysfunction leads to a decrease in nitric oxide levels and an increase in endothelin-1 levels in the affected limb. There is a sterile inflammation caused by an elevated levels of proinflammatory cytokines such as interleukin-6 and tumor necrosis factor-alpha. A neurogenic inflammation by the excretion of neuropeptides from C-fibers and a high level of substance P, bradykinin, and calcitonin gene peptide were also observed. Neurosensitivity is caused by the peripheral degeneration of small fiber neurons in the skin of damaged limbs, leading to improper nerve firing [23,24,25] and catecholamine sensitivity after injury [26]. The researchers reported significant degeneration of large motor Aα nerve fibers, while Aδ nerve fibers survived. They hypothesized that neural signaling imbalance may occur peripherally, increasing Aδ activity and increasing pain. Nevertheless, long-term changes in the peripheral nervous system appear to play an important role [27]. There is also an increase in the expression of α1-adrenoceptors in CRPS-affected organs [28]. Changes in circulating catecholamines can explain clinical development of warm-to-cold limb. In the acute phase, studies show a decrease in circulating norepinephrine, which potentially leads to vasodilation, edema, and warmness. It is believed that over time, this leads to an increase in peripheral catecholamine sensitivity, which in turn leads to excessive vasoconstriction and hyperhidrosis, leading to cooling limb in the chronic phase of the disease [22]. Clinically, an increase in the number of alpha-1 receptors in the affected limb, increased sensitivity of peripheral alpha adrenergic receptors, and chemical coupling between sympathetic neurons and CRPS-induced limb pain caused sympathetic dysfunction and lead to variable vasoconstriction, hypoxia, and sweating abnormalities and involuntary movements characterized by dystonia, and decreased range of motion [29].

Continuous activation of the peripheral nerve after injury has been shown to increase the firing effect of synaptic pain in the dorsal horn and lead to central sensitization [30]. Central mechanisms, such as (super) spinal sensitization via N-methyl-d-aspartate and neurokinin-1 receptors have also been described [31]. CRPS patients due to damaged limbs experience a smaller view of the sensorimotor cortex than the normal limbs [32]. There is cortical reorganization characterized by the significant contraction of the extension of the cortical view of the hand at the injured side, shifting of the hand to the cortical area of the lip, and the reorganization of the opposite side of the S1 cortex. These reorganization are associated with CRPS pain, mechanical hyperalgesia, and neuropathic pain [33]. Recent study showed that S1 representation of the CRPS hand is comparable between affected and unaffected hand map [34].

There is also an evidence of autoimmune-mediated reaction in the development of CRPS. Autoantibodies are believed to be produced against the structures of the autonomic nervous system causing exacerbation of inflammation and symptoms [35]. The mast cells were shown to decrease around atrophied cutaneous nerve fibers in the affected limbs. The researchers hypothesized that abnormal nerve-mast cell interaction occurs, leading to long-term inflammation and delayed tissue repair in CRPS [36]. Research studies have shown that up to 70% of these patients have anti-autonomic antibodies to immunoglobulin G in their serum [37].

The genetic impact on the development of CRPS is currently under investigation and showed that family relationships were associated with early-onset and increased incidence of multi-member involvement [38]. Discovering specific microRNA signatures (miRNAs) is another interesting way to study genetics. These small non-coding fragments of RNA have been shown to directly alter gene expression [37, 39] However, the genetic link is not definitive. A paradoxical study in 2016 examined more than 200,000 single nucleotide polymorphisms between CRPS patients and control groups and found no significant difference in expression between the two [40].

There is evidence that certain mental states can predispose a patient to illness. Patients with post-traumatic stress disorder (PTSD) significantly showed increased CRPS compared with controls [41]. In many of these patients, PTSD precedes the onset of CRPS as indicated by their medical history. In fact, psychological stress seems to affect the progression of the disease. Patients with higher levels of anxiety, disability perception, and fear of pain have been shown to worsen the course of the disease [42].

Clinical Presentation

CRPS describes an array of painful conditions that are characterized by a continuing (spontaneous and/or evoked) pain that is seemingly disproportionate to a given trauma or any inciting event. To wit, an unexpected prolongation of recovery of an uncomplicated fracture characterized this disease. Pain may vacillate between allodynia, signs of autonomic instability, and sensory dysfunction of the skin which include hyperalgesia and mechanical allodynia and hypoalgesia and mechanical hypoesthesia. There are also motor dysfunction which include a reduction in the “range of motion” of affected joints and/or weakness, tremor, involuntary movements, bradykinesia, and dystonia along with an abnormality of cerebral motor processing which are unusually associated with a peripheral process and deep tendon reflex findings. A fracture, or crushing injury or a forceful trauma to the arm is the most common initial event when it occurs in the upper extremity. It usually starts in the limb as an extreme pain, swelling, limited range of motion, and trophic changes in the skin and bones with nearly all patients showing sweating abnormalities (hypohydrosis or hyperhydrosis). It may initially affects one limb (asymmetrical distal extremity pain) and then spreads throughout the body with sensory abnormalities affecting the most distal part of the extremities (“stocking-glove” pattern). Furthermore, the affected area usually manifest symptoms beyond the site of the original injury with varying degrees of pain over time such that pain and other symptoms are often exacerbated with exertion of the affected extremity [43].

To quantify the severity of the disease, Harden et al. (2010) developed the CRPS Severity Score (CSS) . Higher scores were not only positively associated with increased pain and functional limitations, but were also used as a measure to detect the disease and to monitor response to a given treatment (Table 9.2) [16, 44].

Table 9.2 CRPS severity score
Full size table

The clinical progression of the disease can usually be divided into three stages:

  1. 1.

    An acute early stage, with inflammatory symptoms

  2. 2.

    Dystrophic stage characterized by a gradual decrease in edema

  3. 3.

    An atrophic stage can then be seen in which atrophy and skin contractions become common

The first symptoms usually appear within a few weeks after the injury and the affected limb is very painful, erythematous, swollen, and warm. Allodynia, hyperalgesia, trophic changes in the skin and nail growth, and muscle weakness may be present. The affected area is limited and does not have a specific nerve distribution. As the disorder progresses, the pain exacerbates and spreads. Voluntary motor control decreases, negative sensory symptoms (hypostasis, hypoalgesia, and hypothermia) develop, and the limbs become cold, dark, and sweaty. Myoclonus, tremor and dystonia may also occur. Over time, the clinical symptoms can spread to other parts of the body even affecting the contralateral or bilateral sides. A subset of patients with CRPS becomes chronic, and after a long period of illness (>5 years) develop other features such as urological symptoms, syncope, and even mild cognitive impairments. The acute phase and dystrophy are reversible, while the form of atrophy is irreversible [45].

Three distinct vascular regulation patterns related to the duration of the disorder were also identified:

  1. 1.

    In the “warm” (acute) pattern, the affected limb was warmer and the amount of perfusion was greater in CRPS limb.

  2. 2.

    In the “moderate” pattern, the limbs were either warmer or colder.

  3. 3.

    In the “cold” (chronic) pattern, skin temperature and perfusion were lower.

It is suggested that in CRPS I, unilateral inhibition of sympathetic vasoconstrictor neurons leads to warmer limb in the acute phase. Secondary changes in neurovascular transmission may lead to vascular contraction and cold skin in chronic CRPS I, while sympathetic activity is still depressed [46].

Three possible subtypes of CRPS is also described that is useful clinically:

  1. 1.

    Relatively limited syndrome with predominant vasomotor symptoms,

  2. 2.

    Relatively limited syndrome with predominant neuropathic pain/sensory abnormalities,

  3. 3.

    Florid CRPS syndrome, described as “classic RSD”

Subgroup 3 showed the highest levels of motor/trophic symptoms and possible changes due to osteopenia in bone scans, despite the shortest duration of pain in the three groups. The EMG/NCV test indicates that subgroup 2 may reflect CRPS-Type 2 [2].

Diagnosis

The diagnosis and treatment of CRPS has been a challenge to health care providers. Diagnosis is based upon criteria obtained from the medical history and physical examination. Due to the great clinical diversity and heterogeneity of the cause, the diagnosis is not easy. There are many non-standard diagnostic benchmark systems. The new diagnostic criteria were developed by the International Association for the Study of Pain (IASP) based on classification in the consensus workshop in 1994. Subsequent validation research using these criteria have encountered problems differentiating the disease with the possibility of over-diagnosis. In the fall of 2003, diagnostic criteria were reviewed in Budapest which were adopted in 2012 as a new international standard for the diagnosis of CRPS by the IASP and could reduce the CRPS diagnosis by about 50%. The most commonly used criteria are the main IASP criteria and the modified Harden and Bruehl’s diagnostic criteria. The criteria described by Veldman are often used in the Netherlands (Table 9.3). All criteria are essentially empirically determined and have overlapping parameters to some extent. However, the IASP criteria is the most sensitive, while the modified criteria according to Harden and Bruehl is the most specific [16, 42, 47].

Table 9.3 Different diagnostic criteria for CRPS
Full size table

No diagnostic test is considered definitive for CRPS, there are no laboratory tests to diagnose or eliminate it completely. However, other methods can help with the diagnosis. Thermography may be the most common and the most basic diagnostic method used wherein changes of 1 °C or more are considered diagnostic [48].

Standard radiographs can be normal in the early stages (bone mineral depletion occurred within 3–6 weeks of the onset of symptoms, and this change may continue for up to 2 years after the symptoms have resolved). In the absence of clinical signs (autonomic changes and dystrophy) and radiographic examination findings, further tests such as MRI and scintigraphy are done for accurate evaluation. MRI imaging scans show low signal intensity in T1-w images and high signal intensity in STIR or T2-w fat suppression images. These changes indicate an increase in the intracellular and extracellular fluid of the bone marrow, which results from the formation and repair of bone (differential diagnosis on MRI should be made for infection, osteonecrosis, and post-traumatic brain edema). A three-stage bone scan may be positive a few days after the onset of symptoms. Tc99m-MDP increases uptake, indicating a focal increase in capillary permeability, hyperemia, and osteoblastic activity [49]. Three-phase bone scan may show increased absorption of technetium Tc99m bisphosphonate due to increased bone metabolism, although it has no benefit in the management of CRPS and should not be used as a confirmatory measure [50, 51].

Electromyography has shown some validity in some specific patients. Myoclonus, which occurs in CRPS patients, is thought to be distinct from other types of myoclonus and may be detected by electromyography. However, only 11–36% of patients showed myoclonus, greatly limiting its sensitivity as a diagnostic tool [52].

Musculoskeletal ultrasound can also be used to describe physical differences in muscle tissue in CRPS patients, CRPS-affected muscles have significant myoglobular deviation, whereas muscles affected by chronic neuropathic pain have a normal structure [53].

Painful hypersensitivity in persistent CRPS is maintained by autoantibodies, which act by sensitizing pain receptors A and C. Twenty-seven (33%) of the 82 CRPS patients whose serum was available tested positive for ANA, indicating that autoantibodies may be associated with the pathophysiology of CRPS, at least in a subset of patients [54, 55].

Treatment

CRPS treatment guidelines recommend a multidisciplinary approach including physiotherapy, occupational therapy, and psychotherapy (with coping mechanisms for pain, relaxation training, thermal biofeedback, and graded exposure therapy) to improve movement, mobility, quality of life, and the patient ability to manage pain [56]. The graded motor imagery and mirror therapy have the best available data that could improve pain and function in CRPS I patients [57].

Intense exercise therapy is critical to the effective treatment of CRPS and the reduction in the reported high incidence of recurrence in patients treated with physiotherapy alone and cognitive-behavioral therapy. Electrical nerve stimulation (TENS) reduces CRPS 2 pain and when delivered contralateral to a nerve injury best reduces allodynia in a combination of high- and low-frequency [58]. Many CRPS 1 patients receiving neurofeedback training report a significant short-term reduction in their pain experience as well as improvement of symptoms [59].

Pharmacologic Therapy

Based on overlapping pathophysiologic mechanisms of CRPS different pharmacological treatment is recommended. Commonly used drugs are nonsteroidal anti-inflammatory drugs (NSAIDs) such as naproxen or ibuprofen, tramadol, antidepressants such as amitriptyline, doxepin or trazodone; anticonvulsants (e.g. gabapentin), clonidine, clonazepam, baclofen, topical capsaicin cream, lidocaine 5 patch [60].

The effect of NSAIDs in reducing pain in some neuropathic conditions have not been well demonstrated. However, inflammation is involved in CRPS, especially in the early months of the syndrome and may respond effectively to NSAID. Systemic corticosteroids have been studied in various trials and have generally had positive results [61, 62]. A short course of steroids may be indicated in early CRPS with prominent inflammation, but contraindicated for a long course [56].

Neuropathic pain medications for CRPS have not been extensively studied. The use of neuropathic pain medications to treat CRPS is based on their usefulness in the treatment of other neuropathic diseases. Evidence of their use in CRPS is limited; some of these medications include amitriptyline, doxepin, nortriptyline, desipramine, imipramine, and trazodone, serotonin-norepinephrine reuptake inhibitors (SNRIs) duloxetine and venlafaxine. The use of other neuropathic pain medications by pain physicians to treat CRPS is experimental and is based on the preference and experience of each provider [63, 64]. Gabapentin and amitriptyline were effective in reducing pain intensity and improving sleep [65]. Carbamazepine, another anticonvulsant also showed pain relief [66].

Bisphosphonates (e.g., pamidronate, clodronate, alendronate) are one of the most widely used drugs for the treatment of osteoporosis, but as a treatment for CRPS the mechanism of pain relief is unclear. Some theories include the ability of bisphosphonates to modulate inflammation, inhibit the growth and migration of bone marrow cells, and reduce bone marrow acidity [67, 68]. In patients with acute CRPS-1, Neridronate was associated with clinical benefits compared with placebo control group [69].

Anesthetic doses of ketamine, an NMDA receptor antagonist, were used in patients with severe refractory CRPS that was spreading [70]. Intranasal calcitonin showed improvement in pain intensity, but not in all studies [71].

One possible mechanism of CRPS is that it is triggered by an exaggerated inflammatory response to tissue damage caused by the overproduction of oxygen-mediated radicals, so free-radical scavengers (alpha lipoic acid, dimethyl sulfoxide [DMSO], N-acetylcysteine [NAC], and vitamin C) have been studied with some success for the treatment of CRPS [72, 73]. There is also the possibility that vitamin C may be effective in preventing CRPS but due to the varied results and the overall quality of evidence, it is unclear whether vitamin C is generally effective in reducing the prevalence of CRPS after fractures and limb surgeries [74, 75].

Alpha-adrenoceptor antagonists (such as phentolamine, phenoxybenzamine, clonidine, and reserpine) have been used clinically to treat CRPS without good results from prospective randomized trials. Patients who have symptoms of vasomotor hyperactivity leading to cold (intermittent) CRPS may respond to alpha-1 adrenergic blockers such as phenoxybenzamine and trazosine or calcium channel blockers such as nifedipine [43]. Oral clonidine has not been shown to be significantly effective in neuropathic pain and its use is challenging due to its characteristic side effects. It is mostly used as an intrathecal agent [76,77,78]. The transdermal clonidine patch in four CRPS patients with sympathetic pain has shown some benefits. It is also suggested that oral terazosin may be effective in treating sympathetically maintained pain in patients with CRPS. Oral nifedipine or oral phenoxybenzamine was useful for controlling severe vasoconstriction in two uncontrolled cases of patients with CRPS. Intravenous phentolamine has been used to assess pain maintained by the sympathetic, and is not commonly used clinically, however, it may be used to make a diagnosis [77,78,79,80,81,82,83].

Transdermal clonidine and the fentanyl patch, lidocaine patch 5%, eutectic mixture of local anesthetics (EMLA) cream, dimethyl sulfoxide (DMSO), and capsaicin introduced based on their effect on neuropathic pain, but none of which has been directly studied in CRPS. Intravenous lidocaine is used both therapeutically and diagnostically to assess the responsiveness to a subsequent oral sodium channel blocker (e.g., mexiletine, oxcarbazepine, and carbamazepine) [60, 64, 84,85,86]. Bier block with methylprednisolone and lidocaine in CRPS type I does not provide long-term benefit in CRPS. While its short-term benefit is not superior to placebo [87].

There is considerable controversy about the use of opiates to treat chronic noncancerous pain, and this is especially true in CRPS. Opioids are generally thought to be less effective in chronic neuropathic pain conditions than in acute and subacute pain conditions. However, there is good evidence that opiates can reduce pain and improve quality of life in patients with neuropathic pain. However, there are no controlled studies showing long-term improvement in opioid-treated neuropathic pain [88,89,90].

The auto-antigenicity of KRT16 in a murine CRPS model and CRPS patients further reinforce the idea of ​​autoimmune involvement in CRPS, suggesting that new diagnostic tests and treatment strategies may be developed to follow these findings [90]. The use of new immunomodulatory and anti-inflammatory drugs such as thalidomide and lenalidomide (an alpha tumor necrosis factor inhibitor) may offer a new approach to treating CRPS [91]. Low dose naltrexone has unique properties to specifically help the disease cascade of CRPS including attenuation of microglial cells involved in pain transmission, decreased proinflammatory cytokines and toll-like receptor antagonism 4 (TLR4), and stimulation of endorphin secretion. Naltrexone is currently approved for the management of alcohol and opioid disorders. Previous reports have shown that about one-tenth of the dose used for these approved indications may be beneficial for patients with CRPS. A company is developing a new low-dose naltrexone formulation which is due for evaluation [92, 93]. Treatment with low-dose intravenous immunoglobulin (IVIG) may significantly reduce pain in refractory CRPS [94]. Although a trial in 2016 showed that it was “not effective in relieving pain in patients with moderate to severe CRPS between 1 and 5 years of age” [95]. Plasma replacement therapy is also effective in a subset of patients with severe and long-term CRPS [96].

Interventional Therapy

Botulinum toxin type A (BTA) prevents release of acetylcholine from cholinergic nerve terminals, and therefore, intradermal injection of BTX-A has direct analgesic effects in patients with focal chronic neuropathic pain associated with allodynia [97]. BTA-enhanced sympathetic blocks for the treatment of CRPS [98].

CRPS is a very painful condition where patients are unable to move the affected limb much. Because ligaments are very sensitive to immobility, also called stress deprivation, they never heal, although other injuries, such as bone fractures, heal. This unhealed ligament injury continues to activate the sympathetic nervous system, and the patient continues with chronic symptoms, including severe burning pain from CRPS. Ligament relaxation often activates the sympathetic nervous system, and prolotherapy not only relieves pain by stimulating ligament regeneration, but also relieves sympathetic hyperactivity and CRPS-related symptoms [99]. Nerve stimulation which occur through repetitive muscle contractions and a sudden change in the direction of the sensory nerves move between the muscular and facial layers. Cutaneous nerve trauma may cause nerve edema in the proximal and distal regions of the lesion. With perineural prolotherapy, dextrose binds to presynaptic calcium channels and prevents the release of nerve-damaging peptides, thereby reducing nerve inflammation, restoring the normal flow of nerve growth factors, and facilitating nerve repair and produces an almost immediate analgesic effect from hours to days [100]. Stem cell therapy is a new type of regeneration therapy and really an advanced type of prolotherapy. It also has the ability to increase blood flow to damaged tissue and help heal the injured area at the same time. It is a good alternative to RSD treatment and its effect could be monitored by neuro-musculoskeletal thermology [101].

Part of the pathophysiology of CRPS is thought to be related to an autoimmune disorder in the affected limb with an exaggerated response to catecholamines which subsequently causes pain. Sympathetic blocks may facilitate the ratio of sympathetic pain at that point and be of therapeutic benefit, but they cannot exclude or rule out the diagnosis of CRPS. Stellate ganglion blocks and thoracic sympathetic block (T2–T3) are useful in the treatment of sympathetic block of upper extremity pain and lumbar sympathetic block for the lower extremity. Also, a catheter with a stationary sympathetic chain provides continuous pain relief, while it has no motor or sensory dysfunction and may be very effective in allowing the PT to continue working. Single-shot sympathetic blocks must be coordinated with PT sessions, so the patient is painless in all sessions. The successful block is usually controlled by increasing the temperature of the lower part [102,103,104] (Figs. 9.1 and 9.2).

Fig. 9.1
2 images and a photo. 2 ultrasound scan images depict the lumbar sympathetic block labels listed are, erectoe spine, quadratus lumborum, and transverse process. A photo depicts the lower back of a person.

Ultrasound-guided lumbar sympathetic block at L3 inter-transverse space. After visualization of the transverse process by turning the medial side of the probe clock-wise in order to see the anterior border of the vertebral body and psoas muscle. Arrow heads point to a needle shaft and a yellow star shows the anterior fascia of the psoas major muscle. Ps psoas major muscle, QL quadratus lumborum muscle

Full size image
Fig. 9.2
A photo and an image. A photo depicts a scan being performed on a patient. An ultrasound scan image depicts a thoracic paravertebral block, and the labels listed are, superior costotransverse ligament, and transverse process.

Ultrasound-guided thoracic paravertebral (between the T2 and T3). After passing the ligament, inject drug

Full size image

Brachial plexus block is used to treat the somatic part of the CRPS-affected upper limb pain. Different approaches to the current block exist including the supraclavicular block, interscalene block, axillary block and the infraclavicular block with the latter being the most common. Continuous popliteal blocks, sciatic peripheral nerve block and saphenous peripheral nerve blockade are of use in treating the somatic part of CRPS lower extremity pain. Continuous epidural analgesia allows a similar level of pain management for PT. Continuous peripheral nerve catheters reduce pain and facilitate intensive physiotherapy and practical rehabilitation, they resulted in resolution of physical changes associated with CRPS and a decrease need for pharmacological drugs, including opioids. Peripheral nerve blockade treats the symptoms. However, it cannot suppress activity at the dorsal root ganglion and it does not address the chronic sensitization within the disease process. Peripheral nerve catheters have the advantage of continuous epidural infusion and can be used in upper extremity disease, provide unilateral analgesia, provide limited and localized sympathetic blockade, and have no effect on bladder or bowel function. However, continuous peripheral nerve block should be more comfortable at home than continuous epidural analgesia. The use of disposable pumps reduces hospitalization such that this treatment can be continued at home. Stationary epidural catheters, although usually effective in relieving pain, cause additional motor block and/or sensation that the patient cannot participate in PT effectively. This may be harmful because any limb immobilization appears to worsen CRPS [105,106,107,108,109].

For patients with upper extremity CRPS type 1 who experience incurable neuropathic pain that is largely limited to the distribution of a peripheral nerve may benefit from implantation of a percutaneous PNS when other options have failed and thus provide pain relief. Peripheral nerve stimulation to the left ulnar nerve may be used for the treatment of patients with complex type 1 pain syndrome following injury to the left fifth finger [110]. Peripheral nerve stimulation is a useful way to improve function and reduce long-term pain in patients who suffer from CRPS types I and II [111]. Wireless peripheral nerve stimulation (WPNS) has unique properties due to its minimally invasive technique. This system does not involve implanting a battery or its connections. In the case of CRPS I, which affects the upper extremities, a WPNS with radial and median nerve coverage provides good pain relief [112]. The plexus stimulation, such as brachial plexus stimulation, has long been used in the treatment of complex regional pain syndrome of the upper extremities [113]. In refractory cases, neuromodulatory option such as SCS stimulation or DRG stimulation may be considered, in very elite cases. Sympathectomy is also useful for this condition [105, 108] (Figs. 9.3, 9.4, and 9.5).

Fig. 9.3
A scan image of the percutaneous peripheral nerve with the labels, stimulator lead, and ulnar nerve long axis, and a photo of a person’s hand.

Administration of percutaneous peripheral nerve stimulation in CRPS Type 1 following a crush injury to the fifth digit

Full size image
Fig. 9.4
2 scan images depict the S C S lead position.

SCS lead position; the catheter enter from T6 and 7 interspaces with final position at the right side of the C3 body in a refractory case of right arm CRPS

Full size image
Fig. 9.5
3 scan images in C R P S.

CRPS recurrence 2 years after midtibial amputation, L4 dorsal root ganglion stimulation achieved substantial pain relief after a failed trial of SCS

Full size image

Neuropathic pain is defined as “pain from a lesion or disease of the somatosensory system.” Deep brain stimulation (DBS) has been the central implantable nerve stimulation of choice for chronic pain. Some neurosurgeons advocate DBS and its newer target, the anterior cingulate cortex (ACC), while stimulating the motor cortex as “the hall’s last chance” [114]. There are good evidences for interventional therapy of CRPS (Table 9.4) [43, 115].

Table 9.4 Evidence based medicine for interventional pain management in CRPS
Full size table

Algorithmic Approach to CRPS Pain Management

The primary treatment of CRPS consists of early active mobilization by physical therapy combined with pharmacological pain treatment. An early diagnosis is mandatory for therapeutic success and functional outcome. The therapeutic approach with more possibilities of success in the early stages is primarily pharmacological. When conservative treatment with physical and medical treatment fail, multidisciplinary evaluation should be considered. Physical therapy with active mobilization and graded motor imagery treatment, together with a symptom oriented pharmacological treatment, is the best initial approach of CRPS. When there is no improvement in pain and dysfunction, interventional pain management including sympathetic blockade may be performed. If this block is effective, it may be followed by repeated injections or RF treatment. If symptoms persist, a continuous epidural infusion, intermittent or continuous plexus brachialis block in combination with exercise therapy may be useful. And in refractory cases, SCS after a successful trial stimulation period may yield positive results [43] (Fig. 9.6).

Fig. 9.6
An algorithm depicts the C R P S pain management. The steps are, complex regional pain syndrome, other diagnoses are excluded. If no, check differential diagnosis list. If yes, start active physical therapy and which mechanism is prominent to start pharmacological therapy. Inflammation: anti inflammatory therapy. If not, start psychological support and diagnostic block of truncus sympathicus. Positive effect: R F sympathetic block. Negative effect: somatic or central neuraxial block, peripheral nerve block, botox injection, regeneration therapy. P N S, S C S, D R G S, and surgery.

Algorithmic approach to CRPS pain management

Full size image

Conclusion

Currently, there are no drugs approved by FDA specifically for the treatment of CRPS. Early diagnosis is still the key in the success of therapeutic intervention. Interventional pain management in CRPS is a great chance given to us to resolve these difficult cases in the early stages while patients with CRPS have negative bone scans. Chronic CRPS, or a predominantly cold illness are less likely to respond to any treatment modalities [67, 68]. I recommend to start with less invasive and less expensive intervention especially in low income country and a judicious use of any intervention regardless of the country of origin as soon as possible without leaving these cases unsolved.