Introduction

Complex regional pain syndrome (CRPS) is a chronic neurological condition that usually manifests in the upper or lower extremity, either from a traumatic event or unknown origin. Signs and symptoms of CRPS include sensory and autonomic nervous system disturbances such as allodynia, hyperalgesia, edema, changes in skin perfusion or abnormal sudomotor activity. Trophic changes to the skin, hair, and nails as well as motor dysfunction such as weakness, dystonia, and tremors of the affected limb are also reported. CRPS is typically a diagnosis of exclusion, but the Budapest Criteria created in 1999 and updated in 2007 is the most recent and specific diagnostic criteria available for CRPS.1

There are currently three classifications of CRPS: Type I, Type II, and Not Otherwise Specified (NOS). Type I CRPS is characterized by three stages of disease progression. Stage 1 (acute phase) is characterized by burning pain that last up to 3 months. Stage 2 (dystrophic phase) consists of swelling of affected limb and last between 3-12 months. Stage 3 (atrophic) includes soft tissue changes to the affected limb, such as pale, dry, tightly stretched and shiny skin, muscle atrophy, and tendon retraction. This stage typically occurs 1 year after onset.1 Type II CRPS, previously referred to as causalgia, includes the same signs and symptoms as Type I but also involves major nerve damage.2 When neither criterion for Type I nor Type II is met, it is classified as NOS.1

CRPS occurs in 5.4-26.2 per 100,000 people with 70% of cases occurring in the upper extremity. Most cases are CRPS Type I (88%) and occur in females (71%), with an increased risk in post-menopausal females.2,3 Other risk factors include upper extremity trauma, high-velocity trauma, distal limb involvement, and surgically repaired fractures.3

The mechanism behind the development of CRPS is not fully understood, involving the central, peripheral, and autonomic nervous system.3 Through a cascade of upregulation of peripheral afferents, the spinal cord becomes hypersensitive to excitation and increases firing of neurons as well as causing continued activity of the neurons after the stimulus has stopped. This phenomenon is called central sensitization. Central sensitization is maintained by the increased nociceptive input, amplification of this input, and subsequent increased catecholamine release. Mechanical allodynia, characteristic of CRPS, is theorized to be caused by central sensitization.2,4

The central changes that occur in CRPS manifest in the cerebral cortex as well as the midbrain. Cortical gray matter atrophy is observed in patients with CRPS, specifically in the parietal lobe, ventromedial prefrontal cortex, anterior insula, and nucleus accumbens.5,6 These changes in cortical gray matter are termed cortical reorganization and will present as body distortions, lateralized spatial cognition deficits, and disruption of broad cortical neurons.7 Alterations such as these can also contribute to the loss of intracortical inhibition (termed cortical disinhibition) which when paired with central sensitization, contributes to cortical reorganization.8 The reorganization of the parietal lobe is of particular importance in patients with CRPS, as it contributes to the formation of the body schema. Body schema is created by a combination of proprioceptive, somatosensory, vestibular, and other sensory inputs that is then integrated with motor programming to control movement effortlessly. With CRPS, the primary somatosensory cortex of the affected limb is smaller in comparison to the unaffected limb and can explain why 60% of CRPS patients report loss of ownership, recognition, and awareness of the affected limb.6,7 Additionally, the increased activation of the dorsomedial prefrontal cortex indicates that movement is anticipated to produce pain and movement planning becomes linked to pain anticipation. Through more associative learning processes, pain is created through nonnocipetive networks.8,9 This is further supported by the increased resting cerebral blood flow seen on arterial spin labeling in the primary motor cortex, supplemental motor area, and dorsal precuneus which suggests a hypervigilance to movement.9

This narrative review aims to summarize current literature involving the treatment of CRPS through neuromodulation therapies, including mirror therapy, graded motor imagery, cognitive behavioral therapy, and hypnosis. It appears that the largest driver of pain and disability in this patient population stems from altered neural connections in the form of cortical reorganization and central sensitization. Due to the common neural pathways involved in the cortical reorganization, central sensitization, and neuromodulation therapies, it is important to establish the efficacy of these therapies and practicality in treatment.

Methods

A search of articles was conducted on PubMed and MEDLINE Complete. Articles from January 1, 2015 to August 6, 2021 were searched using 6 search terms. The string terms used are the following:

  • Mirror therapy and complex regional pain syndrome

  • Graded motor imagery and complex regional pain syndrome

  • Cognitive behavioral therapy and complex regional pain syndrome

  • Psychotherapy and complex regional pain syndrome

  • Hypnosis and complex regional pain syndrome

Inclusion and exclusion criteria for articles selection is listed below:

Inclusion Criteria

  • Published within 6 years (2015).

  • Meta-analysis, systematic reviews, randomized control trials, case series, case reports.

  • Upper or lower extremity presentation of disease.

  • Conservative neuromodulation and psychological interventions: mirror therapy, graded motor imagery, cognitive behavioral therapy, hypnosis.

Exclusion Criteria

  • Animal studies.

  • Pediatric studies.

  • Study protocols/proposals.

  • Not translated to English.

  • Surgical intervention (spinal cord stimulation).

After each search, each article was evaluated for relevance and if there was duplication of an article in the search. From the search, a total of 208 articles were reviewed by one author, and it was determined that 21 articles met the inclusion criteria. It was recorded when the same article was a result of different search terms (Table 1). Three authors then reviewed the included articles.

Table 1
Table 1

Results

A PubMed search of ‘complex regional pain syndrome AND mirror therapy’ yielded 31 articles and a MEDLINE Complete search of the same string terms yielded 24 articles. Titles and abstracts of these articles were reviewed for relevance and duplication. Our search yielded 9 articles that met the inclusion criteria with the search term ‘complex regional pain syndrome AND mirror therapy.’ In the search, there were 5 systematic reviews, 2 randomized controlled trials, 1 review, and 1 case report.

A PubMed search of ‘complex regional pain syndrome AND graded motor imagery’ yielded 20 articles and a MEDLINE Complete search of the same string terms yielded 20 articles as well. Our search yielded 10 articles that met the inclusion criteria with the search term ‘complex regional pain syndrome AND graded motor imagery’. In this search, 5 articles were duplicates and included in the ‘mirror therapy’ search, as graded motor imagery includes mirror therapy in its protocol and are often employed together. In the search, there were 4 systematic reviews, 1 review, 2 trials, 2 case reports and 1 survey.

A PubMed search using the search ‘complex regional pain syndrome AND cognitive behavioral therapy’ yielded 21 articles, and 47 when using the search ‘complex regional pain syndrome AND psychotherapy’. A MEDLINE Complete search using the same string terms yielded 15 and 26 articles. Of this search, 8 articles met the inclusion criteria, with 2 systematic review, 4 reviews, 1 randomized controlled trial, and 1 case report. One article was also included in the mirror therapy and graded motor imagery search, and one article was included in the hypnosis search.

A PUBMED search using 'complex regional pain AND hypnosis yielded 2 articles and a MEDLINE Complete searching using the same string terms yielded 2 articles. Both articles met the inclusion criteria, and one is a duplicate in the cognitive behavioral therapy search.

Discussion

Mirror Therapy

Mirror therapy is a treatment used in phantom limb and chronic pain cases where the patient observes movement of their healthy limb in a mirror while the affected limb is hidden in a box.10 It is theorized that manipulating the perceived size of the CRPS affected limb can modulate movement-related pain and swelling.7 This is done by correcting cortical body maps and body schema to remove the mismatch between motor control, proprioception, and visual feedback.6–8,11

The included systematic reviews have conflicting reports regarding the effectiveness of mirror therapy as a treatment for CRPS. Méndez-Rebolledo et al. and Thieme et al. report no positive effects with the use of mirror therapy in the treatment of pain in CRPS.12,13 However, Méndez-Rebolledo et al. evaluated a total of 6 articles regarding mirror therapy and does not address CRPS Type II.12 Thieme et al. reports that there is weak evidence and reports that post-stroke CRPS is the most promising subcategory of patients to benefit from mirror therapy.13 In contrast, 3 other systematic reviews report that mirror therapy is effective for the treatment of CRPS in relation to decreased pain, improvement of function, and shorter hospital stays per Duong et al.14–16 However, Żyluk et al. contains the caveat that their report concluded bisphosphonates are the only intervention with consistent positive results.15 Another pattern noted within the systematic reviews was the mention of CRPS Type I due to stroke as a subcategory of CRPS that responded more to certain interventions. Thieme et al., Castelnuovo et al., and Smart et al. each report that this subcategory of patients is the most likely to benefit from mirror therapy and have more improvement compared to other therapies.13,14,17

The 2 RCTs included in this review both show improvement in pain, body schema, and improved function with mirror therapy. Kotiuk et al. specifically addressed the effect of mirror therapy on body schema perception in CRPS I patients and found that 83% of the mirror therapy treatment group experienced improvement in body schema perception compared to the control group who received exercises and medication only. However, evaluation of function and pain were not included in this report.18 Purvane Vural et al. evaluated the effect of mirror therapy on pain, function, and spasticity in post-stroke patients with CRPS I of the upper extremity. Compared to the control group, the mirror therapy group experienced a decrease in pain, improved function, and shorter hospital stays. Limitations of this study include that it is specific to post-stroke patients, outcomes were only evaluated twice, and brain imaging was not employed.19

The reviews included in this study both report benefit from the use of mirror therapy in the treatment of CRPS, specifically in post-stroke patients, and that the effect mirror therapy has on patients supports the role of multisensory conflict in the presentation of symptoms and the ability to correct this. Castelnuovo et al. emphasize the effect mirror therapy has on central reorganization and multisensory involvement of CRPS, specifically supporting the use of mirror therapy in the treatment of post-stroke patients with CRPS. However, there is a bias in that they looked at available data that supported the use of mirror therapy and other neurorehabilitation therapies.17 Kuttikat et al. reviewed the role of somatosensory perceptual disturbances with a focus on top-down processing mechanisms, and states that the effect of mirror therapy on patients with CRPS supports the role of multisensory conflict in patient presentation and symptoms.6 Similar to Kotiuk et al., body schema and multisensory conflict reflect the central organization present in CRPS that can be mediated by mirror therapy, further supporting the rationale for employing these techniques.6,18

The case report included in the search regarding mirror therapy supports its use in both short-term and long-term recovery of CRPS. It involves a 57-year-old female who developed CRPS following an inversion sprain and avulsion fracture of the right talus. Her treatment consisted of pain neuroscience education, graded motor imagery with mirror therapy, and graded functional exposure. In 26 visits over 9 months, she recovered function and strength and reported decreased ankle pain. These gains were still present in a two-year follow-up.20

Based on these findings, mirror therapy can be effective in the treatment of CRPS. The subpopulation of CRPS Type I due to stroke shows more improvement with mirror therapy than other subpopulations of CRPS. Multisensory conflict and cortical reorganization appear to be correctable through mirror therapy, though more studies that use mirror therapy as an isolated intervention are needed to further establish efficacy. It should be noted that the case reports and trials were published after most of the reviews and systematic reviews, demonstrating how newer research is perhaps changing previously established efficacy of these treatments.

Graded Motor Imagery

Graded motor imagery is an extension of this therapy. It is a three-step process that includes laterality training, imagined hand movements, and mirror therapy. It is applied in sequential order without movement. Laterality training involves the patient performing right and left discrimination of a photographed limb. Imagined hand movements has the patient mentally replicate a photographed limb position. Mirror therapy will then be performed once patient progresses with imagined hand movements. Advancements in graded motor imagery is the patient performing actual movement of the CRPS affected limb.10

The 4 systematic reviews included in the search have conflicting reports on the use of graded motor imagery (GMI) in the treatment of CRPS. Méndez-Rebollado et al. reports that there is insufficient evidence to recommend GMI over other therapies due to the limited amount of published evidence available.12 Thieme et al. found conflicting reports in the articles they reviewed, with 2 studies reporting improvement in symptoms with GMI and 5 studies reporting insignificant effects of the intervention.13 Żyluk et al. and Smart et al. both found that graded motor imagery improved pain and disability associated with CRPS.13,14 Included in the Żyluk et al. systematic review were 18 RCTs that found GMI beneficial for CRPS pain and functional disability, but still found bisphosphonates as the only intervention with consistent positive effects.15 Contained within the Smart et al. is low quality evidence in favor of GMI in the treatment of CRPS.14

The 2 trials included in the search also present conflicting results. Elomaa et al. reported on a nonrandomized controlled trial of 12 weeks of multidisciplinary interventions consisting of rehabilitation exercises, 7 weekly cognitive behavioral sessions, weekly GMI, and pharmacological therapy of oral morphine and memantine of gradual increased dosage in addition to the standard neuropathic pain medication. After the trial, patients reported experiencing some improvement in symptoms such as motor function but pain at rest, distress, and quality of life remained unchanged. However, this study reported a high incidence of side effects due to the medication and because so many interventions were employed it is difficult to determine which therapy provided relief.10 Strauss et al. evaluated the amount of functional activation of the brain during hand judgement tasks for GMI therapy using functional magnetic resonance imaging (fMRI). Graded motor imagery was recommended to be performed at least 10 minutes every waking hour and new fMRI studies were taken at intake, week 6, and week 12 with regions of interest identified as primary motor, primary somatosensory, right intraparietal sulcus, bilateral putamen/ventral striate/accumbens, and bilateral anterior insula. Results of this study found that pain at rest was unchanged, but time of recognition during hand lateralization improved significantly, indicating an improvement in spatial relationships. There were also changes in activation of regions of interest that correlated with decreases in pain with movement.21 This supports the evidence that suggests cortical reorganization contributes to the symptoms of complex regional pain syndrome and that they can be reversed through GMI.

Only 1 review was included with our search. Birklein et al. looked to outline the diagnosis and treatment of CRPS. Multiple therapies are mentioned for their ability to help overcome central reorganization, included GMI, physical therapy, and pain exposure. In monocentric studies, GMI is effective in treated CRPS symptoms. However, this result was not present in multicentric studies. This again produces mixed results as results in smaller studies are not able to reproduce similar results on a larger scale.22

A total of 2 case reports were included in the search and they both report improvement in CRPS symptoms following GMI. Shepherd et al. was outlined above and found short-term and long-term improvement with the use of GMI as well as mirror therapy for CRPS that developed after an inversion ankle injury and avulsion fracture of the right talus.20 Quintal et al. presented a case of a 39-year-old male with CRPS of the upper limb following a work-related accident that failed conventional treatment methods. The interventions employed occupational therapist supervised rehabilitation exercises twice a week for 15 weeks followed by once a week for the remaining 80 weeks (22 months total), home exercises to be managed by patient, TENS, cryotherapy, and continuation of previously prescribed pregabalin and celecoxib. The rehabilitation exercises consisted of GMI and somatosensory rehabilitation of pain method. Consistent improvement in all measured outcomes were present following treatment, though still below normal values. However, patient compliance was an issue as he refused to progress to stage 3 of graded motor imagery due to pain. It is also possible that improvement in symptoms would have been seen with or without intervention after 22 months. GMI was also used in combination with other therapies, so it is not certain that this intervention or time period was responsible for the improvement seen.23

The included survey in this review was published in response to the Cochrane Review by Smart et al. The aim as to develop best practice guidelines by first identifying diagnostic criteria used, rehabilitation-based treatments currently being used by practitioners, and clinical experience with these treatments. Results of the survey found that one third of practitioners do not use any diagnostic criteria for CRPS, and mirror therapy and GMI were used less often than patient education and physical activity, contrary for current practice guidelines. This was due to the lack of confidence of practitioners in the efficacy of mirror therapy and GMI based on clinical experience of the practitioner. The survey itself does not evaluate the efficacy of the proposed treatment but shows lack of confidence in proposed treatment options.24

Based on the literature reviewed, GMI is an effective therapy for the treatment of CRPS. Due to graded motor imagery being an extension of mirror therapy, it must be mentioned that mirror therapy and GMI are used in conjunction with each other and there are few studies that address graded motor imagery alone. As stated previously with mirror imagery, GMI is often not used as a solitary intervention and more studies are warranted to further establish its efficacy as a solo intervention. It should be noted here as well that the case reports and trials were published after the reviews and systematic reviews, creating room for updating systemic reviews or meta-analyses.

Cognitive Behavioral Therapy

Psychological treatment addresses multiple factors implicated in chronic pain. It focuses on treating co-presenting anxiety and depression, improving the psychological state of the patient that may be contributing to the maintenance of the central sensitization, and reducing the amount of pain perceived by activating descending inhibitory pathways.17 Psychological stress is associated with altered immune function and increased levels of circulating proinflammatory cytokines that contribute to CRPS, driving the peripheral neurogenic neuroinflammation.2,5 Catastrophizing and negative emotional affect also contribute to the alterations of cytokines, further compounding the proinflammatory state of CRPS.2

Cognitive behavioral therapy (CBT) targets these altered neural connections by promoting brain plasticity to reduce feelings of helplessness, uncontrollability, establish a sense of control over pain, and create behaviors that limit the impact of pain on quality of life.8

The 2 systematic reviews both address the lack of evidence for the use of CBT to treat CRPS and the potential for future use. Żyluk et al. was summarized previously in the graded motor imagery and mirror therapy. Though they do not specifically address CBT and CRPS, they note improved psychosocial well-being in addition to restoration of function following physiotherapy due to improvement of activities and daily living and pain coping. In addition, they note that many interventions do not have sufficient evidence in literature but are often utilized in practice, such as CBT.15 In contrast, Kregel et al. supports the use of CBT in cases of chronic musculoskeletal pain and CRPS. This systemic review specifically included articles that used brain-based images following conservative therapy. A total of 9 articles were included in their study and they concluded that that the use of CBT correlated with functional and structural changes in the prefrontal areas of the brain and was associated with pain management and control, anxiety, and catastrophizing. These changes and associated effects of CBT supports the theory that increased activation of prefrontal areas such as the dorsolateral and ventrolateral prefrontal cortices have a role in descending modulatory pain pathways. However, the articles included had a small sample size and only 2 RCTs were included in their analysis.25

Four reviews were included in the search, one of which is included with mirror therapy and hypnosis. Rand et al., Castelnuovo et al., and Greenwald et al. both support the use of CBT to treat CRPS.17,26,27 However, Rand et al. and Castelnuovo et al. specifies that it should be used as a complementary therapy to help tolerate the physical modalities rather than address the cortical reorganization present in CRPS. They recognize the importance of active self-management strategies and how CBT can help with this by increasing self-efficacy, therefore it should be implemented early in the treatment program as a part of interdisciplinary care.17,26 Greenwald et al. also recommends that CBT should be utilized in the treatment of CRPS due to the neurological mechanisms behind the development and perpetuation of CRPS symptoms. They propose that a weekly session of CBT containing psychoeducation on learned mechanisms of avoidance, cognitive restructuring through reappraisal, attention diversion, and self-regulatory skills is recommended as a holistic mind-body approach to CRPS and other chronic musculoskeletal pain disorder. However, this is only a proposal for treatment based on neuronal mechanisms involved in CBT and CRPS and does not evaluate the effectiveness of the therapy, and it does not specify a duration for the weekly CBT sessions.27 Kessler et al. suggests the use of CBT to treat co-presenting psychiatric disorders in patients with CRPS. Their report found 16% of patients with CRPS had depression and two-thirds of these patients were also diagnosed with at least one psychiatric disorder. They report that these comorbidities present a barrier to recovery and the use of CBT can help address these issues. The study does not report on the use of CBT to treat the cortical reorganization and altered descending neuromodulatory pathways.28

One non-RCT trial was included in our search, found no statistical significance in results with the use of CBT to treat CRPS, reporting increased coping mechanisms following CBT but no statistically significant changes in psychological symptoms were reported. Psychological symptoms reported were depression, anxiety, and pain-related fear. Though improvement was noted in each symptom following 12 weeks of care, it did not reach statistical significance.10

One case report was included in the search. Vargovich et al. reported the case of a patient with chronic upper extremity pain following the failure and removal of a spinal cord stimulator. For 20 days, this patient underwent interdisciplinary care for 6 hours a day, 5 days a week. His treatment consisted of 3 hours of physical rehab and 3 hours and psychological rehab per day, with a weekly medical appointment and 1-2 individual psychotherapy sessions per week. At the end of care, the patient reported a decrease in pain intensity, pain interference, and active distress, all of which were still present at the 6-month follow-up. It was also reported that the interdisciplinary care he received brought more pain relief than the spinal cord stimulator. This supports the use of CBT as a complementary therapy to CRPS, but it is a case report and results may not be applicable to larger populations. The number of interventions and high frequency of care also creates a limitation as it creates confounders, and the patient may have improved in time following surgery.29

Based on the articles included in the search, CBT should be utilized in the treatment of CRPS at least in the role of a complementary therapy. CBT appears to provide benefit for multiple facets of patient care, such as pain coping and fear avoidance, treating co-presenting psychiatric disorders, or addressing the cortical reorganization that occurs in CRPS. However, it must be distinguished within future research whether the psychiatric disorders such as anxiety and depression were present before or after the onset of CRPS. These disorders present both as a risk factor for developing CRPS or develop in response to CRPS. Further research is needed to address the role of CBT in both scenarios.

Hypnosis

Hypnosis is defined as a procedure in which a health professional or researcher suggests that a patient experiences a change in sensations, perceptions, thoughts, or behavior. It is made up of three elements: absorption, dissociation, and suggestibility. Through these three components, the patient is able to be fully involved in an idealization experience, create a mental separation of components of an experience that are usually processed together, and comply with hypnotic instruction.30 Also, it will train the patient to manipulate their focus to pain reduction and self-regulation in the pain experience.31 Often in cases of CRPS, movement becomes processed with pain though associated learning processes. Hypnosis aims to separate these components and decrease the amount of central sensitization present. Functional magnetic resonance imaging (fMRI) studies have established that while under hypnosis, there is an increase in functional connectivity between the primary somatosensory, anterior insular, and prefrontal cortices, all with are altered all in CRPS.8,30 Hypnosis also increases corticothalamic modulation of ascending nociceptive input.32

Castelnuovo et al. looked to evaluate the current evidence regarding the use of psychological interventions for pain reduction in neurological diseases. This article was a comprehensive review for the Italian Consensus Conference on pain in neurorehabilitation in 2016. They concluded that hypnosis is recommended for many neurological conditions, such as amyotrophic lateral sclerosis, Parkinson’s disease, Guillain-Barre Syndrome, and human immunodeficiency virus neuropathy, but does not make a statement specific to CRPS.17 Lebon et al., on the other hand, took a retrospective approach to evaluate the efficacy of physical therapy under hypnosis in patients with CRPS type I of the hand or wrist. Twenty patients were included in this study, and they found that after 6 weeks of intervention, patients experienced a reduction in pain, analgesic use was reduced, range of motion, and pinch grip strength was improved.33

Based on the findings in each of these articles, hypnosis could be viewed as an effective therapy for CRPS. The common neural mechanisms in CRPS and hypnosis alone make it worthy of further investigation.

CRPS and Chiropractic

Current literature surrounding the use of chiropractic in the treatment of CRPS is limited, with one literature review and 3 case reports available.34–37 In all these publications, it was stated that the efficacy of chiropractic treatment in CRPS is not established as the data is limited in this area.34–37 Additionally, there is no curative treatment nor predictive pattern of treatment response as spontaneous recovery and exacerbations are common.37 Though chiropractic may play a role in treating musculoskeletal pain caused by altered biomechanics from pain, direct treatment of the affected limb may not always be appropriate. The allodynia experienced in CRPS patients may create limitations to manual therapy as the patient may not tolerate it well.2,4 Osteopenia of the affected limb may also present a limitation in chiropractic treatment as joint manipulation may not be indicated as osteopenia is considered a relative contraindication for manipulation.2,38 However, chiropractic treatment is not limited to manual therapy. Interventions such as therapeutic exercise and mindfulness-based stress reduction may be considered in cases of chronic pain, including CRPS.38

Limitations

Of the randomized controlled trials included, there was varying diagnostic criteria used in the classification of CRPS. Those used were the Budapest Criteria, Veldman Criteria, International Association for the Study of Pain, or no diagnostic criteria was provided. Due to this variability, the inclusion and exclusion of participants in these trials is not consistent and calls into question the actual efficacy for the treatment for CRPS because it is not clear of the participants were accurately diagnosed with CRPS.

The randomized controlled trials also emphasized an integrated, multimodal approach to treatment, creating confounding factors in the efficacy of the treatments as solo interventions. While the results show that when combined with other therapies it can be effective at symptom reduction, it cannot be guaranteed that each therapy would be effective on its own.

With the purpose of this review looking at cortical reorganization and targeted therapies, only one included article had fMRI studies as an outcome measure. fMRI is more demonstrative to cortical reorganization than self-reported symptom reduction and can truly determine if cortical reorganization occurred. Even with patients reporting symptom reduction, it cannot truly be determined if it is due to cortical reorganization or other mechanisms.

Conclusion

Mirror therapy and graded motor imagery appear to be effective interventions in the treatment of CRPS symptoms. Cognitive behavioral therapy appears effective as a complementary therapy, though randomized controlled trials using cognitive behavioral therapy as the primary intervention are needed to evaluate its effect as an isolated intervention. The evidence surrounding hypnosis and CRPS is lacking, as there are no published randomized controlled trials available on the subject. Similar to cognitive behavioral therapy, more data is needed to evaluate the efficacy of hypnosis as a treatment for CRPS. Overall, the more recent published research indicates promising results with each mentioned therapy and an update of the literature is needed.