Mirror therapy for phantom limb pain: Brain changes and the role of body representation

Pain without presence: a narrative review of the pathophysiological landscape of phantom limb pain

Phantom limb pain (PLP) is defined as the perception of pain in a limb that has been amputated. In the United States, approximately 30,000-40,000 amputations are performed annually with an estimated 2.3 million people living with amputations. The prevalence of PLP among amputees is approximately 64%. Over the years, various theories regarding the etiology of PLP have been proposed, with some gaining more prominence than others. Yet, there is a lack of consensus on PLP mechanisms as the current literature exploring the pathophysiology of PLP is multifactorial, involving complex interactions between the central and peripheral nervous systems, psychosocial factors, and genetic influences. This review seeks to enhance the understanding of PLP by exploring its multifaceted pathophysiology, including genetic predispositions. We highlight historical aspects of pain theories and PLP, examining how these theories have expanded to include psychosocial dimensions associated with chronic pain in amputees. Additionally, we present significant findings from both human and animal studies focused on neuroaxial systems and recent advances in molecular research to further elucidate the complex and multifactorial nature of PLP. Ultimately, we hope that the integration of current theoretical frameworks and findings will lay a more robust foundation for future research on PLP.

Evaluating Mirror Therapy Protocols in Phantom Limb Pain Clinical Trials: A Scoping Review

Mirror therapy is among the most widely used treatments for phantom limb pain. However, discrepancies exist in the way it is conducted, and its effectiveness varies widely. The aim of this scoping review was to evaluate the application of mirror therapy across the literature and to identify treatment features unique to studies with clinically significant pain reduction outcomes. Articles published until July 2024 were identified through a systematic search of the following electronic databases: Medline (via EBSCOhost), PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, PsycINFO (via EBSCOhost), Cumulative Index to Nursing and Allied Health Literature (via EBSCOhost), Africa-Wide Information (via EBSCOhost), and Scopus. Two reviewers independently conducted the screening of titles and abstracts, review of full-text articles, and data extraction. The results were analyzed descriptively. We included 32 studies in this review, 21 of which were deemed effective for achieving clinically significant pain reduction of 50% or 2 points on a 0-10 scale. There were inconsistencies in various treatment components including treatment setting, type of pre-treatment education, treatment technique, method of exercise delivery, treatment duration, and frequency of treatment sessions. Despite identifying common treatment features across studies with clinically significant pain reduction outcomes, we found no evidence of unanimous consensus in the literature towards any specific protocol for mirror therapy. Establishing a standardized treatment protocol could enhance the reliability and reproducibility of treatment outcomes in future studies and ensure a meaningful comparison between mirror therapy and other treatments in clinical trials and meta-analyses.

PhantomAR: gamified mixed reality system for alleviating phantom limb pain in upper limb amputees-design, implementation, and clinical usability evaluation

BACKGROUND

Phantom limb pain (PLP) is a restrictive condition in which patients perceive pain in a limb that is no longer present, greatly reducing their quality of life. Mirror Therapy, wherein patients observe a mirror reflection of their intact limb, has demonstrated efficacy in alleviating PLP. However, its unilateral and seated nature presents limitations. To address these constraints while still reducing PLP, and evaluating the impact of different virtual limb representations (anthropomorphic vs. non-anthropomorphic) on the user's sense of ownership, agency, and embodiment, PhantomAR was developed. Leveraging wearable first-person augmented reality (AR) technology, PhantomAR extends traditional Mirror Therapy by enabling users to move freely and engage in bimanual tasks.

METHODS

The assistive mixed reality game application PhantomAR was deployed on the Microsoft HoloLens 2 and augmented the user's residual limb by superimposing a virtual arm or tentacle that was controlled via residual muscles on their stump using an EMG electrode array. This setup allowed patients to engage in a first-person perspective and manipulate virtual objects with both the healthy and augmented limbs, free from the confines of a seated position. The study enrolled 10 able-bodied individuals and 8 individuals with unilateral, transradial amputation. All amputees experienced PLP. The usability of the PhantomAR application was evaluated using the System Usability Scale (SUS) and a user-centric survey. Additionally, the Game Experience was assessed on a 5-point Likert questionnaire (GEQ). Participants rated their phantom sensations using the Numerical Rating Scale and McGill Pain Questionnaire before, during, and after interaction with PhantomAR. The embodiment and agency of the virtual superimposed arm were evaluated with an altered Prosthesis Embodiment Scale. The study protocol included two sessions of 30 min each, during which participants experienced PhantomAR.

RESULTS

Participants (n = 18) rated PhantomAR highly usable (SUS m = 90.8%, SD = 6.88). Feedback on the Game Experience Questionnaire was overwhelmingly positive, showing high immersion (m = 4.46, SD = 0.08) and positive affect (m = 4.97, SD = 0.05). PLP (n = 8) significantly decreased post-intervention (NRS and McGill Pain Questionnaire, p < .001). Skin temperature in the residual limb increased significantly post-intervention (p < .01) but did not correlate with PLP (r = - 0.08, p = 0.83). Tentacle overlay yielded mixed ownership but high agency ratings.

CONCLUSION

PhantomAR leverages mixed reality to significantly reduce Phantom Limb Pain, enhance user engagement, and alter perceptions of ownership and agency of their augmented limb through bi-manual, dynamic, full-body interactions. Trial registration DRKS00033208 (Jan. 5th 2024).

Examining patient reported outcome measures for phantom limb pain: measurement use in a sample of Veterans with amputation

PURPOSE

Phantom limb pain (PLP) is treated with medications and non-drug treatments. Best clinical practices for measuring treatment outcomes have not been defined. The objective of this study was to evaluate the internal consistency of patient-reported outcomes measures (PROMs) in a sample of Veterans with lower limb amputation.

MATERIALS AND METHODS

The Veteran phone survey included administering PROMs [1) PLP numeric rating scale (NRS), 2) general pain NRS, 3) Pain, Enjoyment, and General Activity (PEG) scale, 4) Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference Short Form 6b Replacement, 5) PROMIS Short Form Depression 4a and 6) PROMIS Short Form Anxiety 4a].

RESULTS

Fifty Veterans (48 male, 2 female; average age: 66 years) completed PROMs. In our sample, 40 Veterans (80%) experienced PLP with an average PLP NRS of 5 (±3.4). Internal consistency of each measure was good to excellent based on Cronbach's alpha co-efficient of >0.80. Correlations were moderate between PLP NRS and all other measures (≤0.32). Although many Veterans expressed bothersome PLP, the scores reflecting pain interference and impact on function were lower than pain intensity. Consistent use of outcome measures is needed to determine the effect of interventions for amputation-related pain.

Examining heterogeneity and reporting of mirror therapy intervention for phantom limb pain: A scoping review

BACKGROUND

Mirror therapy shows promise in the treatment of phantom limb pain but lacks robust evidence.

OBJECTIVES

To address this gap, we conducted a scoping review aiming to comprehensively explore the landscape of mirror therapy practice, gather details about the session content, and offer recommendations for future research.

METHOD

We searched seven databases for published work from 1995 to May 2023. Two independent reviewers selected, assessed, and extracted data from eligible articles. Articles, regardless of study design, were considered eligible if they investigated mirror therapy as an intervention for phantom limb pain.

RESULTS

A total of 44 articles were included, comprising 16 randomized control trials, 14 prospective cohort studies, 15 case reports, and 3 protocols. These studies collectively involved 942 patients, with male patients representing 70 % of the participants. Lower limb amputation, primarily attributed to trauma, accounted for 88 % of the included patients. Pain intensity was predominantly assessed by a visual analog scale (61 %). However, there was a notable absence of detailed descriptions regarding mirror therapy sessions, particularly concerning the number of exercises, duration per exercise, and repetitions. Typically, sessions lasted 15 min each, conducted once daily. The exercises primarily focused on motor exercises targeting the distal part of the limb.

CONCLUSION

The practice of mirror therapy was characterized by poor description, showed significant heterogeneity, and a lack of standardized protocols, which contributes to an overall low level of evidence. Addressing these gaps in practice description and standardization is crucial for improving reproducibility and strengthening the evidence base for the prescription of mirror therapy.

Integrating Complementary Therapies in Managing Phantom Limb Pain: A Case Review

OBJECTIVES

This paper describes phantom limb pain (PLP), its impact on patients, and the various treatment options, including pharmacologic and complementary therapies. It investigates the efficacy of incorporating complementary and alternative therapies, both invasive and noninvasive, for amputees who have not achieved satisfactory results with pharmacologic treatments and suffer from adverse drug events. Furthermore, with the predicted increase in limb amputations, it is crucial for nurses, as frontline providers, to understand PLP, be prepared to manage persistent pain and associated psychological and functional issues and educate patients and families about alternative treatment options.

APPROACH

The review includes recent studies on pharmacologic interventions for PLP, case reports, and randomized clinical trials on non-pharmacologic complementary therapies, covering both invasive and noninvasive modalities. Studies from 2013 to 2022 were identified using the PubMed search engine with terms such as "Amputation," "phantom limb pain," "invasive therapies," and "non-invasive therapies."

RESULTS AND CONCLUSION

The pathogenesis of PLP remains unclear, complicating the identification of causes and the selection of targeted therapies for each patient. Uncontrolled PLP can severely impact the quality of life, causing psychological distress and loss of productivity. Traditional pharmacologic therapy often requires supplementation with other options due to PLP's refractory nature. A comprehensive, multimodal treatment plan, including non-pharmacologic therapies, can enhance rehabilitation and reduce complications. Incorporating these therapies can decrease reliance on medications, particularly opioids, and mitigate side effects. Although many potential PLP treatments exist, further clinical studies are needed to determine their effectiveness and establish protocols for optimizing patient outcomes.

Chronic pain for rheumatological disorders: Pathophysiology, therapeutics and evidence

Pain is the leading reason people seek orthopedic and rheumatological care. By definition, most pain can be classified as nociceptive, or pain resulting from non-neural tissue injury or potential injury, with between 15% and 50% of individuals suffering from concomitant neuropathic pain or the newest category of pain, nociplastic pain, defined as "pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage, or of a disease or lesion affecting the somatosensory system." Pain classification is important because it affects treatment decisions at all levels of care. Although several instruments can assist with classifying treatment, physician designation is the reference standard. The appropriate treatment of pain should ideally involve multidisciplinary care including physical therapy, psychotherapy and integrative therapies when appropriate, and pharmacotherapy with non-steroidal anti-inflammatory drugs for acute, mechanical pain, membrane stabilizers for neuropathic and nociplastic pain, and serotonin-norepinephrine reuptake inhibitors and tricyclic antidepressants for all types of pain. For nonsurgical interventions, there is evidence to support a small effect for epidural steroid injections for an intermediate-term duration, and conflicting evidence for radiofrequency ablation to provide at least 6months of benefit for facet joint pain, knee osteoarthritis, and sacroiliac joint pain. Since pain and disability represent the top reason for elective surgery, it should be reserved for patients who fail conservative interventions. Risk factors for procedural failure are the same as risk factors for conservative treatment failure and include greater disease burden, psychopathology, opioid use, central sensitization and multiple comorbid pain conditions, poorly controlled preoperative and postoperative pain, and secondary gain.

Immersive interfaces for clinical applications: current status and future perspective

Digital immersive technologies have become increasingly prominent in clinical research and practice, including medical communication and technical education, serious games for health, psychotherapy, and interfaces for neurorehabilitation. The worldwide enthusiasm for digital health and digital therapeutics has prompted the development and testing of numerous applications and interaction methods. Nevertheless, the lack of consistency in the approaches and the peculiarity of the constructed environments contribute to an increasing disparity between the eagerness for new immersive designs and the long-term clinical adoption of these technologies. Several challenges emerge in aligning the different priorities of virtual environment designers and clinicians. This article seeks to examine the utilization and mechanics of medical immersive interfaces based on extended reality and highlight specific design challenges. The transfer of skills from virtual to clinical environments is often confounded by perceptual and attractiveness factors. We argue that a multidisciplinary approach to development and testing, along with a comprehensive acknowledgement of the shared mechanisms that underlie immersive training, are essential for the sustainable integration of extended reality into clinical settings. The present review discusses the application of a multilevel sensory framework to extended reality design, with the aim of developing brain-centered immersive interfaces tailored for therapeutic and educational purposes. Such a framework must include broader design questions, such as the integration of digital technologies into psychosocial care models, clinical validation, and related ethical concerns. We propose that efforts to bridge the virtual gap should include mixed methodologies and neurodesign approaches, integrating user behavioral and physiological feedback into iterative design phases.

[Digital technologies and strategies in amputation medicine]

Surgical techniques in amputation medicine did not change for a long time, while prosthesis technology underwent rapid development. The focus shifted to optimising the residual limb for prostheses use. At the same time, digital technologies such as gamification, virtual and mixed reality revolutionised rehabilitation. The use of gamification elements increases motivation and adherence to therapy, while immersive technologies enable realistic and interactive therapy experiences. This is particularly useful in the context of controlling modern prostheses and treating phantom pain. In addition, digital applications contribute to optimised documentation of symptoms and therapy successes. Overall, these technologies open up new, effective and personalised therapeutic approaches that can significantly improve the quality of life of amputation patients.

A randomized controlled pilot study examining immediate effects of embodying a virtual reality superhero in people with chronic low back pain

PURPOSE

In virtual reality, avatar embodiment can spur perceptions and behaviours related the avatars' characteristics. We tested whether embodying superhero-like avatars can change self-perceptions in people with chronic low back pain (CLBP).

DESIGN

A non-blinded pilot randomized controlled trial.

METHODS

Participants were randomly allocated to embody a superhero (VR-SH, n = 20) or a neutral, non-superhero (VR-Play, n = 10) avatar. Primary outcomes related to body image (e.g., self-perceived vulnerability) and pain intensity were assessed at baseline, during exposure, immediately after and at one-week follow-up. Fear of movement, strength and patient impression of change were also recorded.

RESULTS

The VR-SH group reported gains in body image during (p < .001,  η p 2 =0.71) and immediately after (p < .001,  η p 2 =0.66) VR, whereas the VR-Play group reported small gains during VR (p = .021,  η p 2 =0.46) but not immediately after (p = .076, η p 2 =0.31). Pain, strength and fear of movement did not change and there were no sustained effects at follow-up (all ps > .05). A greater proportion of people in the VR-SH group reported at least minimal improvement at follow-up (7/20 vs. 1/10).

CONCLUSION

A VR-SH session produced temporary positive effects on body image. Future research may consider whether larger and sustained effects can be obtained with multisession exposures or explore combined interventions. Implications for rehabilitationPhysical confidence and bodily trust can be significantly enhanced in people with chronic back pain using virtual reality.These positive body image effects may have implications for rehabilitation, such as in enhancing confidence with movementWhether a multisession intervention might produce more robust effects and changes in pain is yet to be determined.

Is Phantom Limb Awareness Necessary for the Treatment of Phantom Limb Pain?

Phantom limb pain is attributed to abnormal sensorimotor cortical representations. Various feedback treatments have been applied to induce the reorganization of the sensorimotor cortical representations to reduce pain. We developed a training protocol using a brain-computer interface (BCI) to induce plastic changes in the sensorimotor cortical representation of phantom hand movements and demonstrated that BCI training effectively reduces phantom limb pain. By comparing the induced cortical representation and pain, the mechanisms worsening the pain have been attributed to the residual phantom hand representation. Based on our data obtained using neurofeedback training without explicit phantom hand movements and hand-like visual feedback, we suggest a direct relationship between cortical representation and pain. In this review, we summarize the results of our BCI training protocol and discuss the relationship between cortical representation and phantom limb pain. We propose a treatment for phantom limb pain based on real-time neuroimaging to induce appropriate cortical reorganization by monitoring cortical activities.

Enhancement of sense of ownership using virtual and haptic feedback

Accomplishing motor function requires multimodal information, such as visual and haptic feedback, which induces a sense of ownership (SoO) over one's own body part. In this study, we developed a visual-haptic human machine interface that combines three different types of feedback (visual, haptic, and kinesthetic) in the context of passive hand-grasping motion and aimed to generate SoO over a virtual hand. We tested two conditions, both conditions the three set of feedback were synchronous, the first condition was in-phase, and the second condition was in antiphase. In both conditions, we utilized passive visual feedback (pre-recorded video of a real hand displayed), haptic feedback (balloon inflated and deflated), and kinesthetic feedback (finger movement following the balloon curvature). To quantify the SoO, the participants' reaction time was measured in response to a sense of threat. We found that most participants had a shorter reaction time under anti-phase condition, indicating that synchronous anti-phase of the multimodal system was better than in-phase condition for inducing a SoO of the virtual hand. We conclude that stronger haptic feedback has a key role in the SoO in accordance with visual information. Because the virtual hand is closing and the high pressure from the balloon against the hand creates the sensation of grasping and closing the hand, it appeared as though the person was closing his/her hand at the perceptual level.

Graded motor imagery and its phases for individuals with phantom limb pain following amputation: A scoping review

OBJECTIVE

Three-phase graded motor imagery (limb laterality, explicit motor imagery, and mirror therapy) has been successful in chronic pain populations. However, when applied to phantom limb pain, an amputation-related pain, investigations often use mirror therapy alone. We aimed to explore evidence for graded motor imagery and its phases to treat phantom limb pain.

DATA SOURCES

A scoping review was conducted following the JBI Manual of Synthesis and Preferred Reporting Items for Systematic Review and Meta-Analyses extension for Scoping Reviews. Thirteen databases, registers, and websites were searched.

REVIEW METHODS

Published works on any date prior to the search (August 2023) were included that involved one or more graded motor imagery phases for participants ages 18+ with amputation and phantom limb pain. Extracted data included study characteristics, participant demographics, treatment characteristics, and outcomes.

RESULTS

Sixty-one works were included representing 19 countries. Most were uncontrolled studies (31%). Many participants were male (75%) and had unilateral amputations (90%) of varying levels, causes, and duration. Most works examined one treatment phase (92%), most often mirror therapy (84%). Few works (3%) reported three-phase intervention. Dosing was inconsistent across studies. The most measured outcome was pain intensity (95%).

CONCLUSION

Despite the success of three-phase graded motor imagery in other pain populations, phantom limb pain research focuses on mirror therapy, largely ignoring other phases. Participant demographics varied, making comparisons difficult. Future work should evaluate graded motor imagery effects and indicators of patient success. The represented countries indicate that graded motor imagery phases are implemented internationally, so future work could have a widespread impact.

Use of virtual reality for the management of phantom limb pain: a systematic review

PURPOSE

To summarize the research on the effectiveness of virtual reality (VR) therapy for the management of phantom limb pain (PLP).

METHODS

Three databases (SCOPUS, Ovid Embase, and Ovid MEDLINE) were searched for studies investigating the use of VR therapy for the treatment of PLP. Original research articles fulfilling the following criteria were included: (i) patients 18 years and older; (ii) all etiologies of amputation; (iii) any level of amputation; (iv) use of immersive VR as a treatment modality for PLP; (v) self-reported objective measures of PLP before and after at least one VR session; (vi) written in English.

RESULTS

A total of 15 studies were included for analysis. Fourteen studies reported decreases in objective pain scores following a single VR session or a VR intervention consisting of multiple sessions. Moreover, combining VR with tactile stimulation had a larger beneficial effect on PLP compared with VR alone.

CONCLUSIONS

Based on the current literature, VR therapy has the potential to be an effective treatment modality for the management of PLP. However, the low quality of studies, heterogeneity in subject population and intervention type, and lack of data on long-term relief make it difficult to draw definitive conclusions.IMPLICATION FOR REHABILITATIONVirtual reality (VR) therapy has emerged as a new potential treatment option for phantom limb pain (PLP) that circumvents some limitations of mirror therapy.VR therapy was shown to decrease PLP following a single VR session as well as after an intervention consisting of multiple sessions.The addition of vibrotactile stimuli to VR therapy may lead to larger decreases in PLP scores compared with VR therapy alone.

Physiotherapy: A potential and novel treatment approach for phantom limb pain in post-amputee patients - A systematic review

Objective

To evaluate the efficacy of conventional and novel non-pharmacologic, non-invasive therapeutic interventions in physiotherapy for the treatment of phantom limb pain (PLP) in post-amputee patients.

Methods

A systematic search for the articles was conducted in multiple electronic databases such as PUBMED, Google Scholar, EMBASE, Cochrane library and Physiotherapy Evidence Database (PEDro), following the PRISMA method and only published articles from the last 12 years (2010-2022) evaluating the efficacy of different physiotherapy interventions for the treatment of PLP in post-amputee patients were included. The methodological quality and risk of bias of the articles were assessed and evaluated by two independent reviewers using the PEDro scale, Methodological index for non-randomized studies scale (MINORS), and Cochrane collaboration's assessment tool.

Result

A total of 1840 articles were identified, out of which 17 articles (11 RCTs and 6 pilot studies) were ultimately chosen after the full-text screening. After reviewing the articles, evidence identified in RCTs and pilot studies indicates towards significant improvement in reducing the severity of PLP in post-amputee patients by using different physiotherapy interventions.

Conclusion and discussion

Physiotherapy interventions with advance modalities and exercises can be used to increase the overall effectiveness of the treatment and to reduce the severity of phantom limb pain in post-amputee patients. However, due to the lack of consistent evidence for a given intervention, it becomes even more difficult to reach a majority consensus as to which intervention better assess all the mechanism of PLP thereby alleviating the problem of PLP in post-amputee patients. Therefore, more rigorous randomized controlled trials will be required in the future to reach a conclusion.

Therapeutic management of the painful nerve: a narrative review of common rehabilitation interventions

There are many ways that rehabilitation therapists, including occupational and physical therapists, treat nerve-related pain. Commonly used interventions include neurodynamic treatment, pain neuroscience education, desensitization, exercise, physical agent modalities, mirror box therapy, and Kinesio taping. Despite common practice and anecdotal support, it can be challenging to determine the appropriate intervention for each patient. In this article, each of these treatment approaches is discussed, including indicated pain phenotypes and diagnoses, timing, efficacy, mechanism, contraindications, and limitations.

Cortical Reorganization after Limb Loss: Bridging the Gap between Basic Science and Clinical Recovery

Despite the increasing incidence and prevalence of amputation across the globe, individuals with acquired limb loss continue to struggle with functional recovery and chronic pain. A more complete understanding of the motor and sensory remodeling of the peripheral and central nervous system that occurs postamputation may help advance clinical interventions to improve the quality of life for individuals with acquired limb loss. The purpose of this article is to first provide background clinical context on individuals with acquired limb loss and then to provide a comprehensive review of the known motor and sensory neural adaptations from both animal models and human clinical trials. Finally, the article bridges the gap between basic science researchers and clinicians that treat individuals with limb loss by explaining how current clinical treatments may restore function and modulate phantom limb pain using the underlying neural adaptations described above. This review should encourage the further development of novel treatments with known neurological targets to improve the recovery of individuals postamputation.Significance Statement In the United States, 1.6 million people live with limb loss; this number is expected to more than double by 2050. Improved surgical procedures enhance recovery, and new prosthetics and neural interfaces can replace missing limbs with those that communicate bidirectionally with the brain. These advances have been fairly successful, but still most patients experience persistent problems like phantom limb pain, and others discontinue prostheses instead of learning to use them daily. These problematic patient outcomes may be due in part to the lack of consensus among basic and clinical researchers regarding the plasticity mechanisms that occur in the brain after amputation injuries. Here we review results from clinical and animal model studies to bridge this clinical-basic science gap.

Pain and Reorganization after Amputation: Is Interoceptive Prediction a Key?

There is an ongoing discussion on the relevance of brain reorganization following amputation for phantom limb pain. Recent attempts to provide explanations for seemingly controversial findings-specifically, maladaptive plasticity versus persistent functional representation as a complementary process-acknowledged that reorganization in the primary somatosensory cortex is not sufficient to explain phantom limb pain satisfactorily. Here we provide theoretical considerations that might help integrate the data reviewed and suppose a possible additional driver of the development of phantom limb pain-namely, an error in interoceptive predictions to somatosensory sensations and movements of the missing limb. Finally, we derive empirically testable consequences based on our considerations to guide future research.

Intuitive movement-based prosthesis control enables arm amputees to reach naturally in virtual reality

Impressive progress is being made in bionic limbs design and control. Yet, controlling the numerous joints of a prosthetic arm necessary to place the hand at a correct position and orientation to grasp objects remains challenging. Here, we designed an intuitive, movement-based prosthesis control that leverages natural arm coordination to predict distal joints missing in people with transhumeral limb loss based on proximal residual limb motion and knowledge of the movement goal. This control was validated on 29 participants, including seven with above-elbow limb loss, who picked and placed bottles in a wide range of locations in virtual reality, with median success rates over 99% and movement times identical to those of natural movements. This control also enabled 15 participants, including three with limb differences, to reach and grasp real objects with a robotic arm operated according to the same principle. Remarkably, this was achieved without any prior training, indicating that this control is intuitive and instantaneously usable. It could be used for phantom limb pain management in virtual reality, or to augment the reaching capabilities of invasive neural interfaces usually more focused on hand and grasp control.

Is mirror therapy combined with a routine physiotherapy protocol effective for children with obstetrical upper brachial plexus palsy?

STUDY DESIGN

Randomized controlled study.

INTRODUCTION

Mirror therapy is a rehabilitation strategy based on the repeated use of the mirror illusion and also one of the treatment choice of brachial plexus injuries.

PURPOSE

We aimed to determine the effects of mirror therapy combined with a routine rehabilitation program on upper limb motor function in children with obstetric brachial plexus injury.

METHODS

Twenty children with obstetric brachial palsy were included in this study. They were randomly allocated to either control (n = 10) or mirror therapy (n = 10) group. The following clinical tools were used to assess the upper extremity function: Active Movement Scale (AMS), Modified Mallet Scale (MMS), Hand Grip Strength (HGS) Test, Finger Grip Strength (FGSM) Test, Box and Block Test (BBT), Nine Hole Peg Test (9-HPT), and goniometric measurement. Both groups received the same routine physiotherapy program for 8 weeks. The study group underwent mirror therapy in addition to the rehabilitation program.

RESULTS

The mean age of the study population was 11.35 ± 4.12 years. There was no change in the goniometric values, AMS and MMS scores after the treatment in both groups (p > 0.05), except for the improvement of the wrist extension in the study group (p < 0.05). There was an increase in both HGS and FGS scores in the study group. Only FGS scores improved in the control group after the intervention (p < 0.05). 9-HPT and BBT scores improved in both groups (p < 0.05). All other parameters tested were comparable between the two groups after the treatment.

CONCLUSIONS

The results of this study did not show any additional benefits of mirror therapy combined with a rehabilitation protocol compared to routine physiotherapy treatment, but was not adequately powered to do so.

Mirror-Brush Illusion: Creating Phantom Tactile Percepts on Intact Limbs

Haptic illusions provide unique insights into how we model our bodies separate from our environment. Popular illusions like the rubber-hand illusion and mirror-box illusion have demonstrated that we can adapt the internal representations of our limbs in response to visuo-haptic conflicts. In this manuscript, we extend this knowledge by investigating to what extent, if any, we also augment our external representations of the environment and its action on our bodies in response to visuo-haptic conflicts. Utilizing a mirror and a robotic brushstroking platform, we create a novel illusory paradigm that presents a visuo-haptic conflict using congruent and incongruent tactile stimuli applied to participants' fingers. Overall, we observed that participants perceived an illusory tactile sensation on their visually occluded finger when seeing a visual stimulus that was inconsistent with the actual tactile stimulus provided. We also found residual effects of the illusion after the conflict was removed. These findings highlight how our need to maintain a coherent internal representation of our body extends to our model of our environment.

Adapting psychedelic medicine for headache and chronic pain disorders

INTRODUCTION

While the majority of current research and development surrounds depression, demoralization, and substance use disorders, there are numerous reports of psychedelics having beneficial effects in other branches of medicine, including for headache disorders and chronic pain.

AREAS COVERED

This perspective reviews conventional forms of treatment for headache and other chronic pain disorders and describes historical, recent, and ongoing investigations of the therapeutic effects of psychedelics in these disorders. The first two clinical trials of psilocybin in headache disorders and recent case reports of psilocybin mushroom self-administration in chronic pain patients are described. This perspective highlights several factors related to the application of psychedelics in chronic pain disorders, comparing this with the standard psychedelic-assisted psychotherapy model of treatment.

EXPERT OPINION

When faced with a more constricted view of psychedelic medicine that features larger doses, underscores subjective effects in the mediation of therapeutic outcomes, and requires adjunctive psychotherapy to ensure safety and efficacy, the application of psychedelics in headache and chronic pain disorders may face challenges. It will be important to allow for flexibility and adaptation in protocols to evaluate different treatment paradigms, mechanisms of action, and the range of pharmacologic and extra-pharmacologic factors that affect psychedelic treatment outcomes.

Similar somatotopy for active and passive digit representation in primary somatosensory cortex

Scientists traditionally use passive stimulation to examine the organisation of primary somatosensory cortex (SI). However, given the close, bidirectional relationship between the somatosensory and motor systems, active paradigms involving free movement may uncover alternative SI representational motifs. Here, we used 7 Tesla functional magnetic resonance imaging to compare hallmark features of SI digit representation between active and passive tasks which were unmatched on task or stimulus properties. The spatial location of digit maps, somatotopic organisation, and inter-digit representational structure were largely consistent between tasks, indicating representational consistency. We also observed some task differences. The active task produced higher univariate activity and multivariate representational information content (inter-digit distances). The passive task showed a trend towards greater selectivity for digits versus their neighbours. Our findings highlight that, while the gross features of SI functional organisation are task invariant, it is important to also consider motor contributions to digit representation.

Managing acute phantom limb pain with transcutaneous electrical nerve stimulation: a case report

INTRODUCTION

Phantom limb pain is characterized by painful sensations in the amputated limb. The clinical presentation of acute phantom limb pain may differ from that of patients with chronic phantom limb pain. The variation observed implies that acute phantom limb pain may be driven by peripheral mechanisms, indicating that therapies focused on the peripheral nervous system might be successful in reducing pain.

CASE PRESENTATION

A 36-year-old African male with acute phantom limb pain in the left lower limb, was treated with transcutaneous electrical nerve stimulation.

CONCLUSION

The assessment results of the presented case and the evidence on acute phantom limb pain mechanisms contribute to the current body of literature, indicating that acute phantom limb pain presents differently to chronic phantom limb pain. These findings emphasize the importance of testing treatments that target the peripheral mechanisms responsible for phantom limb pain in relevant individuals with acquired amputations.

Mirror Therapy in Patients with Somatoform Pain Disorders-A Pilot Study

Patients with chronic pain report reduced quality of life and high symptom burden while often responding insufficiently to treatment options. Mirror therapy has been proven to be effective in treating phantom limb pain and other conditions such as CRPS. This study was designed to investigate the efficacy of mirror therapy in patients with somatoform pain disorders on symptom severity and associated physiological parameters. Fifteen patients with persistent somatoform pain disorder (F45.40) or chronic pain disorder with somatic and psychological factors (F45.41) participated and received four weeks of tablet-based mirror therapy. Symptom severity was measured with established questionnaires, and their thermal detection, pain thresholds, and heart rate variability (HRV) were also assessed. After mirror therapy, pain intensity was reduced (z = -2.878, p = 0.004), and pain thresholds for cold stimuli were also diminished, i.e., the subjects became more sensitive to cold stimuli (z = -2.040, p = 0.041). In addition, a reduction of absolute power in the low-frequency band of HRV (t(13) = 2.536, p = 0.025) was detected. These findings indicate that this intervention may reduce pain intensity and modulate associated physiological parameters. As these results are limited by several factors, e.g., a small sample size and no control group, they should be validated in further studies investigating this novel intervention in these patients.

Evolving techniques for reducing phantom limb pain

At least two million people in the United States of America live with lost limbs, and the number is expected to double by 2050, although the incidence of amputations is significantly greater in other parts of the world. Within days to weeks of the amputation, up to 90% of these individuals develop neuropathic pain, presenting as phantom limb pain (PLP). The pain level increases significantly within one year and remains chronic and severe for about 10%. Amputation-induced changes are considered to underlie the causation of PLP. Techniques applied to the central nervous system (CNS) and peripheral nervous system (PNS) are designed to reverse amputation-induced changes, thereby reducing/eliminating PLP. The primary treatment for PLP is the administration of pharmacological agents, some of which are considered but provide no more than short-term pain relief. Alternative techniques are also discussed, which provide only short-term pain relief. Changes induced by various cells and the factors they release are required to change neurons and their environment to reduce/eliminate PLP. It is concluded that novel techniques that utilize autologous platelet-rich plasma (PRP) may provide long-term PLP reduction/elimination.

Effect of mirror therapy in the treatment of phantom limb pain in amputees: A systematic review of randomized placebo-controlled trials does not find any evidence of efficacy

BACKGROUND AND OBJECTIVE

Phantom limb pain (PLP) concerns >50% of amputees and has a negative impact on their rehabilitation, mental health and quality of life. Mirror therapy (MT) is a promising strategy, but its effectiveness remains controversial. We performed a systematic review to: (i) evaluate the effectiveness of MT versus placebo in reducing PLP, and (ii) determine MT effect on disability and quality of life.

DATABASES AND DATA TREATMENT

We selected randomized-controlled trials in five databases (Medline, Cochrane Library, CINAHL, PEDro and Embase) that included patients with unilateral lower or upper limb amputation and PLP and that compared the effects on PLP of MT versus a placebo technique. The primary outcome was PLP intensity changes and the secondary outcomes were PLP duration, frequency, patients' disability and quality of life.

RESULTS

Among the five studies included, only one reported a significant difference between the MT group and control group, with a positive MT effect at week 4. Only one study assessed MT effect on disability and found a significant improvement in the MT group at week 10 and month 6.

CONCLUSIONS

Our systematic review did not allow concluding that MT reduces PLP and disability in amputees. This lack of strong evidence is probably due to (i) the low methodological quality of the included studies, and (ii) the lack of statistical power. Future trials should include a higher number of patients, increase the number and frequency of MT sessions, have a long-term follow-up and improve the methodological quality.

SIGNIFICANCE

Recent meta-analyses concluded that MT is effective for reducing phantom limb pain. Conversely, the present systematic review that included only studies with the best level of evidence did not find any evidence about its effectiveness for this condition. We identified many ways to improve future randomized-controlled trials on this topic: increasing the number of participants, reducing the intra-group heterogeneity, using a suitable placebo and intensifying the MT sessions and frequency.

Complex pattern of facial remapping in somatosensory cortex following congenital but not acquired hand loss

Cortical remapping after hand loss in the primary somatosensory cortex (S1) is thought to be predominantly dictated by cortical proximity, with adjacent body parts remapping into the deprived area. Traditionally, this remapping has been characterised by changes in the lip representation, which is assumed to be the immediate neighbour of the hand based on electrophysiological research in non-human primates. However, the orientation of facial somatotopy in humans is debated, with contrasting work reporting both an inverted and upright topography. We aimed to fill this gap in the S1 homunculus by investigating the topographic organisation of the face. Using both univariate and multivariate approaches we examined the extent of face-to-hand remapping in individuals with a congenital and acquired missing hand (hereafter one-handers and amputees, respectively), relative to two-handed controls. Participants were asked to move different facial parts (forehead, nose, lips, tongue) during functional MRI (fMRI) scanning. We first confirmed an upright face organisation in all three groups, with the upper-face and not the lips bordering the hand area. We further found little evidence for remapping of both forehead and lips in amputees, with no significant relationship to the chronicity of their phantom limb pain (PLP). In contrast, we found converging evidence for a complex pattern of face remapping in congenital one-handers across multiple facial parts, where relative to controls, the location of the cortical neighbour - the forehead - is shown to shift away from the deprived hand area, which is subsequently more activated by the lips and the tongue. Together, our findings demonstrate that the face representation in humans is highly plastic, but that this plasticity is restricted by the developmental stage of input deprivation, rather than cortical proximity.

The PerPAIN trial: a pilot randomized controlled trial of personalized treatment allocation for chronic musculoskeletal pain-a protocol

BACKGROUND

The therapy of chronic musculoskeletal pain (CMSP) is complex and the treatment results are often insufficient despite numerous therapeutic options. While individual patients respond very well to specific interventions, other patients show no improvement. Personalized treatment assignment offers a promising approach to improve response rates; however, there are no validated cross-disease allocation algorithms available for the treatment of chronic pain in validated personalized pain interventions. This trial aims to test the feasibility and safety of a personalized pain psychotherapy allocation with three different treatment modules and estimate initial signals of efficacy and utility of such an approach compared to non-personalized allocation.

METHODS

This is a randomized, controlled assessor-blinded pilot trial with a multifactorial parallel arm design. CMSP patients (n = 105) will be randomly assigned 1:1 to personalized or non-personalized treatment based on a cluster assignment of the West Haven-Yale Multidimensional Pain Inventory (MPI). In the personalized assignment condition, patients with high levels of distress receive an emotional distress-tailored intervention, patients with pain-related interference receive an exposure/extinction-tailored treatment intervention and patients who adapt relatively well to the pain receive a low-level smartphone-based activity diary intervention. In the control arm, patients receive one of the two non-matching interventions. Effect sizes will be calculated for change in core pain outcome domains (pain intensity, physical and emotional functioning, stress experience, participant ratings of improvement and satisfaction) after intervention and at follow-up. Feasibility and safety outcomes will assess rates of recruitment, retention, adherence and adverse events. Additional data on neurobiological and psychological characteristics of the patients are collected to improve treatment allocation in future studies.

CONCLUSION

Although the call for personalized treatment approaches is widely discussed, randomized controlled trials are lacking. As the personalization of treatment approaches is challenging, both allocation and intervention need to be dynamically coordinated. This study will test the feasibility and safety of a novel study design in order to provide a methodological framework for future multicentre RCTs for personalized pain psychotherapy.

TRIAL REGISTRATION

German Clinical Trials Register, DRKS00022792 ( https://www.drks.de ). Prospectively registered on 04/06/2021.

Neurofeedback Training without Explicit Phantom Hand Movements and Hand-Like Visual Feedback to Modulate Pain: A Randomized Crossover Feasibility Trial

Phantom limb pain is attributed to abnormal sensorimotor cortical representations, although the causal relationship between phantom limb pain and sensorimotor cortical representations suffers from the potentially confounding effects of phantom hand movements. We developed neurofeedback training to change sensorimotor cortical representations without explicit phantom hand movements or hand-like visual feedback. We tested the feasibility of neurofeedback training in fourteen patients with phantom limb pain. Neurofeedback training was performed in a single-blind, randomized, crossover trial using two decoders constructed using motor cortical currents measured during phantom hand movements; the motor cortical currents contralateral or ipsilateral to the phantom hand (contralateral and ipsilateral training) were estimated from magnetoencephalograms. Patients were instructed to control the size of a disk, which was proportional to the decoding results, but to not move their phantom hands or other body parts. The pain assessed by the visual analogue scale was significantly greater after contralateral training than after ipsilateral training. Classification accuracy of phantom hand movements significantly increased only after contralateral training. These results suggested that the proposed neurofeedback training changed phantom hand representation and modulated pain without explicit phantom hand movements or hand-like visual feedback, thus showing the relation between the phantom hand representations and pain. PERSPECTIVE: Our work demonstrates the feasibility of using neurofeedback training to change phantom hand representation and modulate pain perception without explicit phantom hand movements and hand-like visual feedback. The results enhance the mechanistic understanding of certain treatments, such as mirror therapy, that change the sensorimotor cortical representation.

Altered bodily perceptions in chronic neuropathic pain conditions and implications for treatment using immersive virtual reality

Chronic neuropathic pain is highly disabling and difficult to treat and manage. Patients with such conditions often report altered bodily perceptions that are thought to be associated with maladaptive structural and functional alterations in the somatosensory cortex. Manipulating these altered perceptions using body illusions in virtual reality is being investigated and may have positive clinical implications for the treatment of these conditions. Here, we have conducted a narrative review of the evidence for the types of bodily distortions associated with a variety of peripheral and central neuropathic pain conditions. In addition, we summarize the experimental and clinical studies that have explored embodiment and body transformation illusions in immersive virtual reality for neuropathic pain relief, which are thought to target these maladaptive changes, as well as suggesting directions for future research.

Interference of unilateral lower limb amputation on motor imagery rhythm and remodeling of sensorimotor areas

PURPOSE

The effect of sensorimotor stripping on neuroplasticity and motor imagery capacity is unknown, and the physiological mechanisms of post-amputation phantom limb pain (PLP) illness remain to be investigated.

MATERIALS AND METHODS

In this study, an electroencephalogram (EEG)-based event-related (de)synchronization (ERD/ERS) analysis was conducted using a bilateral lower limb motor imagery (MI) paradigm. The differences in the execution of motor imagery tasks between left lower limb amputations and healthy controls were explored, and a correlation analysis was calculated between level of phantom limb pain and ERD/ERS.

RESULTS

The multiple frequency bands showed a significant ERD phenomenon when the healthy control group performed the motor imagery task, whereas amputees showed significant ERS phenomena in mu band. Phantom limb pain in amputees was negatively correlated with bilateral sensorimotor areas electrode powers.

CONCLUSION

Sensorimotor abnormalities reduce neural activity in the sensorimotor cortex, while the motor imagination of the intact limb is diminished. In addition, phantom limb pain may lead to over-activation of sensorimotor areas, affecting bilateral sensorimotor area remodeling.

Effectiveness of mirror therapy in phantom limb pain: A literature review

INTRODUCTION

Phantom limb pain (PLP) is a type of neuropathic pain that affects the territory of an amputated limb or other surgically removed body parts. Between 60% and 90% of amputees suffer from PLP during follow-up. There are a range of therapeutic options for PLP, both pharmacological (gabapentin, amitriptyline, tricyclic antidepressants, etc) and non-pharmacological (transcutaneous electrical nerve stimulation, hypnosis, acupuncture, etc). A widely accepted hypothesis considers PLP to be the consequence of postamputation cortical reorganisation. New treatment approaches, such as mirror therapy (MT), have been developed as a result of Ramachandran's groundbreaking research in the 1990s. This review analyses the current evidence on the efficacy of MT for treating PLP.

DEVELOPMENT

We performed a literature review of publications registered from 2012 to 2017 on the CINAHL, Cochrane, Scopus, and PubMed (including Medline) databases Using the descriptors "phantom limb‿ and "mirror therapy.‿ We identified 115 publications addressing MT in PLP. Of these, 17 (15%) contributed useful information for pooled analysis.

CONCLUSIONS

MT seems to be effective in relieving PLP, reducing the intensity and duration of daily pain episodes. It is a valid, simple, and inexpensive treatment for PLP. The methodological quality of most publications in this field is very limited, highlighting the need for additional, high-quality studies to develop clinical protocols that could maximise the benefits of MT for patients with PLP.

A scoping review of current non-pharmacological treatment modalities for phantom limb pain in limb amputees

PURPOSE

Phantom limb pain (PLP) is a chronic neuropathic pain condition of a missing limb following amputation. Pain management is multi-modal, including various non-pharmacological therapies. The purpose of this scoping review was to investigate the evidence surrounding current non-pharmacological treatment modalities for PLP and provide insight into their clinical feasibility.

METHOD

A systematic search was conducted using four databases (Medline, Embase, PsychInfo, and CINAHL) following the PRISMA-ScR method. Results from papers meeting the inclusion criteria were charted to summarize findings, demographics, and use of neuroimaging.

RESULTS

A total of 3387 papers were identified, and full texts of 142 eligible papers were assessed. Eleven treatment modalities for PLP were identified with varying levels of evidence. Overall, there were 25 RCTs, 58 case reports, and 59 a combination of pilot, quasi-experimental, observational, and other study designs.

CONCLUSIONS

Currently, the evidence surrounding most treatment modalities is limited and only a fraction of studies are supported by strong evidence. The findings of this review demonstrated a clear need to conduct more rigorous research with diverse study designs to better understand which modalities provide the most benefit and to incorporate neuroimaging to better determine the neural correlates of PLP and mechanisms of various treatments.Implications for RehabilitationPhantom limb pain (PLP) is a prevalent and debilitating condition following amputation and health care professionals should incorporate an evidence-based pain management protocol into their rehabilitation program.There exist a number of different non-pharmacological therapies to address PLP, however the scientific rigor and levels of evidence vary across modalities.Prescription of interventions for PLP should consider individual patient differences, accessibility to the patient, and quite possibly, a multi-modal approach, particularly for those who also experience residual limb pain.Imagery-based therapies provide the highest level of current evidence based on robust and large randomized control trials, are readily accessible, and are thus most recommended for relief of PLP.

Sensory discrimination training for adults with chronic musculoskeletal pain: a systematic review

BACKGROUND

Sensory discrimination training (SDT) is a form of feedback guided sensory training used in the treatment of chronic musculoskeletal pain (CMP).

OBJECTIVE

This systematic review aimed to investigate the efficacy and safety of SDT for CMP.

METHODS

MEDLINE, CINAHL, EMBASE, AMED, CENTRAL, PsycINFO, Scopus, OT Seeker, PEDro, ETHOS, Web of Science, and Open Grey were searched for appropriate randomized controlled trials (RCTs). Included papers were assessed for risk of bias, and evidence was graded using the GRADE approach. The protocol was published on PROSPERO (anonymized).

RESULTS

Ten RCTs met the inclusion/exclusion criteria. There was conflicting evidence from seven RCTs for the efficacy of SDT for chronic low back pain (CLBP). There was very low-quality evidence from two studies supporting the efficacy of SDT for phantom limb pain (PLP). There was very low-quality evidence from one RCT for the efficacy of SDT for Fibromyalgia. No adverse effects of SDT were identified.

CONCLUSIONS

SDT has been delivered in multiple forms in the literature. SDT does not appear to be associated with any adverse effects and shows potential regarding its clinical efficacy. However, there is a lack of high-quality evidence upon which to make any firm clinical recommendations.

Pathophysiological and Neuroplastic Changes in Postamputation and Neuropathic Pain: Review of the Literature

Despite advancements in surgical and rehabilitation strategies, extremity amputations are frequently associated with disability, phantom limb sensations, and chronic pain. Investigation into potential treatment modalities has focused on the pathophysiological changes in both the peripheral and central nervous systems to better understand the underlying mechanism in the development of chronic pain in persons with amputations.

Methods

Presented in this article is a discussion outlining the physiological changes that occur in the peripheral and central nervous systems following amputation. In this review, the authors examine the molecular and neuroplastic changes occurring in the nervous system, as well as the state-of-the-art treatment to help reduce the development of postamputation pain.

Results

This review summarizes the current literature regarding neurological changes following amputation. Development of both central sensitization and neuronal remodeling in the spinal cord and cerebral cortex allows for the development of neuropathic and phantom limb pain postamputation. Recently developed treatments targeting these pathophysiological changes have enabled a reduction in the severity of pain; however, complete resolution remains elusive.

Conclusions

Changes in the peripheral and central nervous systems following amputation should not be viewed as separate pathologies, but rather two interdependent mechanisms that underlie the development of pathological pain. A better understanding of the physiological changes following amputation will allow for improvements in therapeutic treatments to minimize pathological pain caused by amputation.

Adults with unilateral lower-limb amputation: greater spatial extent of pain is associated with worse adjustment, greater activity restrictions, and less prosthesis satisfaction

OBJECTIVES

This study's primary purpose was to determine if the extent of bodily pain, as evaluated with pain body diagrams, is associated with prosthetic-related activity restrictions, adjustment, and satisfaction among adults with a major unilateral lower-limb amputation. A secondary objective was to evaluate between-days, test-retest reliability for pain body diagrams among adults with lower-limb amputation.

METHODS

Adults with a lower-limb amputation that occurred ≥1 year prior participated in an online, cross-sectional research study. Outcome measures included pain body diagrams and the Trinity Amputation and Prosthesis Experience Scales-Revised, which evaluates post-amputation activity restrictions, psychosocial adjustment, and prosthesis satisfaction. Linear regression modeling was used to evaluate associations between the number of painful body regions and prosthetic outcomes, after considering covariates (alpha ≤ 0.010). A subset of participants recompleted pain body diagrams to evaluate between-days, test-retest reliability.

RESULTS

Data from 74 participants (n = 32 female; n = 42 transtibial-level; n = 27 traumatic etiology) were available. Beyond covariates (i.e., age, sex, amputation level), the total number of painful body regions was significantly associated with all Trinity Amputation and Prosthesis Experience Scales-Revised subscales (p < 0.001-0.006), with the exception of Social Adjustment (p = 0.764). The total number of painful body regions explained 14.5, 11.8, 11.6, and 7.4% of the variance in Functional Satisfaction with the Prosthesis, Adjustment to Limitation, General Adjustment, and Activity Restriction, respectively. In a subset (n = 54), test-retest reliability for total number of painful body regions per body diagrams was good [intraclass correlation coefficient (ICC)3,1 = 0.84].

CONCLUSIONS

A greater number of painful body regions is associated with greater activity restriction, worse adjustment, and lower prosthesis satisfaction, supporting the need to enhance post-amputation pain management and both amputated- and secondary-site pain prevention.

ETHICAL COMMITTEE NUMBER

IRB #1611862.

Involvement of visual signals in kinaesthesia: A virtual reality study

Body movements are invariably accompanied by various proprioceptive, visual, tactile and/or motor signals. It is therefore difficult to completely dissociate these various signals from each other in order to study their specific involvement in the perception of movement (kinaesthesia). Here, we manipulated visual motion signals in a virtual reality display by using a humanoid avatar. The visual signals of movement could therefore be manipulated freely, relative to the participant's actual movement or lack of movement. After an embodiment phase in which the avatar's movements were coupled to the participant's voluntary movements, kinaesthetic illusions were evoked by moving the avatar's right forearm (flexion or extension) while the participant's right arm remained static. The avatar's left forearm was hidden from view. In parallel, somaesthetic signals could be masked by agonist-antagonist co-vibration or be amplified (by agonist vibration only or antagonist vibration only) so that the real impact of visual cues of movement in kinaesthesia could be studied. In a study of 24 participants, masking the somaesthetic signals (which otherwise provide signals indicating that the arm is static) was associated with a greater intensity and shorter latency of the visually evoked illusions. These results confirm the importance of carefully considering somaesthetic signals when assessing the contribution of vision to kinaesthesia. The use of a combination of virtual reality and somaesthetic signal manipulation might be of clinical value.

Psychedelics as preventive treatment in headache and chronic pain disorders

The effects of psychedelic drugs in headache and chronic pain disorders have been reported for several decades, and now controlled studies are emerging. The existing evidence supports a lasting therapeutic benefit after limited dosing, a unique feature of the drug class that distinguishes it from conventional treatment. This commentary summarizes these reports of preventive effects of psychedelic drugs in headache and chronic pain disorders. The recently published controlled trial of psilocybin in migraine is reviewed, including its limitations. Several neurobiological targets of psychedelics that are related to headache and chronic pain are highlighted, though a clear separation of acute and lasting effects is key in uncovering the unique clinical effects of this drug class. Considerable investigation is required before the effects, safety, and mechanism of action of psychedelics in headache and chronic pain disorders can be known.

Making sense of phantom limb pain

Phantom limb pain (PLP) impacts the majority of individuals who undergo limb amputation. The PLP experience is highly heterogenous in its quality, intensity, frequency and severity. This heterogeneity, combined with the low prevalence of amputation in the general population, has made it difficult to accumulate reliable data on PLP. Consequently, we lack consensus on PLP mechanisms, as well as effective treatment options. However, the wealth of new PLP research, over the past decade, provides a unique opportunity to re-evaluate some of the core assumptions underlying what we know about PLP and the rationale behind PLP treatments. The goal of this review is to help generate consensus in the field on how best to research PLP, from phenomenology to treatment. We highlight conceptual and methodological challenges in studying PLP, which have hindered progress on the topic and spawned disagreement in the field, and offer potential solutions to overcome these challenges. Our hope is that a constructive evaluation of the foundational knowledge underlying PLP research practices will enable more informed decisions when testing the efficacy of existing interventions and will guide the development of the next generation of PLP treatments.

Clinical and Neurophysiological Effects of Progressive Movement Imagery Training for Pathological Pain

Movement limitation is a common characteristic of chronic pain such that pain prevents the very movement and activity that is most likely to promote recovery. This is particularly the case for pathological pain states such as complex regional pain syndrome (CRPS). One clinical approach to CRPS that has growing evidence of efficacy involves progressive movement imagery training. Graded Motor Imagery (GMI) targets clinical and neurophysiological effects through a stepwise progression through implicit and explicit movement imagery training, mirror therapy and then functional tasks. Here we review experiences from over 20 years of clinical and research experience with GMI. We situate GMI in terms of its historical underpinnings, the benefits and outstanding challenges of its implementation, its potential application beyond CRPS. We then review the neuropathological targets of GMI and current thought on its effects on neurophysiological biomarkers. Perspective This article provides an overview of our experiences with graded motor imagery training over the last 20 years focussing on the treatment of CRPS. It does both cover the theoretical underpinnings for this treatment approach, biomarkers which indicate potential changes driven by GMI, and experiences for achieving optimal treatment results.

Multisensory Integration in Bionics: Relevance and Perspectives

Purpose of review

The goal of the review is to highlight the growing importance of multisensory integration processes connected to bionic limbs and somatosensory feedback restoration.

Recent findings

Restoring quasi-realistic sensations by means of neurostimulation has been shown to provide functional and motor benefits in limb amputees. In the recent past, cognitive processes linked to the artificial sense of touch seemed to play a crucial role for a full prosthesis integration and acceptance.

Summary

Artificial sensory feedback implemented in bionic limbs enhances the cognitive integration of the prosthetic device in amputees. The multisensory experience can be measured and must be considered in the design of novel somatosensory neural prostheses where the goal is to provide a realistic sensory experience to the prosthetic user. The correct integration of these sensory signals will guarantee higher-level cognitive benefits as a better prosthesis embodiment and a reduction of perceived limb distortions.

Efficacy of mirror therapy and virtual reality therapy in alleviating phantom limb pain: a meta-analysis and systematic review

INTRODUCTION

Amputations result from trauma, war, conflict, vascular diseases and cancer. Phantom limb pain (PLP) is a potentially debilitating form of chronic pain affecting around 100 million amputees across the world. Mirror therapy and virtual reality (VR) are two commonly used treatments, and we evaluated their respective success rates.

METHODS

A meta-analysis and systematic review was undertaken to investigate mirror therapy and VR in their ability to reduce pain levels. A mean difference (MD) model to compare group pain levels pretreatment and post-treatment via aggregating these results from numerous similar studies was employed. Meta-analysis was conducted using RevMan (V.5.4) and expressed in MD for visual analogue scale (VAS) score.

RESULTS

A total of 15 studies met our search criteria; they consisted of eight mirror therapy with 214 participants and seven VR including 86 participants, totalling 300 participants. Mean age ranged from 36 to 63 years, 77% male, of which 61% were lower body amputees. Both led to a VAS reduction (mirror therapy mean reduction VAS score was 2.54, 95% CI 1.42 to 3.66; p<0.001; VR 2.24, 95% CI 1.28 to 3.20; p<0.001). There was no statistically significant difference in pain alleviation between mirror therapy and VR (p=0.69).

CONCLUSIONS

Mirror therapy and VR are both equally efficacious in alleviating PLP, but neither is more effective than the other. However, due to small sample size and limited number of studies, factors such as gender, cause of amputation, site of limb loss or length of time from amputation, which may influence treatment success, could not be explored.

Unveiling the phantom: What neuroimaging has taught us about phantom limb pain

Phantom limb pain (PLP) is a complicated condition with diverse clinical challenges. It consists of pain perception of a previously amputated limb. The exact pain mechanism is disputed and includes mechanisms involving cerebral, peripheral, and spinal origins. Such controversy limits researchers' and clinicians' ability to develop consistent therapeutics or management. Neuroimaging is an essential tool that can address this problem. This review explores diffusion tensor imaging, functional magnetic resonance imaging, electroencephalography, and magnetoencephalography in the context of PLP. These imaging modalities have distinct mechanisms, implications, applications, and limitations. Diffusion tensor imaging can outline structural changes and has surgical applications. Functional magnetic resonance imaging captures functional changes with spatial resolution and has therapeutic applications. Electroencephalography and magnetoencephalography can identify functional changes with a strong temporal resolution. Each imaging technique provides a unique perspective and they can be used in concert to reveal the true nature of PLP. Furthermore, researchers can utilize the respective strengths of each neuroimaging technique to support the development of innovative therapies. PLP exemplifies how neuroimaging and clinical management are intricately connected. This review can assist clinicians and researchers seeking a foundation for applications and understanding the limitations of neuroimaging techniques in the context of PLP.

Development and Testing of a Portable Virtual Reality-Based Mirror Visual Feedback System with Behavioral Measures Monitoring

Virtual Reality (VR) is a technology that has been used to provide the Mirror Visual Feedback (MVF) illusion to patients with promising results. In the present work, the goal is to design, develop and test a portable VR-based MVF system that monitors behavioral information about the performance of a simple motor task. The developed application runs in a stand-alone VR system and allows the researcher to select the real and virtual hands used to perform the motor task. The system was evaluated with a group of twenty healthy volunteers (12 men and 8 women) with ages between 18 and 66 years. Participants had to repetitively perform a motor task in four different experimental conditions: two mirror conditions (performing real movements with the dominant and with the non-dominant hand) and two non-mirror conditions. A significant effect of the experimental condition on embodiment score (p < 0.001), response time (p < 0.001), performance time (p < 0.001), trajectory length (p < 0.004) and trajectory maximum horizontal deviation (p < 0.001) was observed. Furthermore, a significant effect of the experimental moment (initial, middle and final parts of the training) on the performance time was observed (p < 0.001). These results show that the monitored parameters provide relevant information to evaluate the participant’s task performance in different experimental conditions.

Psychedelics in the Treatment of Headache and Chronic Pain Disorders

The therapeutic potential of psychedelics in headache and chronic pain disorders is documented over decades of anecdotal and early investigational reports, which have paved the way for the first controlled studies of psilocybin and lysergic acid diethylamide (LSD) in these disorders. The reported lasting clinical effects after limited dosing with psychedelics present a novel means for disease management, but considerable further study will be required to address disease-specific treatments, uncover mechanism(s) of action, and verify safety. In this chapter, these topics are reviewed with particular attention to the neurobiological systems that offer potential sources of psychedelics' unique clinical effects in headache and pain.