Mirror Visual Feedback for Phantom Pain: International Experience on Modalities and Adverse Effects Discussed by an Expert Panel: A Delphi Study

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.

An Overview of the Body Schema and Body Image: Theoretical Models, Methodological Settings and Pitfalls for Rehabilitation of Persons with Neurological Disorders

Given the widespread debate on the definition of the terms "Body Schema" and "Body Image", this article presents a broad overview of the studies that have investigated the nature of these types of body representations, especially focusing on the innovative information about these two representations that could be useful for the rehabilitation of patients with different neurological disorders with motor deficits (especially those affecting the upper limbs). In particular, we analyzed (i) the different definitions and explicative models proposed, (ii) the empirical settings used to test them and (iii) the clinical and rehabilitative implications derived from the application of interventions on specific case reports. The growing number of neurological diseases with motor impairment in the general population has required the development of new rehabilitation techniques and a new phenomenological paradigm placing body schema as fundamental and intrinsic parts for action in space. In this narrative review, the focus was placed on evidence from the application of innovative rehabilitation techniques and case reports involving the upper limbs, as body parts particularly involved in finalistic voluntary actions in everyday life, discussing body representations and their functional role.

Perception of Heaviness Induced by Sensorimotor Incongruence Is Associated with Pain Prognosis: A Pilot Study

Background. Patients with chronic musculoskeletal pain experience not only pain but also abnormal body perception. Such abnormal body perception has been reported to be caused by incongruence between motor intentions and sensory feedback (i.e., sensorimotor incongruence). However, the influence of abnormal body perception with sensorimotor incongruence on pain prognosis in musculoskeletal pain patients has not been investigated. Objective. We aimed at clarifying the influence of abnormal body perception on pain prognosis using an experimental procedure for inducing sensorimotor incongruence in patients with musculoskeletal pain. Methods. We recruited 18 patients within 2 months after limb fracture or ligament injury. In the experiment, patients sat with the intact upper or lower limb reflected in a large mirror aligned with the sagittal plane. A motor task was performed for 20 seconds in each of the congruent and incongruent conditions. In the congruent condition, patients were asked to perform flexion-extension movements with the intact and affected limbs in-phase, while observing the intact limb in the mirror. In the incongruent condition, patients were asked to perform flexion-extension movements antiphase, while observing the intact limb in the mirror. After performing the congruent and incongruent conditions, patients were asked to complete a questionnaire about abnormal body perception. These procedures were conducted within 2 months after the fracture (first), 2 weeks after the first measurement (second), and 4 weeks (third) after the first measurement. Results. Pain, heaviness, and peculiarity were more likely to be experienced in incongruent conditions. Additionally, structural equation modeling indicated that heaviness at the first time point predicted the pain intensity at the second and third time points. Conclusions. Heaviness caused by sensorimotor incongruence may predict pain prognosis in patients with musculoskeletal pain after one month.

Inter-lateral Referral of Sensation in Health and Disease Using a Mirror Illusion-A Scoping Review

OBJECTIVE

Perception of touch is expected at the location where it is applied. However, there are indications that being touched may be perceived on the contralateral side when seen as a reflection in a mirror at midline. Such inter-lateral referral of sensation (RS) lacks evidence, as mirror therapy research usually focusses on movement-based techniques. This study aimed to map out existing research across disciplines regarding the effect of RS in health and disease, and to understand whether there is rehabilitation potential in RS.

METHOD

A scoping review was conducted to map out concepts and keywords across disciplines interested in this topic, using keywords in several languages, and a wide range of databases and additional sources.

RESULTS

The review revealed mostly cross-sectional experiments and included over 486 participants: healthy, or with stroke, complex regional pain syndrome, amputation, nerve graft surgery or radial fracture. Procedures varied regarding stimulation tool, time and location, with two stimulating replacements, one the face and one a variety of areas. Response rates ranged from 0 to 100%.In general, RS was regarded as a phenomenon or even as a predictor of maladaptive neuroplasticity. There was little research into using RS stimulation as a modulatory tool to improve sensory perception.

CONCLUSIONS

RS challenges the understanding of touch perception and elicits a range of questions regarding neuro-processing. A modulatory approach using RS has not been described, requires investigation and, if promising, development as an intervention.

Mirror therapy for phantom limb and stump pain: a randomized controlled clinical trial in landmine amputees in Cambodia

Background and aims The aim of the study was to examine the effect of mirror and tactile therapy on phantom and stump pain in patients with traumatic amputations, with particular reference to amputees in low-income communities. Methods The study was conducted with an open, randomized, semi-crossover case-control design in rural Cambodia. A study sample of 45 landmine victims with trans-tibial amputations was allocated to three treatment arms; mirror therapy, tactile therapy, and combined mirror-and-tactile therapy. Non-responders from the mono-therapy interventions were crossed over to the alternative intervention. The intervention consisted of 5 min of treatment every morning and evening for 4 weeks. Endpoint estimates of phantom limb pain (PLP), stump pain, and physical function were registered 3 months after the treatment. Results All three interventions were associated with more that 50% reduction in visual analogue scale (VAS)-rated PLP and stump pain. Combined mirror-tactile treatment had a significantly better effect on PLP and stump pain than mirror or tactile therapy alone. The difference between the three treatment arms were however slight, and hardly of clinical relevance. After treatment, the reduction of pain remained unchanged for an observation period of 3 months. Conclusions The study documents that a 4-week treatment period with mirror and/or tactile therapy significantly reduces PLP and stump pain after trans-tibial amputations. Implications The article reports for the first time a randomized controlled trial of mirror therapy in a homogenous sample of persons with traumatic amputations. The findings are of special relevance to amputees in low-resource communities.

Mirror therapy versus augmented/virtual reality applications: towards a tailored mechanism-based treatment for phantom limb pain

Phantom limb pain (PLP) is a clinically relevant consequence of limb amputation and its treatment is still challenging. Mirror therapy, in other words, observing and engaging in the intact limb's mirrored movements, offers a promising, mechanism-based treatment for PLP. However, intervention and patient characteristics, such as the realism of mirrored exercises and perceptions related to the phantom limb, might influence treatment effectiveness. Novel approaches using augmented and virtual reality setups represent an alternative to traditional mirror therapy. In this paper, based on recent studies in the field, we compare both approaches and discuss their unique advantages and disadvantages. We argue for the necessity of a tailored treatment for PLP that is personalized to the patients’ characteristics, preferences and psychological needs.

Effect of one session of mirror therapy on phantom limb pain and recognition of limb laterality in military traumatic lower limb amputees: a pilot study

Up to 70 % of military amputees suffer phantom limb pain (PLP), which is difficult to treat. PLP has been attributed to cortical reorganisation and associated with impaired laterality. Repeated sessions of mirror therapy (MT) can benefit PLP; however, anecdotal evidence suggests one MT session could be effective. In a one-group pretest and post-test design, 16 UK military unilateral lower limb amputees (median age: 31.0, 95% CI 25.0 to 36.8 years) undertook one 10 min MT session. Visual analogue scale (VAS) pain and laterality (accuracy and reaction time) measurements were taken pre-MT and post-MT. Median VAS PLP did not differ significantly between pre-MT 15 mm (2-53 mm) and post-MT 12 mm (1-31) (p=0.875) scores. For the amputated limb, there were no significant differences between pre-MT and post-MT scores for laterality accuracy, 95.3%, 95% CI 90.5% to 97.6% and 96.7%, 95% CI 90.0% to 99.4%, respectively (p=0.778), or reaction time, 1.42 s, 95% CI 1.11 to 2.11 s and 1.42 s, 95% CI 1.08 to 2.02 s, respectively (p=0.629). Laterality was also not different between limbs for accuracy, p=0.484, or reaction time, p=0.716, and did not correlate with PLP severity. No confounding variables predicted individual responses to MT. Therefore, one 10 min MT session does not affect laterality and is not effective as standard treatment for PLP in military lower limb amputees. However, substantial PLP improvement for one individual and resolution of a stuck phantom limb for another infers that MT may benefit specific patients. No correlation found between PLP and laterality implies associated cortical reorganisation may not be the main driver for PLP. Further research, including neuroimaging, is needed to help clinicians effectively target PLP.

An investigation into enlarging and reducing the size of mirror reflections of the hand on experimentally-induced cold-pressor pain in healthy human participants

BACKGROUND AND AIMS

Mirror visual feedback may be a useful clinical tool for reducing pain. Research suggests that reducing the size of a non-painful reflected hand can alleviate complex regional pain syndrome in the affected hand that is out of view. In contrast, research on healthy humans exposed to experimentally induced pain suggests that reducing the appearance of the size of a reflected body part can increase pain. The aim of this study was to investigate the effect of enlarging and reducing the visual appearance of the size of a hand using mirror visual feedback on pain threshold, intensity and tolerance in healthy human participants exposed to cold-pressor pain.

METHODS

Participants were a convenience sample of 20 unpaid, healthy pain free volunteers aged 18 years or above. Each participant took part in one experiment where they completed cold-pressor pain tests whilst observing normal, enlarged and reduced size reflections of a hand congruent to a hand immersed in the ice cold water. A 4×2 factorial repeated measures analysis of variance (ANOVA) was performed on time to pain threshold and pain tolerance, and pain intensity with Condition (four levels: no reflection, reduced reflection, normal reflection, enlarged reflection) being the within-subject factors and Sex (two levels: female, male) between-subject factors.

RESULTS

There were no significant effects for Condition, Sex, or Condition×Sex interaction for pain threshold, intensity or tolerance (p>0.05). There were no significant differences between the 3 mirror reflection conditions for agreement with the statements: "It felt like I was looking directly at my hand rather than at a mirror image"; "It felt like the hand I was looking at was my hand"; and "Did it seem like the hand you saw was a right hand or a left hand?".

CONCLUSION

Enlarging or reducing the size of a hand using mirror visual feedback did not alter pain perception in healthy human participants exposed to cold-pressor pain. The different sizes of hands generated by mirror visual feedback created an illusion of looking at their own hand but this was not as strong as looking directly at the hand.

IMPLICATIONS

In future, investigators and clinicians using mirror visual feedback may consider including an adaptive phase to ensure the reflection has been perceptually embodied. Reasons for the lack of effects are explored to inspire further research in the field.

Negative body image associated with changes in the visual body appearance increases pain perception

Changing the visual body appearance by use of as virtual reality system, funny mirror, or binocular glasses has been reported to be helpful in rehabilitation of pain. However, there are interindividual differences in the analgesic effect of changing the visual body image. We hypothesized that a negative body image associated with changing the visual body appearance causes interindividual differences in the analgesic effect although the relationship between the visual body appearance and analgesic effect has not been clarified. We investigated whether a negative body image associated with changes in the visual body appearance increased pain. Twenty-five healthy individuals participated in this study. To evoke a negative body image, we applied the method of rubber hand illusion. We created an “injured rubber hand” to evoke unpleasantness associated with pain, a “hairy rubber hand” to evoke unpleasantness associated with embarrassment, and a “twisted rubber hand” to evoke unpleasantness associated with deviation from the concept of normality. We also created a “normal rubber hand” as a control. The pain threshold was measured while the participant observed the rubber hand using a device that measured pain caused by thermal stimuli. Body ownership experiences were elicited by observation of the injured rubber hand and hairy rubber hand as well as the normal rubber hand. Participants felt more unpleasantness by observing the injured rubber hand and hairy rubber hand than the normal rubber hand and twisted rubber hand (p<0.001). The pain threshold was lower under the injured rubber hand condition than with the other conditions (p<0.001). We conclude that a negative body appearance associated with pain can increase pain sensitivity.