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sj-docx-1-cre-10.1177_02692155231204185 - Supplemental material for Graded motor imagery and its phases for individuals with phantom limb pain following amputation: A scoping review
GUID: 9698A4F5-5ADB-4E43-B57B-CB47287AD83ESupplemental material, sj-docx-1-cre-10.1177_02692155231204185 for Graded motor imagery and its phases for individuals with phantom limb pain following amputation: A scoping review by Kierra Jean Falbo, Hannah Phelan, Dawn Hackman, Rebecca Vogsland and Tonya L Rich in Clinical Rehabilitation
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.
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.
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.
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%).
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.
Keywords: Amputees, intervention, chronic pain, rehabilitation, occupational therapyPhantom limb pain after amputation is complex and multifactorial. The mechanisms contributing to this type of pain are not fully understood, making it difficult to treat and clinically manage. 1,2 One mechanistic theory of phantom limb pain is maladaptive plasticity wherein cortical reorganization occurs due to the loss of or changes in sensory and motor input from the amputated limb. 3 Neuroimaging evidence shows that individuals with amputations can experience changes in the sensory and motor maps in the cortex of the brain, which may contribute to the pain experience. 3,4
Graded motor imagery is a non-pharmacological treatment that aims to address hypothesized cortical reorganization associated with chronic pain. 5,6 Graded motor imagery has shown success in reducing other types of chronic pain and restoring function. 7 –13 Traditional graded motor imagery protocol includes the three phases of (1) left/right discrimination of limbs or limb laterality, (2) explicit motor imagery, and (3) mirror therapy. 6 In limb laterality, patients are shown images of limbs in different orientations and asked to judge whether the image depicts a left or a right limb. 14 In the second phase of graded motor imagery, explicit motor imagery involves imagined movements without physically moving the body or activating the muscle. Visualizing these movements can activate similar cortical areas as are activated when physically performing the movements. 15 In the third and last phase, mirror therapy, a long mirror or mirror box is traditionally placed between the two limbs, so that the contralateral limb is reflected in the mirror and the painful limb is out of view. When looking in the mirror, the patient receives visual feedback of both limbs moving together pain-free. 16 Graded motor imagery is designed to progress the patient's experience through each of these phases to gradually increase the sensory-motor feedback to the brain. However, treatment can also involve just one phase of graded motor imagery, and there is debate amongst clinicians as to the protocol that constitutes best practice. 5,17,18
Mirror therapy has been reported often in individuals with phantom limb pain, and the evidence for mirror therapy has been evaluated in recent systematic reviews. 19 –21 However, mirror therapy represents just one of three phases of graded motor imagery intervention. The three-phase graded motor imagery protocol may provide more pain relief, but little is known about the evidence supporting the three phases of graded motor imagery as they relate to amputation. Therefore, in order to provide an overview of the current research landscape, a scoping review of the current literature on the three phases of graded motor imagery is warranted. The objective of this scoping review is to explore and describe the extent and type of evidence of three-phase graded motor imagery and its individual phases for phantom limb pain after limb amputation.
Although three-phase graded motor imagery was originally designed and tested in individuals with phantom limb pain, 9 most published works since then have focused on mirror therapy. 20,21 To better understand how others have used the phases of graded motor imagery either in isolation or combination and describe key concepts (e.g. dosing, individual characteristics, etc.), we used scoping review methodology to capture the current landscape of research on this topic. Consistent with a scoping review, there is no intent to analyze the effectiveness of treatment. 22,23 Instead, this project was designed to explore participant demographics, treatment protocols (i.e. phases, session structure, and dosing), amputation-specific modifications, and outcome measures to inform future intervention and study design.
This scoping review was conducted according to the JBI Manual for Evidence Synthesis and is being reported in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses extension for Scoping Reviews guidelines. 24,25 The protocol, covering the objectives, inclusion/exclusion criteria, and methods of this scoping review, was registered with the Open Science Framework (https://osf.io/jra9t/) prior to the start of the study.
A comprehensive search strategy was created using both natural language (i.e. keywords) and controlled vocabulary (i.e. subject headings) to examine the phases of graded motor imagery. Initial searches were conducted by D.H. from March to June 2021 and were repeated in December 2022 and August 2023. The search strategy was executed across the following databases, registers, and websites: Medical Literature Analysis and Retrieval System Online, Embase, and American Psychological Association PsycInfo (all via Ovid), Cumulative Index to Nursing and Allied Health Literature, ClinicalTrials.gov, the Cochrane Library (via Wiley), Scopus, SportDiscus, Physiotherapy Evidence Database (pedro.org.au/), Occupational Therapy Search, African Journals Online (www.ajol.info), Latin American and Caribbean Health Sciences Literature (lilacs.bvsalud.org/en/), and the World Health Organization International Clinical Trials Registry Platform (trialsearch.who.int/). Filters were used to limit retrieval to studies published in English but not by publication date. The decision not to restrict the search based on publication date was due to the original graded motor imagery work being published in 2006, so no works eligible for this review were expected previous to this date. 9 In accordance with Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines, the full search strategy for one database can be found in Appendix 1. 25 The entire search strategy, including updates, employed for this review can be found on the Open Science Framework (https://osf.io/jra9t/).
Studies were included in this scoping review if the study design involved one or more phases of graded motor imagery for participants over the age of 18 with phantom limb pain due to amputation. Peer-reviewed publications, published conference abstracts, letters to the editor, and similar works were considered for inclusion. Works that may have not gone through a review process, also known as grey literature, were included since the intent of this scoping review was to describe the extent of current evidence and not evaluate the quality of evidence. In the case of clinical trials without an attached publication, authors were contacted in an attempt to gather additional information and obtain any published results. Literature reviews and retrospective analyses of previously published works were excluded, as were published conference abstracts that preceded included peer-reviewed publications in an attempt to eliminate duplicate information. Studies that included participants under the age of 18 were excluded as there is a potential that the mechanisms of pain in pediatric participants differ from those in adults, making comparisons between these groups difficult. 26 Similarly, studies that included participants with phantom limb pain resulting from etiologies other than amputation (e.g. brachial plexus avulsions and complex regional pain syndrome) were excluded from synthesis to design a homogeneous population for this scoping review, unless the work explicitly reported demographic information and results separately for the participants with amputations.
The title and abstract of each work were reviewed for inclusion independently by two authors (KF and HP) based on the criteria listed above. Conflicts in the screening decisions were resolved by a third author (RV). The full text of the remaining items was then reviewed by two authors (KF and HP) to determine final inclusion, and any conflicts were again resolved by a third author (RV). The blinded screening was performed in Rayyan (https://www.rayyan.ai).
Data were extracted from each article independently by two authors (KF and HP). A spreadsheet specifically created for this study for recording data was piloted prior to full data extraction. Each of the two authors recorded data in a separate spreadsheet. The two authors then compared the extracted data and attempted to resolve any conflicts through discussion. Any remaining conflicts after this discussion were resolved by a third author (TR).
The following data were extracted from each of the included articles: citation information, type of publication, study design, country of study, participant demographics, amputation characteristics (i.e. level of amputation, unilateral or bilateral amputations, cause of amputation, and time since amputation), use of prostheses, use of medications, authors’ definition of acute and/or chronic pain, graded motor imagery phase (i.e. limb laterality, explicit motor imagery, and mirror therapy), dosing of treatment, outcomes studied, outcome measures used, binary report of results (i.e. positive or negative results), and protocol on which the work was based. Working definitions of the study designs were adapted from the Cochrane Collaboration 27 and are listed in Appendix 2 with working definitions of graded motor imagery phases and related approaches. Any data that were not reported from these categories were recorded in the spreadsheet.
The extracted data were reviewed to examine similarities and differences between the included works. In particular, comparisons of the participant characteristics, the features of the interventions, and the outcomes measured were examined. This review involved both quantitative methods through frequency counts as well as qualitative methods through overall similarities.
The searches yielded 3028 unique records. Duplicates were identified and removed using Rayyan, leaving 1763 works to be screened based on titles and abstracts. During this screening, 1791 works were excluded, resulting in 151 works for full-text screening. Of those, 61 works fit our inclusion criteria and are included in this review ( Figure 1 ). Six authors were contacted by email to inquire about results from their clinical trials that were not able to be located through publication searches. Three authors responded to the inquiry but had no additional results to share, keeping the final number of works in this review to 61.