Prävalenz und Risikofaktoren von Phantomschmerzen und Phantomwahrnehmungen in Deutschland: Eine bundesweite Befragung

Assessment of efficiency of mirror therapy in preventing phantom limb pain in patients undergoing below-knee amputation surgery-a randomized clinical trial

PURPOSE AND OBJECTIVES

Phantom limb pain (PLP) is a major cause of physical limitation and disability accounting for about 85% of amputated patients. Mirror therapy is used as a therapeutic modality for patients with phantom limb pain. Primary objective was to study the incidence of PLP at 6 months following below-knee amputation between the mirror therapy group and control group.

METHODS

Patients posted for below-knee amputation surgery were randomized into two groups. Patients allocated to group M received mirror therapy in post-operative period. Two sessions of therapy were given per day for 7 days and each session lasted for 20 min. Patients who developed pain from the missing portion of the amputated limb were considered to have PLP. All patients were followed up for six months and the time of occurrence of PLP and intensity of the pain were recorded among other demographic factors.

RESULTS

A total of 120 patients completed the study after recruitment. The demographic parameters were comparable between the two groups. Overall incidence of phantom limb pain was significantly higher in the control group (Group C) when compared to the mirror therapy (Group M) group [Group M = 7 (11.7%) vs Group C = 17 (28.3%); p = 0.022]. Intensity of PLP measured on the Numerical Rating Scale (NRS) was significantly lower at 3 months in Group M compared to Group C among patients who developed PLP [NRS - median (Inter quartile range): Group M 5 (4,5) vs Group C 6 (5,6); p 0.001].

CONCLUSION

Mirror therapy reduced the incidence of phantom limb pain when administered pre-emptively in patients undergoing amputation surgeries. The severity of the pain was also found to be lower at 3 months in patients who received pre-emptive mirror therapy.

TRIAL REGISTRATION

This prospective study was registered in the clinical trial registry of India.

TRIAL REGISTRATION NUMBER

CTRI/2020/07/026488.

Botulinum toxin in the treatment of residual limb hyperhidrosis: A systematic review

The aim of the study was to analyze the current evidence regarding the effect of intradermal injections of botulinum toxin on residual limb hyperhidrosis. A comprehensive search of the MEDLINE and Scopus databases from inception until December 2021 was performed according to the PRISMA guidelines. The search terms used were "botulinum toxins", "botulinum toxins, Type A", "rimabotulinumtoxinB", "amputees", "amputation stumps", "amputation" and "residual limbs". The specific controlled vocabulary of each database was also used (e.g., MeSH). One hundred and thirty-one different studies met this search criteria and were reviewed. Two independent reviewers assessed the quality of the manuscripts. Eight studies met the inclusion criteria for this review. The results demonstrated an improvement in residual limb hyperhidrosis in all studies. Botulinum toxin A or B can be regarded as safe and effective for the treatment of residual limb hyperhidrosis, as well as improving prosthesis use and quality of life.

Percutaneous treatments for residual and/or phantom limb pain in adults with lower-extremity amputations: A narrative review

Residual limb pain (RLP) and phantom limb pain (PLP) profoundly affect the lives of many individuals who have undergone lower- or upper-extremity amputation. Despite the considerable impact of RLP/PLP on quality of life in persons with amputation, there have been few attempts to evaluate the efficacy of percutaneous interventions in the treatment of RLP and/or PLP. This narrative review evaluates the effectiveness of percutaneous treatments for RLP and/or PLP in patients after lower-extremity amputation. Peripheral nerve stimulation, alcohol neurolysis, conventional thermal radiofrequency ablation, perineural corticosteroid injection, botulinum toxin injection, and etanercept injection were associated with varying success rates. Wide confidence intervals and small treatment cohorts impede assessments of overall success. High-quality studies of nonsurgical, percutaneous treatments for RLP and/or PLP are lacking. Well-designed randomized controlled trials and large cohort studies with comparison groups using validated outcomes are needed to determine the effectiveness of nonsurgical interventions for the treatment of RLP and PLP.

Mind over matter: Perceived phantom/prosthesis co-location contributes to prosthesis embodiment in lower limb amputees

Prosthesis embodiment - the cognitive integration of a prosthesis into an amputees' body representation - has been identified as important for prosthetic rehabilitation. However, the underlying cognitive mechanisms remain unclear. There is reason to assume that phantom limbs that are experienced as part of the bodily self (phantom self-consciousness) can affect prosthesis embodiment, but only if the phantom and the prosthesis can be brought into perceived co-location (phantom prosthesis tolerance, PPT). In the present study, phantom-prosthesis interactions were examined in lower limb amputees, and a PPT component was psychometrically extracted. Mediation analysis revealed an indirect-only effect, where the relationship between phantom self-consciousness and prosthesis embodiment was mediated by PPT, indicating that phantom limbs can transfer their immanent vividness to the prosthesis. Subsequent analyses suggested that this effect can compensate for negative consequences on prosthesis embodiment that arise from phantom limb awareness. These results shape theoretical considerations about the cognitive processes contributing to the bodily self.

Body Schema Self-Awareness and Related Dream Content Modifications in Amputees Due to Cancer

PURPOSE

the evaluation of body image perception, pain coping strategies, and dream content, together with phantom limb and telescoping phenomena in patients with sarcoma who underwent surgery for limb amputation.

MATERIAL AND METHODS

consecutive outpatients were evaluated at T0 (within 3 weeks after surgery) and T1 (4-6 months after surgery) as follows: demographic and clinical data collection; the Groningen Questionnaire Problems after Arm Amputation; the West Haven-Yale Multidimensional Pain Inventory; the Body Image Concern Inventory, a clinical trial to identify telescoping; and a weekly diary of dreams. Dream contents were coded according to the Hall and Van de Castle coding system.

RESULTS

Twenty patients completed the study (15 males and 5 females, mean age: 53.9 ± 24.6, education: 7.8 ± 3.4). All subjects experienced phantom limb and 35% of them experienced telescoping soon after surgery, and 25% still after 4-6 months. Both at T0 and T1, that half of the subjects reported dreams about still having their missing limbs. At T1 the patients' perceptions of being able to deal with problems were lower, and pain and its interference in everyday life were higher yet associated with significant engagement in everyday activities and an overall good mood. The dream content analysis highlighted that males were less worried about health problems soon after amputation, and women showed more initial difficulties that seemed to be resolved after 4-6 months after surgery.

CONCLUSIONS

The dream content analysis may improve clinicians' ability to support their patients during their therapeutic course.

The Prevalence and Characteristics of Phantom Limb Pain and Non-Painful Phantom Phenomena in a Nationwide Survey of 3,374 Unilateral Limb Amputees

The experience of phantom limb pain (PLP) is a common consequence of limb amputation, resulting in severe impairments of the affected person. Previous studies have shown that several factors such as age at or site of amputation are associated with the emergence and maintenance of PLP. In this cross-sectional study we assessed the presence of several phantom phenomena including PLP and other amputation-related information in a sample of 3,374 unilateral upper and lower limb amputees. Clinical and demographic variables (age at amputation, level of amputation) explained 10.6% of the variance in PLP and perceptual variables (intensity of phantom limb sensation [PLS], referred sensations, intensity of telescoping, residual limb pain [RLP] intensity) explained 16.9% of the variance. These variables were specific for PLP and not for RLP. These results suggest that distinct variables are associated with PLP (age at amputation, level of amputation, PLS intensity, referred sensations, intensity of telescoping, RLP intensity) and RLP (PLP intensity) and point at partly different mechanisms for the emergence and maintenance of PLP and RLP. PERSPECTIVE: Clinical/demographic variables as well as perceptual variables are 2 major components related to PLP and explain ∼11% and ∼17% of the variance. These results could potentially help clinicians to understand which factors may contribute to chronic phantom limb pain.

Factors related to phantom limb pain and its effect on quality of life

AIMS

This study aims to investigate phantom limb pain (PLP), PLP-related factors, and the effect of PLP on quality of life in patients who had undergone upper or lower extremity amputation.

METHODS

One hundred four patients with unilateral amputation of the upper or lower extremity were included in this cross-sectional study. The patients were divided into two groups as patients with PLP and without PLP. Patients' demographic (age, gender, marital status, education level, employment status) and clinical information (date of amputation, amputated limb, the side, level and cause of amputation, phantom limb sensation and pain, sleep disorder) and quality of life (Nottingham extended activities of daily living index) were compared between the groups. In addition, factors associated with PLP were analysed.

RESULTS

Of the 104 patients, 47 patients (45.19%) had PLP. In the group with PLP, phantom sensation and sleep disturbance were significantly higher, whereas the time elapsed after amputation and Nottingham extended activities of daily living index score were significantly lower (p < 0.05). The relationship between PLP and sleep disorder and between PLP and marital status was significant (p < 0.05).

CONCLUSIONS

Our study results showed that PLP was associated with sleep disorder and marital status, and the quality of life was low in the group with PLP. Therefore, PLP evaluation should not be disregarded in amputees; PLP should be treated to increase quality of life.

Effects of mirror therapy on phantom limb sensation and phantom limb pain in amputees: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the effects of mirror therapy on phantom limb sensation and phantom limb pain in amputees.

DATA SOURCES

Nine electronic databases (PubMed, EMBASE, MEDLINE, Web of Science, the Cochrane Library, CINAHL, PsycInfo, PreQuest, PEDro) were searched from their inception to May 10th, 2021.

METHODS

Two authors independently selected relevant studies and extracted the data. The effect sizes were calculated under a random-effects model meta-analysis, and heterogeneity was assessed using the I² test. The risk of bias was evaluated by the Cochrane risk of bias tool, and the methodological quality was appraised by the PEDro scale. The GRADE approach was applied to assess the confidence of the effect.

RESULTS

A total of 11 RCTs involving 491 participants were included in this review and nine RCTs involving 372 participants were included in meta-analysis. The quality of these studies was from poor to good with scores ranging from 2 to 8 points according to PEDro scale. The pooled SMD showed that mirror therapy reduced the pain with a large effect size (-0.81; 95% CI = -1.36 to -0.25; P = 0.005; I² = 82%; n = 372) compared with other methods (four covered mirror, one phantom exercise, three mental visualization, one sensorimotor exercise, one transcutaneous electrical nerve stimulation, one tactile stimuli). The quality of evidence for the outcome pain intensity was determined to be fair according to GRADE approach.

CONCLUSION

There is fair-quality evidence that MT is beneficial for reducing phantom limb pain.

Phantom limb pain after unilateral arm amputation is associated with decreased heat pain thresholds in the face

BACKGROUND

The mechanisms underlying chronic phantom limb pain (PLP) are complex and insufficiently understood. Altered sensory thresholds are often associated with chronic pain but quantitative sensory testing (QST) in PLP has so far been inconclusive due to large methodological variation between studies and small sample sizes.

METHODS

In this study, we applied QST in 37 unilateral upper-limb amputees (23 with and 14 without PLP) and 19 healthy controls. We assessed heat pain (HPT), pressure pain, warmth detection and two-point discrimination thresholds at the residual limb, a homologous point and the thenar of the intact limb as well as both corners of the mouth.

RESULTS

We did not find significant differences in any of the thresholds between the groups. However, PLP intensity was negatively associated with HPT at all measured body sites except for the residual limb, indicating lower pain thresholds with higher PLP levels. Correlations between HPT and PLP were strongest in the contralateral face (r = -0.65, p < 0.001). Facial HPT were specifically associated with PLP, independent of residual limb pain (RLP) and various other covariates. HPT at the residual limb, however, were significantly associated with RLP, but not with PLP.

CONCLUSION

We conclude that the association between PLP and, especially facial, HPT could be related to central mechanisms.

SIGNIFICANCE

Phantom limb pain (PLP) is still poorly understood. We show that PLP intensity is associated with lower heat pain thresholds, especially in the face. This finding could be related to central nervous changes in PLP.

Relationship of prosthesis ownership and phantom limb pain: results of a survey in 2383 limb amputees

ABSTRACT

Phantom limb pain (PLP) accounts for a significant reduction in quality of life and is difficult to treat. Prosthesis use has been shown to negatively covary with PLP. Recent research on body perception in amputees suggest that prosthesis ownership, defined as the extent to which a prosthesis is experienced as being part of the body rather than an artificial device foreign to the body, might interact with PLP. We used survey data from 2383 unilateral prosthesis-using upper-limb or lower-limb amputees and performed regression analyses to determine the relationship between prosthesis ownership and PLP. To test for specificity, we examined the role of prosthesis ownership also for residual limb pain (RLP) and nonpainful phantom limb sensations (npPLS). Prosthesis ownership was reduced in older participants and higher in lower-limb compared to upper-limb amputees. A longer residual limb and more frequent prosthesis use as well as a longer time since amputation also yielded higher values. Prostheses based on natural principles were associated with higher prosthesis ownership. Phantom limb pain and RLP were lower with higher prosthesis ownership, and RLP but not PLP was lower when prosthesis use was frequent. There were no significant associations for npPLS. The regression results differ in some aspects from those revealed by univariate analyses, emphasizing the importance of multivariate statistical approaches. Our findings provide insights into the interplay of body- and pain-related sensations after amputation, and could help to develop new treatment approaches for both PLP and RLP.

Factors Associated With Prosthesis Embodiment and Its Importance for Prosthetic Satisfaction in Lower Limb Amputees

Perceptual integration of a prosthesis into an amputee's body representation, that is, prosthesis embodiment, has been proposed to be a major goal of prosthetic treatment, potentially contributing to the user's satisfaction with the device. However, insufficient knowledge about individual or prosthetic factors associated with prosthesis embodiment challenges basic as well as rehabilitation research. In the present study, hierarchical multiple regression analyses on prosthesis embodiment—as assessed with the recently introduced Prosthesis Embodiment Scale—were applied to the survey data of a large sample of prosthesis-using lower limb amputees, entering relevant objective-descriptive (i.e., unbiased characteristics of the amputation or the prosthesis) and subjective-evaluative variables (i.e., the amputee's perceptions related to the amputation or the prosthesis) as first- or second-level regressors, respectively. Significant regressors identified in these analyses together explained R² = 36.3% of prosthesis embodiment variance in the present sample, with a lower level of amputation, less intense residual limb pain, more realistic visual appearance of the device, higher prosthetic mobility, and more positive valence of prosthesis-induced residual limb stimulations representing significantly associated factors. Using the identical set of regressors hierarchically complemented by prosthesis embodiment on measures of prosthetic satisfaction—as assessed with the Trinity Amputation and Prosthesis Experience Scales—revealed that prosthesis embodiment was significantly and positively associated with aesthetic as well as functional prosthesis satisfaction. These findings emphasize the importance of psychological factors for the integration of a prosthesis into the amputee's body representation, which itself represents a crucial factor associated with prosthesis satisfaction. The results might have important implications for future prosthetic treatment; however, replication of the findings in an independent sample is required, as well as sophisticated experimental designs in order to elucidate the causality of effects.

Neurophysiological models of phantom limb pain: what can be learnt

Phantom Limb Pain (PLP) is a dysesthesic painful sensations perceived in the lost limb, resulting from complex interactions between structural and functional nervous systems changes. We analyze its main pathogenetic models and speculate on candidate therapeutic targets. The neuroma model considers PLP to arise from spontaneous activity of residual limb injured axons. Other peripheral-origin models attribute PLP to damage of somatosensory receptors or vascular changes. According to the cortical remapping model, the loss of bidirectional nervous flow and the need to enhance alternative functions trigger reorganization and arm and face skin afferents "invade" the hand territory. On the contrary, the persistent representation model suggests that continued inputs preserve the lost limb representation and that, instead to a shrinkage, PLP is associated with larger representation and stronger cortical activity. In the neuromatrix model, the mismatch between body representation, which remains intact despite limb amputation, and real body appearance generates pain. Another hypothesis is that proprioceptive memories associate specific limb positions with pre-amputation pain and may be recalled by those positions. Finally, the stochastic entanglement model offers a direct relationship between sensorimotor neural reorganization and pain. Amputation disrupts motor and somatosensory circuits, allowing for maladaptive wiring with pain circuits and causing pain without nociception. Relief of PLP depends solely on motor and somatosensory circuitry engagement, making anthropomorphic visual feedback dispensable. Existing and apparently contradicting theories might not be mutually exclusive. All of them involve several intertwined potential mechanisms by which replacing the amputated limb by an artificial one could counteract PLP.

The prevalence and risk factors for phantom limb pain in people with amputations: A systematic review and meta-analysis

Background

Phantom limb pain (PLP)—pain felt in the amputated limb–is often accompanied by significant suffering. Estimates of the burden of PLP have provided conflicting data. To obtain a robust estimate of the burden of PLP, we gathered and critically appraised the literature on the prevalence and risk factors associated with PLP in people with limb amputations.

Methods

Articles published between 1980 and July 2019 were identified through a systematic search of the following electronic databases: MEDLINE/PubMed, PsycINFO, PsycArticles, Cumulative Index to Nursing and Allied Health Literature, Africa-Wide Information, Health Source: Nursing/Academic Edition, SCOPUS, Web of Science and Academic Search Premier. Grey literature was searched on databases for preprints. Two reviewers independently conducted the screening of articles, data extraction and risk of bias assessment. The meta-analyses were conducted using the random effects model. A statistically significant level for the analyses was set at p<0.05.

Results

The pooling of all studies demonstrated a prevalence estimate of 64% [95% CI: 60.01–68.05] with high heterogeneity [I² = 95.95% (95% CI: 95.10–96.60)]. The prevalence of PLP was significantly lower in developing countries compared to developed countries [53.98% vs 66.55%; p = 0.03]. Persistent pre-operative pain, proximal site of amputation, stump pain, lower limb amputation and phantom sensations were identified as risk factors for PLP.

Conclusion

This systematic review and meta-analysis estimates that six of every 10 people with an amputation report PLP–a high and important prevalence of PLP. Healthcare professionals ought to be aware of the high rates of PLP and implement strategies to reduce PLP by addressing known risk factors, specifically those identified by the current study.

[Two-point discrimination through electrical stimulation of receptive fields]

The effect of two-point discrimination described in this case report indicates a cortical reorganization through electrical stimulation of receptive fields. The "intervention units" compared to the "baseline" show clear effects. The pain behavior in both "intervention units" showed a clear change in the phantom phenomena, which in both "wash out" phases moved back towards "baseline". Thus, electrical stimulation of receptive fields could be another therapy for the treatment of phantom pain, given the change in two-point discrimination.

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.

Robotic hand illusion with tactile feedback: Unravelling the relative contribution of visuotactile and visuomotor input to the representation of body parts in space

The rubber hand illusion describes a phenomenon in which participants experience a rubber hand as being part of their body by the synchronous application of visuotactile stimulation to the real and the artificial limb. In the recently introduced robotic hand illusion (RobHI), a robotic hand is incorporated into one’s body representation due to the integration of synchronous visuomotor information. However, there are no setups so far that combine visuotactile and visuomotor feedback, which is expected to unravel mechanisms that cannot be detected in experimental designs applying this information in isolation. We developed a robotic hand, controlled by a sensor glove and equipped with pressure sensors, and varied systematically and separately the synchrony for motor feedback (MF) and tactile feedback (TF). In Experiment 1, we implemented a ball-grasping task and assessed the perceived proprioceptive drift of one’s own hand as a behavioral measure of the spatial calibration of body coordinates as well as explicit embodiment experiences by a questionnaire. Results revealed significant main effects of both MF and TF for proprioceptive drift data, but we only observed main effects for MF on perceived embodiment. Furthermore, for the proprioceptive drift we found that synchronous feedback in one factor compensates for asynchronous feedback in the other. In Experiment 2, including a new sample of naïve participants, we further explored this finding by adding unimodal conditions, in which we manipulated the presence or absence of MF and/or TF. These findings replicated the results from Experiment 1 and we further found evidence for a supper-additive multisensory effect on spatial body representation caused by the presence of both factors. Results on conscious body perception were less consistent across both experiments. The findings indicate that sensory and motor input equally contribute to the representation of spatial body coordinates which for their part are subject to multisensory enhancing effects. The results outline the potential of human-in-the-loop approaches and might have important implications for clinical applications such as for the future design of robotic prostheses.

Can phantom limb pain be reduced/eliminated solely by techniques applied to peripheral nerves?

About 0.5% of the US population (1.7 million) is living with a lost limb and this number is expected to double by 2050. This number is much higher in other parts of the world. Within days to weeks of an extremity amputation, up to 80% of these individuals develop neuropathic pain presenting as phantom limb pain (PLP). The level of PLP increases significantly by one year and remains chronic and severe for about 10% of individuals. PLP has a serious negative impact on individuals’ lives. Current pain treatment therapies, such pharmacological approaches provide limited to no pain relief, some other techniques applied to the central nervous system (CNS) and peripheral nervous system (PNS) reduce or block PLP, but none produces long-term pain suppression. Therefore, new drugs or novel analgesic methods must be developed that prevent PLP from developing, or if it develops, to reduce the level of pain. This paper examines the potential causes of PLP, and present techniques used to prevent the development of PLP, or if it develops, to reduce the level of pain. Finally it presents a novel technique being developed that eliminates/reduces chronic neuropathic pain and which may induce the long-term reduction/elimination of PLP.

Feel-Good Robotics: Requirements on Touch for Embodiment in Assistive Robotics

The feeling of embodiment, i.e., experiencing the body as belonging to oneself and being able to integrate objects into one's bodily self-representation, is a key aspect of human self-consciousness and has been shown to importantly shape human cognition. An extension of such feelings toward robots has been argued as being crucial for assistive technologies aiming at restoring, extending, or simulating sensorimotor functions. Empirical and theoretical work illustrates the importance of sensory feedback for the feeling of embodiment and also immersion; we focus on the the perceptual level of touch and the role of tactile feedback in various assistive robotic devices. We critically review how different facets of tactile perception in humans, i.e., affective, social, and self-touch, might influence embodiment. This is particularly important as current assistive robotic devices – such as prostheses, orthoses, exoskeletons, and devices for teleoperation–often limit touch low-density and spatially constrained haptic feedback, i.e., the mere touch sensation linked to an action. Here, we analyze, discuss, and propose how and to what degree tactile feedback might increase the embodiment of certain robotic devices, e.g., prostheses, and the feeling of immersion in human-robot interaction, e.g., in teleoperation. Based on recent findings from cognitive psychology on interactive processes between touch and embodiment, we discuss technical solutions for specific applications, which might be used to enhance embodiment, and facilitate the study of how embodiment might alter human-robot interactions. We postulate that high-density and large surface sensing and stimulation are required to foster embodiment of such assistive devices.

Relieving phantom limb pain with multimodal sensory-motor training

OBJECTIVE

The causes for the disabling condition of phantom limb pain (PLP), affecting 85% of amputees, are so far unknown, with few effective treatments available. Sensory feedback based strategies to normalize the motor commands to control the phantom limb offer important targets for new effective treatments as the correlation between phantom limb motor control and sensory feedback from the motor intention has been identified as a possible mechanism for PLP development.

APPROACH

Ten upper-limb amputees, suffering from chronic PLP, underwent 16 days of intensive training on phantom-limb movement control. Visual and tactile feedback, driven by muscular activity at the stump, was provided with the aim of reducing PLP intensity.

MAIN RESULTS

A 32.1% reduction of PLP intensity was obtained at the follow-up (6 weeks after the end of the training, with an initial 21.6% reduction immediately at the end of the training) reaching clinical effectiveness for chronic pain reduction. Multimodal sensory-motor training on phantom-limb movements with visual and tactile feedback is a new method for PLP reduction.

SIGNIFICANCE

The study results revealed a substantial reduction in phantom limb pain intensity, obtained with a new training protocol focused on improving phantom limb motor output using visual and tactile feedback from the stump muscular activity executed to move the phantom limb.

The Stochastic Entanglement and Phantom Motor Execution Hypotheses: A Theoretical Framework for the Origin and Treatment of Phantom Limb Pain

Phantom limb pain (PLP) is a debilitating condition common after amputation that can considerably hinder patients' quality of life. Several treatments have reported promising results in alleviating PLP. However, clinical evaluations are usually performed in small cohorts and rigorous clinical trials are scarce. In addition, the underlying mechanisms by which novel interventions alleviate PLP are often unclear, potentially because the condition itself is poorly understood. This article presents a theoretical framework of PLP that can be used as groundwork for hypotheses of novel treatments. Current hypotheses on the origins of PLP are discussed in relation to available clinical findings. Stochastic entanglement of the pain neurosignature, or connectome, with impaired sensorimotor circuitry is proposed as an alternative hypothesis for the genesis of PLP, and the implications and predictions this hypothesis entails are examined. In addition, I present a hypothesis for the working mechanism of Phantom Motor Execution (PME) as a treatment of PLP, along with its relation to the aforementioned stochastic entanglement hypothesis, which deals with PLP's incipience. PME aims to reactivate the original central and peripheral circuitry involved in motor control of the missing limb, along with increasing dexterity of stump muscles. The PME hypothesis entails that training of phantom movements induces gradual neural changes similar to those of perfecting a motor skill, and these purposefully induced neural changes disentangle pain processing circuitry by competitive plasticity. This is a testable hypothesis that can be examined by brain imaging and behavioral studies on subjects undergoing PME treatment. The proposed stochastic entanglement hypothesis of PLP can be generalized to neuropathic pain due to sensorimotor impairment, and can be used to design suitable therapeutic treatments.

Psychological Factors Associated with Phantom Limb Pain: A Review of Recent Findings

Phantom limb pain (PLP) is a common phenomenon occurring after the amputation of a limb and can be accompanied by serious suffering. Psychological factors have been shown to play an important role in other types of chronic pain, where they are pivotal in the acquisition and maintenance of pain symptoms. For PLP, however, the interaction between pain and psychological variables is less well documented. In this review, we summarize research on the role of emotional, motivational, cognitive, and perceptual factors in PLP. The reported findings indicate that emotional factors modulate PLP but might be less important compared to other types of chronic pain. Additional factors such as the amount of disability and adjustment to the amputation appear to also play a role. Bidirectional relationships between stress and PLP have been shown quite consistently, and the potential of stress and tension reduction in PLP treatment could be further exploited. Little is known about the role of cognitive variables such as attention or expectation. Catastrophizing seems to aggravate PLP and could be targeted in treatment. Body perception is altered in PLP and poses a potential target for novel mechanistic treatments. More research on psychological factors and their interactions in PLP is needed.

Feel-Good Robotics: Requirements on Touch for Embodiment in Assistive Robotics

The feeling of embodiment, i.e., experiencing the body as belonging to oneself and being able to integrate objects into one's bodily self-representation, is a key aspect of human self-consciousness and has been shown to importantly shape human cognition. An extension of such feelings toward robots has been argued as being crucial for assistive technologies aiming at restoring, extending, or simulating sensorimotor functions. Empirical and theoretical work illustrates the importance of sensory feedback for the feeling of embodiment and also immersion; we focus on the the perceptual level of touch and the role of tactile feedback in various assistive robotic devices. We critically review how different facets of tactile perception in humans, i.e., affective, social, and self-touch, might influence embodiment. This is particularly important as current assistive robotic devices - such as prostheses, orthoses, exoskeletons, and devices for teleoperation-often limit touch low-density and spatially constrained haptic feedback, i.e., the mere touch sensation linked to an action. Here, we analyze, discuss, and propose how and to what degree tactile feedback might increase the embodiment of certain robotic devices, e.g., prostheses, and the feeling of immersion in human-robot interaction, e.g., in teleoperation. Based on recent findings from cognitive psychology on interactive processes between touch and embodiment, we discuss technical solutions for specific applications, which might be used to enhance embodiment, and facilitate the study of how embodiment might alter human-robot interactions. We postulate that high-density and large surface sensing and stimulation are required to foster embodiment of such assistive devices.

Capsaicin 8% patch treatment for amputation stump and phantom limb pain: a clinical and functional MRI study

Purpose

The aim of this study was to measure the efficacy of a single 60 min application of capsaicin 8% patch in reducing chronic amputation stump and phantom limb pain, associated hypersensitivity with quantitative sensory testing, and changes in brain cortical maps using functional MRI (fMRI) scans.

Methods

A capsaicin 8% patch (Qutenza) treatment study was conducted on 14 patients with single limb amputation, who reported pain intensity on the Numerical Pain Rating Scale ≥4/10 for chronic stump or phantom limb pain. Pain assessments, quantitative sensory testing, and fMRI (for the lip pursing task) were performed at baseline and 4 weeks after application of capsaicin 8% patch to the amputation stump. The shift into the hand representation area of the cerebral cortex with the lip pursing task has been correlated with phantom limb pain intensity in previous studies, and was the fMRI clinical model for cortical plasticity used in this study.

Results

The mean reduction in spontaneous amputation stump pain, phantom limb pain, and evoked stump pain were −1.007 (p=0.028), −1.414 (p=0.018), and −2.029 (p=0.007), respectively. The areas of brush allodynia and pinprick hypersensitivity in the amputation stump showed marked decreases: −165 cm², −80% (p=0.001) and −132 cm², −72% (p=0.001), respectively. fMRI analyses provided objective evidence of the restoration of the brain map, that is, reversal of the shift into the hand representation of the cerebral cortex with the lip pursing task (p<0.05).

Conclusion

The results show that capsaicin 8% patch treatment leads to significant reduction in chronic pain and, particularly, in the area of stump hypersensitivity, which may enable patients to wear prostheses, thereby improving mobility and rehabilitation. Phantom limb pain (“central” pain) and associated brain plasticity may be modulated by peripheral inputs, as they can be ameliorated by the peripherally restricted effect of the capsaicin 8% patch.

[Automated two-point discrimination (TPD) for phantom pain : Effect of a 3‑week automated therapy based on TPD for a transtibial amputee with phantom pain]

There is preliminary evidence that phantom pain is associated with disturbed organization of the sensory cortex and that this organization can be normalized with two-point discrimination (TPD) training. In this case study, a reduction in phantom pain and painful phantom sensation during a test period of 19 days, was achieved using an automated TPD procedure. In a patient with a transtibial amputation, pain levels decreased from a mean of 2.3/10 on the visual analog scale (VAS) to 1.3/10 (VAS) and the painful phantom sensation level decreased from a mean 3.7/10 (VAS) to 2.0/10 (VAS). These results show a positive trend, but are (except of the nocturnal pain attacks) rather of limited clinical relevance.

The effect of electromagnetic shielding on phantom limb pain: A placebo-controlled double-blind crossover trial

BACKGROUND

Environmental electromagnetic fields influence biological systems. Evidence suggests these have a role in the experience of phantom limb pain in patients with amputations.

OBJECTIVES

This article followed a previous study to investigate the effect of electromagnetic field shielding with a specially designed prosthetic liner.

STUDY DESIGN

Randomised placebo-controlled double-blind crossover trial.

METHODS

Twenty suitable participants with transtibial amputations, phantom pain at least 1 year with no other treatable cause or pathology were requested to record daily pain, well-being, activity and hours of prosthetic use on pre-printed diary sheets. These were issued for three 2-week periods (baseline, electromagnetic shielding (verum) and visually identical placebo liners - randomly allocated).

RESULTS

Thirty-three per cent of the recruited participants were unable to complete the trial. The resulting N was therefore smaller than was necessary for adequate power. The remaining data showed that maximum pain and well-being were improved from baseline under verum but not placebo. More participants improved on all variables with verum than placebo.

CONCLUSION

Electromagnetic field shielding produced beneficial effects in those participants who could tolerate the liner. It is suggested that this might be due to protection of vulnerable nerve endings from nociceptive effects of environmental electromagnetic fields.

CLINICAL RELEVANCE

Electromagnetic field shielding with a suitable limb/prosthesis interface can be considered a useful technique to improve pain and well-being in patients with phantom limb pain.

Preoperative state anxiety, acute postoperative pain, and analgesic use in persons undergoing lower limb amputation

OBJECTIVES

The current study examined the relationship between preoperative anxiety and acute postoperative phantom limb pain (PLP), residual limb pain (RLP), and analgesic medication use in a sample of persons undergoing lower limb amputation.

MATERIALS AND METHODS

Participants included 69 adults admitted to a large level 1 trauma hospital for lower limb amputation. Participants' average pain and anxiety during the previous week were assessed before amputation surgery. RLP, PLP, and analgesic medication use were measured on each of the 5 days following amputation surgery.

RESULTS

Results of partial-order correlations indicated that greater preoperative anxiety was significantly associated with greater ratings of average PLP for each of the 5 days following amputation surgery, after controlling for preoperative pain ratings and daily postoperative analgesic medication use. Partial correlation values ranged from 0.30 to 0.62, indicating medium to large effects. Preoperative anxiety was also significantly associated with ratings of average RLP only on postoperative day 1, after controlling for preoperative pain ratings and daily postoperative analgesic medication use (r=0.34, P<0.05). Correlations between preoperative anxiety and daily postoperative analgesic medication dose became nonsignificant when controlling for preamputation and postamputation pain ratings.

DISCUSSION

These findings suggest that anxiety may be a risk factor for acute postamputation PLP and RLP, and indicate that further research to examine these associations is warranted. If replicated, the findings would support research to examine the extent to which modifying preoperative anxiety yields a reduction in postoperative acute PLP and RLP.

The relationship between prosthesis use, phantom pain and psychiatric symptoms in male traumatic limb amputees

OBJECTIVES

The purpose of this study was to identify psychiatric symptoms by comparing male patients with traumatic leg amputations (LAs) with healthy controls and to determine the association between these psychiatric symptoms and phantom pain and prosthesis use characteristics.

METHODS

One hundred four volunteers, 51 LA patients (group 1) and 53 healthy controls (group 2) were included. Demographic data including age, height, weight, time since amputation, duration of prosthesis use, and Satisfaction with Prosthesis Questionnaire scores were recorded. Phantom pain was measured a visual analog scale (VAS). Psychiatric symptoms were measured using the Symptom Checklist-90-R, Beck Depression Inventory, Pittsburgh Sleep Quality Index, Rosenberg Self-Esteem Scale, and State-Trait Anxiety Inventory. Correlations were determined between time since amputation, duration of prosthesis use and satisfaction with prosthesis questionnaire scores and psychiatric scale scores.

RESULTS

Amputee patients had higher phobic anxiety, state anxiety, trait anxiety and sleep disturbance scores (p<0.05) than the controls. No difference was determined in terms of psychiatric symptoms between the phantom pain and no phantom pain groups (p>0.05). There were significant negative correlations between time since amputation, duration of prosthesis use, duration of daily prosthesis use, and satisfaction with prosthesis questionnaire scores and psychiatric symptoms.

CONCLUSIONS

Apart from anxiety (state, trait or phobic) and disturbed sleep, other psychiatric symptoms in amputee patients undergoing lengthy prosthetic rehabilitation may not differ from those of healthy controls. The presence and severity of phantom pain appear to be unrelated to general psychiatric symptomatology. Length of time since amputation, length of prosthesis use, daily length of prosthesis use and prosthesis satisfaction are negatively correlated with general psychiatric symptoms. These characteristics must be borne in mind in psychiatric and prosthetic rehabilitation.

Epigenetics in the perioperative period

The perioperative period is characterized by profound changes in the body's homoeostatic processes. This review seeks to address whether epigenetic mechanisms may influence an individual's reaction to surgery and anaesthesia. Evidence from animal and human studies suggests that epigenetic mechanisms can explain many facets of susceptibility to acute and chronic pain, making them potential therapeutic targets. Modern pain management is still based upon opiates, and both the developmental expression of opioid receptors and opioid-induced hyperalgesia have been linked to epigenetic mechanisms. In general, opiates seem to increase global DNA methylation levels. This is in contrast to local anaesthetics, which have been ascribed a global demethylating effect. Even though no direct investigations have been carried out, the potential influence of epigenetics on the inflammatory response that follows surgery seems a promising area for research. There is a considerable body of evidence that supports the involvement of epigenetics in the complex process of wound healing. Epigenetics is an important emerging research topic in perioperative medicine, with a huge potential to positively influence patient outcome.

Post-amputation pain is associated with the recall of an impaired body representation in dreams-results from a nation-wide survey on limb amputees

The experience of post-amputation pain such as phantom limb pain (PLP) and residual limb pain (RLP), is a common consequence of limb amputation, and its presence has negative effects on a person's well-being. The continuity hypothesis of dreams suggests that the presence of such aversive experiences in the waking state should be reflected in dream content, with the recalled body representation reflecting a cognitive proxy of negative impact. In the present study, we epidemiologically assessed the presence of post-amputation pain and other amputation-related information as well as recalled body representation in dreams in a sample of 3,234 unilateral limb amputees. Data on the site and time of amputation, residual limb length, prosthesis use, lifetime prevalence of mental disorders, presence of post-amputation pain, and presence of non-painful phantom phenomena were included in logistic regression analyses using recalled body representation in dreams (impaired, intact, no memory) as dependent variable. The effects of age, sex, and frequency of dream recall were controlled for. About 22% of the subjects indicated that they were not able to remember their body representation in dreams, another 24% of the amputees recalled themselves as always intact, and only a minority of less than 3% recalled themselves as always impaired. Almost 35% of the amputees dreamed of themselves in a mixed fashion. We found that lower-limb amputation as well as the presence of PLP and RLP was positively associated with the recall of an impaired body representation in dreams. The presence of non-painful phantom phenomena, however, had no influence. These results complement previous findings and indicate complex interactions of physical body appearance and mental body representation, probably modulated by distress in the waking state. The findings are discussed against the background of alterations in cognitive processes after amputation and hypotheses suggesting an innate body model.

Causes and prevention of chronic postsurgical pain

PURPOSE OF REVIEW

Surgical incision invariably causes some measure of nerve damage and inflammatory response that, in most cases, heals quickly without long-term negative consequence. However, a subset of these patients go on to develop lasting neuropathic pain that is difficult to treat and, in many cases, prevents the return to normal activities of life. It remains unknown why two patients with identical surgical interventions may go on to develop completely divergent pain phenotypes or no pain at all. Aggressive, early analgesic therapy has been shown to reduce the incidence of chronic postsurgical pain (CPSP), but no specific regional anesthetic technique or systemic pharmacologic therapy has been shown to prevent CPSP.

RECENT FINDINGS

Inflammation and glial cell activation have recently been shown to be just as important in the transition from normal acute pain to pathologic chronic pain as nerve injury itself and that central sensitization may not be solely due to repetitive nociceptive firing at the time of nerve injury. This has opened a number of new therapeutic possibilities for prevention of CPSP.

SUMMARY

Here, we discuss the causes of CPSP and current useful preventive strategies in the perioperative period. We also discuss future potential disease-modifying treatments of CPSP.

Phantom limb pain in daily practice--still a lot of work to do!

OBJECTIVES

Effective treatment of phantom limb pain (PLP, pain felt in the part of the body of an amputated limb) is still difficult to achieve, and improved treatment is needed. It is therefore of paramount interest to understand the current practice of PLP therapy outside pain centers.

DESIGN

As a part of a nationwide survey, 537 amputees were asked 11 questions related to their treatment experiences and the pain relief. Furthermore, the patients' opinion about the quality of medical care was also asked.

RESULTS

Five hundred thirty-seven out of 1088 amputees returned the questionnaire (49.4%). Four hundred (74.5%) suffered from PLP. The patients rated their caregivers' knowledge about PLP lower than their own. Many (41.6%) of PLP patients had never been informed about the possibility of occurrence and mechanisms of PLP. The vast majority of the PLP patients did not try any treatment. Among those treated, more than 30% consulted more than three physicians for beneficial treatment. A >50% pain reduction was achieved in only 12.7% of PLP patients. The most successful treatments were opioids (67.4%) and anticonvulsants (51.7%). Surgery was performed in 46.4% of all PLP patients and in 29.7% due to a clinically suspected neuroma. After surgery, pain was worse or unchanged in 50% and improved in 41.6%, and 7.4% were pain-free.

CONCLUSIONS

Our results suggest that there are primary needs for better information about PLP pathophysiology and treatment not only for patients but also for caregivers. Limited therapeutic success reveals a further need for increased research in PLP management.

Prevention of chronic pain after surgical nerve injury: amputation and thoracotomy

Although techniques for acute pain management have improved in recent years, a dramatic reduction in the incidence and severity of chronic pain following surgery has not occurred. Amputation and thoracotomy, although technically different, share the commonalities of unavoidable nerve injury and the frequent presence of persistent postsurgical neuropathic pain. The authors review the risk factors for the development of chronic pain following these surgeries and the current evidence that supports analgesic interventions. The inconclusive results from many preemptive analgesic studies may require us to reconceptualize the perioperative treatment period as a time of gradual neurologic remodeling.

Phantom Limb Pain After Lower Limb Trauma

Phantom sensations, that is, sensations perceived in a body part that has been lost, are a common consequence of accidental or clinical extremity amputations. Most amputation patients report a continuing presence of the limb, with some describing additional sensations such as numbness, tickling, or cramping of the phantom limb. The type, frequency, and stability of these phantom sensations can vary immensely. The phenomenon of painful phantom sensations, that is, phantom limb pain, presents a challenge for practitioners and researchers and is often detrimental to the patient’s quality of life. In addition to the use of conventional therapies for chronic pain disorders, recent years have seen the development of novel treatments for phantom limb pain, based on an increasing body of research on neurophysiological changes after amputation. This article describes the current state of research in regard to the demographics, causal factors, and treatments of phantom limb pain.

Relationship between bodily illusions and pain syndromes

SUMMARY Apart from their contribution to the overall knowledge of perception and related processes, sensory illusions have been used in recent years to treat and better understand pain disorders such as phantom limb pain or complex regional pain syndrome. With the help of modern imaging techniques, we can examine connections between basic processes of integrative perception and the occurrence of chronic pain. This article gives an overview of recent developments in the area of body illusions and pain, and provides suggestions on how they might lead to novel and effective treatments for chronic pain.

21. Phantom pain

Phantom pain is pain caused by elimination or interruption of sensory nerve impulses by destroying or injuring the sensory nerve fibers after amputation or deafferentation. The reported incidence of phantom limb pain after trauma, injury or peripheral vascular diseases is 60% to 80%. Over half the patients with phantom pain have stump pain as well. Phantom pain can also occur in other parts of the body; it has been described after mastectomies and enucleation of the eye. Most patients with phantom pain have intermittent pain, with intervals that range from 1 day to several weeks. Even intervals of over a year have been reported. The pain often presents itself in the form of attacks that vary in duration from a few seconds to minutes or hours. In most cases, the pain is experienced distally in the missing limb, in places with the most extensive innervation density and cortical representation. Although there are still many questions as to the underlying mechanisms, peripheral as well as central neuronal mechanisms seem to be involved. Conservative therapy consists of drug treatment with amitriptyline, tramadol, carbamazepine, ketamine, or morphine. Based on the available evidence some effect may be expected from drug treatment. When conservative treatment fails, pulsed radiofrequency treatment of the stump neuroma or of the spinal ganglion (DRG) or spinal cord stimulation could be considered (evidence score 0). These treatments should only be applied in a study design.

The menacing phantom: what pulls the trigger?

Phantom phenomena are frequent following amputation, but how this often painful experience is modified or triggered by spontaneous events or sensations often puzzles amputees and clinicians alike. We explored triggers of phantom phenomena in a heterogeneous sample of 264 upper and lower limb adult amputees with phantom sensations. Participants completed a structured questionnaire to determine the prevalence and nature of the triggers of phantom phenomena. The four categories of triggers identified include: (a) a quarter of participants experiencing psychological, emotional or autonomic triggers; (b) half experiencing behavioral triggers, "forgetting" the limb's absence and attempting to use the phantom; (c) one-fifth experiencing weather-induced triggers; and (d) one-third experiencing sensations referred from parts of the body. Upper limb amputees; and were more likely to experience weather-induced phantom phenomena than lower limb amputees; and upper and lower limb amputees were equally likely to experience referred sensations from the genitals, contradicting the homuncular remapping hypothesis. Traumatic amputees were more likely to report emotional triggers. Further, while those with emotional triggers exhibited poorer acceptance of the limitations of amputation, they were more likely to employ adaptive coping mechanisms. Finally, habitual "forgetting" behaviors were most common soon after amputation, whereas other more adaptive schemata (e.g., self-defense) were equally likely to be performed at any time following amputation. Various likely inter-related mechanisms are discussed in relation to phantom triggers. Ultimately, optimizing stump and neuroma management, as well as restoring function of central networks for pain, limb movement, and amputation-related memories, should help manage spontaneously triggered phantom phenomena.