Characterisation of Phantom Limb Pain in Traumatic Lower-Limb Amputees

Case Report: Reduction in post-amputation phantom limb pain intensity accompanying the onset of phantom limb telescoping

Introduction

Individuals with limb loss frequently report post-amputation phenomena, including nonpainful phantom sensations, phantom limb pain (PLP), and residual limb pain (RLP). Although post-amputation pain is common, not all patients benefit from widely accepted treatments. A greater understanding of phantom limb "telescoping", the experience of one's phantom hand or foot gradually approaching the residual limb, may assist in developing more effective interventions for reducing post-amputation pain. This case report explores the relationships between PLP, RLP, telescoping, and psychosocial experience in one person with a lower limb amputation. The aim of this case is to illustrate one possible relationship between telescoping and PLP as the mechanisms linking the two remain equivocal.

Methods

The participant is a 35-year-old male who underwent a transfemoral amputation due to a traumatic injury to his right leg approximately 4 years prior. He responded to questionnaires evaluating demographic and health-related information (e.g., age, sex, marital status, reason for amputation), pain and psychological variables via the Brief Pain Inventory (BPI-SF), ID Pain Questionnaire (IDPQ), Pain Catastrophizing Scale (PSC-4), Patient Health Questionnaire-4 (PHQ-4), Life Orientation Test-Revised (LOT-R), Connor-Davidson Resilience Scale (CD-RISC2), and Chronic Pain Acceptance Questionnaire (CPAQ-8) and telescoping, measured by a newly developed app. The participant completed a semi-structured interview that was designed to ascertain patterns in the overlapping experience of phantom limb telescoping and post-amputation pain.

Results

The participant rated his average PLP as 10 on a Numeric Rating Scale (NRS) from 0 ("no pain") to 10 ("worst pain imaginable") shortly after amputation. Approximately 12 months later, the participant noticed a shortening of his phantom limb, with a concurrent decrease in PLP. At present, his average NRS pain intensity is a 5/10. The participant described how the daily, debilitating PLP intensity diminished to weekly, manageable pain over time. Most notably, his responses on questionnaires were consistent with neuropathic PLP, mild to moderate levels of pain interference, a high level of catastrophic thinking about pain, low optimism, and mild symptoms of anxiety and depression.

Discussion

In this report, telescoping appeared to be preceded by an initial reduction in PLP intensity but these findings are based on a single case report and must be replicated with a large sample size before we have a clearer idea of the relationship between telescoping and PLP. This study provides insight into factors that may maintain PLP, generating targets for further investigation.

Clinical Characteristics Associated with the PLP-PLS Index, a New Potential Metric to Phenotype Phantom Limb Pain

BACKGROUND

Phantom limb pain (PLP) is highly prevalent after amputation. However, the influence of non-painful sensations (PLS) remains unclear. This study examines the PLP-PLS index as a novel tool to differentiate PLP from PLS and explores the association of clinical factors with the index.

METHODS

We conducted a cross-sectional analysis of baseline data from 112 participants in a previous factorial trial in patients with unilateral traumatic lower limb amputation. Linear regression models were used to examine the associations between the index and various demographic, psychological and clinical factors. Logistic and Poisson regression, and e-value calculation were utilized for sensitivity analyses.

RESULTS

Adjusted multivariable linear regression models demonstrated significant associations of phantom movement sensation (β: -1.532; 95% CI: -2.615 to -0.449; p = 0.006) and time since amputation (β: 0.005; 95% CI: 0.0006 to 0.0101; p = 0.026) with the PLP-PLS index. These findings were confirmed by multivariable logistic regression (phantom movement sensation OR: 0.469; 95% CI: 0.200 to 1.099, p = 0.082; time since amputation OR: 1.003; 95% CI: 1.00003 to 1.007; p = 0.048) and sensitivity analyses.

CONCLUSIONS

Time since amputation and phantom movement sensation likely reflect distinct phenotypes and potential mechanisms for PLP and PLS. The PLP-PLS index is a promising clinical tool for selecting therapies to prevent/treat PLP and for measuring treatment effects to modulate phantom pain. These findings emphasize the importance of understanding the mechanisms underlying PLP and PLS for improving clinical management and guiding future research.

Prevalence of chronic pain after severe lower limb injury (SLLI): A systematic review and meta-analysis

BACKGROUND

Globally, severe lower limb injuries (SLLIs) are the predominant cause of long-term injury related disability and poor functional outcomes. Chronic pain is a major source of this morbidity, but the magnitude of the contribution is not clearly understood. The aim of this systematic review and meta-analysis was to determine the prevalence of chronic pain following SLLIs in civilian and military patients.

METHOD

This systematic review was prospectively registered with The International Prospective Register of Systematic Reviews (PROSPERO) with study ID CRD42022313615. A systematic literature search (Medline, Embase, Ovid, and Web of Science) was performed to identify original studies that reported chronic pain outcomes for adults who underwent surgical treatment for SLLIs in a civilian or military setting. Risk of bias in included studies was assessed using the ROBINS-E tool, and quality assessment was reported at study level using the Newcastle-Ottawa Scale, and at outcome-level using the GRADE framework. Absolute (proportional) and relative (odds ratio) outcome measures were calculated and pooled using a random effects model.

RESULTS

Forty-three studies reporting the outcomes of 5601 patients were included. Estimated overall prevalence of pain was 63 % (CI 55-70 %). The prevalence of chronic pain in amputees (64 % (CI 55-73 %)) was similar to those who underwent limb salvage (56 % (CI 44-67 %)). The prevalence of chronic pain in civilian populations was 70 % (CI 63-77 %) compared to military populations (51 % (CI 35-66 %)). In amputees, the prevalence of residual limb pain was similar to phantom limb pain (OR 1.06 [0.64-1.78], p = 0.81, I2 = 92 %).

CONCLUSION

Most people who sustain a SLLI will suffer from chronic pain. Healthcare systems must continue to research interventions that can reduce the incidence and severity of long-term pain and ensure adequate resources are allocated for this common and debilitating complication.

Distinct patterns of metabolic motor cortex activity for phantom and residual limb pain in people with amputations: A functional near-infrared spectroscopy study

BACKGROUND

Phantom pain limb (PLP) has gained more attention due to the large number of people with amputations around the world and growing knowledge of the pain process, although its mechanisms are not completely understood.

OBJECTIVES

The aim of this study was to understand, in patients with amputations, the association between PLP and residual limb pain (RLP), and the brain metabolic response in cortical motor circuits, using functional near-infrared spectroscopy (fNIRS).

METHODS

Sixty participants were recruited from the rehabilitation program in São Paulo, Brazil. Included patients were aged over 18 years, with traumatic unilateral lower-limb amputation, with PLP for at least 3 months after full recovery from amputation surgery. PLP and RLP levels were measured using visual analogue scales. fNIRS was performed during motor execution and motor mirror tasks for 20 s. In order to highlight possible variables related to variation in pain measures, univariate linear regression analyses were performed for both experimental conditions, resulting in four fNIRS variables (two hemispheres x two experimental conditions). Later, in order to test the topographic specificity of the models, eight multivariate regression analyses were performed (two pain scales x two experimental conditions x two hemispheres), including the primary motor cortex (PMC) related channel as an independent variable as well as five other channels related to the premotor area, supplementary area, and somatosensory cortex. All models were controlled for age, sex, ethnicity, and education.

RESULTS

We found that: i) there is an asymmetric metabolic activation during motor execution and mirror task between hemispheres (with a predominance that is ipsilateral to the amputated limb), ii) increased metabolic response in the PMC ipsilateral to the amputation is associated with increased PLP (during both experimental tasks), while increased metabolic response in the contralateral PMC is associated with increased RLP (during the mirror motor task only); ii) increased metabolic activity of the ipsilateral premotor region is associated with increased PLP during the motor mirror task; iii) RLP was only associated with higher metabolic activity in the contralateral PMC and lower metabolic activity in the ipsilateral inferior frontal region during motor mirror task, but PLP was associated with higher metabolic activity during both tasks.

CONCLUSION

These results suggest there is both task and region specificity for the association between the brain metabolic response and the two different types of post-amputation pain. The metabolic predominance that is ipsilateral to the amputated limb during both tasks was associated with higher levels of PLP, suggesting a cortical motor network activity imbalance due to potential interhemispheric compensatory mechanisms. The present work contributes to the understanding of the underlying topographical patterns in the motor-related circuits associated with pain after amputations.

Calcitonin in the Treatment of Phantom Limb Pain: A Systematic Review

INTRODUCTION

Phantom limb pain (PLP) refers to pain perceived in a part of the body removed by amputation or trauma. Despite the high prevalence of PLP following amputation and the significant morbidity associated with it, robust therapeutic approaches are currently lacking. Calcitonin, a polypeptide hormone, has recently emerged as a novel analgesic with documented benefits in the treatment of several pain-related conditions.

METHODS

We present a systematic review that comprehensively evaluates the analgesic effects of calcitonin for patients with PLP. We searched MEDLINE, OLDMEDLINE, and PubMed Central databases with the key words "calcitonin" "phantom limb pain" and "phantom pain" to identify clinical studies evaluating the efficacy or effectiveness of calcitonin administration, in any form and dose, for the treatment of PLP. Additionally, Google Scholar was searched manually with the search term "calcitonin phantom limb pain". All four databases were searched from inception until 1 December 2022. The methodological quality of each included study was assessed using the Downs and Black checklist and the GRADE criteria were used to assess effect certainty and risk of bias.

RESULTS

Our search identified 4108 citations, of which six ultimately met the criteria for inclusion in the synthesis. The included articles described a mix of open-label (n = 2), prospective observational cohort (n = 1), and randomized clinical trials (n = 3). The most common treatment regimen in the current literature is a single intravenous infusion of 200 IU salmon-derived calcitonin.

CONCLUSION

The available evidence supported the use of calcitonin as either monotherapy or adjuvant therapy in the treatment of PLP during the acute phase, while the evidence surrounding calcitonin treatment in chronic PLP is heterogeneous. Given the limited treatment options for the management of PLP and calcitonin's relatively wide therapeutic index, further research is warranted to determine the role that calcitonin may play in the treatment of PLP and other pain disorders.