Pathophysiology and management of phantom limb pain

Patient care for postamputation pain and the complexity of therapies: living experiences

AIM

Limb amputation traumatically alters body image. Sensations rapidly prevail that the limb is still present and 85% of patients portray phantom limb pain. Throughout the testimonies of amputated patients with intense phantom limb pain, we show the difficulty in treating this chronic pain with current pharmacological and nonpharmacological therapies.

PATIENTS & METHODS

We qualitatively analyzed the therapeutic choices of five amputees, the effectiveness of the treatments chosen and the impact on patients' quality-of-life.

RESULTS & CONCLUSION

In general, patients who are refractory to pharmacological treatments are in favor of trying alternative therapies. It is therefore crucial to design a combined and personalized therapeutic plan under the coordination of a multidisciplinary team for the wellbeing of the patient.

A review of the management of phantom limb pain: challenges and solutions

BACKGROUND

Phantom limb pain (PLP) occurs in 50% and 80% of amputees. Although it is often classified as a neuropathic pain, few of the large-scale trials of treatments for neuropathic pain included sufficient numbers of PLP sufferers to have confidence that they are effective in this condition. Many therapies have been administered to amputees with PLP over the years; however, as of yet, there appears to be no first-line treatment.

OBJECTIVES

To comprehensively review the literature on treatment modalities for PLP and to identify the challenges currently faced by clinicians dealing with this pain.

METHOD

MEDLINE, EMBASE, CINAHL, British Nursing Index, Cochrane and psycINFO databases were searched using "Phantom limb" initially as a MeSH term to identify treatments that had been tried. Then, a secondary search combining phantom limb with each treatment was performed to find papers specific to each therapy. Each paper was assessed for its research strength using the GRADE system.

RESULTS

Thirty-eight therapies were identified. Overall, the quality of evidence was low. There was one high-quality study which used repetitive transcutaneous magnetic stimulation and found a statistical reduction in pain at day 15 but no difference at day 30. Significant results from single studies of moderate level quality were available for gabapentin, ketamine and morphine; however, there was a risk of bias in these papers. Mirror therapy and associated techniques were assessed through two systematic reviews, which conclude that there is insufficient evidence to support their use.

CONCLUSION

No decisions can be made for the first-line management of PLP, as the level of evidence is too low. Robust studies on homogeneous populations, an understanding of what amputees consider a meaningful reduction in PLP and agreement of whether pain intensity is the legitimate therapeutic target are urgently required.

Usefulness of milnacipran in treating phantom limb pain

BACKGROUND

Amputation of an extremity often results in the sensation of a "phantom limb" where the patient feels that the limb that has been amputated is still present. This is frequently accompanied by "phantom limb pain". We report here the use of milnacipran, a serotonin and norepinephrine reuptake inhibitor, to treat phantom limb pain after amputation of injured or diseased limbs in three patients.

METHODS AND RESULTS

The severity of phantom pain before and during treatment was quantified using a visual analog scale. In one case, phantom limb pain responded partially to treatment with high doses of paroxetine, and then replacement with milnacipran further improved the pain relief and long-term full pain relief was achieved. In the two other cases, milnacipran was used as first-line treatment and phantom limb pain responded rapidly.

CONCLUSION

These results suggest that milnacipran administration may be useful in phantom limb pain, possibly as a first-line treatment.

Psychosocial factors and adjustment to chronic pain in persons with physical disabilities: a systematic review

OBJECTIVE

To systematically review the research findings regarding the associations between psychosocial factors and adjustment to chronic pain in persons with physical disabilities.

DATA SOURCES

A key word literature search was conducted using articles listed in PubMed, PsychInfo, and CINAHL up to March 2010, and manual searches were made of all retrieved articles to identify published articles that met the review inclusion criteria.

STUDY SELECTION

To be included in the review, articles needed to (1) be written in English, (2) include adults with a physical disability who report having pain, (3) include at least 1 measure of a psychosocial predictor domain, (4) include at least 1 criterion measure of pain or patient functioning, and (5) report the results of associations between the psychosocial factors and criterion measures used in the study. Twenty-nine studies met the inclusion criteria.

DATA EXTRACTION

Three reviewers tabulated study details and findings.

DATA SYNTHESIS

The disability groups studied included spinal cord injury (SCI), acquired amputation, cerebral palsy (CP), multiple sclerosis (MS), and muscular dystrophy (MD). Psychosocial factors were shown to be significantly associated with pain and dysfunction in all disability groups. The psychosocial factors most closely associated with pain and dysfunction across the samples included (1) catastrophizing cognitions; (2) task persistence, guarding, and resting coping responses; and (3) perceived social support and solicitous responding social factors. Pain-related beliefs were more strongly associated with pain and dysfunction in the SCI, CP, MS, and MD groups than in the acquired amputation group.

CONCLUSIONS

The findings support the importance of psychosocial factors as significant predictors of pain and functioning in persons with physical disabilities. Clinical trials to test the efficacy of psychosocial treatments for pain and dysfunction are warranted, as are studies to determine whether psychosocial factors have a causal influence on pain and adjustment in these populations.

A Prospective Study of Factors Associated With the Presence of Phantom Limb Pain Six Months After Major Lower Limb Amputation in Patients With Peripheral Vascular Disease

Because of a lack of evidence to support any treatment for phantom limb pain (PLP), interest has turned to preventing it instead. However, like other areas of PLP research, there is little consensus regarding factors that may be associated with the development of PLP. This study was devised to identify physical and psychological factors associated with PLP development and maintenance. It was a prospective study of 59 patients listed for amputation of a lower limb due to peripheral vascular disease. Each was interviewed before amputation, and the survivors were reinterviewed 6 months afterward. Pain and coping style were the primary outcome measures. The use of high levels of passive coping strategies (P = .001), especially catastrophizing (P = .02) before amputation, were found to be associated with PLP development. Pain was only weakly associated with the presence of PLP 6 months after amputation. The ability to move the phantom (P = .01) and stump pain (P = .01) were postamputation factors associated with PLP. The complexity of the relationship between previous pain and coping style and the development of PLP is discussed alongside aspects of pain memory. Pre-emptive treatment of PLP will need to include psychological as well as physical interventions.

PERSPECTIVE

During this study, preamputation passive coping (especially catastrophizing) was found to be associated with the development of PLP. This knowledge will help researchers and clinicians to identify future targets for pre-emption of this condition because once established, PLP is difficult to treat.

A focus group study of health professionals' views on phantom sensation, phantom pain and the need for patient information

Focus groups with 32 health professionals from pre- and post-amputation care in central Scotland were used to explore perceptions of phantom sensation and pain, and current practice and potential improvements to patient information. Findings were compared to our parallel study of patients' experiences of phantom phenomena and information needs. Professionals' perceptions of phantom phenomena did not always match patient experiences: few professionals were fully aware of the nature, or the problems associated with phantom pain. There was uncertainty about who provided information and reported information was inconsistent and only weakly grounded in theory and mechanism-based management. Whilst there was awareness of the benefits of information, content, mode of delivery and co-ordination were all identified as areas for improvement. Our findings suggest that the information given to patients on phantom phenomena is inconsistent and insufficient. Possible solutions are the development of minimum standards of information and specifically targeted interprofessional education.

Nerve sheath catheter analgesia after amputation

Although continuous infusion of local anesthetic through nerve sheath catheters provides excellent pain control after amputation, the influence of this technique on the incidence of phantom limb pain is controversial. The current retrospective study examined the influence of continuous nerve sheath catheter analgesia and primary anesthetic technique (general or regional anesthesia) on the incidence of phantom limb pain. After institutional review board approval, data were gathered on patients who had amputation from 1990 to 1999. Medical records were reviewed to determine the level of and indication for amputation, age at time of amputation, current disease status, date of diagnosis and surgery, and primary anesthetic technique. Six months after amputation, preoperative pain, phantom limb sensations, and phantom limb pain were assessed using a verbal scale ranging from 0 (no pain) to 10 (worst pain) and methods of pain control also were evaluated. Thirty-nine patients completed the study. The incidence of phantom limb pain (visual analog scale score > or = 3) was 67% and was lower than the historic incidence (80%) before the use of this analgesia technique. Incidence of phantom limb pain was higher for patients requiring proximal versus distal amputations. The primary anesthetic technique (general versus regional) did not affect the incidence of phantom limb pain. Long-term followup showed that the incidence of phantom limb pain in patients receiving continuous nerve sheath catheter infusion is lower than previously reported for patients who had amputation for oncologic indications.

Electroconvulsive therapy for phantom limb pain

Phantom limb pain is common in amputees. Although several treatments are available, a significant number of patients are refractory. Electroconvulsive therapy (ECT), which is usually given to patients with psychiatric disorders such as major depression, has shown efficacy in patients with a variety of pain syndromes occurring along with depression. Two patients are described herein with severe phantom limb pain refractory to multiple therapies, without concurrent psychiatric disorder, who received ECT. Both patients enjoyed substantial pain relief. In one case, phantom pain was still in remission 3.5 years after ECT. It is concluded that phantom limb patients who are refractory to multiple therapies may respond to ECT.

Phantom limb, residual limb, and back pain after lower extremity amputations

This study describes the sensations and pain reported by persons with unilateral lower extremity amputations. Participants (n = 92) were recruited from two hospitals to complete the Prosthesis Evaluation Questionnaire which included questions about amputation related sensations and pain. Using a visual analog scale, participants reported the frequency, intensity, and bothersomeness of phantom limb, residual limb, and back pain and nonpainful phantom limb sensations. A survey of medication use for each category of sensations also was included. Statistical analyses revealed that nonpainful phantom limb sensations were common and more frequent than phantom limb pain. Residual limb pain and back pain were also common after amputation. Back pain surprisingly was rated as more bothersome than phantom limb pain or residual limb pain. Back pain was significantly more common in persons with above knee amputations. These results support the importance of looking at pain as a multidimensional rather than a unidimensional construct. They also suggest that back pain after lower extremity amputation may be an overlooked but very important pain problem warranting additional clinical attention and study.

Coping with amputation and phantom limb pain

Phantom limb pain is a common, distressing phenomenon that can occur after the amputation or denervation of a part of the body. No conclusive etiological models or theories have emerged, although the problem was identified some time ago. This empirical-diagnostic study deals with correlations between coping with limb loss, body image, and the occurrence of phantom limb pain. It is based on Melzack's concept of a neuromatrix. Coping strategies were evaluated using semistructured interviews and analysis of patients' drawings of their body images. The results of the study, based on 43 amputees, show a significant association between coping strategies and pain. Patients who cope better with the loss suffer less from phantom limb pain. A difference can also be noted in subjective representation of the body image: patients suffering from phantom limb pain tend to have an image of their bodies as a complete and undamaged entity.

Phantom limb pain: a review of the literature on attributes and potential mechanisms

This study presents a review of the literature on the attributes and potential mechanisms involved in phantom limb pain, encompassing studies describing pain in the residual limb, phantom sensation and phantom limb pain, and the difficulties that may arise when making these distinctions. A variety of theories have been proposed to explain causal mechanisms for phantom limb pain. Conceptually, research into phantom limb pain is informed by the particular theory of chronic pain that is dominant at the time the research is undertaken. For example, early physiological theories on the etiology of phantom limb pain were grounded in specificity or pattern theories of pain. Later physiological research was based on the framework provided by Gate Control Theory and focused on identifying peripheral, spinal, and central neural mechanisms. Psychological explanations were grounded in psychoanalytic or personality theories of chronic pain which propose that phantom limb pain results from pre-amputation psychological disturbance. Despite numerous studies examining phantom limb pain, much of this research has both conceptual and methodological shortcomings. As such, the application of these research findings to clinical practice has limited utility.

Central representation of phantom limb phenomenon in amputees studied with single photon emission computerized tomography

To explore the possible mechanisms of phantom limb discomfort after amputation, three amputees with phantom limb pain were studied. This study examined the change of regional cerebral blood flow using technetium-99m hexamethylpropyleneamine oxime-single photon emission computerized tomography, which was arranged at the time of severe phantom limb discomfort and after the discomfort subsided or was completely relieved. Nine representative transverse slices parallel to the orbitomeatal line were selected for quantification. The cortical ribbon (2-cm thickness) was equally subdivided into 12 symmetrical pairs of sector regions of interest in each slice. The irregularly shaped regions of interest were drawn manually around the right thalamus and basal ganglion and then mirrored to the left thalamus and basal ganglion. The contralateral to ipsilateral ratio of regional cerebral blood flow for each area was calculated. The intensity of phantom limb pain was evaluated on a 0 to 10 visual analog scale. In Cases 1 and 2, the contralateral to ipsilateral regional cerebral blood flow ratios of multiple areas of the frontal, temporal, or parietal lobes were increased at the time of more severe phantom limb pain, and the ratios were normalized or even decreased when the phantom limb pain subsided. In Case 3, increased contralateral to ipsilateral regional cerebral blood flow ratios were also found over the frontal, temporal, and parietal lobe. However, most of the increased regional cerebral blood flow ratios of regions of interest in the first study persisted in the follow-up study. Also, the regional cerebral blood flow ratios of greater number of regions of interest of the same gyrus and new gyrus were increased. There was no significant right-left difference of regional cerebral blood flow over bilateral thalami and basal ganglia in all three cases. The results suggested that phantom limb pain might be associated with cortical activation involving the frontal, temporal, or parietal cortex, and it may imply the possibility of the existence of an ascending polysynaptic pathway that conveys the uncomfortable phantom limb sensation to the cerebral cortex. These findings may also indicate that reorganization of the cortical blood flow occurs in amputees. However, it is still difficult to conclude that the changes in regional cerebral blood flow were attributable directly to pain. With no comparison group of amputees and because of the small number of cases, it is hard to generalize about cerebrocortical involvement in phantom pain, and it is possible that the findings represent a normal phenomenon seen after 'amputation. Another possibility is that the findings represent increased arousal caused by pain rather than an intrinsic pain pathway. Further study is worthwhile.

Phantom limb pain: elusive, yet real

Phantom limb pain is reported by almost all people who have had an amputation and by others who have dysfunction of their afferent nervous system pathways. Those who experience it indicate that the pain is real and that it is the body part that is "phantom." Although this phenomenon is widely recognized, it is not well understood. The seeming incongruence of pain in a missing body part, combined with the difficulty of successfully treating this pain, result in severe chronic pain in a majority of people who have had an amputation. Treatment with drugs that reduce the number of functional sodium channels has been tried with success, as have various neurophysiological manipulations. This article addresses issues related to sensory experiences associated with phantom body parts and the treatment of pain associated with those experiences.

Regional anaesthesia for repeat Caesarean section in a patient with phantom limb pain

The triggering of phantom limb pain by subarachnoid or epidural anaesthesia has been well described leading to the suggestion that neuraxial regional anaesthesia is relatively contraindicated in lower limb amputees. We report our experience of the provision of anaesthesia for repeat Caesarean section on two occasions in such a patient. Intrathecal fentanyl and morphine supplementation of bupivacaine successfully abolished peri-operative phantom limb pain, whereas epidural anaesthesia was associated with recurrence of phantom limb pain upon regression of the block.