Phantom Limb Pain

Incidence and characteristics. It is helpful to distinguish between painless phantom sensations, stump pain, and pain in the amputated parts of the body as there are implications for pathophysiology, outcome, and treatment²⁰. Few studies have looked at traumatic amputees and most trials are in elderly arteriopaths, but the reason for amputation does not seem to influence the long-term complication rate. Military casualties suffer the same type and frequency of problem as civilians²¹.

Phantom sensations are experiences of the missing limb as though it were still present. Like PLP, they can start at the time of operation or much later. They can vary from vivid sensations moving in a complex fashion, to a vague and fixed awareness of fingers or toes attached to the stump ("telescoping"). Stump pain is pain felt in the stump only and not the absent limb. Phantom limb pain occurs commonly both in children^22,23 and in adults^20,23-25. Patients may not mention it for fear of being ridiculed.

PLP varies greatly in frequency and intensity²¹. Emotional and autonomic influences can provoke or reduce it. The pain is generally felt in the more distal part of the amputated limb (toes, fingers) and has been described by Jensen et al.²⁰ as either exteroceptive (stabbing, burning) or proprioceptive (squeezing, cramp-like) in nature. It can be continuous or intermittent, and its intensity may be mild to excruciating. Phantom sensations, stump pain, and PLP are closely associated. PLP usually is less severe in amputees without phantom sensations or stump pain^24,25. It seems to be less likely if the initial amputation is treated actively and a prosthesis promptly used²⁶.

A recent survey in 590 ex-servicemen found that PLP persisted in 47% of the amputees, disappeared in 16%, and required treatment in 55%. In this survey PLP was so severe (VAS 8.7) in 25% that they sought pain consultation. A large, older military survey found nearly identical figures²⁵.

Predisposing factors. Age, site of amputation, or pre-amputation pain intensity seem not to influence the persistence of late (>6 months) PLP^20,23-25,27. No conclusive data link the type of anesthetic used during amputation and the incidence of PLP.

Despite earlier claims^28,29, a well-controlled, randomized trial did not show a reduction in the incidence of PLP by preemptive epidural analgesia³⁰. This question is important as preamputation epidural analgesia is not without risk. The study did, however, show that active pain control decreased the incidence and severity of chronic pain problems.

Treatment. Treatments must reflect solid clinical experience or experimental evidence. No single form of treatment claims success¹⁹.

Recently it has been suggested that transcutaneous electrical nerve stimulation (TENS), paracetamol (with or without a weak opioid), and nonsteroidal anti-inflammatory drugs (NSAIDs) are more effective for PLP than injections, "centrally acting" analgesics like tricyclics or anticonvulsants, and strong opioids²⁴. Simpler methods of pain relief appear to be more effective and are more accessible in countries with landmine problems. Clinical experience³¹ and that of the voluntary agency Douleur Sans Frontières in the developing world suggests that neurolytic blockade of neuromas may reduce stump pain and that TENS can reduce PLP³².

Evidence for efficacy of second-line therapies for PLP usually is based on small numbers and limited follow-up^33-39. These treatments include calcitonin, beta-blockers, neuroleptics, injection of local anesthetic drugs into the contralateral side, neurosurgery, and central stimulation. Other treatment methods may have been tried unsuccessfully and not reported, or not published owing to negative results.

There is increased interest in the use of NMDA antagonists in chronic pain conditions even though side effects limit their current use. They may also have a place in the preemptive management of postamputation pain problems. The wide use of ketamine in developing countries may yield data about the role of this NMDA antagonist to reduce PLP^40,41.

Sympathetic blockade has been used diagnostically and therapeutically. However, neurolytic block normally requires radiologic control and its effect gradually wears off⁴². 

Discussion

Those who produce and use armaments rarely consider their long-term effects upon health. From a military point of view landmines continue to be considered an effective weapon, due to their low cost and deterrent capabilities.

Implementation of a total ban on production, sale, stockpiling, and use of these weapons will prove difficult if not impossible, as has been the case with biological and chemical weapons. According to the World Health Organization (WHO), at current rates more than ten centuries would be required to remove the more than 100 million landmines already scattered around the globe.

Preventive measures in the countries afflicted with large numbers of mines include awareness programs on the risk of handling and efforts to clear or recover mines for commercial gain. Treatment and rehabilitation of victims will continue to be the principal humanitarian action needed. Rehabilitation and pain control for landmine survivors have gained little attention so far. Instructions for the treatment of postamputation pain and PLP should be made available for use by relief agencies and local health care workers.

The precise impact of PLP on the outcome of rehabilitation of minefield victims in the developing world must be assessed before we can estimate the response needed. However, data collection must not impede continued efforts by relief and medical agencies such as Douleur Sans Frontières. The incidence of severe PLP is at least 25 % in published surveys. PLP may prevent use of prostheses. In the case of single lower limb amputation, injury to the remaining limb may make weight-bearing more hazardous, further jeopardizing rehabilitation.

Treating the individual with relatively inexpensive and effective treatments is possible, and neurolytic blockade of neuromas and TENS have been shown to be effective under these circumstances (J. Meynadier, personal observation). The authors' observations support the multimodal treatment plan advocated by Sherman and colleagues^19,21. They encourage a sympathetic discussion between health care worker and patient about phantom sensation and PLP and emphasize use of a prosthesis. They also advocate use of TENS and minor analgesics to disrupt the pain-anxiety-tension cycle. Their recommendation for referral to multidisciplinary pain treatment, however, is often difficult to carry out in practice.

Public discussion of landmines has taken place more as a political than a medical dialogue⁴³. For other sources of pain such as cancer, burns, or operation, society's perspective is evolving from a view of the individual as an anonymous host of a pathophysiological process toward a patient-centered focus. As this evolution advances, the importance of pain control for optimal quality of life and long-term rehabilitation is increasingly obvious. In parallel fashion, the crucial yet still unmet need for pain control among victims of landmine injury must now receive the attention of pain specialists worldwide. 

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International Association for the Study of Pain (IASP)

9th World Congress on Pain, Vienna, Austria, August 22-27, 1999

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