The article “Mirror therapy for phantom limb and stump pain: a randomized controlled clinical trial in landmine amputees in Cambodia” by Husum et al. in this issue of the Scandinavian Journal of Pain, describes a unique clinical study of subjects with phantom limb and stump pain after lower leg amputation secondary to land mine injuries. A treatment paradigm with mirror therapy and/or systematic desensitization is described and each therapy as well as the combination were shown to have a remarkably high success rate of about 90%.
2 An important study of mirror-therapy
This research project is important for several reasons and the surprisingly successful outcome deserves closer scrutiny and discussion. As the authors indicate, there are few good studies of the effects of mirror therapy on stump and phantom limb pain. Two recent systematic reviews [1, 2] confirm this. The results of both pharmacological and non-pharmacological trials to date are mixed. Mirror therapy was first proposed by Ramachandran et al.  for post stroke and phantom limb pain but, as the reviews state, most trials are of poor quality and there are few controlled trials currently published. The literature on systematic desensitization is even more sparse. The study reported here is one of the largest trials for these difficult problems and is unique in that it has an active control. From the results, it is also possible to compare two non-pharmacological therapies against each other and against the combination. The methodology is complex with a cross-over arm and a combined arm that makes the statistics a bit difficult to follow but with the support of a previous study by one of the authors using the same paradigm.
The use of an active comparator in pharmacological studies is rare despite the recommendation by the Helsinki Declaration update that supports a “gold standard” comparator in studies over the use of a placebo . To have an active comparator for a controlled non-pharmacologic trial in a complex pain problem is not so unique but since there is no “gold standard” for treatment of phantom limb or stump pain, the choice of systematic desensitization was either prescient or some luck was involved when we review the results. It appears that Husum et al. were somewhat surprised, as is this author, that the effect of desensitization therapy was so successful although this has been so poorly studied in the past.
There are several other unique features of this study that make it important. The first is that a simple treatment strategy has been used in a rural population with a limited educational background (assumed). This same strategy, a combination of desensitization and mirror therapy, could also be used in many countries ravaged by war with poor medical resources and a significant prevalence of land mine injuries leading to amputation. No sophisticated equipment, expensive pharmacology nor highly trained personnel were needed. Stump and phantom limb pain do not respond well to most therapies and the majority of studies from Western countries use pharmacology or neuromodulation but with poor results.
3 Too good to be true?
Some will doubt the high success rate of the treatments for both stump pain and phantom pain and the explanation of this remarkable effectiveness is difficult. It is not clear about how culture may have a strong effect but I would assume that this is a major reason for the success of the treatments. Before therapy began, all subjects were given an explanation of the problem in their own language discussing the central processes involved. Far better than the Western World’s explanation of this being an imagined problem, or worse, a psychopathology as it was in the 50’s and 60’s  when patients were felt to “imagine” phantom sensations and pain. Ron Melzack was a pioneer in trying to unravel this difficult issue  and the Melzack-Wall gate theory  led to a better understanding of the complexities of the central nervous system so that “imagined” phantom sensations and other enigmatic pain syndromes could be better understood and patients could be believed . It may be that the local culture’s philosophy of the body’s function and central control makes the explanation very plausible to these subjects. It would be interesting to have a translation of the words used by the team in explaining the phenomena.
4 Strong positive cultural context-sensitive effects
Just the fact that there was an interest by the healthcare system in helping with the pains may have had a strong effect. Also, those involved with the “hands on” management of the study were local and I would assume had a strong belief in the efficacy of the therapies. The fact that not only the family, but all the subjects’ villages became involved would have an enormous impact on the effectiveness as well as would the frequent contact with the investigators. The combination of the explanation, family and local involvement, and close contact by the research team all may have had a strong context effect which should not detract at all from the success of the therapies .
These facts are supported by the high compliance rate and in most similar studies, drop out due to minimal effect has been seen. Local culture and the structure of the study appear to have kept the subjects involved. However, this may not completely explain the rapid onset of effects, the long-lasting pain reduction and high success of both therapies in both stump and phantom pain. This is what makes local culture and a strong support system seem to be a very important part of the success rate.
5 Implications and recommendations
Given these factors, it would seem important for this study to be repeated in a developed world environment. It would also be important to repeat the study with some modifications in the same environment. If the covered mirror control group that has been used in other studies as a control were used , would we still see a similar success rate?
Perhaps more importantly, this simple paradigm should spread in the region and also be used in the Middle East where the fragmented healthcare system and significant number of amputees make this protocol an attractive attempt at solving a difficult problem. Could this therapy also decrease the time and expense of the often futile medication and neurostimulation trials commonly used in Western countries?
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About the article
Published Online: 2018-08-31
Published in Print: 2018-10-25
Conflict of interest: None declared.
Citation Information: Scandinavian Journal of Pain, Volume 18, Issue 4, Pages 561–562, ISSN (Online) 1877-8879, ISSN (Print) 1877-8860, DOI: https://doi.org/10.1515/sjpain-2018-0115.