Doctors in America have shown that a mirror is an effective therapy for the "phantom" pain experienced by 90% of patients undergoing limb amputation.
Writing in the New England Journal of Medicine, Bethesda-based researcher Jack Tsao and his colleagues describe how they recruited 22 lower limb amputees. The volunteers were randomly divided into three groups; in one group, the "mirror group", the reflection of the subject's intact limb was used to create the illusion that the missing body part was still present. The patients were told to try to make movements with their absent limb by watching the reflection of their intact leg making the same movement. In the second "control" group the mirror was covered with an opaque sheet, whilst the third group of patients were instructed just to imagine making movements with their amputated leg.
The results were shocking - after four weeks of treatment 100% of the patients in the mirror group reported that their pain had improved, although patients in the other two groups faired less well. Amongst the covered-mirror volunteers 50% felt that their pain had worsened (although one patient reported improvement), and the visualisation group fared worst of all - 67% said their pain had intensified. Next the researchers switched the patients from the visualisation and covered-mirror groups to mirror therapy, and their pain improved dramatically, becoming similar to that reported by the first group of mirror patients. The researchers aren't certain how the technique works but suspect that a population of appropriately-termed "mirror" neurones in the brain may be responsible. These nerve cells fire when a person makes a movement or watches another individual performing the same movement, so it may be that the reflected image fools these cells into responding as though the amputated limb were still present, altering the pain perception.