What is the role of a non-pharmacological pain treatment like mirror therapy in the treatment of one-sided phantom limb or chronic regional pain syndrome (CRPS)?
There are multiple forms of non-pharmacological treatments of chronic pain. Common to many of these, is that it is difficult to do randomised and truly well controlled trials (RCTs). Sham acupuncture is never free from the expectation of relief. Traditional spinal cord stimulation cannot be compared with sham procedures because optimal placement of the electrodes has to be verified by paraesthesia to the painful area. High-frequency spinal cord stimulation does not cause paraesthesia, and therefore well controlled RCTs are possible. Mirror therapy also cannot be studied with a blinded control in a traditional RCT.
Case reports and comparison of mirror therapy with mental visualisation indicate that there is a real effect on the pain experience.1,2 We believe this may be due to the effect of the mirror imaging on dysfunctional pain modulator-systems in the central nervous system (CNS). The hypothesis of this effect is that unconscious processes in the brain appear to accept the mirror image of the healthy side’s limb as the painful limb. When the healthy hand (or leg-foot) moves while the patient is looking at the healthy limb in the mirror, the patient experiences this occurring with the painful limb that has been immobilised by the pain. In our experience when repeated often and long enough, the defective pain modulating network of the CNS is gradually restored to a more normal state.
Mirror therapy appears not to have any serious adverse effects. This is contrary to many pharmacological treatments, and different from spinal cord stimulation (SCS). This is important for clinicians who want to try mirror therapy for phantom pain or CRPS, despite the rather negative systematic reviews of poor quality studies.3 High quality RCTs on mirror therapy are not possible if the requirements are blinding of therapy in a control group. The context sensitive therapeutic effect of mirror therapy is bound to be positive when the team administering the therapy signals strong belief in the effect of the therapy.4 The pain relieving effect of any treatment can disappear with a sceptical attitude among those who are administering the therapy.4
Post-stroke pain is common in paralysed limbs; mirror therapy is used primarily to restore function in post-stroke limbs.5 Restoration of function is always beneficial for pain that occurs in limbs that are immobilised. Recovering functions of a paralysed limb can be measured objectively, reduction of the subjective pain from the paralysed and useless post-stroke limb is equally important for the patient.
- Harald Breivik is emeritus professor of anaesthesiology, Universitetet i Oslo, Norway. He is also editor-in-chief of the Scandinavian Journal of Pain
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- Al Sayegha S, Filén T, et al. Scandinavian Journal of Pain 2013;4:200–207.
- Chan BL, Witt R, et al. New England Journal of Medicine 2007;357:2206–2207.
- Barbin J, Seetha V, et al. Annals of Physical and Rehabilitation Medicine 2016;59:270–5.
- Breivik H. Scandinavian Journal of Pain 2017;14:76–77.
- Pérez-Cruzado D, Merchán-Baeza JA, et al. Australian Occupational Therapy Journal. 2016. doi: 10.1111/1440-1630.12342. [Epub ahead of print].
Date of preparation: April 2017; MINT/PAEU-17014