NEMJ Mirror Therapy – comment by Lorimer Moseley

The New England Medical Journal recently published an article on Mirror Therapy for Chronic Complex Regional Pain Syndrome Type 1 after Stroke (see below for a look at what they had to say). It seems to be a really good study. That said, I wish it wasn’t published as a letter only, because it is hard to rule out all the usual threats to validity – I think they have about 400 words to tell the story of a randomised controlled crossover trial – that is a very big ask. However, on what is printed it looks good. The drop in pain is huge – really huge, especially considering that the patients were more than a year after their stroke.  I wish they had included the motor function stuff because that would be the icing on the cake.

I wonder if they are going to naughtily sneak out an extra publication with the functional or motor data – although that application of mirrors has been around for some time[1,2] and there are RCT’s[3] that show improved function (on a motor assessment scale, MAS), it would be nice to see if pain reduction and motor improvement are related. How does mirror therapy work here? Other people[4] showed that mirrors facilitates primary motor cortex excitability and one has got to consider that the mirror neuron system might be involved – this is a good review of mirror neuron stuff as it might be relevant[5]. I don’t really know how mirror therapy works – I tend to conclude that there are a few possibilities but none just yet that have been supported very well by empirical data.

References

  1. Sathian K, Greenspan AI & Wolf SL (2000) Doing It with Mirrors: A Case Study of a Novel Approach to Neurorehabilitation. Neurorehabilitation and Neural Repair, Vol. 14, 1, 73-6
  2. Altschuler EL, Wisdom SB, Stone L, Foster C, Glalasko D, Llewellyn DM, Ramachandran VS (1999) Rehabilitation of hemiparesis after stroke with a mirror. The Lancet 353, 2035-6
  3. Yavuzer G, Selles R, Sezer N, Stbeyaz S, Bussmann JB, Kseogl, F, Atay MB, & Stam HJ (2008) Mirror Therapy Improves Hand Function in Subacute Stroke: A Randomized Controlled Trial. Archives of Physical Medicine and Rehabilitation 89,3, 393-8
  4. Garry MI, Loftus A, Summers JJ (2005) Mirror, mirror on the wall: viewing a mirror reflection of unilateral hand movements facilitates ipsilateral M1 excitability. Experimental Brain Research 163,1, 118-22
  5. Pomeroy VM, Clark CA, Miller JSG, Baron JC, Markus HS, Tallis RC (2005) The potential for utilizing the “mirror neurone system” to enhance recovery of the severely affected upper limb early after stroke: A review and hypothesis. Neurorehabilitation and Neural Repair 19,1 4-13

Here’s a snapshot of what they had to say: New England Medical Journal: Mirror Therapy for Chronic Complex Regional Pain Syndrome Type 1 and Stroke

Complex regional pain syndrome type 1 is characterized by pain, sensory disturbances (e.g., pain evoked by light brushing of the skin [allodynia]), motor impairment (e.g., weakness), and sympathetic dysfunction (e.g., edema). Pain in this syndrome may be induced by a mismatch between proprioceptive feedback and motor action.[1] Visual feedback as a substitute for inappropriate proprioceptive feedback may reduce pain.[1,2]

Visual feedback may be achieved with mirror therapy, which was originally used to treat phantom pain.[2] However, the use of mirror therapy[3] and therapy involving imagery of movement[4] in patients with chronic complex regional pain syndrome type 1 (lasting 6 months or more) remains controversial.

…Our results indicate that, unlike imagery therapy, mirror therapy effectively reduces pain and enhances motor function in the arm of patients with stroke and chronic complex regional pain syndrome type 1 in the arm. The traditional view that in patients with stroke, chronic complex regional pain syndrome type 1 in the arm is refractory to mirror therapy needs to be reconsidered.

Read the full article at NEMJ, 361:634-636

References

  1. Maihöfner C, Handwerker HO, Neundörfer B, Birklein F. Patterns of cortical reorganization in complex regional pain syndrome. Neurology 2003;61:1707-1715. [Free Full Text]
  2. Ramachandran VS, Rogers-Ramachandran D. Synaesthesia in phantom limbs induced with mirrors. Proc Biol Sci 1996;263:377-386. [Free Full Text]
  3. McCabe CS, Haigh RC, Ring EFJ, Halligan PW, Wall PD, Blake DR. A controlled pilot study of the utility of mirror visual feedback in the treatment of complex regional pain syndrome (type 1). Rheumatology (Oxford) 2003;42:97-101.
  4. Moseley GL. Imagined movements cause pain and swelling in a patient with complex regional pain syndrome. Neurology 2004;62:1644-1644. [Free Full Text]