Is successful rehabilitation of complex regional pain syndrome due to sustained attention to the affected limb? A randomised clinical trial

In complex regional pain syndrome (CRPS1) initiated by wrist fracture, a motor imagery program (MIP), consisting of hand laterality recognition followed by imagined movements and then mirror movements, reduces pain and disability, but the mechanism of effect is unclear. Possibilities include sustained attention to the affected limb, in which case the order of MIP components would not alter the effect, and sequential activation of cortical motor networks, in which case it would. Twenty subjects with chronic CRPS1 initiated by wrist fracture and who satisfied stringent inclusion criteria, were randomly allocated to one of three groups: hand laterality recognition, imagined movements, mirror movements (RecImMir, MIP); imagined movements, recognition, imagined movements (ImRecIm); recognition, mirror movements, recognition (RecMirRec). At 6 and 18 weeks, reduced pain and disability were greater for the RecImMir group than for the other groups (P<0.05). Hand laterality recognition imparted a consistent reduction in pain and disability across groups, however, this effect was limited in magnitude. Imagined movements imparted a further reduction in pain and disability, but only if they followed hand laterality recognition. Mirror movements also imparted a reduction in pain and disability, but only when they followed imagined movements. The effect of the MIP seems to be dependent on the order of components, which suggests that it is not due to sustained attention to the affected limb, but is consistent with sequential activation of cortical motor networks.