Neuroplasticity, learning and recovery after stroke: a critical evaluation of constraint-induced therapy

Constraint-induced movement therapy (CIMT) has been hailed as a radical new approach to stroke rehabilitation. The guiding theory is that impairment of hand function is exacerbated by learned non-use and that this in turn leads to a loss of cortical representation of the upper limb. It is claimed that these processes can be reversed by two weeks of constraint of the unaffected limb combined with intensive practice in use of the paretic hand, and numerous small-scale studies have suggested that CIMT can lead to large improvements in function more than a year after stroke. However, the theory of learned non-use is open to question and there is uncertainty about the nature of the improvements induced by CIMT. The greatest effect seems to be increased spontaneous use of the hand, either through reduction of learned non-use or by overcoming the sense of effort during movement. There is also evidence of some improvement on dexterity tests but no studies have analysed in detail whether this reflects reduction of basic motor impairment or learning of compensatory movement strategies. The current weight of evidence is in favour of compensatory learning. Cortical changes detected by transcranial magnetic stimulation (TMS) or functional imaging may reflect this compensatory motor skill learning rather than restoration of representations lost due to the infarct or non-use of the limb. If future studies confirm this then the clinical implication is that direct teaching of unimanual or bimanual compensatory strategies might be a more productive approach than constraint.