Putting some excitement into constraint-induced movement therapy

Abstract

This commentary is on the original article by Gillick et al. on pages 44–52 of this issue. Following publication of the Cochrane review in 2007,1 constraint-induced movement therapy (CIMT) has moved beyond the realm of experiment to a treatment, supported by some of the strongest evidence for children with cerebral palsy (CP). Paradoxically, studies evaluating CIMT have also led to the establishment of similarly strong evidence for bimanual upper limb therapy.2 With 33 published clinical or randomized controlled trials, results from studies of CIMT provide strong support for upper limb treatment models that provide time-limited, top-down or goal-directed, intensive blocks of training. Gone are the days for using bottom-up approaches where a child has therapy ‘done to them’. CIMT studies support two key components of motor learning: the initiation and active ‘doing’ of activities and the repetition of these at a sufficient intensity and level of challenge. Importantly, many models of CIMT embed the practice and learning of skills in a child's natural environment including home, pre-school, and school. These modifications, along with the knowledge that parents and carers, etc. who have received education can implement CIMT, challenge previous concerns that CIMT may not be feasible in a clinical setting. Models of CIMT, and for that matter, bimanual upper limb therapy, can be simple to implement, family-friendly, low-cost, yet very effective in improving outcomes in children with unilateral CP. In the ongoing pursuit to maximize the effect of treatment, a growing list of adjunct interventions, including functional electrical stimulation botulinum toxin-type A, and virtual reality, have been combined with CIMT. The addition of primed, low-frequency repetitive transcranial magnetic stimulation (rTMS) by Gillick et al.3 is an exciting addition to this list. To varying degrees in children with early unilateral brain lesion, the persistence of contralesional corticomotor projections from the non-lesioned cortex is an environmental response to provide movement to a more affected upper limb. Recent data suggest, however, that these projections may negatively influence the quality of unimanual and bimanual upper limb performance and also influence response to CIMT.4, 5 The science of upper limb treatment has, therefore, focused on encouraging repetitive, self-initiated movement of the more affected limb to stimulate activation of ipsilesional corticomotor projections and promote improved crossed corticospinal tract integrity. In a group of children, aged 8 to 17 years, with congenital hemiparesis and intact crossed corticospinal tract integrity, Gillick et al. primed the contralesional primary motor area (M1) using low frequency rTMS. In a fascinating twist, priming the cortex membrane of the contralesional hemisphere using rTMS results in subsequent inhibition of this hemisphere. Releasing, or disinhibiting the ipsilesional hemisphere from the shackles of contralesional hemisphere dominance, provides an advantage for the recruitment of ipsilesional corticomotor projections. The repetitive use of the more affected upper limb (CIMT) during this period facilitates an increase in the excitability of dormant neurons in the ipsilesional M1 and improves the potential to establish crossed projections from the lesioned hemisphere. Put simply, the addition of rTMS to CIMT is a novel method to ramp up the potential for activity-dependent plasticity in older children. This is an exciting preliminary study and despite the potentially invasive nature, no serious adverse events were reported. Larger studies, ensuring baseline group equivalence for ability level and age, are warranted. The nature of rTMS does limit its use to older children. However, this certainly does not mean younger children will be missing out. In fact, quite the opposite. While rTMS may potentially boost outcomes in older children, preliminary data from animal studies strongly support the notion of ‘the earlier the better’ for CIMT.6 Very early therapy during the critical period of brain development (<12 mo of age) moves away from a restorative paradigm to one of prevention. It is an exciting time for upper limb rehabilitation.