Children with hemiplegic cerebral palsy (CP) have unilateral sensory and motor impairments that may lead to developmental disuse of the affected upper extremity and/or reduced ability to use the affected upper extremity during tasks requiring two hands. Since many functional activities do require the coordinated use of both hands (e.g. dressing, self-care), these impairments may dramatically impact daily function. Thus, understanding the development of bimanual upper extremity use in this population is important, however, such knowledge is largely lacking.
In an exciting and ambitious new study, Holmefur and colleagues at the Karolinska Institute report the findings of a prospective longitudinal study of bimanual upper extremity use in 43 children with hemiplegic CP.1 Children were followed on average 4 and a half years using the Assisting Hand Assessment (AHA), a Rasch-based measure that effectively describes how the affected upper extremity is used as a non-dominant assist during bimanual activities. Overall they found that bimanual proficiency did improve during the course of development, but that the developmental rate and subsequent plateau depended on the initial score at 18 months of age. Specifically, children with higher (better) AHA scores in early childhood developed bimanual skills faster and reached their limit earlier than children with lower AHA scores. Interestingly, the development of bimanual upper extremity use differs from that of gross motor activities,2 where mildly affected children reach their limit later. Thus importantly, gross motor function cannot be used as a proxy for predicting bimanual hand use.
While this is not the first study of hand development in children with CP,3–5 this is the first study of bimanual hand use using a standardized measure. The findings of the AHA differ from those of the Manual Ability Classification System in the same children, which is in line with the other developmental studies to date indicating that various aspects of hand development progress with different time courses and rates. It is at first disheartening to think that prognosis may be predetermined early on. However, the ‘glass half-full’ view is that this information may be clinically important for treatment decisions such as when and how often to engage children in conventional treatments and intensive therapies such as constraint-induced movement therapy6 and bimanual training.7
Holmefur et al. have taken an important step in understanding the ontology of hand function in children with hemiplegic CP. However, it should be noted that the development of hand function in children with hemiplegic CP younger than the study participants (<18mo) is largely unknown. Being able to detect early signs of impairments and relate them to subsequent development is critical since hemiplegia is typically diagnosed between 4 and 6 months of age, only after one upper extremity begins to demonstrate visible impoverished movement. This is correlated with the simultaneous strengthening of ipsilateral projections and retraction of contralateral projections of the corticospinal tract to the spinal cord.8 Using an animal model of hemiplegia, Martin et al.9 at Columbia University have shown that such structural changes in neural substrates are exacerbated by reduced activity in the contralateral motor cortex, associated with the emerging disuse of the affected extremity. Conversely, such damage can be circumvented if sufficient activity is provided at a young enough age.10 Thus, objective quantification and predictive development of hand function at an early age is imperative in order to begin targeted treatment to break this vicious cycle whereby lesions reduce movement, which in turn prohibits normal neural development and further reduces movement. Thus, a challenge to the neuroscience and pediatric rehabilitation community is to extend the present findings to early hand development so that subsequent therapies can target emerging deficits and truly take advantage of the remarkable structural and neural plasticity of the developing infant central nervous system.