Structural brain lesions and action observation therapy outcomes in unilateral cerebral palsy: an exploratory study

Introduction Unilateral cerebral palsy (UCP) results from early brain injury, leading to motor impairments primarily affecting one upper limb. Action Observation Therapy (AOT), which engages the mirror neuron system to enhance motor function, represents a promising rehabilitative approach. However, its efficacy in UCP has been inconsistent across studies, possibly due to methodological differences or individual variability in brain damage. This observational longitudinal study within an intervention group aimed to explore whether structural brain lesions are associated with changes in motor dexterity and bimanual performance following AOT in children with UCP. Methods Sixteen children with UCP underwent a structured AOT home training program. Motor function was assessed through the Box and Block Test (BBT) and the Assisting Hand Assessment (AHA) at four or five time points (T0, T1/T1_plus, T2, T3), totaling 64 evaluation sessions. Brain lesions were evaluated using the semi-quantitative magnetic resonance imaging (sqMRI) scale. Data were analyzed using linear mixed-effects models. Results A significant increase in BBT scores for the dominant hand (BBT_dom) was observed at all post-treatment time points, while significant improvements in the non-dominant hand (BBT_non_dom) were observed at T2. AHA scores significantly increased at T1 and T2. Lesions involving the temporal lobe, thalamus, brainstem, and corpus callosum showed the strongest associations with reduced improvements in AHA and BBT_non_dom scores. Discussion These findings suggest that structural brain lesions may influence the response to AOT in children with UCP. Further studies are required to confirm these results and to evaluate whether tailoring interventions according to neuroanatomical profiles could enhance rehabilitation outcomes in children with UCP.