The impact of brain lesion characteristics and the corticospinal tract wiring pattern on mirror movement characteristics in unilateral cerebral palsy

Background. Mirror movements (MM) influence bimanual performance in children with unilateral cerebral palsy (uCP). Whilst MM are related to brain lesion characteristics and the corticospinal tract (CST) wiring pattern, the combined impact of these neurological factors remains unknown. Objective. To investigate the combined impact of neurological factors on MM. Methods. Forty-nine children with uCP (mean age 10y6mo) performed a repetitive squeezing task to quantify similarity between MM activity (MM-similarity) and strength of the MM activity (MM-intensity). We used MRI to evaluate lesion type (periventricular white matter, N=30) cortico-subcortical, N=19), the extent of ipsilesional damage and damage to basal ganglia, thalamus and corpus callosum. The CST wiring pattern (17 CSTcontralateral, 16 CSTipsilateral, 16 CSTbilateral) was assessed with Transcranial Magnetic Stimulation. Data was analyzed with simple and multiple regression analyses. Results. MM-similarity in the more-affected hand was higher with more damage to the corpus callosum. MM-intensity was higher in children with CSTcontralateral with damage to the basal ganglia and thalamus. In the less-affected hand, MM-similarity was explained by the interaction between lesion type and CST wiring pattern, with higher MM-similarity in children with cortico-subcortical lesions in the CSTcontralateral group. MM-intensity was higher with larger damage to the corpus callosum and unilateral lesions. Conclusions. A complex combination of neurological factors influences MM characteristics and the mechanisms differ between hands.