Corticospinal tract wiring and brain lesion characteristics in unilateral cerebral palsy: determinants of upper limb motor and sensory function

Background Brain lesion characteristics (timing, location, and extent) and the type corticospinal tract (CST) wiring have been proposed as determinants of upper limb (UL) motor function in unilateral cerebral palsy (uCP), yet an investigation of the relative combined impact of these factors on both motor and sensory function is still lacking. Here, we first investigated whether structural brain lesion characteristics could predict the underlying type of CST wiring, and we explored the role of CST wiring and brain lesion characteristics on UL motor and sensory function in uCP. Methods Fifty-two participants with uCP (mean age (SD): 11y3m (3y10m)) underwent a single-pulse Transcranial Magnetic Stimulation session to determine CST wiring between the motor cortex and the more affected hand (n=17 contralateral; n=19 ipsilateral; n=16 bilateral) and an MRI to determine lesion timing (n=34 periventricular (PV) lesion; n=18 cortico-subcortical (CSC) lesion), location and extent. Lesion location and extent were evaluated with a semi-quantitative scale. A standardized protocol included UL motor (grip strength, unimanual capacity, bimanual performance) and sensory measures. Linear discriminant analysis was used to determine CST wiring group membership based on the brain lesion characteristics. Multiple (linear, ordinal, or logistic) regression analyses were conducted to predict UL motor and sensory deficits based on the type of CST wiring and lesion timing, location, and extent. Statistical analysis was carried out with SPSS 24.0 and α was set at 0.05. Results A combination of lesion locations (damage to the PLIC and frontal lobe) significantly contributed to differentiate between the CST wiring groups, re-classifying the participants in their original group with 57% of accuracy. Although motor and sensory function were influenced by the brain lesion characteristics and the type of CST wiring (p<0.05) in a simple linear regression analysis, the multiple regression identified the main significant predictors. Motor function was mostly predicted (R2 (range)=0.46-0.60) by the type of CST wiring (more preserved in individuals with contralateral CST wiring (p<0.01)), the lesion extent and the damage to the basal ganglia and thalamus. Sensory function seemed to be best predicted by the combination of a large and later lesion, and an ipsilateral or bilateral CST wiring, which led to increased sensory deficits (p