Diffusion tensor imaging (DTI) of callosal motor fibers correlates with functional impairment in children with periventricular leukomalacia

Purpose: The corpus callosum represents a key structure for hand motor development and is accessible to investigation by diffusion tensor MR imaging (DTI). DTI of transcallosal motor fibers is a potential paradigmatic parameter for hand motor function. We aimed to evaluate the microstructure (DTI), interhemispheric inhibitory competence as measured by transcranial magnetic stimulation (TMS) and hand motor function in healthy subjects during motor development and in children with mild cerebral palsy.

Methods: We examined 10 children, 10 adolescents and 10 adults (mean ages 8.3, 15.6 and 25.9 years) with DTI, TMS and a computer-based hand motor function test. Additionally we examined 8 children (mean age 15.1±2.3) with known mild bilateral cerebral palsy and periventricular leukomalacia (PVL). Relative and fractional anisotropy (RA, FA) values were calculated for the callosal motor fibers and correlated to parameters of interhemispheric inhibitory competence and degree of mirror movements as measured by a computer-based hand motor function test.

Results: Anisotropy values were significantly different in transcallosal motor fibers between the 3 age-groups of healthy subjects, with higher anisotropy values in the older age groups (p<0.01). Anisotropy values were significantly lower in children with PVL as compared to healthy controls (p=0.008). FA and RA values correlated with parameters of hemispheric inhibitory competence of TMS as well as with the degree of mirror movements (p<0.05). Mirror movements were generally elevated in the PVL group by the factor 2.

Conclusion: Anisotropy values of transcallosal motor fibers appear to correlate with hand motor development and are a potential parameter for functional impairment of hand motor function in children with PVL.