Abstract
Background. The etiology of motor impairments in preterm infants is multifactorial and incompletely understood. Whether corpus callosum development is related to impaired motor function is unclear. Potential associations between motor-related measures and diffusion tensor imaging (DTI) of the corpus callosum in preterm infants were explored. Methods. Eight very preterm infants (gestational age of 28–32 weeks) underwent the Hammersmith neonatal neurological examination and DTI assessments at gestational age of 42 weeks. The total Hammersmith score and a motor-specific score (sum of Hammersmith motor subcategories) were calculated. Six corpus callosum regions of interest were defined on the mid-sagittal DTI slice—genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. The fractional anisotropy (FA) and mean diffusivity (MD) of these regions were computed, and correlations between these and Hammersmith measures were sought. Results. Anterior midbody FA measures correlated positively with total Hammersmith (rho = 0.929, P = 0.001) and motor-specific scores (rho = 0.857, P = 0.007). Total Hammersmith scores also negatively correlated with anterior midbody MD measures (rho = −0.714, P = 0.047). Discussion. These results suggest the integrity of corpus callosum axons, particularly anterior midbody axons, is important in mediating neurological functions. Greater callosal maturation was associated with greater motor function. Corpus callosum DTI may prove to be a valuable screening or prognostic marker.
Highlights
Preterm infants are at a high risk of motor de cits in later life, with approximately fourteen percent of very preterm infants developing cerebral palsy (CP) [1], and up to forty percent of very preterm infants demonstrating mild motor de cits [2]. e mechanisms underlying such motor impairments have not yet been fully elucidated, but have been related to a number of factors, including abnormal cerebral development [3], conditions such as periventricular leukomalacia, peri-intraventricular hemorrhage [4], and/or stressors in the neonatal intensive care unit (NICU) environment [5]
Since the corpus callosum is a highly organized myelinated structure, with axons typically running in packed parallel bundles, a high fractional anisotropy (FA) value and low mean diffusivity (MD) value is suggestive of greater structural maturation [9]
Ompson et al found that very preterm infants had signi cantly reduced corpus callosum cross-sectional area, lower FA and higher MD values compared to term infants, suggesting that corpus callosum development is altered in preterm-born infants compared to term-born infants [10]
Summary
Preterm infants are at a high risk of motor de cits in later life, with approximately fourteen percent of very preterm infants developing cerebral palsy (CP) [1], and up to forty percent of very preterm infants demonstrating mild motor de cits [2]. e mechanisms underlying such motor impairments have not yet been fully elucidated, but have been related to a number of factors, including abnormal cerebral development ( in sensorimotor regions) [3], conditions such as periventricular leukomalacia, peri-intraventricular hemorrhage [4], and/or stressors in the neonatal intensive care unit (NICU) environment [5]. E maturation or structural development of the corpus callosum, that is, the organisation of axon ber bundles and the degree of axonal myelination and microstructural integrity, can be studied using diffusion tensor imaging (DTI), via the measures of fractional anisotropy (FA) and mean diffusivity (MD). Rose et al investigated the relationship between DTI measures of the genu and splenium (the most anterior and posterior subregions of the corpus callosum, resp.) taken at term age with neurological assessments (Amiel-Tison scale, gross motor function classi cation system, and Bayley scales of infant development) performed at eighteen months in preterm-born children [11]. Rademaker et al found a strong positive association between the midsagittal surface area of the corpus callosum on T1-weighted magnetic resonance imaging (MRI) scans and concomitant motor function in preterm-born children, studied at school age [15]. The ratio for the splenium was highly correlated with the extent of motor impairment [16]. is suggests that corpus callosum development is closely related to motor function
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