P11-15 Gestation length and fetal growth have independent effects on corticospinal development in children: the PREMOCODE study

Abstract

Objectives: Children born preterm (i.e. <37 weeks gestational age [GA]) often exhibit motor dysfunction at school age when compared to their term-born peers suggesting preterm birth alters normal corticospinal development. However, some preterm children are also experience fetal growth restriction in utero. Here we used transcranial magnetic stimulation to characterise the effects of GA at birth on corticospinal development in non-cerebral palsy children and differentiate its effects from those of sub-optimal fetal growth i.e. birthweight centile (BW%). Methods: 148 children (11.6±0.6 years) born at 22 41 weeks GA participated. Active (aMT), resting motor thresholds (rMT) and stimulusresponse curves were obtained for left and right motor cortex (M1) projections to a hand muscle. BW% was calculated using the GROW centile calculator. Data were analysed using repeated measures ANCOVA, correlation and regression analyses. Results: At least one MT and one stimulus-response curve was obtained from 137 and 58 children respectively. None of these had a GA<27 weeks. Shortened GA was linearly associated with increased rMT and aMT in both hemispheres, and reduced maximal evoked response amplitude (F[2,58] = 4.1, P = 0.05) and area under the left M1 curve only (F[2,58] = 5.1, P = 0.03). Low BW% was independently associated with increased rMT only in the right M1 (r = 0.31, P = 0.008, N = 78). Conclusions: Even in the mildly preterm, reduced GA and BW% are associated with delayed or abnormal corticospinal development that is still evident in late childhood. Left motor cortex (M1) excitability appears most affected by shortened GA, while low BW% preferentially reduces right M1 excitability. These data may underestimate the effect as children with the lowest cortical excitability could not be fully assessed with TMS. Delayed or abnormal corticospinal development probably contributes to non-cerebral palsy motor dysfunction in preterm children.