Abstract
Children born preterm are at risk of impairments in oromotor control, with implications for early feeding and speech development. In this study, we aimed to identify (a) neuroanatomical markers of persistent oromotor deficits using diffusion-weighted imaging (DWI) tractography and (b) evidence of compensatory neuroplasticity using functional MRI (fMRI) during a language production task. In a cross-sectional study of 36 adolescents born very preterm (<33 weeks’ gestation) we identified persistent difficulties in oromotor control in 31% of cases, but no clinical diagnoses of speech-sound disorder (e.g., dysarthria, dyspraxia). We used DWI-tractography to examine the microstructure (fractional anisotropy, FA) of the corticospinal and corticobulbar tracts. Compared to the unimpaired group, the oromotor-impaired group showed (i) reduced FA within the dorsal portion of the left corticobulbar tract (containing fibres associated with movements of the lips, tongue, and larynx) and (ii) greater recruitment of right hemisphere language regions on fMRI. We conclude that, despite the development of apparently normal everyday speech, early injury to the corticobulbar tract leads to persistent subclinical problems with voluntary control of the face, lips, jaw, and tongue. Furthermore, we speculate that early speech problems may be ameliorated by cerebral plasticity – in particular, recruitment of right hemisphere language areas.
Highlights
Our understanding of the impact of preterm birth on the cerebral white matter has been furthered by diffusion-weighted imaging (DWI) (Ment et al, 2009; Pandit et al, 2013; Travis et al, 2015a; Pecheva et al, 2017)
We previously found that left corticobulbar tract injury predicted dysarthria and oromotor dysfunction after traumatic brain injury in childhood (Liegeois et al, 2013)
We applied the same diffusion tractography method in the previously reported group of adolescents born preterm, who are at risk of bilateral periventricular white matter injury (Guo et al, 2017), and hypothesised that persistent oromotor impairment would be associated with reduced FA in the left corticobulbar tract
Summary
Our understanding of the impact of preterm birth on the cerebral white matter has been furthered by diffusion-weighted imaging (DWI) (Ment et al, 2009; Pandit et al, 2013; Travis et al, 2015a; Pecheva et al, 2017). A large proportion of children with prematurity-related brain injury have long-lasting oromotor difficulties (Northam et al, 2012a) These children struggle with the deliberate control of the jaw, lips, face, and tongue during the speech and nonspeech movements. On DWI, this impaired subgroup shows reduced fractional anisotropy (FA, a measure of water diffusivity) in the posterior limb of the internal capsule of the left cerebral hemisphere. This suggests motor tract involvement but does not identify which specific pathways have been compromised. We applied the same diffusion tractography method in the previously reported group of adolescents born preterm, who are at risk of bilateral periventricular white matter injury (Guo et al, 2017), and hypothesised that persistent oromotor impairment would be associated with reduced FA in the left corticobulbar tract
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