Sexual Dimorphisms and Asymmetries of the Thalamo-Cortical Pathways and Subcortical Grey Matter of Term Born Healthy Neonates: An Investigation with Diffusion Tensor MRI.

Fadoua Saadani-Makki,Mahshid Fouladivanda,Malek Makki,Ardalan Aarabi,Karman Kazemi

doi:10.3390/diagnostics11030560

Abstract

Diffusion-tensor-MRI was performed on 28 term born neonates. For each hemisphere, we quantified separately the axial and the radial diffusion (AD, RD), the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA) of the thalamo-cortical pathway (THC) and four structures: thalamus (TH), putamen (PT), caudate nucleus (CN) and globus-pallidus (GP). There was no significant difference between boys and girls in either the left or in the right hemispheric THC, TH, GP, CN and PT. In the combined group (boys + girls) significant left greater than right symmetry was observed in the THC (AD, RD and ADC), and TH (AD, ADC). Within the same group, we reported left greater than right asymmetry in the PT (FA), CN (RD and ADC). Different findings were recorded when we split the group of neonates by gender. Girls exhibited right > left AD, RD and ADC in the THC and left > right FA in the PT. In the group of boys, we observed right > left RD and ADC. We also reported left > right FA in the PT and left > right RD in the CN. These results provide insights into normal asymmetric development of sensory-motor networks within boys and girls.

Highlights

IntroductionAt 24 weeks post-conception age, brain development is characterized by the migration of thalamo-cortical afferents from the subplate into the overlying cerebral cortex [16]
diffusion-tensor spin-echo (DTI), we investigated whether 1) there are microstructural asymmetries in the caudate nucleus (CN), PT, globus pallidus (GP), TH and THC pathways can be observed in neonates under 1 month of age and 2) whether there is a gender effect in these subcortical areas
Left and right comparisons of the combined group demonstrated significantly higher axial diffusion (p = 0.009) and apparent diffusion coefficient (ADC) (p = 0.023) in the right thalamus compared to the left (Figure 2A)

Summary

Introduction

At 24 weeks post-conception age, brain development is characterized by the migration of thalamo-cortical afferents from the subplate into the overlying cerebral cortex [16] During this critical phase, any damage to these cell populations could impact the microstructural development of the subcortical gray matter and the cortex, disrupting the connective white matter fibers [17,18]. Any damage to these cell populations could impact the microstructural development of the subcortical gray matter and the cortex, disrupting the connective white matter fibers [17,18] These connections form a set of parallel and segregated cortico-thalamic loops that project to the majority of the cortex and act as a link between the basal ganglia and cortex [19,20]. The thalamo-cortical network features widespread connectivity throughout the TH involving the primary sensory motor, temporal, medial prefrontal, anterior cingulate, and fronto-parietal insular cortices, and others are mainly limited to their areas of dominance (primary auditory, primary visual and lateral parietal) [12]

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