MR-determined hippocampal asymmetry in full-term and preterm neonates
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Published on: August 5, 2017
Deanne K Thompson1, Stephen J Wood, Lex W Doyle
1Neuroimaging and Neuroinformatics, Howard Florey Institute, University of Melbourne, Victoria, Australia. deanne.thompson@florey.edu.au
Insights
Hippocampal asymmetry is present at birth, with the right hippocampus larger. Preterm birth may alter this asymmetry, suggesting in-utero development of this brain feature.
Area of Science:
- Neuroscience
- Developmental Biology
- Pediatrics
Background:
- Hippocampal asymmetry, with a larger right side, is documented in children and adults.
- Previous research has not confirmed if this asymmetry is present at birth.
- Factors like stress and injury are linked to altered hippocampal asymmetry, raising concerns for preterm infants.
Purpose of the Study:
- To determine if hippocampal asymmetry is evident at birth.
- To investigate potential gender differences in neonatal hippocampal asymmetry.
- To examine if preterm birth influences hippocampal asymmetry.
Main Methods:
- Volumetric magnetic resonance imaging (MRI) was used.
- Left and right hippocampal volumes were compared in preterm and full-term infants at term-equivalent age.
- Total hemispheric and brain tissue volumes were considered for adjustments.
Main Results:
- Both full-term and preterm infants exhibited rightward hippocampal asymmetry at birth.
- No significant gender differences in hippocampal asymmetry were found in neonates.
- Preterm infants showed reduced hippocampal asymmetry compared to full-term infants, particularly after correcting for brain volumes.
Conclusions:
- This study provides the first evidence of normal hippocampal asymmetry at birth.
- Neonatal hippocampal asymmetry does not appear to be influenced by gender.
- Preterm birth is associated with altered hippocampal asymmetry, suggesting potential impacts on brain development.
Abstract:
Hippocampi are asymmetrical in children and adults, where the right hippocampus is larger. To date, no literature has confirmed that hippocampal asymmetry is evident at birth. Furthermore, gender differences have been observed in normal hippocampal asymmetry, but this has not been examined in neonates. Stress, injury, and lower IQ have been associated with alterations to hippocampal asymmetry. These same factors often accompany preterm birth. Therefore, prematurity is possibly associated with altered hippocampal asymmetry. There were three aims of this study: First, we assessed whether hippocampi were asymmetrical at birth, second whether there was a gender effect on hippocampal asymmetry, and third whether the stress of preterm birth altered hippocampal asymmetry. This study utilized volumetric magnetic resonance imaging to compare left and right hippocampal volumes in 32 full-term and 184 preterm infants at term. Full-term infants demonstrated rightward hippocampal asymmetry, as did preterm infants. In the case of preterm infants, hippocampal asymmetry was proportional to total hemispheric asymmetry. This study is the first to demonstrate that the normal pattern of hippocampal asymmetry is present this early in development. We did not find gender differences in hippocampal asymmetry at term. Preterm infants tended to have less asymmetrical hippocampi than full-term infants, a difference which became significant after correcting for hemispheric brain tissue volumes. This study may suggest that hippocampal asymmetry develops in utero and is maintained into adulthood in infants with a normal neurological course.