Regional Hippocampal Thinning and Gyrification Abnormalities and Associated Cognition in Children with Prenatal Alcohol Exposure

Background: Prenatal alcohol exposure (PAE) impacts hippocampal structure and function, contributing to deficits in memory and decision-making in affected individuals. Here, we evaluate hippocampal anomalies in children with PAE and an unexposed comparison group using advanced MRI methods that characterize hippocampal curvature and thickness.

Methods: Participants, ages 8 to 16 years, included children with PAE (n = 48) and an unexposed comparison group (n = 46) who underwent a dysmorphology exam, neuropsychological assessment, and an MRI scan. Height, weight, head circumference, and dysmorphic facial features were evaluated. Of those with PAE, 4.2% had fetal alcohol syndrome (FAS), 22.9% had partial FAS, and 72.9% had alcohol-related neurodevelopmental disorder. Neuropsychological testing included measures of intelligence and memory functioning. T1-weighted anatomical data were processed with the Hippunfold pipeline, which "unfolds" the complex hippocampal structure onto a template surface and provides measures of thickness and gyrification/curvature at each vertex. Permutation Analysis of Linear Models (PALM) was used to test for group differences (PAE vs. comparison) in hippocampal thickness and gyrification at each vertex and also to assess correlations with cognitive functioning.

Results: There were significant regional differences in thickness and gyrification across bilateral hippocampi, with the PAE group showing substantially thinner tissue and less curvature than the comparison group, especially in CA1 and subiculum regions. For those with PAE, thinner subicular tissue (bilateral) was associated with lower IQ. Also in the PAE group, lower episodic memory performance was associated with thinness in the right hippocampus, especially in the subiculum region. There were no significant regional hippocampal patterns that were associated with cognitive functioning for individuals in the unexposed comparison group.

Conclusions: We used a novel MRI method to evaluate hippocampal structure in children with PAE and an unexposed comparison group. The data suggest that PAE disrupts hippocampal development, impacting both the early-stage folding of the structure and its ultimate thickness. The data also demonstrate that these developmental anomalies have functional consequences in terms of core memory functions as well as global intellectual functioning in children with PAE.