Increased Notching of the Corpus Callosum in Fetal Alcohol Spectrum Disorder: A Callosal Misunderstanding?

Spectral-based thickness profiling of the corpus callosum enhances anomaly detection in fetal alcohol spectrum disorders

Introduction

Fetal alcohol spectrum disorders (FASD) range from fetal alcohol syndrome (FAS) to non-syndromic forms (NS-FASD). The neuroanatomical consequences of prenatal alcohol exposure are mainly the reduction in brain size, but also focal abnormalities such as those of the corpus callosum (CC). We previously showed a narrowing of the CC for brain size, using manual measurement and its usefulness to improve diagnostic certainty. Our aim was to automate these measurements of the CC and identify more recurrent abnormalities in FAS subjects, independently of brain size reduction.

Methods

We developed a fast, automated, and normalization-free method based on spectral analysis to generate thicknesses of the CC continuously and at singular points (genu, body, isthmus, and splenium), and its length (LCC). We applied it on midsagittal section of the CC extracted from T1-anatomical brain MRI of 89 subjects with FASD (52 FAS, 37 NS-FASD) and 126 with typically development (6-20 y-o). After adjusting for batch effect, we compared the mean profiles and thicknesses of the singular points across the 3 groups. For each parameter, we established variations with age (growth charts) and brain size in the control group (scaling charts), then identified participants with abnormal measurements (<10th percentile).

Results

We confirmed the slimming of the posterior half of the CC in both FASD groups, and of the genu section in the FAS group, compared to the control group. We found a significant group effect for the LCC, genu, median body, isthmus, and splenium thicknesses (p < 0.05). We described a body hump whose morphology did not differ between groups. According to the growth charts, there was an excess of FASD subjects with abnormal LCC and isthmus, and of FAS subjects with abnormal genu and splenium. According to the scaling charts, this excess remained only for LCC, isthmus and splenium, undersized for brain size.

Conclusion

We characterized size-independent anomalies of the posterior part of the CC in FASD, with an automated method, confirming and extending our previous study. Our new tool brings the use of a neuroanatomical criterion including CC damage closer to clinical practice. Our results suggest that an FAS signature identified in NS-FASD, could improve diagnosis specificity.

Corpus callosum morphometry in children with prenatal alcohol exposure

Alcohol is known to have a neurotoxic effect on the brain of offspring of mothers consuming alcohol during pregnancy. Impact on the neurodevelopment in children who were exposed to alcohol specifically during the antenatal period without any clinically detectable features of fetal alcohol syndrome is less well studied. In this cross-sectional study, structural magnetic resonance imaging (MRI) of the brain was acquired in 28 children whose mothers had consumed alcohol during pregnancy and 30 children of mothers who did not consume alcohol during pregnancy. Areas of Corpus callosum (CC) and its parts in the mid-sagittal section were calculated using morphometric analysis of MRI through Witelson's method. Midbody of CC was found to be significantly smaller in children exposed to alcohol during the prenatal period. CC is a sensitive white matter structure to neurotoxic effects of alcohol during prenatal life. This impact could be visible in developmental age even in those without any clinically detectable features of alcohol exposure.