THE FOCUS ON NEUROANATOMICAL ABNORMALITIES
The neurodevelopmental toxicity of ethanol is evidenced by two consequences of severe prenatal alcohol exposure (EPA): the high prevalence of neurodevelopmental disorders and congenital brain anomalies. Yet, severe prenatal alcohol exposure remains a common and underdiagnosed cause of cognitive and behavioral disorders.
The pathological consequences of severe prenatal alcohol exposure are grouped under the general diagnosis of fetal alcohol spectrum disorders (FASD). They range from Fetal Alcohol Syndrome (FAS), with these specific clinical features, to non-syndromic and non-specific forms (FASD-NS), when these physical criteria are absent or incomplete, and a causal link can be assumed between FAS and neurodevelopmental disorders.
Unlike dysmorphic facial features, neuroanatomical abnormalities provide little or no etiologic specificity in the diagnosis of FASD, even though the brain is a major target of ethanol developmental toxicity. The most obvious neuroanatomical abnormality in FASD is a global deficit in brain growth that may be clinically manifested as microcephaly. More focal brain abnormalities, for example in the corpus callosum or cerebellum, visible only on brain imaging, have also been described, although there is no clear consensus on the possible correlation between their presence and the diagnosis of FASD.
IDENTIFYING ANOMALIES WITH DIAGNOSTIC VALUE
Researchers from the InDEV team (UNIACT, NeuroSpin, UMR NeuroDiderot) therefore analyzed retrospective monocentric data, including 52 individuals with FAS, 37 with FASD-NS and 94 typically developing individuals. Their goal was to characterize recurrent abnormalities on brain MRI whose combination could have diagnostic value in FASD. In their study published in Developmental Medicine & Child Neurology, they considered measures of brain size, corpus callosum, and vermis, and compared individual values seen in FAS with age and brain size distributions in controls.
Using brain imaging (MRI), they were able to identify that the thinned corpus callosum isthmus, smaller vermis and abnormal foliation of the vermis correspond to frequent abnormalities in FAS individuals (nearly 40% of FAS have at least 2 of these abnormalities and 19% have all 3), while not being trivially explained by a brain growth deficit. Finally, they concluded that combinations between small brain size and several of the anomalies could be accounted for in the diagnosis, constituting an additional argument for estimating causality with FAS (27% of FASD have at least 2 of the 3 anomalies).
These results suggest that adding a composite neuroanatomical-radiological criterion could improve the diagnostic process of FASD-NOS. It would provide accuracy where a lack of specificity may deter diagnosis and ultimately limit patient care.