Radiological studies of fetal alcohol spectrum disorders in humans and animal models: An updated comprehensive review

Prenatal exposure to alcohol and its impact on reward processing and substance use in adulthood

Heavy maternal alcohol drinking during pregnancy has been associated with altered neurodevelopment in the child but the effects of low-dose alcohol drinking are less clear and any potential safe level of alcohol use during pregnancy is not known. We evaluated the effects of prenatal alcohol on reward-related behavior and substance use in young adulthood and the potential sex differences therein. Participants were members of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) prenatal birth cohort who participated in its neuroimaging follow-up in young adulthood. A total of 191 participants (28-30 years; 51% men) had complete data on prenatal exposure to alcohol, current substance use, and fMRI data from young adulthood. Maternal alcohol drinking was assessed during mid-pregnancy and pre-conception. Brain response to reward anticipation and reward feedback was measured using the Monetary Incentive Delay task and substance use in young adulthood was assessed using a self-report questionnaire. We showed that even a moderate exposure to alcohol in mid-pregnancy but not pre-conception was associated with robust effects on brain response to reward feedback (six frontal, one parietal, one temporal, and one occipital cluster) and with greater cannabis use in both men and women 30 years later. Moreover, mid-pregnancy but not pre-conception exposure to alcohol was associated with greater cannabis use in young adulthood and these effects were independent of maternal education and maternal depression during pregnancy. Further, the extent of cannabis use in the late 20 s was predicted by the brain response to reward feedback in three out of the nine prenatal alcohol-related clusters and these effects were independent of current alcohol use. Sex differences in the brain response to reward outcome emerged only during the no loss vs. loss contrast. Young adult men exposed to alcohol prenatally had significantly larger brain response to no loss vs. loss in the putamen and occipital region than women exposed to prenatal alcohol. Therefore, we conclude that even moderate exposure to alcohol prenatally has long-lasting effects on brain function during reward processing and risk of cannabis use in young adulthood.

Brain Volume in Fetal Alcohol Spectrum Disorders Over a 20-Year Span

Importance

Anomalous brain development and mental health problems are prevalent in fetal alcohol spectrum disorders (FASD), but there is a paucity of longitudinal brain imaging research into adulthood. This study presents long-term follow-up of brain volumetrics in a cohort of participants with FASD.

Objective

To test whether brain tissue declines faster with aging in individuals with FASD compared with control participants.

Design, Setting, and Participants

This cohort study used magnetic resonance imaging (MRI) data collected from individuals with FASD and control individuals (age 13-37 years at first magnetic resonance imaging [MRI1] acquired 1997-2000) compared with data collected 20 years later (MRI2; 2018-2021). Participants were recruited for MRI1 through the University of Washington Fetal Alcohol Syndrome (FAS) Follow-Up Study. For MRI2, former participants were recruited by the University of Washington Fetal Alcohol and Drug Unit. Data were analyzed from October 2022 to August 2023.

Main Outcomes and Measures

Intracranial volume (ICV) and regional cortical and cerebellar gray matter, white matter, and cerebrospinal fluid volumes were quantified automatically and analyzed, with group and sex as between-participant factors and age as a within-participant variable.

Results

Of 174 individuals with MRI1 data, 48 refused participation, 36 were unavailable, and 24 could not be located. The remaining 66 individuals (37.9%) were rescanned for MRI2, including 26 controls, 18 individuals with nondysmorphic heavily exposed fetal alcohol effects (FAE; diagnosed prior to MRI1), and 22 individuals with FAS. Mean (SD) age was 22.9 (5.6) years at MRI1 and 44.7 (6.5) years at MRI2, and 35 participants (53%) were male. The FAE and FAS groups exhibited enduring stepped volume deficits at MRI1 and MRI2; volumes among control participants were greater than among participants with FAE, which were greater than volumes among participants with FAS (eg, mean [SD] ICV: control, 1462.3 [119.3] cc at MRI1 and 1465.4 [129.4] cc at MRI2; FAE, 1375.6 [134.1] cc at MRI1 and 1371.7 [120.3] cc at MRI2; FAS, 1297.3 [163.0] cc at MRI1 and 1292.7 [172.1] cc at MRI2), without diagnosis-by-age interactions. Despite these persistent volume deficits, the FAE participants and FAS participants showed patterns of neurodevelopment within reference ranges: increase in white matter and decrease in gray matter of the cortex and decrease in white matter and increase in gray matter of the cerebellum.

Conclusions and Relevance

The findings of this cohort study support a nonaccelerating enduring, brain structural dysmorphic spectrum following prenatal alcohol exposure and a diagnostic distinction based on the degree of dysmorphia. FASD was not a progressive brain structural disorder by middle age, but whether accelerated decline occurs in later years remains to be determined.

Factors predicting general health concerns and atypical behaviours in children with prenatal alcohol exposure and other adverse exposures

Background

Prenatal alcohol exposure (PAE) can have significant negative consequences on the health outcomes of children. Children with PAE often experience other prenatal and postnatal adverse exposures. Increased rates of general health concerns and atypical behaviours are seen in both children with PAE as well as with other patterns of adverse exposures, although these have not been systematically described. The association between multiple adverse exposures and adverse health concerns and atypical behaviours in children with PAE is unknown.

Methods

Demographic information, medical history, adverse exposures, health concerns, and atypical behaviours were collected from children with confirmed PAE (n = 22; 14 males, age range = 7.9-15.9 years) and their caregivers. Support vector machine learning classification models were used to predict the presence of health concerns and atypical behaviours based on adverse exposures. Associations between the sums of adverse exposures, health concerns, and atypical behaviours were examined using correlation analysis.

Results

All children experienced health concerns, the most common being sensitivity to sensory inputs (64%; 14/22). Similarly, all children engaged in atypical behaviours, with atypical sensory behaviour (50%; 11/22) being the most common. Prenatal alcohol exposure was most important factor for predicting some health concerns and atypical behaviours, and alone and in combination with other factors. Simple associations between adverse exposures could not be identified for many health concerns and atypical behaviours.

Conclusion

Children with PAE and other adverse exposures experience high rates of health concerns and atypical behaviours. This study demonstrates the complex effects of multiple adverse exposures on health and behaviour in children.

Combining neuroanatomical features to support diagnosis of fetal alcohol spectrum disorders

AIM

To identify easily accessible neuroanatomical abnormalities useful for diagnosing fetal alcohol spectrum disorders (FASD) in fetal alcohol syndrome (FAS) but more importantly for the probabilistic diagnosis of non-syndromic forms (NS-FASD).

METHOD

We retrospectively collected monocentric data from 52 individuals with FAS, 37 with NS-FASD, and 94 paired typically developing individuals (6-20 years, 99 males, 84 females). On brain T1-weighted magnetic resonance imaging, we measured brain size, corpus callosum length and thicknesses, vermis height, then evaluated vermis foliation (Likert scale). For each parameter, we established variations with age and brain size in comparison individuals (growth and scaling charts), then identified participants with abnormal measurements (<10th centile).

RESULTS

According to growth charts, there was an excess of FAS with abnormally small brain, isthmus, splenium, and vermis. According to scaling charts, this excess remained only for isthmus thickness and vermis height. The vermis foliation was pathological in 18% of those with FASD but in no comparison individual. Overall, 39% of those with FAS, 27% with NS-FASD, but only 2% of comparison individuals presented with two FAS-recurrent abnormalities, and 19% of those with FAS had all three. Considering the number of anomalies, there was a higher likelihood of a causal link with alcohol in 14% of those with NS-FASD.

INTERPRETATION

Our results suggest that adding an explicit composite neuroanatomical-radiological criterion for FASD diagnosis may improve its specificity, especially in NS-FASD.

WHAT THIS PAPER ADDS

Neuroanatomical anomalies independent of microcephaly can be measured with clinical-imaging tools. Small-for-age brain, small-for-brain-size callosal isthmus or vermian height, and disrupted vermis foliation are fetal alcohol syndrome (FAS)-recurrent anomalies. Associations of these anomalies are frequent in fetal alcohol spectrum disorder (FASD) even without FAS, while exceptional in typically developing individuals. These associations support higher likelihood of causal link with alcohol in some individuals with non-syndromic FASD. A new explicit and composite neuroanatomical-radiological criterion can improve the specificity of FASD diagnosis.

Spectrum of MRI findings of foetal alcohol syndrome disorders-what we know and what we need to know!

The exposure to alcohol in utero has been known to damage the developing foetus. Foetal alcohol spectrum disorders is an umbrella term that highlights a range of adverse effects linked to alcohol exposure in utero. Multiple studies have shown specific brain abnormalities, including a reduction in brain size, specifically in the deep nuclei and cerebellum, and parietal and temporal lobe white matter changes. While studies ascertained that other prenatal risk factors, such as maternal use of illicit drugs or lack of pre-natal care, and post-natal risk factors, such as physical or sexual abuse and low socioeconomic status, may be involved in the pathology of variances in foetal neurological abnormalities, prenatal alcohol exposure remained the strongest factor for effects on brain structure and function. Particularly, the number of days of alcohol consumption per week and drinking during all three trimesters of the pregnancy indicating the strongest relationship with brain abnormalities. Further studies are needed to explain pre-natal risk factors in isolation as well as in combination for neurodevelopmental outcomes. The diverse phenotypic presentations described indicate that the diagnostic criteria of foetal alcohol spectrum disorder must be refined to better represent the range of neurologic anomalies.

Fetal alcohol spectrum disorders

Alcohol readily crosses the placenta and may disrupt fetal development. Harm from prenatal alcohol exposure (PAE) is determined by the dose, pattern, timing and duration of exposure, fetal and maternal genetics, maternal nutrition, concurrent substance use, and epigenetic responses. A safe dose of alcohol use during pregnancy has not been established. PAE can cause fetal alcohol spectrum disorders (FASD), which are characterized by neurodevelopmental impairment with or without facial dysmorphology, congenital anomalies and poor growth. FASD are a leading preventable cause of birth defects and developmental disability. The prevalence of FASD in 76 countries is >1% and is high in individuals living in out-of-home care or engaged in justice and mental health systems. The social and economic effects of FASD are profound, but the diagnosis is often missed or delayed and receives little public recognition. Future research should be informed by people living with FASD and be guided by cultural context, seek consensus on diagnostic criteria and evidence-based treatments, and describe the pathophysiology and lifelong effects of FASD. Imperatives include reducing stigma, equitable access to services, improved quality of life for people with FASD and FASD prevention in future generations.

Inhibitory control in young adult women with fetal alcohol syndrome: Findings from a pilot functional magnetic resonance imaging study

BACKGROUND

Executive dysfunction, especially impaired inhibitory control, is a common finding in individuals with fetal alcohol syndrome (FAS). Previous research has mostly focused on neural correlates of inhibitory deficits in children and adolescents. We investigated inhibitory functions and underlying cerebral activation patterns in young adult women with FAS.

METHODS

Task performance and functional magnetic resonance imaging (fMRI) data were acquired during a Go/NoGo (GNG) inhibition task in 19 young adult women with FAS and 19 healthy female control subjects. Whole-brain activation and task performance analyses were supplemented by region of interest (ROI) analyses of fMRI data within a predefined cognitive control network (CCN).

RESULTS

Task performance did not differ significantly between groups on errors of commission, associated with inhibitory control. Similarly, overall activation within the preselected ROIs did not differ significantly between groups for the main inhibitory contrast NoGo > Go. However, whole-brain analyses revealed activation differences in the FAS group when compared to controls under inhibitory conditions. This included hyperactivations in the left inferior frontal, superior temporal, and supramarginal gyri in the FAS group. Likewise, lateralization tendencies toward right-hemispheric ROIs were weaker in FAS subjects. In contrast to comparable inhibitory performance, attention-related errors of omission were significantly higher in the FAS group. Correspondingly, FAS subjects had lower activity in attention-related temporal and parietal areas.

CONCLUSIONS

The known alterations of inhibitory functions associated with prenatal alcohol exposure in children and adolescents were not seen in this adult sample. However, differential brain activity was observed, reflecting potential compensatory mechanisms. Secondary results suggest that there is impaired attentional control in young adult women with FAS.

Fetal alcohol spectrum disorders and the risk of crime

Fetal alcohol spectrum disorders (FASD) are an important preventable global health concern. FASD is an umbrella term describing a range of mild to severe cognitive and behavioral problems among individuals prenatally exposed to alcohol. Alcohol causes FASD by interfering with molecular pathways during fetal development involving increased oxidative stress, disturbed organ development, and change of epigenetic gene expression control. Neuroimaging studies into FASD show several neuropathological abnormalities including abnormal brain structure, cortical development, white matter microstructure, and functional connectivity. Individuals with FASD experience a wide range of cognitive and behavioral challenges. Risks of violent behavior, criminality, and criminalization have been indicated by a limited number of epidemiological studies. The relationship between prenatal alcohol exposure and the increase of these risks remains unclear. This is further impeded by the complexity of an FASD diagnosis, the lack of a clear dose-response relationship of brain impact to alcohol use, and the lack of a clear FASD behavioral phenotype. Literature with respect to FASD and crime is still in its infancy. From the studies available, it is recommended to pay close attention to individuals with FASD and the relation with the criminal justice system and the risk for discrimination. There is a clear need for FASD-related stigma reduction programs within the correctional system. Further investigations into reliable biomarkers for diagnosis and treatment are needed.

Dose-Related Reduction in Hippocampal Neuronal Populations in Fetal Alcohol Exposed Vervet Monkeys

Fetal alcohol spectrum disorder (FASD) is a chronic debilitating condition resulting in behavioral and intellectual impairments and is considered the most prevalent form of preventable mental retardation in the industrialized world. We previously reported that 2-year-old offspring of vervet monkey (Chlorocebus sabeus) dams drinking, on average, 2.3 ± 0.49 g ethanol per Kg maternal body weight 4 days per week during the last third of pregnancy had significantly lower numbers of CA1 (−51.6%), CA2 (−51.2%) and CA3 (−42.8%) hippocampal neurons, as compared to age-matched sucrose controls. Fetal alcohol-exposed (FAE) offspring also showed significantly lower volumes for these structures at 2 years of age. In the present study, we examined these same parameters in 12 FAE offspring with a similar average but a larger range of ethanol exposures (1.01–2.98 g/Kg/day; total ethanol exposure 24–158 g/Kg). Design-based stereology was performed on cresyl violet-stained and doublecortin (DCX)-immunostained sections of the hippocampus. We report here significant neuronal deficits in the hippocampus with a significant negative correlation between daily dose and neuronal population in CA1 (r² = 0.486), CA2 (r² = 0.492), and CA3 (r² = 0.469). There were also significant correlations between DCX population in the dentate gyrus and daily dose (r² = 0.560). Both correlations were consistent with linear dose-response models. This study illustrates that neuroanatomical sequelae of fetal ethanol exposure are dose-responsive and suggests that there may be a threshold for this effect.

Reduced and delayed myelination and volume of corpus callosum in an animal model of Fetal Alcohol Spectrum Disorders partially benefit from voluntary exercise

1 in 20 live births in the United States is affected by prenatal alcohol exposure annually, creating a major public health crisis. The teratogenic impact of alcohol on physical growth, neurodevelopment, and behavior is extensive, together resulting in clinical disorders which fall under the umbrella term of Fetal Alcohol Spectrum Disorders (FASD). FASD-related impairments to executive function and perceptual learning are prevalent among affected youth and are linked to disruptions to corpus callosum growth and myelination in adolescence. Targeted interventions that support neurodevelopment in FASD-affected youth are nonexistent. We evaluated the capacity of an adolescent exercise intervention, a stimulator of myelinogenesis, to upregulate corpus callosum myelination in a rat model of FASD (third trimester-equivalent alcohol exposure). This study employs in vivo diffusion tensor imaging (DTI) scanning to investigate the effects of: (1) neonatal alcohol exposure and (2) an adolescent exercise intervention on corpus callosum myelination in a rodent model of FASD. DTI scans were acquired twice longitudinally (pre- and post-intervention) in male and female rats using a 9.4 Tesla Bruker Biospec scanner to assess alterations to corpus callosum myelination noninvasively. Fractional anisotropy values as well as radial/axial diffusivity values were compared within-animal in a longitudinal study design. Analyses using mixed repeated measures ANOVA’s confirm that neonatal alcohol exposure in a rodent model of FASD delays the trajectory of corpus callosum growth and myelination across adolescence, with a heightened vulnerability in the male brain. Alterations to corpus callosum volume are correlated with reductions to forebrain volume which mediates an indirect relationship between body weight gain and corpus callosum growth. While we did not observe any significant effects of voluntary aerobic exercise on corpus callosum myelination immediately after completion of the 12-day intervention, we did observe a beneficial effect of exercise intervention on corpus callosum volume growth in all rats. In line with clinical findings, we have shown that prenatal alcohol exposure leads to hypomyelination of the corpus callosum in adolescence and that the severity of damage is sexually dimorphic. Further, exercise intervention improves corpus callosum growth in alcohol-exposed and control rats in adolescence.

Trajectories of brain white matter development in young children with prenatal alcohol exposure

Prenatal alcohol exposure (PAE) is associated with alterations to brain white matter microstructure. Previous studies of PAE have demonstrated different findings in young children compared to older children and adolescents, suggesting altered developmental trajectories and highlighting the need for longitudinal research. 122 datasets in 54 children with PAE (27 males) and 196 datasets in 89 children without PAE (45 males) were included in this analysis. Children underwent diffusion tensor imaging between 2 and 8 years of age, returning approximately every 6 months. Mean fractional anisotropy (FA) and mean diffusivity (MD) were obtained for 10 major brain white matter tracts and examined for age-related changes using linear mixed effects models with age, sex, group (PAE vs. control) and an age-by-group interaction. Children with PAE had slower decreases of MD over time in the genu of the corpus callosum, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, and uncinate fasciculus. No significant age-by-group interactions were noted for FA. These findings show slower white matter development in young children with PAE than in unexposed controls. This connects previous cross-sectional findings of lower MD in young children with PAE to findings of higher MD in older children and adolescents with PAE, and further helps to understand brain development in children with PAE. This deviation from typical development trajectories may reflect altered brain plasticity, which has implications for cognitive and behavioral learning in children with PAE.

High-resolution diffusion tensor imaging identifies hippocampal volume loss without diffusion changes in individuals with prenatal alcohol exposure

BACKGROUND

Magnetic resonance imaging (MRI) studies of prenatal alcohol exposure (PAE) commonly report reduced hippocampal volumes, which animal models suggest may result from microstructural changes that include cell loss and altered myelination. Diffusion tensor imaging (DTI) is sensitive to microstructural changes but has not yet been used to study the hippocampus in PAE.

METHODS

Thirty-six healthy controls (19 females; 8 to 24 years) and 19 participants with PAE (8 females; 8 to 23 years) underwent high-resolution (1 mm isotropic) DTI, anatomical T1-weighted imaging, and cognitive testing. Whole-hippocampus, head, body, and tail subregions were manually segmented to yield DTI metrics (mean, axial, and radial diffusivities-MD, AD, and RD; fractional anisotropy-FA), volumes, and qualitative assessments of hippocampal morphology and digitations. Automated segmentation of T1-weighted images was used to corroborate manual whole-hippocampus volumes.

RESULTS

Gross morphology and digitation counts were similar in both groups. Whole-hippocampus volumes were 18% smaller in the PAE than the control group on manually traced diffusion images, but automated T1-weighted image segmentations were not significantly different. Subregion segmentation on DTI revealed reduced volumes of the body and tail, but not the head. There were no significant differences in diffusion metrics between groups for any hippocampal region. Correlations between age and volume were not significant in either group, whereas negative correlations between age and whole-hippocampus MD/AD/RD, and head/body (but not tail) MD/AD/RD were significant in both groups. There were no significant effects of sex, group by age, or group by sex for any hippocampal metric. In controls, seven positive linear correlations were found between hippocampal volume and cognition; five of these were left lateralized and included episodic and working memory, and two were right lateralized and included working memory and processing speed. In PAE, left tail MD positively correlated with executive functioning, and right head MD negatively correlated with episodic memory.

CONCLUSIONS

Reductions of hippocampal volumes and altered relationships with memory suggest disrupted hippocampal development in PAE.

Distinctive neural correlates of phonological and reading impairment in fetal alcohol-exposed adolescents with and without facial dysmorphology

Prenatal alcohol exposure (PAE) has been linked to atypical brain and cognitive development, including poor academic performance in reading. This study utilized functional magnetic resonance imaging and diffusion tensor imaging to characterize functional and structural mechanisms mediating reading deficits in 26 adolescents with PAE-related facial dysmorphology (fetal alcohol syndrome (FAS)/partial FAS (PFAS)), 29 heavily-exposed (HE) non-syndromal adolescents, in comparison with 19 typically developing controls. The FAS/PFAS and HE groups were balanced in terms of levels of PAE and reading (dis)ability. While neural alterations in the posterior association cortices were evident in both PAE groups, distinctive neural correlates of reading (dis)abilities were observed between adolescents with and without facial dysmorphology. Specifically, compared to the HE and control groups, the syndromal adolescents showed greater activation in the right precentral gyrus during phonological processing and rightward lateralization in an important reading-related tract (inferior longitudinal fasciculus, ILF), suggesting an atypical reliance on the right hemisphere. By contrast, in the HE, better reading skills were positively correlated with neural activation in the left angular gyrus and white matter organization of the left ILF, although the brain function-behavior relation was weaker than among the controls, suggesting less efficient function of the typical reading network. Our findings provide converging evidence at both the neural functional and structural levels for distinctive brain mechanisms underlying atypical reading and phonological processing in PAE adolescents with and without facial dysmorphology.

Evaluation of Brain Alterations and Behavior in Children With Low Levels of Prenatal Alcohol Exposure

IMPORTANCE

High levels of prenatal alcohol exposure (PAE) are associated with widespread behavioral and cognitive problems as well as structural alterations of the brain. However, it remains unclear whether low levels of PAE affect brain structure and function, and prior studies generally have not had well-matched control populations (eg, for sociodemographic variables).

OBJECTIVE

To compare structural brain alterations and behavioral changes in children with lower levels of PAE with those of well-matched controls with no PAE.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, participants were selected from the Adolescent Brain Cognitive Development study. Children with PAE were compared with controls matched for age, sex, family income, maternal educational level, and caregiver status. Neither group had prenatal exposure to other adverse substances (eg, tobacco, cannabis, illicit drugs). Data were collected from September 1, 2016, to November 15, 2018, and analyzed from October 14, 2020, to February 14, 2022.

EXPOSURES

Diffusion tensor imaging, resting-state functional magnetic resonance imaging (MRI), and Child Behavior Checklist (CBCL) administration.

MAIN OUTCOMES AND MEASURES

Fractional anisotropy (FA); mean, axial, and radial diffusivity from diffusion tensor imaging; brain functional signal variations from functional MRI; and several scores, including internalizing and externalizing behavior problems, from the CBCL. Spearman correlation coefficients between diffusion tensor imaging and functional MRI measures and the CBCL scores were calculated.

RESULTS

A total of 270 children were included in the analysis (mean [SD] age, 9.86 [0.46] years; 141 female [52.2%] and 129 male [47.8%]), consisting of 135 children with PAE (mean [SD] age, 9.85 [0.65] years; 73 female [54.1%] and 62 male [45.9%]) (mean exposure, 1 drink/wk) and 135 unexposed controls (mean [SD] age, 9.87 [0.04] years; 68 female [50.4%] and 67 male [49.6%]). Children with PAE had lower mean (SD) FA in white matter of the left postcentral (0.35 [0.05] vs 0.36 [0.04]; mean difference, -0.02 [95% CI, -0.03 to -0.01]), left inferior parietal (0.31 [0.07] vs 0.33 [0.06]; mean difference, -0.03 [95% CI, -0.04 to -0.01]), left planum temporale (0.26 [0.04] vs 0.28 [0.03]; mean difference, -0.02 [95% CI, -0.03 to -0.01]), left inferior occipital (0.30 [0.07] vs 0.32 [0.05]; mean difference, -0.03 [95% CI, -0.04 to -0.01]), and right middle occipital (0.30 [0.04] vs 0.31 [0.04]; mean difference, -0.01 [95% CI, -0.02 to -0.01]) areas compared with controls, and higher FA in the gray matter of the putamen (0.22 [0.03] vs 0.21 [0.02]; mean difference, 0.01 [95% CI, 0.005-0.02]). Externalizing behavior scores were higher (worse) in children with PAE than in controls (mean [SD], 45.2 [9.0] vs 42.8 [9.0]; mean difference, 2.39 [95% CI, 0.30-4.47]). Several of these regions had significant group-behavior interactions, such that the higher FA was associated with less problematic behaviors in controls (ρ range, -0.24 to -0.08) but no associations were present in the PAE group (ρ range, 0.02-0.16).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, children with low levels of PAE had lower FA and more behavioral problems compared with a well-matched control group. These results suggest that PAE, even in small amounts, has a measurable effect on brain structure in children.

Alcohol and the Brain

Alcohol works on the brain to produce its desired effects, e.g., sociability and intoxication, and hence the brain is an important organ for exploring subsequent harms. These come in many different forms such as the consequences of damage during intoxication, e.g., from falls and fights, damage from withdrawal, damage from the toxicity of alcohol and its metabolites and altered brain structure and function with implications for behavioral processes such as craving and addiction. On top of that are peripheral factors that compound brain damage such as poor diet, vitamin deficiencies leading to Wernicke-Korsakoff syndrome. Prenatal alcohol exposure can also have a profound impact on brain development and lead to irremediable changes of fetal alcohol syndrome. This chapter briefly reviews aspects of these with a particular focus on recent brain imaging results. Cardiovascular effects of alcohol that lead to brain pathology are not covered as they are dealt with elsewhere in the volume.

Chronic alcohol exposure during critical developmental periods differentially impacts persistence of deficits in cognitive flexibility and related circuitry

Cognitive flexibility in decision making depends on prefrontal cortical function and is used by individuals to adapt to environmental changes in circumstances. Cognitive flexibility can be measured in the laboratory using a variety of discrete, translational tasks, including those that involve reversal learning and/or set-shifting ability. Distinct components of flexible behavior rely upon overlapping brain circuits, including different prefrontal substructures that have separable impacts on decision making. Cognitive flexibility is impaired after chronic alcohol exposure, particularly during development when the brain undergoes rapid maturation. This review examines how cognitive flexibility, as indexed by reversal and set-shifting tasks, is impacted by chronic alcohol exposure in adulthood, adolescent, and prenatal periods in humans and animal models. We also discuss areas for future study, including mechanisms that may contribute to the persistence of cognitive deficits after developmental alcohol exposure and the compacting consequences from exposure across multiple critical periods.

White matter alterations in young children with prenatal alcohol exposure

Prenatal alcohol exposure (PAE) can lead to cognitive, behavioural, and social-emotional challenges. Previous neuroimaging research has identified structural brain alterations in newborns, older children, adolescents, and adults with PAE; however, little is known about brain structure in young children. Extensive brain development occurs during early childhood; therefore, understanding the neurological profiles of young children with PAE is critical for early identification and effective intervention. We studied 54 children (5.21 ± 1.11 years; 27 males) with confirmed PAE (94% also had other prenatal exposures, 74% had adverse postnatal experiences) compared with 54 age- and sex-matched children without PAE. Children underwent diffusion tensor imaging between 2 and 7 years of age. Mean fractional anisotropy (FA) and mean diffusivity (MD) were obtained for 10 major white matter tracts. Univariate analyses of covariance were used to test group differences (PAE vs. control) controlling for age and sex. The PAE group had higher FA in the genu of the corpus callosum and lower MD in the bilateral uncinate fasciculus. The PAE group also had lower tract volume in the corpus callosum, the bilateral inferior fronto-occipital fasciculi, and the right superior longitudinal fasciculus. Our findings align with studies of newborns with PAE reporting lower diffusivity, but contrast those in older populations with PAE, which consistently report lower FA and higher MD. Further research is needed to understand trajectories of white matter development and how our results of higher FA/lower MD in young children connect with lower FA/higher MD observed at older ages.

Functional connectivity of the attention networks is altered and relates to neuropsychological outcomes in children with prenatal alcohol exposure

Cognitive and functional brain alterations can occur in children with prenatal alcohol exposure (PAE). We examined the functional connectivity (FC) among regions within and between attention networks, and whether inter- and intranetwork FC moderated cognition in children with PAE (n = 37; age 12.8 ± 2.8 years) and nonexposed controls (n = 40; age 13.2 ± 2.8 years). Participants completed standardized attention and executive functioning tasks and resting state functional MRI. Inter- and intra-network FC and graph-theoretical metrics were calculated among attention network regions. Relative to controls, PAE was associated with reduced FC between the left temporoparietal junction and left ventral frontal cortex and anterior insula/frontal operculum (aI/fO), and between the left intraparietal sulcus and bilateral aI/fO. PAE was associated with increased FC between the right precuneus and intraparietal lobes, the right anterior prefrontal cortex and left ventral frontal cortex and aI/fO, and the left thalamus and dorsal frontal cortex. Graph-theoretical metrics did not differ by group. FC predicted cognitive performance, negatively in the children with PAE and positively in controls. Increased intra-network together with reduced internetwork FC suggests inefficient network specialization and impaired long-range FC among attention network regions after PAE. Results further suggest that those alterations may underlie attention and executive dysfunction in children with PAE.

Characterization of motor function in mice developmentally exposed to ethanol using the Catwalk system: Comparison with the triple horizontal bar and rotarod tests

Studies with human subjects indicate that ethanol exposure during fetal development causes long-lasting alterations in motor coordination that are, in part, a consequence of cerebellar damage. Studies with rats exposed to ethanol during the neonatal brain growth spurt have consistently recapitulated these deficits. However, studies with mice have yielded mixed results. We hypothesized that the use of highly sensitive motor function tests, such as the Catwalk test, would reliably detect motor function deficits in mice developmentally exposed to ethanol. Venus-vesicular GABA transporter transgenic mice were ethanol exposed during postnatal days 4-9 using vapor inhalation chambers and then subjected to the Catwalk test during adolescence. Catwalk data were rigorously analyzed using an innovative multistep statistical approach. For comparison, motor coordination and strength were assessed with the triple horizontal bar and rotarod tests. Unexpectedly, we found that out of 186 parameters analyzed in the Catwalk test, only one was affected by ethanol exposure (i.e., reduced coupling between left front paw and the right hind paw). In the triple horizontal bar test, ethanol-exposed mice were able to hold to the bars for less time than controls. Surprisingly, ethanol-exposed mice performed better in the rotarod test than controls. These data indicate that neonatal ethanol exposure of mice causes mixed effects on motor function during adolescence. The Catwalk test suggests that gait is generally preserved in these mice, whereas the triple horizontal bar test revealed deficits on motor strength and the rotarod test an increase in motor coordination.

GABAa receptor density alterations revealed in a mouse model of early moderate prenatal ethanol exposure using [18F]AH114726

INTRODUCTION

Prenatal ethanol exposure (PEE) has been shown to alter the level and function of receptors in the brain, one of which is GABA_a receptors (GABA_aR), the major inhibitory ligand gated ion channels that mediate neuronal inhibition. High dose PEE in animals resulted in the upregulation of GABA_aR, but the effects of low and moderate dose PEE at early gestation have not been investigated. This study aimed at examining GABA_aR density in the adult mouse brain following PEE during a period equivalent to the first 3 to 4 weeks in human gestation. It was hypothesized that early moderate PEE would cause alterations in brain GABA_aR levels in the adult offspring.

METHODS

C57BL/6J mice were given 10% v/v ethanol during the first 8 gestational days. Male offspring were studied using in-vivo Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI), biodistribution, in-vitro autoradiography using [¹⁸F]AH114726, a novel flumazenil analogue with a high affinity for the benzodiazepine-binding site, and validated using immunohistochemistry.

RESULTS

In vivo PET and biodistribution did not detect alteration in brain tracer uptake. In vitro radiotracer studies detected significantly reduced GABA_aR in the olfactory bulbs. Immunohistochemistry detected reduced GABA_aR in the cerebral cortex, cerebellum and hippocampus, while Nissl staining showed that cell density was significantly higher in the striatum following PEE.

CONCLUSION

Early moderate PEE may induce long-term alterations in the GABA_aR system that persisted into adulthood.

In utero MRI identifies consequences of early-gestation alcohol drinking on fetal brain development in rhesus macaques

One factor that contributes to the high prevalence of fetal alcohol spectrum disorder (FASD) is binge-like consumption of alcohol before pregnancy awareness. It is known that treatments are more effective with early recognition of FASD. Recent advances in retrospective motion correction for the reconstruction of three-dimensional (3D) fetal brain MRI have led to significant improvements in the quality and resolution of anatomical and diffusion MRI of the fetal brain. Here, a rhesus macaque model of FASD, involving oral self-administration of 1.5 g/kg ethanol per day beginning prior to pregnancy and extending through the first 60 d of a 168-d gestational term, was utilized to determine whether fetal MRI could detect alcohol-induced abnormalities in brain development. This approach revealed differences between ethanol-exposed and control fetuses at gestation day 135 (G135), but not G110 or G85. At G135, ethanol-exposed fetuses had reduced brainstem and cerebellum volume and water diffusion anisotropy in several white matter tracts, compared to controls. Ex vivo electrophysiological recordings performed on fetal brain tissue obtained immediately following MRI demonstrated that the structural abnormalities observed at G135 are of functional significance. Specifically, spontaneous excitatory postsynaptic current amplitudes measured from individual neurons in the primary somatosensory cortex and putamen strongly correlated with diffusion anisotropy in the white matter tracts that connect these structures. These findings demonstrate that exposure to ethanol early in gestation perturbs development of brain regions associated with motor control in a manner that is detectable with fetal MRI.

Graded Cerebellar Lobular Volume Deficits in Adolescents and Young Adults with Fetal Alcohol Spectrum Disorders (FASD)

The extensive prenatal developmental growth period of the cerebellum renders it vulnerable to unhealthy environmental agents, especially alcohol. Fetal alcohol spectrum disorders (FASD) is marked by neurodysmorphology including cerebral and cerebellar volume deficits, but the cerebellar lobular deficit profile has not been delineated. Legacy MRI data of 115 affected and 59 unaffected adolescents and young adults were analyzed for lobular gray matter volume and revealed graded deficits supporting a spectrum of severity. Graded deficits were salient in intracranial volume (ICV), where the fetal alcohol syndrome (FAS) group was smaller than the fetal alcohol effects (FAE) group, which was smaller than the controls. Adjusting for ICV, volume deficits were present in VIIB and VIIIA of the FAE group and were more widespread in FAS and included lobules I, II, IV, V, VI, Crus II, VIIB, and VIIIA. Graded deficits (FAS < FAE) were consistently present in lobules VI; neither group showed volume deficits in Crus I or IX. Neuroradiological readings blind to diagnosis identified 20 anomalies, 8 involving the cerebellum, 5 of which were in the FAS group. We speculate that the regional cerebellar FASD-related volume deficits may contribute to diagnostically characteristic functional impairment involving emotional control, visuomotor coordination, and postural stability.

Altered brain white matter connectome in children and adolescents with prenatal alcohol exposure

Diffuson tensor imaging (DTI) has demonstrated widespread alterations of brain white matter structure in children with prenatal alcohol exposure (PAE), yet it remains unclear how these alterations affect the structural brain network as a whole. The present study aimed to examine changes in the DTI-based structural connectome in children and adolescents with PAE compared to unexposed controls. Participants were 121 children and adolescents with PAE (51 females) and 119 typically-developing controls (49 females) aged 5-18 years with DTI data collected at one of four research centers across Canada. Graph-theory based analysis was performed on the connectivity matrix constructed from whole-brain white matter fibers via deterministic tractography. The PAE group had significantly decreased whole-brain global efficiency, degree centrality, and participation coefficients, as well as increased shortest path length and betweenness centrality compared to unexposed controls. Individuals with PAE had decreased connectivity between the attention, somatomotor, and default mode networks compared to controls. This study demonstrates decreased structural white matter connectivity in children and adolescents with PAE at a whole-brain level, suggesting widespread alterations in how networks are connected with each other. This decreased connectivity may underlie cognitive and behavioural difficulties in children with PAE.

Radiological Findings on Structural Magnetic Resonance Imaging in Fetal Alcohol Spectrum Disorders and Healthy Controls

BACKGROUND

Fetal alcohol spectrum disorders (FASD) describe a range of physical, behavioral, and cognitive impairments stemming from prenatal alcohol exposure (PAE). Although case studies have demonstrated striking visible brain abnormalities in humans (enlargement of the lateral ventricles, thinning or absence of the corpus callosum, etc.), few studies have systematically determined how these radiological findings generalize to the wider population of individuals living with FASD.

METHODS

This study examines rates of structural brain anomalies on magnetic resonance imaging (MRI) as determined by 2 radiologists in a retrospective blinded review of 163 controls and 164 individuals with PAE who were previously scanned as participants of past research studies. Incidental findings were categorized as normal variants, nonclinically significant incidental findings, or clinically significant incidental findings. Rates were compared between diagnostic subgroups using chi-square analysis.

RESULTS

There was no significant difference in the overall rate of incidental findings between groups: 75% of controls and 73% of PAE participants had no incidental findings of any kind, and only 1% of controls and 3% of PAE participants had incidental finding of clinical significance (the remaining findings were considered nonsignificant anomalies or normal variants). When the PAE group was split by diagnosis, low-lying cerebellar tonsils, polymicrogyria, and ventricular asymmetry/enlargement were all most prevalent in subjects with fetal alcohol syndrome/partial fetal alcohol syndrome. In addition, the overall rate of incidental findings was higher (41%) in participants with FAS/pFAS, compared to 25% in controls. No participants in this relatively large sample had corpus callosum agenesis.

CONCLUSIONS

Although advanced quantitative MRI research has uncovered a range of differences in brain structure associated with FASD, this qualitative radiological study suggests that routine clinical MRI does not reveal a consistent pattern of brain abnormalities that can be used diagnostically in this population.

Magnetic Resonance Imaging and Micro-Computed Tomography reveal brain morphological abnormalities in a mouse model of early moderate prenatal ethanol exposure

BACKGROUND

This study investigated the effects of early moderate prenatal ethanol exposure (PEE) on the brain in a mouse model that mimics a scenario in humans, whereby moderate daily drinking ceases after a woman becomes aware of her pregnancy.

METHODS

C57BL/6J pregnant mice were given 10% v/v ethanol from gestational day 0-8 in the drinking water. The male offspring were used for imaging. Anatomical and diffusion Magnetic Resonance Imaging were performed in vivo at postnatal day 28 (P28, adolescence) and P80 (adulthood). Micro-Computed Tomography was performed on fixed whole heads at P80. Tensor-based morphometry (TBM) was applied to detect alterations in brain structure and voxel-based morphometry (VBM) for skull morphology. Diffusion tensor and neurite orientation dispersion and density imaging models were used to detect microstructural changes. Neurofilament (NF) immunohistochemistry was used to validate findings by in vivo diffusion MRI.

RESULTS

TBM showed that PEE mice exhibited a significantly smaller third ventricle at P28 (family-wise error rate (FWE), p < 0.05). All other macro-structural alterations did not survive FWE corrections but when displayed with an uncorrected p < 0.005 showed multiple regional volume reductions and expansions, more prominently in the right hemisphere. PEE-induced gross volume changes included a bigger thalamus, hypothalamus and ventricles at P28, and bigger total brain volumes at both P28 and P80 (2-sample t-tests). Disproportionately smaller olfactory bulbs following PEE were revealed at both time-points. No alterations in diffusion parameters were detected, but PEE animals exhibited reduced NF positive staining in the thalamus and striatum and greater bone density in various skull regions.

CONCLUSION

Our results show that early moderate PEE can cause alterations in the brain that are detectable during development and adulthood.

The brain's functional connectome in young children with prenatal alcohol exposure

Prenatal alcohol exposure (PAE) can lead to altered brain function and structure, as well as lifelong cognitive, behavioral, and mental health difficulties. Previous research has shown reduced brain network efficiency in older children and adolescents with PAE, but no imaging studies have examined brain differences in young children with PAE, at an age when cognitive and behavioral problems often first become apparent. The present study aimed to investigate the brain's functional connectome in young children with PAE using passive viewing fMRI. We analyzed 34 datasets from 26 children with PAE aged 2-7 years and 215 datasets from 87 unexposed typically-developing children in the same age range. The whole brain functional connectome was constructed using functional connectivity analysis across 90 regions for each dataset. We examined intra- and inter-participant stability of the functional connectome, graph theoretical measurements, and their correlations with age. Children with PAE had similar inter- and intra-participant stability to controls. However, children with PAE, but not controls, showed increasing intra-participant stability with age, suggesting a lack of variability of intrinsic brain activity over time. Inter-participant stability increased with age in controls but not in children with PAE, indicating more variability of brain function across the PAE population. Global graph metrics were similar between children with PAE and controls, in line with previous studies in older children. This study characterizes the functional connectome in young children with PAE for the first time, suggesting that the increased brain variability seen in older children develops early in childhood, when participants with PAE fail to show the expected age-related increases in inter-individual stability.

Clinical presentation, diagnosis, and management of fetal alcohol spectrum disorder

Although prenatal alcohol exposure causes craniofacial anomalies, growth retardation, neurological abnormalities, cognitive impairment, and birth defects, fetal alcohol spectrum disorder is underdiagnosed. Global prevalence of fetal alcohol spectrum disorder is 0·77%, with a higher prevalence of 2-5% in Europe and North America, highlighting the need for increased diagnosis and treatment. However, diagnosis remains challenging because of the poor reliability of self-reported maternal drinking histories, an absence of sensitive biomarkers, and the infrequency of diagnostic dysmorphic facial features among individuals with fetal alcohol spectrum disorder. Different diagnostic systems and disagreements over criteria have slowed progress in the diagnosis and management of the disorder. Neuroimaging shows abnormalities in brain structure, cortical development, white matter microstructure, and functional connectivity in individuals with fetal alcohol spectrum disorder. These abnormalities modify developmental trajectories and are associated with deficits in cognition, executive function, memory, vision, hearing, motor skills, behaviour, and social adaptation. Promising trials of nutritional interventions and cognitive rehabilitation therapies are underway, with the aim of treating cognitive deficits in fetal alcohol spectrum disorders.

Effects of prenatal exposure to alcohol, tobacco and other drugs of abuse on retinal development

PURPOSE

To assess structural changes in the retina using optical coherence tomography (OCT) in children prenatally exposed to toxic substances.

METHODS

The study included a total of 49 infants, aged between 5 and 18years, exposed to toxic substances during pregnancy. Among the exposed children, 25 were exposed to tobacco, 20 were exposed to alcohol, and 4 children were exposed to other drugs of abuse. All children underwent a complete ophthalmology examination, including an OCT. The results were compared against a control group composed of 25 infants, age matched with controlled pregnancy, and not exposed to toxic substances.

RESULTS

Children prenatally exposed to toxic substances showed significantly thinner average retinal nerve fibre layer (RNFL) compared with control children (81.5 vs. 99.7μm; P<.005), as well as RNFL thinning in its four quadrants (superior RNFL: 97.5 vs. 127.5μm; P<.005; nasal RNFL: 61.5 vs. 72.3μm; P<.005; inferior RNFL: 99.8 vs. 128.6μm; P<.005, temporal RNFL: 58.3 vs. 68.2μm; P<.005). Exposed children also exhibited a thinner ganglion cell layer (72.9 vs. 85.9; P<.005). Greater RNFL thinning was observed in children exposed to drugs of abuse (RNFL thinner average=72), followed by children exposed to alcohol (RNFL thinner average=72.9), and finally the least affected were those children exposed to tobacco during pregnancy (RNFL=94.6).

CONCLUSION

Toxic substances during pregnancy interfere in retinal development. These results strengthen the evidence about the avoidance of any toxic substance during pregnancy.

Neurobiology of substance use in adolescents and potential therapeutic effects of exercise for prevention and treatment of substance use disorders

Substance use (e.g., alcohol, marijuana, opioids, cocaine., etc,) use often initiates during adolescence, a critical period of physiological and social development marked by an increase in risk-taking due, in part, to heightened motivation to obtain arousal from rewards. Substance use during adolescence has been associated with a greater risk of substance use disorders (SUD) in adulthood. Although use rates for most substances have remained relatively stable, the frequency of marijuana use and the perception that regular marijuana use is not harmful has increased in adolescents. Furthermore, the nonmedical use of opioids has increased, particularly in the South, Midwest, and rural low-income communities. Substance use in adolescence has been associated with adverse structural and functional brain changes and, may exacerbate the natural "imbalance" between frontal/regulatory and cortical-subcortical circuits, leading to further heightened impulsive and reward-driven behaviors. Exercise increases growth and brain-derived neurotrophic factors that stimulate endogenous dopaminergic systems that, in turn, enhance general plasticity, learning, and memory. Exercise may help to reinforce the "naïve" or underdeveloped connections between neurological reward and regulatory processes in adolescence from the "bottom up" and "offset" reward seeking from substances, while concomitantly improving cardiovascular health, as well as academic and social achievement. In this review, we provide an overview of the current state of substance use in adolescents and rationale for the utilization of exercise, particularly "assisted" exercise, which we have shown increases neural activity in cortical-subcortical regions and may modulate brain dopamine levels during adolescence, a unique window of heightened reward sensitivity and neural plasticity, for the prevention and adjunctive treatment of SUD.

Regional Patterns of Alcohol-Induced Neuronal Loss Depend on Genetics: Implications for Fetal Alcohol Spectrum Disorder

BACKGROUND

Alcohol exposure during pregnancy can kill developing neurons and lead to fetal alcohol spectrum disorder (FASD). However, affected individuals differ in their regional patterns of alcohol-induced neuropathology. Because neuroprotective genes are expressed in spatially selective ways, their mutation could increase the vulnerability of some brain regions, but not others, to alcohol teratogenicity. The objective of this study was to determine whether a null mutation of neuronal nitric oxide synthase (nNOS) can increase the vulnerability of some brain regions, but not others, to alcohol-induced neuronal losses.

METHODS

Immunohistochemistry identified brain regions in which nNOS is present or absent throughout postnatal development. Mice genetically deficient for nNOS (nNOS^-/- ) and wild-type controls received alcohol (0.0, 2.2, or 4.4 mg/g/d) over postnatal days (PD) 4 to 9. Mice were sacrificed in adulthood (~PD 115), and surviving neurons in the olfactory bulb granular layer and brain stem facial nucleus were quantified stereologically.

RESULTS

nNOS was expressed throughout postnatal development in olfactory bulb granule cells but was never expressed in the facial nucleus. In wild-type mice, alcohol reduced neuronal survival to similar degrees in both cell populations. However, null mutation of nNOS more than doubled alcohol-induced cell death in the olfactory bulb granule cells, while the mutation had no effect on the facial nucleus neurons. As a result, in nNOS^-/- mice, alcohol caused substantially more cell loss in the olfactory bulb than in the facial nucleus.

CONCLUSIONS

Mutation of the nNOS gene substantially increases vulnerability to alcohol-induced cell loss in a brain region where the gene is expressed (olfactory bulb), but not in a separate brain region, where the gene is not expressed (facial nucleus). Thus, differences in genotype may explain why some individuals are vulnerable to FASD, while others are not, and may determine the specific patterns of neuropathology in children with FASD.