Structural brain anomalies in healthy adolescents in the NCANDA cohort: relation to neuropsychological test performance, sex, and ethnicity

A longitudinal study of the relationship between alcohol-related blackouts and attenuated structural brain development

PURPOSE

Alcohol-related blackouts (ARBs) are common in adolescents and emerging adults. ARBs may also be indicative of persistent, alcohol-related neurocognitive changes. This study explored ARBs as a predictor of altered structural brain development and associated cognitive correlates.

METHODS

Longitudinal growth curve modeling estimated trajectories of brain volume across 6 years in participants from the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA) study (n = 800, 213 with lifetime ARB history). While controlling for demographics and overall alcohol use, ARB history was analyzed as a predictor of brain volume growth in regions associated with alcohol-related cognitive change. Post hoc analyses examined whether ARBs moderated relationships between brain morphology and cognition.

RESULTS

ARBs significantly predicted attenuated development of fusiform gyrus and hippocampal volume at unique timepoints compared to overall alcohol use. Alcohol use without ARBs significantly predicted attenuated fusiform and hippocampal growth at earlier and later timepoints, respectively. Despite altered development in regions associated with memory, ARBs did not significantly moderate relationships between brain volume and cognitive performance.

CONCLUSION

ARBs and overall alcohol use predicted altered brain development in the fusiform gyrus and hippocampus at different timepoints, suggesting ARBs represent a unique marker of neurocognitive risk in younger drinkers.

Volumetric segmentation in the context of posterior fossa-related pathologies: a systematic review

BACKGROUND

Segmentation tools continue to advance, evolving from manual contouring to deep learning. Researchers have utilized segmentation to study a myriad of posterior fossa-related conditions, such as Chiari malformation, trigeminal neuralgia, post-operative pediatric cerebellar mutism syndrome, and Crouzon syndrome. Herein, we present a summary of the current literature on segmentation of the posterior fossa. The review highlights the various segmentation techniques, and their respective strengths and weaknesses, employed along with objectives and outcomes of the various studies reported in the literature.

METHODS

A literature search was conducted in PubMed, Embase, Cochrane, and Web of Science up to November 2023 for articles on segmentation techniques of posterior fossa. The two senior authors searched through databases based on the keywords of the article separately and then enrolled joint articles that met the inclusion and exclusion criteria.

RESULTS

The initial search identified 2205 articles. After applying inclusion and exclusion criteria, 77 articles were selected for full-text review after screening of titles/abstracts. 52 articles were ultimately included in the review. Segmentation techniques included manual, semi-automated, and fully automated (atlas-based, convolutional neural networks). The most common pathology investigated was Chiari malformation.

CONCLUSIONS

Various forms of segmentation techniques have been used to assess posterior fossa volumes/pathologies and each has its advantages and disadvantages. We discuss these nuances and summarize the current state of literature in the context of posterior fossa-associated pathologies.

Interindividual differences in posterior fossa morphometry affect cerebellar tDCS-induced electric field strength

OBJECTIVE

Clinical, behavioural, and neurophysiological effects of cerebellar transcranial direct current stimulation (tDCS) are highly variable and difficult to predict. We aimed to examine associations between cerebellar tDCS-induced electric field strength, morphometric posterior fossa parameters, and skin-cerebellum distance. As a secondary objective, field characteristics were compared between cephalic and extracephalic electrode configurations.

METHODS

Electric field simulations of midline cerebellar tDCS (7 × 5 cm electrodes, current intensities of 2 mA) were performed on MRI-based head models from 37 healthy adults using buccinator, frontopolar, and lower neck reference electrodes. Average field strengths were determined in eight regions of interest (ROIs) covering the anterior and posterior vermis and cerebellar hemispheres. Besides skin-cerebellum distance, various angles were measured between posterior fossa structures. Multivariable linear regression models were used to identify predictors of field strength in different ROIs.

RESULTS

Skin-cerebellum distance and "pons angle" were independently associated with field strength in the anterior and posterior vermis. "Cerebellar angle" and skin-cerebellum distance affected field strength in anterior and posterior regions of the right cerebellar hemisphere. Field strengths in all examined cerebellar areas were highest in the frontopolar and lowest in the lower neck montage, while the opposite was found for field focality. The lower neck montage induced considerably less spreading toward anterior cerebellar regions compared with the buccinator and frontopolar montages, which resulted in a more evenly distributed field within the cerebellum.

CONCLUSION

In addition to skin-cerebellum distance, interindividual differences in posterior fossa morphometry, specifically pons and cerebellar angle, explain part of the variability in cerebellar tDCS-induced electric field strength. Furthermore, when targeting the midline cerebellum with tDCS, an extracephalic reference electrode is associated with lower field strengths and higher field focality than cephalic montages.

SIGNIFICANCE

This study identifies two novel subject-specific anatomical factors that partly determine cerebellar tDCS-induced electric field strength and reveals differences in field characteristics between electrode montages.

White matter microstructural integrity continues to develop from adolescence to young adulthood in mice and humans: Same phenotype, different mechanism

As direct evaluation of a mouse model of human neurodevelopment, adolescent and young adult mice and humans underwent MR diffusion tensor imaging to quantify age-related differences in microstructural integrity of brain white matter fibers. Fractional anisotropy (FA) was greater in older than younger mice and humans. Despite the cross-species commonality, the underlying developmental mechanism differed: whereas evidence for greater axonal extension contributed to higher FA in older mice, evidence for continuing myelination contributed to higher FA in human adolescent development. These differences occurred in the context of species distinctions in overall brain growth: whereas the continued growth of the brain and skull in the murine model can accommodate volume expansion into adulthood, human white matter volume and myelination continue growth into adulthood within a fixed intracranial volume. Appreciation of the similarities and differences in developmental mechanism can enhance the utility of animal models of brain white matter structure, function, and response to exogenous manipulation.

Radiologically Isolated Syndrome and the Multiple Sclerosis Prodrome in Pediatrics: Early Features of the Spectrum of Demyelination

Radiologically isolated syndrome refers to the clinical scenario in which individuals have imaging concerning for multiple sclerosis and would otherwise satisfy radiographic dissemination in space criteria, but do not have any attributable signs or symptoms. Radiologically isolated syndrome has been increasingly recognized in the pediatric population and it is understood certain individuals will transition to a formal diagnosis of multiple sclerosis over time. This review aims to outline the available data within this unique population including the diagnostic criteria, epidemiology, risk factors associated with transitioning to multiple sclerosis, and the current therapeutic landscape. Radiologically isolated syndrome will also be positioned within a broader spectrum of demyelinating disease as recent data has pointed towards a likely prodromal phase that precedes a first clinical event and diagnosis of multiple sclerosis. Characterizing the radiographic features, clinical symptoms, and biomarkers that constitute this prodromal phase of multiple sclerosis would help identify patients who may most benefit from early intervention in the future.

Prevalence of incidental intracranial findings on magnetic resonance imaging: a systematic review and meta-analysis

BACKGROUND

As the volume and fidelity of magnetic resonance imaging (MRI) of the brain increase, observation of incidental findings may also increase. We performed a systematic review and meta-analysis to determine the prevalence of various incidental findings.

METHODS

PubMed/MEDLINE, EMBASE and SCOPUS were searched from inception to May 24, 2021. We identified 6536 citations and included 35 reports of 34 studies, comprising 40,777 participants. A meta-analysis of proportions was performed, and age-stratified estimates for each finding were derived from age-adjusted non-linear models.

RESULTS

Vascular abnormalities were observed in 423/35,706 participants (9.1/1000 scans, 95%CI 5.2-14.2), ranging from 2/1000 scans (95%CI 0-7) in 1-year-olds to 16/1000 scans (95%CI 1-43) in 80-year-olds. Of these, 204/34,306 were aneurysms (3.1/1000 scans, 95%CI 1-6.3), which ranged from 0/1000 scans (95%CI 0-5) at 1 year of age to 6/1000 scans (95%CI 3-9) at 60 years. Neoplastic abnormalities were observed in 456/39,040 participants (11.9/1000 scans, 95%CI 7.5-17.2), ranging from 0.2/1000 scans (95%CI 0-10) in 1-year-olds to 34/1000 scans (95%CI 12-66) in 80-year-olds. Meningiomas were the most common, in 246/38,076 participants (5.3/1000 scans, 95%CI 2.3-9.5), ranging from 0/1000 scans (95%CI 0-2) in 1-year-olds to 17/1000 scans (95%CI 4-37) in 80-year-olds. Chiari malformations were observed in 109/27,408 participants (3.7/1000 scans, 95%CI 1.8-6.3), pineal cysts in 1176/32,170 (9/1000 scans, 95%CI 1.8-21.4) and arachnoid cysts in 414/36,367 (8.5/1000 scans, 95%CI 5.8-11.8).

CONCLUSION

Incidental findings are common on brain MRI and may result in substantial resource expenditure and patient anxiety but are often of little clinical significance.

Subclinical Anxiety and Posttraumatic Stress Influence Cortical Thinning During Adolescence

OBJECTIVE

Adolescence is a sensitive period for the development and emergence of anxiety and mood disorders. Research suggests that symptoms ranging from subclinical to clinical levels are associated with pathological developmental changes in the neocortex. However, much of this research has been cross-sectional, limiting the field's ability to identify the neurodevelopmental impacts of these symptoms. The present study examined how early reported symptoms predict baseline cortical thickness and surface area, and trajectories of change in these measures during adolescence.

METHOD

A total of 205 typically developing individuals 9 to 15 years of age (103 male and 102 female participants) completed 3T structural magnetic resonance imaging annually for 3 years. From these, we extracted mean cortical thickness and total surface area for each year. Youth self-reported their anxiety, depressive, and posttraumatic stress symptoms during their first visit. We used latent growth curve modeling to determine how these symptoms along with sex interactions predicted baseline thickness and surface area, and rates of change in these measures over the 3-year period.

RESULTS

Higher anxiety was associated with lower baseline thickness and slowed cortical thinning over time. Conversely, greater posttraumatic stress predicted higher baseline thickness and accelerated thinning over time. Sex interactions suggested that the effects were dampened among female compared to male participants. Depressive symptoms were not related to cortical thickness or surface area.

CONCLUSION

Female adolescents may express more regionally specific effects of symptoms sets on cortical thickness, although this requires further investigation. Cortical thickness in male adolescents appears to be preferentially susceptible to anxiety and posttraumatic stress symptoms, exhibiting global changes across multiple years.

Prevalence of radiologically isolated syndrome in a pediatric population-based cohort: A longitudinal description of a rare diagnosis

BACKGROUND

Radiologically isolated syndrome (RIS) is typified by multiple sclerosis (MS)-like lesions on imaging, without clinical MS symptoms. The prevalence of pediatric RIS is largely unknown.

OBJECTIVE

The objective of the study is to provide an estimated RIS prevalence in a population-based cohort of children.

METHODS

We used data from the Generation R study to identify the childhood RIS prevalence.

RESULTS

In 5238 participants, only one RIS case was identified (prevalence: 0.02%; 95% confidence interval (CI): 0.00-0.11). During a 62-month follow-up, imaging examinations showed accrual of new focal demyelinating lesions; however, no clinical MS symptoms occurred.

CONCLUSIONS

This study shows that the occurrence of RIS in children from the general population is rare.

Rates of Incidental Findings in Brain Magnetic Resonance Imaging in Children

Importance

Incidental findings (IFs) are unexpected abnormalities discovered during imaging and can range from normal anatomic variants to findings requiring urgent medical intervention. In the case of brain magnetic resonance imaging (MRI), reliable data about the prevalence and significance of IFs in the general population are limited, making it difficult to anticipate, communicate, and manage these findings.

Objectives

To determine the overall prevalence of IFs in brain MRI in the nonclinical pediatric population as well as the rates of specific findings and findings for which clinical referral is recommended.

Design, Setting, and Participants

This cohort study was based on the April 2019 release of baseline data from 11 810 children aged 9 to 10 years who were enrolled and completed baseline neuroimaging in the Adolescent Brain Cognitive Development (ABCD) study, the largest US population-based longitudinal observational study of brain development and child health, between September 1, 2016, and November 15, 2018. Participants were enrolled at 21 sites across the US designed to mirror the demographic characteristics of the US population. Baseline structural MRIs were centrally reviewed for IFs by board-certified neuroradiologists and findings were described and categorized (category 1, no abnormal findings; 2, no referral recommended; 3; consider referral; and 4, consider immediate referral). Children were enrolled through a broad school-based recruitment process in which all children of eligible age at selected schools were invited to participate. Exclusion criteria were severe sensory, intellectual, medical, or neurologic disorders that would preclude or interfere with study participation. During the enrollment process, demographic data were monitored to ensure that the study met targets for sex, socioeconomic, ethnic, and racial diversity. Data were analyzed from March 15, 2018, to November 20, 2020.

Main Outcomes and Measures

Percentage of children with IFs in each category and prevalence of specific IFs.

Results

A total of 11 679 children (52.1% boys, mean [SD] age, 9.9 [0.62] years) had interpretable baseline structural MRI results. Of these, 2464 participants (21.1%) had IFs, including 2013 children (17.2%) assigned to category 2, 431 (3.7%) assigned to category 3, and 20 (0.2%) assigned to category 4. Overall rates of IFs did not differ significantly between singleton and twin gestations or between monozygotic and dizygotic twins, but heritability analysis showed heritability for the presence or absence of IFs (h2 = 0.260; 95% CI, 0.135-0.387).

Conclusions and Relevance

Incidental findings in brain MRI and findings with potential clinical significance are both common in the general pediatric population. By assessing IFs and concurrent developmental and health measures and following these findings over the longitudinal study course, the ABCD study has the potential to determine the significance of many common IFs.

Characterization of MR Imaging-Visible Perivascular Spaces in the White Matter of Healthy Adolescents at 3T

BACKGROUND AND PURPOSE

Perivascular spaces play a role in cerebral waste removal and neuroinflammation. Our aim was to provide data regarding the burden of MR imaging-visible perivascular spaces in white matter in healthy adolescents using an automated segmentation method and to establish relationships between common demographic characteristics and perivascular space burden.

MATERIALS AND METHODS

One hundred eighteen 12- to 21-year-old subjects underwent T1- and T2-weighted 3T MR imaging as part of the National Consortium on Alcohol and Neurodevelopment in Adolescence. Perivascular spaces were identified in WM on T2-weighted imaging using a local heterogeneity approach coupled with morphologic constraints, and their spatial distribution and geometric characteristics were assessed.

RESULTS

MR imaging-visible perivascular spaces were identified in all subjects (range, 16-287). Males had a significantly higher number of perivascular spaces than females: males, mean, 98.4 ± 50.5, versus females, 70.7 ± 36.1, (P < .01). Perivascular space burden was bilaterally symmetric (r > 0.4, P < .01), and perivascular spaces were more common in the frontal and parietal lobes than in the temporal and occipital lobes (P < .01). Age and pubertal status were not significantly associated with perivascular space burden.

CONCLUSIONS

Despite a wide range of burden, perivascular spaces are present in all healthy adolescents. Perivascular space burden is higher in adolescent males than in females, regardless of age and pubertal status. In this population, perivascular spaces are highly symmetric. Although widely reported as a feature of the aging brain, awareness of the presence of perivascular spaces in a cohort of healthy adolescents provides the foundation for further research regarding the role of these structural variants in health and disease.

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.

Unique near-complete deletion of GLI2 in a patient with combined pituitary hormone deficiency and post-axial polydactyly

INTRODUCTION

Combined pituitary hormone deficiency (CPHD) can cause a broad spectrum of health problems, ranging from short stature only, to convulsions or even death. In the majority of patients, the cause is unknown.

METHODS

The idex case had unexplained CPHD, pituitary anomalies on MRI and polydactyly. In the patients and her unaffected parents, we performed SNP array analysis and Whole Exome Sequencing, after candidate gene analysis turned out negative.

RESULTS

We found a unique de novo heterozygous 229.9 kb deletion in the index case on chr. 2q14.2. This deletion covered 12 out of the 13 coding exons of the GLI2 gene, a transcription factor involved in midline formation and previously associated with CPHD. As reported GLI2 deletions and mutations show a large phenotypic variability, we performed a genotype-phenotype analysis. This revealed that GLI2 missense mutations usually present with a 'ppp-only' phenotype (pituitary anomalies ± postaxial polydactyly without brain phenotype), whereas the 'ppp-plus' phenotype (with major brain malformations and/or intellectual disabilities) is more frequent in patients with larger deletions, and those with frameshift mutations/point mutations or splice variants resulting in a stop codon (p < .001).

CONCLUSION

The present case shows that a deletion of the GLI2 gene only (not affecting any of the adjacent genes) causes pituitary anomalies without brain phenotype. This suggests that brain phenotype only occurs when additional genes adjacent to GLI2 are deleted, or when mutations result in truncated GLI2 mRNA/protein. However, due to the lack of functional data for many GLI2 mutations and based on the available information regarding variable penetrance, phenotype-genotype correlations need to be made with caution.

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.

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.

Biomedical ethics and clinical oversight in multisite observational neuroimaging studies with children and adolescents: The ABCD experience

Observational neuroimaging studies with children and adolescents may identify neurological anomalies and other clinically relevant findings. Planning for the management of this information involves ethical considerations that may influence informed consent, confidentiality, and communication with participants about assessment results. Biomedical ethics principles include respect for autonomy, beneficence, non-maleficence, and justice. Each project presents unique challenges. The Adolescent Brain and Cognitive Development study (ABCD) collaborators have systematically developed recommendations with written guidelines for identifying and responding to potential risks that adhere to biomedical ethics principles. To illustrate, we will review the ABCD approach to three areas: (1) hazardous substance use; (2) neurological anomalies; and (3) imminent potential for self-harm or harm to others. Each ABCD site is responsible for implementing procedures consistent with these guidelines in accordance with their Institutional Review Board approved protocols, state regulations, and local resources. To assure that each site has related plans and resources in place, site emergency procedures manuals have been developed, documented and reviewed for adherence to ABCD guidelines. This article will describe the principles and process used to develop these ABCD bioethics and medical oversight guidelines, the concerns and options considered, and the resulting approaches advised to sites.