A small pons as a characteristic finding in Down syndrome: A quantitative MRI study

Biometric magnetic resonance imaging analysis of fetal brain development in Down syndrome

OBJECTIVES

To assess brain development in living fetuses with Down syndrome (DS) by biometric measurements on fetal brain magnetic resonance images (MRI).

METHODS

We scanned 10 MRIs of fetuses with confirmed trisomy 21 at birth and 12 control fetal MRIs without any detected anomalies. Fetal brain MRIs were analyzed using 14 fetal brain and skull biometric parameters. We compared measures between DS and controls in both raw MRIs and motion-corrected and anterior-posterior commissure-aligned images.

RESULTS

In the reconstructed images, the measured values of the height of the cerebellar vermis (HV) and anteroposterior diameter of the cerebellar vermis (APDV) were significantly smaller, and the anteroposterior diameter of the fourth ventricle (APDF) was significantly larger in fetuses with DS than controls. In the raw MRIs, the measured values of the right lateral ventricle were significantly larger in fetuses with DS than in controls. Logistic regression analyses revealed that a new parameter, the cerebellar-to-fourth-ventricle ratio (i.e., (APDV * Height of the vermis)/APDF), was significantly smaller in fetuses with DS than controls and was the most predictive to distinguish between fetuses with DS and controls.

CONCLUSIONS

The study revealed that fetuses with DS have smaller cerebellums and larger fourth ventricles compared to the controls.

Distinct neuroanatomical and neuropsychological features of Down syndrome compared to related neurodevelopmental disorders: a systematic review

Objectives

We critically review research findings on the unique changes in brain structure and cognitive function characteristic of Down syndrome (DS) and summarize the similarities and differences with other neurodevelopmental disorders such as Williams syndrome, 22q11.2 deletion syndrome, and fragile X syndrome.

Methods

We conducted a meta-analysis and systematic literature review of 84 studies identified by searching PubMed, Google Scholar, and Web of Science from 1977 to October 2022. This review focuses on the following issues: (1) specific neuroanatomic and histopathological features of DS as revealed by autopsy and modern neuroimaging modalities, (2) language and memory deficits in DS, (3) the relationships between these neuroanatomical and neuropsychological features, and (4) neuroanatomic and neuropsychological differences between DS and related neurodevelopmental syndromes.

Results

Numerous post-mortem and morphometric neuroimaging investigations of individuals with DS have reported complex changes in regional brain volumes, most notably in the hippocampal formation, temporal lobe, frontal lobe, parietal lobe, and cerebellum. Moreover, neuropsychological assessments have revealed deficits in language development, emotional regulation, and memory that reflect these structural changes and are more severe than expected from general cognitive dysfunction. Individuals with DS also show relative preservation of multiple cognitive, linguistic, and social domains compared to normally developed controls and individuals with other neurodevelopmental disorders. However, all these neurodevelopment disorders exhibit substantial heterogeneity among individuals.

Conclusion

People with Down syndrome demonstrate unique neurodevelopmental abnormalities but cannot be regarded as a homogenous group. A comprehensive evaluation of individual intellectual skills is essential for all individuals with neurodevelopment disorders to develop personalized care programs.

Heart Rate Variability in Individuals with Down Syndrome: A Scoping Review with Methodological Considerations

Individuals with Down syndrome (DS) present similar heart rate variability (HRV) parameters at rest but different responses to selected movement maneuvers in comparison to individuals without DS, which indicates reduced vagal regulation. The present study undertakes a scoping review of research on HRV in individuals with DS, with special attention paid to the compliance of the studies with standards and methodological paper guidelines for HRV assessment and interpretation. A review was performed using PubMed, Web of Science and CINAHL databases to search for English language publications from 1996 to 2020 with the MESH terms "heart rate variability" and "down syndrome", with the additional inclusion criteria of including only human participants and empirical investigations. From 74 studies, 15 were included in the review. None of the reviewed studies met the recommendations laid out by the standards and guidelines for providing the acquisition of RR intervals and necessary details on HRV analysis. Since authors publishing papers on this research topic do not adhere to the prescribed standards and guidelines when constructing the methodology, results of the research papers on the topic are not directly comparable. Authors need to design the study methodology more robustly by following the aforementioned standards, guidelines and recommendations.

Pediatrik Popülasyonda Pons Gelişiminin Yaşa ve Cinsiyete Göre Manyetik Rezonans Görüntüleme ile Morfometrik Değerlendirilmesi

Amaç: Pons, vital merkezleri içeren önemli bir posterior fossa yapısıdır. Bu yapının gelişimsel ve edinsel hastalıklarının erken tanısında ponsun ortalama morfometrik ölçüm değerlerinin bilinmesi önemlidir.Yöntem: Çalışmamız sağlıklı bir pediatrik popülasyonda yapıldı. Dört yaş grubu vardır: 0-2 yaş (bebekler), 3-6 yaş (küçük çocuklar), 7-11 yaş (çocuklar) ve 12-17 yaş (ergenler) ve her yaş grubundan 50 kız ve 50 erkek. Bu olguların beyin manyetik rezonans görüntüleme (MRG) tetkikleri, klinik muayeneleri ve takipleri normal olarak değerlendirildi. MRG incelemesi Philips Achieva MR cihazından 1,5 Tesla manyetik alan gücünde elde edildi.Bulgular: Pons alanı ve pons kraniyo-kaudal (KK) uzunluğu her iki cinsiyette de yaşla birlikte arttı. Öte yandan, pons anteriyor-posteriyor (AP) çapı 7-11 yaş grubuna kadar önemli ölçüde artmış ve daha sonra bu artış hızı azalarak plato haline gelmiştir. Cinsiyetler karşılaştırıldığında 7-11 yaş grubu hariç tüm yaş gruplarında pons alanı erkeklerde kadınlara göre anlamlı olarak daha büyüktü. Pons AP çapı erkeklerde 0-2 yaş grubunda kadınlara göre anlamlı olarak daha büyüktü. Pons KK uzunluğu, 3-6 yaş grubu dışındaki tüm gruplarda erkek cinsiyette anlamlı olarak daha yüksekti.Sonuç: Bu çalışma, ponsun morfolojik gelişiminde ve bu yapının cinsiyetler arasındaki farklılıklarında esastır. Bu çalışmada elde edilen veriler, rutin klinik uygulamada posterior fossa patolojilerinin ayırıcı tanısına yardımcı olabilir.

Molecular Organization and Patterning of the Medulla Oblongata in Health and Disease

The medulla oblongata, located in the hindbrain between the pons and the spinal cord, is an important relay center for critical sensory, proprioceptive, and motoric information. It is an evolutionarily highly conserved brain region, both structural and functional, and consists of a multitude of nuclei all involved in different aspects of basic but vital functions. Understanding the functional anatomy and developmental program of this structure can help elucidate potential role(s) of the medulla in neurological disorders. Here, we have described the early molecular patterning of the medulla during murine development, from the fundamental units that structure the very early medullary region into 5 rhombomeres (r7–r11) and 13 different longitudinal progenitor domains, to the neuronal clusters derived from these progenitors that ultimately make-up the different medullary nuclei. By doing so, we developed a schematic overview that can be used to predict the cell-fate of a progenitor group, or pinpoint the progenitor domain of origin of medullary nuclei. This schematic overview can further be used to help in the explanation of medulla-related symptoms of neurodevelopmental disorders, e.g., congenital central hypoventilation syndrome, Wold–Hirschhorn syndrome, Rett syndrome, and Pitt–Hopkins syndrome. Based on the genetic defects seen in these syndromes, we can use our model to predict which medullary nuclei might be affected, which can be used to quickly direct the research into these diseases to the likely affected nuclei.

Hearing impairment in murine model of Down syndrome

Hearing impairment is a cardinal feature of Down syndrome (DS), but its clinical manifestations have been attributed to multiple factors. Murine models could provide mechanistic insights on various causes of hearing loss in DS. To investigate mechanisms of hearing loss in DS in the absence of the cadherin 23 mutation, we backcrossed our DS mice, Dp(16)1Yey, onto normal-hearing CBA/J mice and evaluated their auditory function. Body weights of wild type (WT) and DS mice were similar at 3-months of age, but at 9-months, WT weighed 30% more than DS mice. Distortion product otoacoustic emissions (DPOAE), a test of sensory outer hair cell (OHC) function negatively impacted by conductive hearing loss, were reduced in amplitude and sensitivity across all frequencies in DS mice. The middle ear space in DS mice appeared normal with no evidence of infection. MicroCT structural imaging of DS temporal bones revealed a smaller tympanic membrane diameter, oval window, and middle ear space and localized thickening of the bony otic capsule, but no gross abnormalities of the middle ear ossicles. Histological analysis of the cochlear and vestibular sensory epithelium revealed a normal density of cochlear and vestibular hair cells; however, the cochlear basal membrane was approximately 0.6 mm shorter in DS than WT mice so that the total number of hair cells was greater in WT than DS mice. In DS mice, the early and late peaks in the auditory brainstem response (ABR), reflecting neural responses from the cochlear auditory nerve followed by subsequent neural centers in the brainstem, were reduced in amplitude and ABR thresholds were elevated to a similar degree across all frequencies, consistent with a conductive hearing impairment. The latency of the peaks in the ABR waveform were longer in DS than WT mice when compared at the same intensity; however, the latency delays disappeared when the data were compared at the same intensity above thresholds to compensate for the conductive hearing loss. Future studies using wideband tympanometry and absorbance together with detailed histological analysis of the middle ear could illuminate the nature of the conductive hearing impairment in DS mice.

Developmental Neuropathology and Neurodegeneration of Down Syndrome: Current Knowledge in Humans

Individuals with Down syndrome (DS) suffer from developmental delay, intellectual disability, and an early-onset of neurodegeneration, Alzheimer’s-like disease, or precocious dementia due to an extra chromosome 21. Studying the changes in anatomical, cellular, and molecular levels involved may help to understand the pathogenesis and develop target treatments, not just medical, but also surgical, cell and gene therapy, etc., for individuals with DS. Here we aim to identify key neurodevelopmental manifestations, locate knowledge gaps, and try to build molecular networks to better understand the mechanisms and clinical importance. We summarize current information about the neuropathology and neurodegeneration of the brain from conception to adulthood of foetuses and individuals with DS at anatomical, cellular, and molecular levels in humans. Understanding the alterations and characteristics of developing Down syndrome will help target treatment to improve the clinical outcomes. Early targeted intervention/therapy for the manifestations associated with DS in either the prenatal or postnatal period may be useful to rescue the neuropathology and neurodegeneration in DS.

Structural magnetic resonance imaging demonstrates volumetric brain abnormalities in down syndrome: Newborns to young adults

Down syndrome (DS) is a genetic disorder caused by the presence of an extra full or partial copy of chromosome 21 and characterized by intellectual disability. We hypothesize that performing a retrospective analysis of 73 magnetic resonance imaging (MRI) examinations of participants with DS (aged 0 to 22 years) and comparing them to a large cohort of 993 brain MRI examinations of neurotypical participants (aged 0 to 32 years), will assist in better understanding what brain differences may explain phenotypic developmental features in DS, as well as to provide valuable confirmation of prospective literature findings clinically. Measurements for both absolute volumes and volumes corrected as a percentage of estimated total intracranial volume (%ETIV) were extracted from each examination. Our results presented novel findings such as volume increases (%ETIV) in the perirhinal cortex, entorhinal cortex, choroid plexus, and Brodmann's areas (BA) 3a, 3b, and 44, as well as volume decreases (%ETIV) in the white matter of the cuneus, the paracentral lobule, the postcentral gyrus, and the supramarginal gyrus. We also confirmed volumetric brain abnormalities previously discussed in the literature. Findings suggest the presence of volumetric brain abnormalities in DS that can be detected clinically with MRI.

Mechanistic Analysis of Age-Related Clinical Manifestations in Down Syndrome

Down syndrome (DS) is the most common genetic cause of Alzheimer's disease (AD) due to trisomy for all or part of human chromosome 21 (Hsa21). It is also associated with other phenotypes including distinctive facial features, cardiac defects, growth delay, intellectual disability, immune system abnormalities, and hearing loss. All adults with DS demonstrate AD-like brain pathology, including amyloid plaques and neurofibrillary tangles, by age 40 and dementia typically by age 60. There is compelling evidence that increased APP gene dose is necessary for AD in DS, and the mechanism for this effect has begun to emerge, implicating the C-terminal APP fragment of 99 amino acid (β-CTF). The products of other triplicated genes on Hsa21 might act to modify the impact of APP triplication by altering the overall rate of biological aging. Another important age-related DS phenotype is hearing loss, and while its mechanism is unknown, we describe its characteristics here. Moreover, immune system abnormalities in DS, involving interferon pathway genes and aging, predispose to diverse infections and might modify the severity of COVID-19. All these considerations suggest human trisomy 21 impacts several diseases in an age-dependent manner. Thus, understanding the possible aging-related mechanisms associated with these clinical manifestations of DS will facilitate therapeutic interventions in mid-to-late adulthood, while at the same time shedding light on basic mechanisms of aging.

Magnetic resonance imaging of the brainstem in children, part 1: imaging techniques, embryology, anatomy and review of congenital conditions

Part 1 of this series of two articles describes conventional and advanced MRI techniques that are useful for evaluating brainstem pathologies. In addition, it provides a review of the embryology, normal progression of myelination, and clinically and radiologically salient imaging anatomy of the normal brainstem. Finally, it discusses congenital diseases of the brainstem with a focus on distinctive imaging features that allow for differentiating pathologies. Part 2 of this series of two articles includes discussion of neoplasms; infections; and vascular, demyelinating, toxic and metabolic, and miscellaneous disease processes affecting the brainstem. The ultimate goal of this pair of articles is to empower the radiologist to add clinical value in the care of pediatric patients with brainstem pathologies.

Pons Anteroposterior and Cerebellar Vermis Craniocaudal Diameters in Fetuses With Down Syndrome

OBJECTIVES

To investigate the pons anteroposterior diameter (APD) and cerebellar vermis craniocaudal diameter (CCD) of fetuses with Down syndrome (DS).

METHODS

This was a prospective observational study including 200 low-risk pregnancies and 18 pregnancies with fetuses who had DS. A midsagittal view was obtained to measure the pons APD and cerebellar vermis CCD. Gestational age-related 5th, mean, and 95th percentiles for the pons APD and cerebellar vermis CCD between 18 and 32 weeks' gestation were created from the low-risk population. Each measurement of a fetus with DS was plotted on growth charts, and those below the 5th percentile for gestational age were considered small.

RESULTS

The pons APD and cerebellar vermis CCD measurements were below the 5th percentile for gestational age in 7 of the 18 (38.8%) fetuses with DS. Fetuses who had pons APDs below the 5th percentile for gestational age also had cerebellar vermis CCDs below the 5th percentile. Fetuses who had pons and cerebellar vermis measurements below the 5th percentile for gestational age on the initial examination continued to have small measurements during follow-up.

CONCLUSIONS

Fetal pons and cerebellar vermis abnormalities could be observed prenatally in fetuses with DS, which could help in the antenatal counseling and postnatal follow-up of such pregnancies.

Hypoplasia of cerebellar afferent networks in Down syndrome revealed by DTI-driven tensor based morphometry

Quantitative magnetic resonance imaging (MRI) investigations of brain anatomy in children and young adults with Down syndrome (DS) are limited, with no diffusion tensor imaging (DTI) studies covering that age range. We used DTI-driven tensor based morphometry (DTBM), a novel technique that extracts morphometric information from diffusion data, to investigate brain anatomy in 15 participants with DS and 15 age- and sex-matched typically developing (TD) controls, ages 6-24 years (mean age ~17 years). DTBM revealed marked hypoplasia of cerebellar afferent systems in DS, including fronto-pontine (middle cerebellar peduncle) and olivo-cerebellar (inferior cerebellar peduncle) connections. Prominent gray matter hypoplasia was observed in medial frontal regions, the inferior olives, and the cerebellum. Very few abnormalities were detected by classical diffusion MRI metrics, such as fractional anisotropy and mean diffusivity. Our results highlight the potential importance of cerebro-cerebellar networks in the clinical manifestations of DS and suggest a role for DTBM in the investigation of other brain disorders involving white matter hypoplasia or atrophy.

A preliminary examination of brain morphometry in youth with Down syndrome with and without parent-reported sleep difficulties

BACKGROUND

Down syndrome is associated with poor sleep but little is known about its neural correlates.

AIMS

The current research compared brain morphometry in youth with Down syndrome with parent-reported sleep problems (DS-S) to peers with Down syndrome (DS) and typical development (TD) without parent-reported sleep problems matched on age (M = 15.15) and sex ratio (62 % female).

METHODS AND PROCEDURES

Magnetic resonance imaging was completed on a 3 T scanner. Participants were stratified into groups based on parent-report: DS-S (n = 17), DS (n = 9), TD (n = 22). Brain morphometry, processed with the FreeSurfer Image Analysis Suite, was compared across groups. In addition, the co-occurrence of medical conditions in the DS groups was examined.

OUTCOMES AND RESULTS

Youth with DS-S had reduced total, frontal, parietal, and temporal brain volumes relative to DS and TD peers. They also had higher rates of congenital heart defects than the DS-only group; however, this comorbidity did not appear to account for morphometry differences.

CONCLUSIONS AND IMPLICATIONS

Parent-reported sleep problems in DS appear to relate to global and localized volume reductions. These preliminary results have implications for understanding the neural correlates of poor sleep in DS; they also highlight the importance of examining relations between sleep and other medical comorbidities.

Structural Magnetic Resonance Imaging-Based Brain Morphology Study in Infants and Toddlers With Down Syndrome: The Effect of Comorbidities

BACKGROUND

Down syndrome (DS) is the most prevalent chromosomal disorder characterized by intellectual disability, multiple organ anomalies, generalized muscular hypotonia, and characteristic physical features. The presence of DS-associated medical comorbidities has contributed to brain morphologic changes. The aim of this study was to evaluate brain morphologic characteristics during infant and toddler ages in patients with DS using structural brain magnetic resonance imaging.

METHODS

Structural brain T1-weighted magnetic resonance images from participants with DS with complete chromosome 21 trisomy (n = 20; 1.6 ± 0.6 [mean ± standard deviation] years old) were analyzed using FreeSurfer. The measurements were compared with those of 60 gender- and age-matched neurotypical controls by Cohen's d statistic and unpaired t test with false discovery rate correction for multiple comparisons and analyzed using a univariate general linear model with the following DS-associated medical comorbidities: congenital cardiac disease, infantile spasms, and hypothyroidism.

RESULTS

We identified 27 candidate measurements with large effect sizes (absolute d > 0.8) and statistically significant differences (P < 6.9 × 10^-3). Among them were decreased volumes in bilateral cerebellar gray matter and right cerebellar white matter and brainstem and cortical abnormalities in the right superior temporal, right rostral anterior cingulate, and left rostral middle frontal gyrus, independent of comorbid effects. Only bilateral cerebellar gray matter volumes and brainstem volume showed differences between DS and healthy groups during infancy.

CONCLUSION

These results suggest that cerebellar gray matter and brainstem may represent the primary regions affected by the presence of an additional copy of chromosome 21.

Outcomes of High-Dose Steroid Therapy for Infantile Spasms in Children With Trisomy 21

OBJECTIVE

We performed a retrospective chart review of patients with trisomy 21 and infantile spasms in our university-based pediatric epilepsy center between 2002 and 2016 in order to describe the clinical characteristics of children with these diagnoses as well as to evaluate their response to first-line treatments.

METHODS

Patients with infantile spasms were identified via the neurophysiology database. Charts were reviewed with attention to infantile spasms diagnosis, presence of trisomy 21, age of reported clinical onset, treatment lag, treatments used, response to treatment, imaging findings, electroencephalography (EEG) data, and developmental outcomes.

RESULTS

Of the 310 patients with infantile spasms, 24 also had trisomy 21. Three patients did not meet inclusion criteria. Ten of the 21 patients received nonstandard therapies first line; 2 of the 10 (20%) achieved spasm control, and 4 of the 8 who failed therapy (50%) progressed to Lennox-Gastaut syndrome. Eleven of the 21 patients received standard therapies as first-line treatments (10 with prednisolone according to the protocol in the United Kingdom Infantile Spasms Study [UKISS] and 1 with adrenocorticotrophic hormone [ACTH]). Nine of the 10 patients (90%) who received prednisolone achieved spasm resolution, 6 (60%) of these without relapse. The final patient (10%) failed prednisolone as well as ACTH. One patient received ACTH first line with success.

CONCLUSION

This is the only series to follow children with trisomy 21 and infantile spasms in which a significant proportion received UKISS-protocol prednisolone. It adds to current knowledge about safety, tolerability, and effectiveness of prednisolone in this group.

Brain MRI abnormalities in patients with infantile spasms and Down syndrome

INTRODUCTION

Infantile spasms (IS) are the most frequent epilepsy syndrome in children with Down syndrome (DS). In DS, cellular (synaptic/dendritic changes) and molecular mechanisms are believed to contribute to epileptogenesis, rather than gross structural anomalies. Neuroimaging is a standard part of the evaluation of newly diagnosed infantile epilepsy including IS and, in this age group, often requires sedation. It is unclear if neuroimaging provides additional clinically useful etiologic information in IS associated with DS.

METHODS

We conducted a retrospective chart review and detailed neuroimaging review in 36 patients (24 males) with IS and DS, cared for at Boston Children's Hospital.

RESULTS

Incidental imaging abnormalities were common (42%), but potentially relevant etiologic abnormalities were rare (16%). Structural congenital or acquired abnormalities were associated with ongoing antiepileptic drug (AED) use (p = 0.02), as well as refractory epilepsy (p = 0.04). However, neuroimaging did not alter the treatment plan for any of these patients.

CONCLUSIONS

Clinicians must carefully weigh the benefits and risks of neuroimaging in infants with DS and IS, as neuroimaging did not lead to any changes in clinical management in our patients but may offer information regarding prognosis.