Quantitative Structural Brain Magnetic Resonance Imaging Analyses: Methodological Overview and Application to Rett Syndrome

Understanding the multidimensional neurodevelopmental outcomes in children after congenital Zika virus exposure

Since 2016, international research groups have focused on assessing outcomes of children with in utero Zika virus (ZIKV) exposure. While the more severe outcomes of congenital Zika syndrome (CZS) occur in up to 10% of children with antenatal exposure, early findings among ZIKV-exposed children without CZS ages 0-5 years suggest that they may also have differences in multiple domains of neurodevelopment. Thus, longitudinal follow-up of all children with antenatal ZIKV exposure has been recommended. This review presents a summary of neurodevelopmental phenotypes of infants and children following antenatal ZIKV exposure. We present a multidimensional framework to understand child neurodevelopment from an interdisciplinary and whole-child perspective (International Classification of Functioning, Disability and Health model) and multi-domain ZIKV Outcome Toolboxes. The toolboxes are for clinicians, researchers, child educators, and others to implement longitudinal multi-domain neurodevelopmental assessments between ages 0-12 years. Recent innovations in telehealth and neuroimaging can help evaluate outcomes in ZIKV exposed children. The objective is to describe the multiple facets of neurodevelopmental focused care that can support the health, function, and well-being of children with antenatal ZIKV exposure. The research and clinical follow-up strategies are applicable to ZIKV and other congenital infectious or environmental exposures that can impact child neurodevelopment. IMPACT: International longitudinal cohort studies have revealed a range of differences in neurodevelopment among children with antenatal Zika virus (ZIKV) exposure. A multidimensional and whole-child framework is necessary to understand the neurodevelopment of children with antenatal ZIKV exposure in relation to family life, community participation, and environment. Multi-domain toolboxes that utilize parent questionnaires and child evaluations are presented. These toolboxes can be used internationally alongside telehealth, brain imaging, and other innovations to improve understanding of child outcomes.

Insulin Resistance and Cognitive Impairment: Evidence From Neuroimaging

Insulin is a peptide well known for its role in regulating glucose metabolism in peripheral tissues. Emerging evidence from human and animal studies indicate the multifactorial role of insulin in the brain, such as neuronal and glial metabolism, glucose regulation, and cognitive processes. Insulin resistance (IR), defined as reduced sensitivity to the action of insulin, has been consistently proposed as an important risk factor for developing neurodegeneration and cognitive impairment. Although the exact mechanism of IR-related cognitive impairment still awaits further elucidation, neuroimaging offers a versatile set of novel contrasts to reveal the subtle cerebral abnormalities in IR. These imaging contrasts, including but not limited to brain volume, white matter (WM) microstructure, neural function and brain metabolism, are expected to unravel the nature of the link between IR, cognitive decline, and brain abnormalities, and their changes over time. This review summarizes the current neuroimaging studies with multiparametric techniques, focusing on the cerebral abnormalities related to IR and therapeutic effects of IR-targeting treatments. According to the results, brain regions associated with IR pathophysiology include the medial temporal lobe, hippocampus, prefrontal lobe, cingulate cortex, precuneus, occipital lobe, and the WM tracts across the globe. Of these, alterations in the temporal lobe are highly reproducible across different imaging modalities. These structures have been known to be vulnerable to Alzheimer's disease (AD) pathology and are critical in cognitive processes such as memory and executive functioning. Comparing to asymptomatic subjects, results are more mixed in patients with metabolic disorders such as type 2 diabetes and obesity, which might be attributed to a multifactorial mechanism. Taken together, neuroimaging, especially MRI, is beneficial to reveal early abnormalities in cerebral structure and function in insulin-resistant brain, providing important evidence to unravel the underlying neuronal substrate that reflects the cognitive decline in IR. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 2.

microRNA Biology on Brain Development and Neuroimaging Approach

Proper brain development requires the precise coordination and orchestration of various molecular and cellular processes and dysregulation of these processes can lead to neurological diseases. In the past decades, post-transcriptional regulation of gene expression has been shown to contribute to various aspects of brain development and function in the central nervous system. MicroRNAs (miRNAs), short non-coding RNAs, are emerging as crucial players in post-transcriptional gene regulation in a variety of tissues, such as the nervous system. In recent years, miRNAs have been implicated in multiple aspects of brain development, including neurogenesis, migration, axon and dendrite formation, and synaptogenesis. Moreover, altered expression and dysregulation of miRNAs have been linked to neurodevelopmental and psychiatric disorders. Magnetic resonance imaging (MRI) is a powerful imaging technology to obtain high-quality, detailed structural and functional information from the brains of human and animal models in a non-invasive manner. Because the spatial expression patterns of miRNAs in the brain, unlike those of DNA and RNA, remain largely unknown, a whole-brain imaging approach using MRI may be useful in revealing biological and pathological information about the brain affected by miRNAs. In this review, we highlight recent advancements in the research of miRNA-mediated modulation of neuronal processes that are important for brain development and their involvement in disease pathogenesis. Also, we overview each MRI technique, and its technological considerations, and discuss the applications of MRI techniques in miRNA research. This review aims to link miRNA biological study with MRI analytical technology and deepen our understanding of how miRNAs impact brain development and pathology of neurological diseases.