Embryology of the Brain and Molecular Genetics of Central Nervous System Malformation

The debated neuroanatomy of the fourth ventricle

The fourth ventricle is a small, fluid-filled cavity located within the brain that plays a vital role in the body's physiological functions. Therefore, the anatomical elements forming it bear significant clinical relevance. However, the exact relations between the elements that form its roof are still debated in the neuroanatomical literature; the inferior medullary velum, and the ventricle's median aperture in particular. In some atlases, the inferior medullary velum is placed in the midline, while in others, it is placed in the transverse plane. The median aperture is also displayed in different ways in midsagittal drawings: as a round perforation of a midline velum, as a foramen in an uncharacterized part of the ventricle, and as a gap between the nodule and the brainstem. This work aims to provide a comprehensive review of the different descriptions of the fourth ventricle, in order to gain a clearer understanding of the ventricular system's structure.

Craniofacial Anomaly Association with the Internal Malformations in the Pediatric Age Group in Al-Fallujah City-Iraq

Objectives

To estimate the prevalence of craniofacial anomalies among Iraqi people and its association with other congenital malformations.

Methods

A hospital-based cohort study. It was conducted in Iraq, Fallujah city from Jan 2019-April 2019. The pediatric age group below 16 years attending the consultation clinic.

Results

The prevalence rate of craniofacial anomalies was 2%. There were 43 (54%) males and 37 (46%) females. A 55 cases (69%) out of total 80 cases have an association with other internal congenital malformations, and 25 cases (31%) have no association. Those associated internal malformations were categorized according to their types into congenital heart disease 33(60%), Renal diseases 9 (16%), CNS anomalies 8(15%), and GIT anomalies 5(9%).

Conclusions

Craniofacial anomalies showed a relatively higher prevalence rate in comparison to other studies worldwide. It was found that the majority of craniofacial anomalies might be associated with other congenital systemic malformations. Furthermore, the necessary actions to identify the frequency and risk factors associated with craniofacial anomalies in the Iraqi population are emphasized to put a better strategy to establish future preventive programs and treatment.

The Other Side of the Fascia: The Smooth Muscle Part 1

According to current scientific standards, the fascia is a connective tissue derived from two separate germ layers, the mesoderm (trunk and limbs, part of the neck) and the ectoderm (cervical tract and skull). The fascia has the property of maintaining the shape and function of its anatomical district, but it also can adapt to mechanical-metabolic stimuli. Smooth muscle and non-voluntary striated musculature originated from the mesoderm have never been properly considered as a type of fascia. They are some of the viscera present in the mediastinum, in the abdomen and in the pelvic floor. This text represents the first article in the international scientific field that discusses the inclusion of some viscera in the context of what is considered fascia, thanks to the efforts of our committee for the definition and nomenclature of the fascial tissue of the Foundation of Osteopathic Research and Clinical Endorsement (FORCE).

The Other Side of the Fascia: Visceral Fascia, Part 2

In osteopathic clinical practice and in the teaching of osteopathic medicine, the visceral manipulation approach is included. The knowledge that some viscera satisfy the definition of fascial tissue will allow the osteopath to improve its practice. In the second part of the article, we will give a conclusive definition of fascia, and we will explain the embryological development of the heart and how the fascial tissue can be subject to manual treatment. This text is the first in the international scientific field that discusses the inclusion of some viscera in the context of what is considered fascia, through our committee for the definition and nomenclature of the fascial tissue of the Foundation of Osteopathic Research and Clinical Endorsement (FORCE).

[Dandy-Walker malformation]

The Dandy-Walker malformation is the most frequent cerebral malformation. It is defined by hypoplasia and upward rotation of the vermis cerebelli, a cystic enlargement of the fourth ventricle and in total an enlarged posterior fossa with cranially shifted position of the lateral sinus, tentorium and torcula herophili. This malformation was first described by Dandy and Blackfan in 1914 then supplemented again by Taggart and Walker in 1942. The current description as Dandy-Walker malformation was introduced in 1954 by Bender. In addition to these classical findings, the Dandy-Walker malformation is characterized by other abnormalities and malformations of the central nervous system (CNS) including agenesis of the corpus callosum, heterotopia, occipital meningocele, visual deficits and epilepsy. Neurogenetic and imaging examinations have led to a better understanding of this malformation.

Microglia: Housekeeper of the Central Nervous System

Microglia, of myeloid origin, play fundamental roles in the control of immune responses and the maintenance of central nervous system homeostasis. These cells, just like peripheral macrophages, may be activated into M1 pro-inflammatory or M2 anti-inflammatory phenotypes by appropriate stimuli. Microglia do not respond in isolation, but form part of complex networks of cells influencing each other. This review addresses the complex interaction of microglia with each cell type in the brain: neurons, astrocytes, cerebrovascular endothelial cells, and oligodendrocytes. We also highlight the participation of microglia in the maintenance of homeostasis in the brain, and their roles in the development and progression of age-related neurodegenerative disorders.

Fetal segmental spinal dysgenesis and unusual segmental agenesis of the anterior spinal artery

Segmental spinal dysgenesis (SSD) is a rare congenital spinal abnormality characterized by segmental dysgenesis or agenesis of the thoracolumbar or lumbar spine, congenital kyphosis, and abnormal configuration of the underlying spinal cord. A unique feature of SSD is that the vertebrae are present above and below the defect, and there is often a lower cord segment in the caudal spinal canal. We report a fetal MRI case of SSD with postmortem and neuropathological correlations. Our report confirms already published findings including the presence of a neurenteric cyst but is the first to document anterior spinal artery segmental agenesis in SSD.

Congenital basis of posterior fossa anomalies

The classification of posterior fossa congenital anomalies has been a controversial topic. Advances in genetics and imaging have allowed a better understanding of the embryologic development of these abnormalities. A new classification schema correlates the embryologic, morphologic, and genetic bases of these anomalies in order to better distinguish and describe them. Although they provide a better understanding of the clinical aspects and genetics of these disorders, it is crucial for the radiologist to be able to diagnose the congenital posterior fossa anomalies based on their morphology, since neuroimaging is usually the initial step when these disorders are suspected. We divide the most common posterior fossa congenital anomalies into two groups: 1) hindbrain malformations, including diseases with cerebellar or vermian agenesis, aplasia or hypoplasia and cystic posterior fossa anomalies; and 2) cranial vault malformations. In addition, we will review the embryologic development of the posterior fossa and, from the perspective of embryonic development, will describe the imaging appearance of congenital posterior fossa anomalies. Knowledge of the developmental bases of these malformations facilitates detection of the morphological changes identified on imaging, allowing accurate differentiation and diagnosis of congenital posterior fossa anomalies.

Congenital brain malformations in the neonatal and early infancy period

Congenital brain malformations are a major cause of morbidity and mortality in pediatric patients who are younger than 2 years. Optimization of patient care requires accurate diagnosis, which can be challenging as congenital brain malformations include an extensive variety of anomalies. Radiologic imaging helps to identify the malformations and to guide management. Understanding radiologic findings necessitates knowledge of central nervous system embryogenesis. This review discusses the imaging of congenital brain malformations encountered in patients who are younger than 2 years in the context of brain development.

Neuroimaging of Dandy-Walker malformation: new concepts

Dandy-Walker malformation (DWM) is the most common human cerebellar malformation, characterized by hypoplasia of the cerebellar vermis, cystic dilation of the fourth ventricle, and an enlarged posterior fossa with upward displacement of the lateral sinuses, tentorium, and torcular. Although its pathogenesis is not completely understood, there are several genetic loci related to DWM as well as syndromic malformations and congenital infections. Dandy-Walker malformation is associated with other central nervous system abnormalities, including dysgenesis of corpus callosum, ectopic brain tissue, holoprosencephaly, and neural tube defects. Hydrocephalus plays an important role in the development of symptoms and neurological outcome in patients with DWM, and the aim of surgical treatment is usually the control of hydrocephalus and the posterior fossa cyst. Imaging modalities, especially magnetic resonance imaging, are crucial for the diagnosis of DWM and distinguishing this disorder from other cystic posterior fossa lesions. Persistent Blake's cyst is seen as a retrocerebellar fluid collection with cerebrospinal fluid signal intensity and a median line communication with the fourth ventricle, commonly associated with hydrocephalus. Mega cisterna magna presents as an extraaxial fluid collection posteroinferior to an intact cerebellum. Retrocerebellar arachnoid cysts frequently compress the cerebellar hemispheres and the fourth ventricle. Patients with DWM show an enlarged posterior fossa filled with a cystic structure that communicates freely with the fourth ventricle and hypoplastic vermis. Comprehension of hindbrain embryology is of utmost importance for understanding the cerebellar malformations, including DWM, and other related entities.