Developmental Diseases of the Nervous System
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
Induction of the nervous system is regulated by genes controlling dorsal–ventral longitudinal organization and genes affecting the anterior–posterior axis, creating transverse divisions or segments. Patterning of the dorsal–ventral axis results in four longitudinal domains of the central nervous system (CNS). Patterning along the anterior–posterior axis results in segmentation of the CNS into the forebrain, midbrain, hindbrain, and spinal cord (Figure 9.3). The rostral end of the neural tube undergoes extensive changes, forming three dilations or segments: the prosencephalon or forebrain, the mesencephalon or midbrain, and the rhombencephalon or hindbrain. The prosencephalon divides transversely to form the telencephalon and diencephalon. Lateral division or cleavage of the telencephalon produces two paired structures, which become the cerebral hemispheres. The rhombencephalon eventually divides into the metencephalon, which becomes the pons and cerebellum, and the myelencephalon, which becomes the medulla (Figure 9.3).1
Neonatal Nasal Obstruction
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
This abnormality, first described in 1988, is a very rare condition leading to nasal obstruction in the neonate which arises due to bony overgrowth of the nasal process of the maxilla (Figure 23.5).17 The piriform aperture is the narrowest part of the nasal airway and so even minimal reduction in diameter here can cause significant problems. Symptoms similar to bilateral choanal atresia occur and epiphora is also often seen secondary to bony involvement of the nasolacrimal ducts. Diagnosis is suggested by the inability to pass a narrow gauge nasogastric tube or 2.2 mm endoscope through the anterior nasal vestibule due to the bony obstruction. CT scan confirms the diagnosis with an aperture width of less than 11 mm measured on an axial CT at the level of the inferior meatus (in a term neonate). CT can also demonstrate a single central incisor, which exists in some affected individuals. This single central incisor is associated with an absent upper frenulum and arch-shaped lower lip. In this subgroup with a ‘megaincisor’ there is a suggested association with holoprosencepaly, a rare condition in which the developing forebrain fails to divide appropriately to form the cerebral hemispheres, diencephalon, and optic and olfactory bulbs. These patients should undergo further evaluation for central nervous system defects with an MRI and particularly the hypothalamic–pituitary–thyroid axis. There are variable reports on the incidence rates of this condition with piriform aperture stenosis, but a figure of around 50% is generally accepted.18
Neuroanatomical and Neurobehavioral Effects of Heavy Prenatal Alcohol Exposure
John Brick in Handbook of the Medical Consequences of Alcohol and Drug Abuse, 2012
Another neuropathological finding is holoprosencephaly (Coulter et al., 1993; Jellinger et al., 1981), a condition in which the forebrain fails to completely develop into two hemispheres. In the most severe cases, known as alobar holoprosencephaly, there is a complete fusion of all forebrain structures. Ronen and Andrews (1991) presented one case of alobar holoprosencephaly and two less-severe cases of semilobar holoprosencephaly. In all three cases, there was only a single “square-shaped ventricle” and midline fusion of the basal ganglia and thalamic nuclei (p. 152). Holoprosencephaly has been induced in nonhuman primate and mouse models of FAS (Siebert, Astley, and Clarren, 1991; Sulik and Johnston, 1982), further strengthening the suggestion that alcohol exposure is one possible cause of this disorder. Finally, it is interesting to note that infants with FAS or holoprosencephaly both exhibit midline facial anomalies (Ronen and Andrews, 1991), although the anomalies observed in the two disorders are not identical. In both disorders, the severity of these craniofacial anomalies may covary with the severity of the underlying neuropathological abnormalities (Swayze et al., 1997).
Optic Nerve Parameters and Cognitive Function in the Northern Finland Birth Cohort Eye Study
Published in Ophthalmic Epidemiology, 2022
Joel Pitkänen, Juha Veijola, Jennifer Barnett, Johanna Liinamaa, Ville Saarela
Cognition refers to the ability to process external or internal stimuli, to establish the relevant from the irrelevant from these stimuli and to generate appropriate responses as well as aspects of storing of the processed information.1 The process takes place in the central nervous system (CNS).1 The optic nerve and the forebrain both develop from the same embryonic origin and retinal neurons share anatomical, molecular and pathological similarities with neurons of the cerebrum.2,3 The optic nerve head (ONH) is the only part of the CNS that can be studied directly as it can be viewed through the transparent medium of the eye. The retinal nerve fibre layer (RNFL) represents the unfolding of the fibres of the optic nerve.4 Thus, it can be theorized that by examining the properties or pathological changes occurring in the optic nerve, it may be possible to reveal certain attributes or pathological findings of the brain.
Presurgical naso-alveolar molding paired with cheiloplasty to treat median cleft lip deformity in holoprosencephaly
Published in Case Reports in Plastic Surgery and Hand Surgery, 2020
Satoshi Takagi, Ayumu Tsukamoto, Yoshihisa Kawakami, Sachio Tamaoki, Hiroyuki Ohjimi
Holoprosencephaly is a malformation sequence with a basic feature of impaired midline cleavage of the embryonic forebrain. Among clinical features, facial anomalies are the most easily perceived in the patient, which have varying severities according to the extent of brain damage [5]. Besides facial abnormalities, holoprosencephaly can associate with complications including neurocognitive impairment, seizures, diabetes insipidus, autonomic instability, recurrent respiratory infections, and major organ dysfunction. Moreover, the life expectancy may be shortened based on the severity. Still, some parents may choose reconstructive surgery for the facial deformities in their infants. When the patients can well tolerate the general anesthesia, surgical intervention, and perioperative care under general surgical conditions, medical practitioners should recommend cheiloplasty as an effective treatment option since it enables relatively higher developmental abilities in the patients than without. This not only helps them achieve speech development but also helps in creating better social interactions.
Biometric Alterations of Mouse Embryonic Eye Structures Due to Short-Term Folic Acid Deficiency
Published in Current Eye Research, 2018
Ouafa Sijilmassi, José Manuel López-Alonso, Aurora Del Río Sevilla, Jorge Murillo González, María del Carmen Barrio Asensio
Eye morphogenesis in vertebrates begins in the early stages of development. The first appearance of the optic primordium in the human embryo begins forming on about day 22 as bilateral evaginations of the neuroectoderm of the forebrain (prosencephalon) which still remains open.1 In the mouse it appears at about the 9th day of gestation.2 These evaginations, optic vesicles, continue to proliferate laterally and gradually approach the surface ectoderm as the forebrain closes. Finally, the distal portion of the vesicle makes contact with the overlying surface which induces the formation of lens primordia, the lens placodes. In a next step, coordinated invagination of the optic vesicle and the lens placode result in the formation of a double-layered optic cup and the lens vesicle, providing the first indication of the final shape of the eye. The inner layer of the optic cup forms the neural retina, while the outer layer of the optic cup gives rise to the retinal pigment epithelium.3
Related Knowledge Centers
- Anatomy
- Diencephalon
- Hindbrain
- Midbrain
- Subthalamus
- Brain
- Brain Vesicle
- Development of The Nervous System
- Thalamus
- Hypothalamus