Congenital basis of posterior fossa anomalies

Abstract

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.

Non‐visualization of choroid plexus of fourth ventricle as first‐trimester predictor of posterior fossa anomalies and chromosomal defects

“…After the seminal observation describing the identification of the fourth ventricle as a technique for early , CHD TOP 2 48 2.5 30 Trisomy 18 FGR TOP 3 49 5.7 38 Trisomy 13 Hydrops TOP 4 53 2.3 37 Triploidy Bilateral CLP, CHD, malposition of feet, SUA screening for OSB 1 , first-trimester ultrasound examination of the posterior fossa has received considerable interest. The pathophysiological explanation for the partial or total disappearance of the fourth ventricle in fetuses with OSB is leakage of cerebrospinal fluid with subsequent caudal displacement of the hindbrain; the posterior edge of the BS then approaches the occipital bone, thereby displacing the fourth ventricle backwards, with concomitant effacement of the cisterna magna 7,[28][29][30] . This would explain the final position of the CP-4V juxtaposed with the edge of the occipital bone.…”

Dandy-Walker Malformation-Like Condition Revealed by Refractory Schizophrenia: A Case Report and Literature Review

“…The diagnostic range of congenital anomalies in the posterior fossa reflects their anatomical predominance and the fact that the classification and the terms “DWM” and “DWV” have been controversial [62]. Advances in genetics and imaging have provided a better understanding of the embryologic origins of these abnormalities [63]. Five entities are commonly described in cases of posterior fossa cystic malformations: DWM, MCM, PFAC, Blake’s pouch cyst, and isolated inferior vermian hypoplasia (IIVH).…”

A case of congenital obstruction of magendie’s foramen: embryologic analysis and treatment

“…The hindbrain structures derive from differentiation of rhombencephalon to an upper vesicle, the metencephalon and to a lower vesicle: the myelencephalon. Subsequently, the myelencephalon gives the pons and the medulla oblongata and this division occurs at the same time that the pontine flexure develops [6]. The rhombic flexure causes the dorsal aspect of the neural tube to open exposing the floor of the 4th ventricle.…”

“…The CSF fills the inferior part and expands caudally to give the "Blake pouch" on which a secondary permeabilization permit the CSF to be accumulated in the inferior part of the cerebellum to form the cistern magna [7]. The regression of the Blake pouch will result of formation of the Magendie's foramen at the midline and then the lateral angle of the rhomboid fossa give rise to the Luschka's foramen [6]. The non-regression of the Blake pouch results to an isolated congenital atresia of the Magendie's foramen.…”