Imaging findings of the developing temporal bone in fetal specimens (original) (raw)
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Scientific Reports, 2017
Little is known about middle and inner ear development during the second and third parts of human fetal life. Using ultra-high resolution Microcomputed Tomography coupled with bone histology, we performed the first quantitative middle and inner ear ossification/mineralization evaluation of fetuses between 17 and 39 weeks of gestational age. We show distinct ossification paces between ossicles, with a belated development of the stapes. A complete cochlear bony covering is observed within the time-frame of the onset of hearing, whereas distinct time courses of ossification for semicircular canal envelopes are observed in relation to the start of vestibular functions. The study evidences a spatiotemporal relationship between middle and inner ear structure development and the onset of hearing and balance, critical senses for the fetal adaptation to birth. Hearing is a complex multilevel process. The first auditory step is performed by three compartments, the external, middle and inner ears, located inside the temporal bones, bilateral osseous structures situated on each side of the base of the skull. In mammals, sound vibrates the tympanic membrane and relays through the three middle ear ossicles to the inner ear whose characteristics in human allow responses to sound frequencies from 20 Hz up to 20 kHz. Inner ear structures are involved in both hearing and balance functions with the cochlea and the vestibule, respectively situated in the antero-inferior and posterior-superior parts of the labyrinth. The three ossicles, malleus, incus and stapes, and their articulations (incudomalleal and incudostapedial) exhibit specific morphological and histological properties required to optimize sound transduction (conversion of pressure waves into oscillating displacements) and transmission, amplification of the signal by a lever action and matching of the acoustic air impedance with the higher cochlear liquid impedance in order to deliver high energy vibrations to the fluid-filled inner ear structures. The auditory signal from the middle ear is delivered via the stapes to the fluid-filled membranous labyrinth of the spiral organ of hearing, known as the Organ of Corti, located within the cochlear duct and whose hair cells distributed along the length of the cochlear basilar membrane convert and encode vibrations into electroneural stimulations through the auditory nerve to the auditory system. On the posterior part of the membranous labyrinth, the inner ear balance system consists of three semicircular canals (SCC), functioning as gyroscopes which detect rotations, and two gravity receptors, the utricule and saccule (otolith system) which respond to both linear acceleration and gravity. These structures allow the vestibule to act as a high sensitive sensor, which detects head movements along any axis, and serves three main functions: (1) the control of spinal reflexes involved in posture
BMC Developmental Biology, 2019
Background: Progressive transformation of the otic placode into the functional inner ear during gestational development in humans leads to the acquisition of hearing perception via the cochlea and balance and spatial orientation via the vestibular organ. Results: Using a correlative approach involving micro-computerized tomography (micro-CT), transmission electron microscopy and histological techniques we were able to examine both the morphological and cellular changes associated with human inner ear development. Such an evaluation allowed for the examination of 3D geometry with high spatial and temporal resolution. In concert with gestational progression and growth of the cochlear duct, an increase in the distance between some of the Crista ampullaris is evident in all the specimens examined from GW12 to GW36. A parallel increase in the distances between the macular organs-fetal utricle and saccule-is also evident across the gestational stages examined. The distances between both the utricle and saccule to the three cristae ampullares also increased across the stages examined. A gradient in hair cell differentiation is apparent from apex to base of the fetal cochlea even at GW14. Conclusion: We present structural information on human inner ear development across multiple levels of biological organization, including gross-morphology of the inner ear, cellular and subcellular details of hearing and vestibular organs, as well as ultrastructural details in the developing sensory epithelia. This enabled the gathering of detailed information regarding morphometric changes as well in realizing the complex developmental patterns of the human inner ear. We were able to quantify the volumetric and linear aspects of selected gestational inner ear specimens enabling a better understanding of the cellular changes across the fetal gestational timeline. Moreover, these data could serve as a reference for better understanding disorders that arise during inner ear development.
The ear in fetal MRI: what can we really see?
Neuroradiology, 2011
Introduction The aim of this study was to investigate the ability to depict the components of the ear on brain-oriented fetal MRI studies. Methods Retrospective evaluation of the ear in MRI studies was performed post-mortem in 16 fetuses ranging from 15 to 22 gestation weeks (GW), and in 122 examinations in vivo of fetuses ranging from 20 to 38 GW. The cochlea, vestibular apparatus, middle ear, and external auditory canal were separately graded according to the components that were delineated. Results The components of the inner and middle ear were fully delineated in 100% of the post-mortem examinations, but the external auditory canals were only seen in only 25%.
Current Problems in Diagnostic Radiology, 2021
Hearing loss in pediatric age group is associated with many congenital temporal bone disorders. Aberrant development of various ear structures leads into either conductive or sensorineural hearing loss. Knowledge of the embryology and anatomical details of various compartments of the ear help better understanding of such disorders. In general, abnormalities of external and middle ears result in conductive hearing loss. Whereas abnormalities of inner ear structures lead into sensorineural hearing loss. These abnormalities could occur as isolated or part of syndromes. Temporal bone disorders are a significant cause of morbidity and developmental delays in children. Imaging evaluation of children presented with hearing loss is paramount in early diagnosis and proper management planning. Our aim is to briefly discuss embryology and anatomy of the pediatric petrous temporal bones. The characteristic imaging features of commonly encountered congenital temporal bone disorders and their associated syndromes will be discussed.
Contribution of fetal MRI to the diagnosis of inner ear abnormalities: report of two cases
Pediatric Radiology, 2006
We report two cases of fetal inner ear abnormalities diagnosed by MRI. Cerebral MRI was performed on two fetuses, at 32 and 30 weeks gestation, following US that demonstrated multiple malformations suggestive of CHARGE syndrome in one fetus and ventriculomegaly and poor visibility of the posterior fossa in the other. MRI revealed vestibular hypoplasia and agenesis of the semicircular canals in
MR, CT, and Plain Film Imaging of the Developing Skull Base in Fetal Specimens
2000
BACKGROUND AND PURPOSE:The developing fetal skull base has previously been studied via dissection and low-resolution CT. Most of the central skull base develops from endochon- dral ossification through an intermediary chondrocranium. We traced the development of the normal fetal skull base by using plain radiography, MR imaging, and CT. METHODS: Twenty-nine formalin-fixed fetal specimens ranging from 9 to 24 weeks'
International archives of otorhinolaryngology, 2018
The literature shows that there are anatomical changes on the temporal bone anatomy during the first four years of life in children. Therefore, we decided to evaluate the temporal bone anatomy regarding the cochlear implant surgery in stillbirths between 32 and 40 weeks of gestational age using computed tomography to simulate the trajectory of the drill to the scala timpani avoiding vital structures. To measure the distances of the simulated trajectory to the facial recess, cochlea, ossicular chain and tympanic membrane, while performing the minimally invasive cochlear implant technique, using the Improvise imaging software (Vanderbilt University, Nashville, TN, US). An experimental study with 9 stillbirth specimens, with gestational ages ranging between 32 and 40 weeks, undergoing tomographic evaluation with individualization and reconstruction of the labyrinth, facial nerve, ossicular chain, tympanic membrane and cochlea followed by drill path definition to the scala tympani. I...