The link between inner ear malformations and the rest of the body: what we know so far about genetic, imaging and histology (original) (raw)
Related papers
Early Fetal Development of the Human Cochlea
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2011
The cochlear scalas are differentiated from a single tube with a lining by the tall epithelium, that is, the cochlear duct. However, we have no information about the mechanism involved in the formation of the scalas. We evaluated histological sections taken from 20 fetuses: eight each at 8-9 weeks [early stage; 28-45 mm crown-rump length (CRL)] and 11-12 weeks (middle stage; 52-74 mm CRL), and four at 14-15 weeks (late stage; 90-110 mm CRL) of gestation. In four of eight early-stage and in all eight middle-stage specimens, we observed irregular perilymphatic spaces and their fusion; these spaces tended to be larger in the future scala tympani than in the future scala vestibuli. The cochlear duct epithelium was positive for cytokeratin 19 in contrast to the other parts of the cochlea. The tectorial membrane appeared in two of eight middle-stage and all four late-stage specimens. After 16 weeks, mesothelial lining of the scala may follow the development of aquaporin-positive thin blood vessels along the scala wall. Notably, gap formation of the cochlear duct epithelium at a site facing the scala tympani consistently occurred before the development of S100 protein-negative organ of Corti. This gap is likely to correspond to a site occupied finally by Hensen's cells. All these steps likely started in the basal coil and extended to the apical side of the cochlea. These findings suggest that leakage through the epithelial gap of endolymph, with a high concentration of potassium ions, causes mesenchymal cell death, leading to the coalescence of vacuoles containing low potassium perilymph.
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.
Congenital malformations of the ear
The Indian Journal of Pediatrics, 1992
Tile external ear develops from I and II branchial arches commencing on 38th day of fetal life. The middle ear is formed from the ends of Ist pharyngeal puch and the surrounding mesenchyme, which also is part of the I and II branchial arches. The congenital defects of the external and middle ear usually occurs in combination, and many times with congenital defects of other systems. The cochlear functions i.e. bone conduction is normal in 50% of these cases, thus rehabilitation of these patients with congenital anomalies of external and middle ear is possible. The coexistence of congenital aural atresia with varying degrees of malformation of inner ear may be more frequent than generally assumed. Moderate and severe forms of congenital aural atresia area encountered in about 1 in 10,000 to 20,000 individualJ Tile more severe forms of congenital auricular malformation are always associated with meatal atresia, whereas meatal atresia may, in a few cases be seen in patients with a normal pinna. Atresia of the meatus may be membranous or osseus, membranous atresia is much less common and is characterised by rudimentary cartilagenous canal sep~ated from the middle ear by a dense structure of con
Cell and Tissue Research, 2019
Expression patterns of transcription factors leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), transforming growth factor-β-activated kinase-1 (TAK1), SRY (sex-determining region Y)-box 2 (SOX2), and GATA binding protein 3 (GATA3) in the developing human fetal inner ear were studied between the gestation weeks 9 and 12. Further development of cochlear apex between gestational weeks 11 and 16 (GW11 and GW16) was examined using transmission electron microscopy. LGR5 was evident in the apical poles of the sensory epithelium of the cochlear duct and the vestibular end organs at GW11. Immunostaining was limited to hair cells of the organ of Corti by GW12. TAK1 was immune positive in inner hair cells of the organ of Corti by GW12 and colocalized with p75 neurotrophic receptor expression. Expression for SOX2 was confined primarily to the supporting cells of utricle at the earliest stage examined at GW9. Intense expression for GATA3 was presented in the cochlear sensory ep...
From labyrinthine aplasia to otocyst deformity
Neuroradiology, 2010
Introduction Inner ear malformations (IEMs) are rare and it is unusual to encounter the rarest of them, namely labyrinthine aplasia (LA) and otocyst deformity. They do, however, provide useful pointers as to the early embryonic development of the ear. LA is characterised as a complete absence of inner ear structures. While some common findings do emerge, a clear definition of the otocyst deformity does not exist. It is often confused with the common cavity first described by Edward Cock. Our purpose was to radiologically characterise LA and otocyst deformity. Methods Retrospective analysis of CT and MRI data from four patients with LA or otocyst deformity. Middle and inner ear findings were categorised by two neuroradiologists. Results The bony carotid canal was found to be absent in all patients. Posterior located cystic structures were found in association with LA and otocyst deformity. In the most severe cases, only soft tissue was present at the medial border of the middle ear cavity. The individuals with otocyst deformity also had hypoplasia of the petrous apex bone. Conclusions These cases demonstrate gradual changes in the two most severe IEMs. Clarification of terms was necessary and, based on these findings, we propose defining otocyst deformity as a cystic structure in place of the inner ear, with the cochlea, IAC and carotid canal absent. This condition needs to be differentiated from the common cavity described by Edward Cook. A clear definition of inner ear malformations is essential if outcomes following cochlear implantation are to be compared.