Anatomy
Stanley A. Gelfand in Hearing, 2017
The major divisions of the ear are shown in Figure 2.2, and their relative positions within the head are given in Figure 2.3. The outer ear is made up of the pinna (auricle) and ear canal (external auditory meatus). The eardrum (tympanic membrane) separates the outer and middle ears, and is generally considered to be part of the latter. The middle ear also includes the tympanic (middle ear) cavity; the ossicular chain with its associated muscles, tendons, and ligaments; and the eustachian (auditory) tube. The inner ear begins at the oval window. It includes the sensory organs of hearing (the cochlea) and of balance (the semicircular canals, utricle, and saccule). While the balance system is certainly important, the concern here is hearing, and accordingly the balance apparatus is mentioned only insofar as it is directly associated with the auditory system.
The Twentieth Century
Arturo Castiglioni in A History of Medicine, 2019
In otology more knowledge has been obtained of the functions of the oval window. Various “fenestration” operations for otosclerosis, based on the newer knowledge, have come into vogue, beginning with Maurice sourdille’s (b. 1885) three-stage operation opening a new window into a semicircular canal. In 1938 J. lempert (now of New York) elaborated a successful one-stage operation, which, in spite of its difficulties, has achieved some excellent results. Due to the brilliant work, chiefly by Americans, of such men as E. H. campbell, K. M. day, Walter hughson (1891–1944), and J. R. page, good results in suitable cases have been obtained in more than half the cases operated upon.
Anatomy of the Cochlea and Vestibular System: Relating Ultrastructure to Function
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
The height and width of all the three scalae decrease systematically from base to apex of the spiral (Figure 47.1c). At the basal end, the scala tympani terminates at the round window (Figure 47.1a,b), a flexible membrane formed of two epithelial sheets sandwiching connective tissue, containing collagen and blood vessels.70,71 The apical surface of the outer epithelium is exposed to air in the middle ear; that of the inner epithelium is bathed in perilymph. The scala vestibuli at its basal end is continuous with the vestibule and the perilymphatic compartment of the vestibular system. The oval window, opening over the vestibule, is covered by a membrane and is filled with the footplate of the stapes. The gap between the border of the stapes footplate and the edge of the oval window is sealed with a ligament. At the apical end of the cochlea, the scala media is closed by epithelial tissue, arising partly by extension of Reissner’s membrane, leaving a small opening, the helicotrema, through which the scala vestibuli and scala tympani are connected. Sound-induced movements of the tympanic membrane drive piston-like ‘in–out’ movements of the stapes footplate displacing incompressible perilymph along the scala vestibuli, through the helicotrema and down the scala tympani leading to ‘out–in’ movements of the round window. As fluid is displaced, the pressure difference across the scala media between the scala vestibuli and scala tympani, produces vibrational movement of the basilar membrane, described by Von Békésy. This ‘travelling wave’ stimulates the sensory cells housed in the organ of Corti that sits on the vibrating basilar membrane.
Peristapedial bulb: an indicator of spontaneous CSF leak in cochlear candidates with Mondini dysplasia
Published in Acta Oto-Laryngologica, 2021
Xinbo Xu, Weiliang Chen, Xiao Han, Ruru Qiao, Xiaojie Ma, Yuanping Ding, Hanbing Zhang
When a CI candidate with bilateral Mondini anomaly has a history of meningitis, the optimal surgical strategy should allow both effective CSF leak control and unimpeded electrode array insertion. The vestibule is an interlinked bony space containing the saccule beneath the oval window and the initial portion of the cochlear duct beneath the round window. Therefore, vestibular obliteration may induce the fibrosis of the cochlear duct, which further impedes the electrode placement. As the infeasibility of electrode placement after vestibular packing, the two procedures should be conducted concurrently. Despite the active CSF leakage into the middle ear or the obvious labyrinthine defect in HRCT, many CSF fistulas are occult and inconspicuous, thus the bilateral vestibular obliteration better fit these patients, which means the bilateral CI should also be performed. Although Binaural implantation indeed provides the patient with a better auditory outcome, the cost and trauma may not be accepted by every patient. So, in clinical practice of some regions, this set of patients may be inclined to choose a single side-ear procedure to both resolves the potential intracranial infection and restores the hearing, so, correct diagnosis of the ear which leads to meningitis is a basis and key point of the surgery. Our study of the peristapedial bulb provides the otologists a new indicator to diagnose the correct candidate operating ear beside the traditional method.
Implications from cochlear implant insertion for cochlear mechanics
Published in Cochlear Implants International, 2020
Michal Kaufmann-Yehezkely, Ronen Perez, Haim Sohmer
It is generally thought that hearing is elicited by sound pressures impinging on the tympanic membrane, inducing its vibration, leading to vibrations of the ossicular chain and of the stapes footplate in the oval window. Since the inner ear is completely enveloped in bone, containing incompressible fluid, the vibrations of the stapes footplate in the oval window are accompanied by opposite phase vibrations of the round window, with bulk fluid flow between the two windows. This induces fluid pressure differences across the basilar membrane and its displacement. As a result of the gradients in physical properties (mass and stiffness) along the length of the basilar membrane, the induced fluid pressure differences across the membrane cause passive displacements of the basilar membrane which begin at the base and progress toward the apex. This gives the impression of an apparent mechanical wave progressing along the basilar membrane from the base to the apex, the traveling wave, described by von Bekesy in cadaver ears (1960). The energy for the traveling wave comes from the sound stimulus. The vibrations of the basilar membrane lead to bending of the stereocilia of the outer hair cells in a direction which opens ion channels, activating the motor protein prestin, leading to motility of the outer hair cells, adding active displacements (cochlear amplifier) of the cells and the basilar membrane which sum with the passive displacements, exciting the inner hair cells and the auditory nerve fibers (Oghalai, 2004). The energy for these active displacements comes from electro-chemical gradients maintained by metabolism.
Effect of ossicular chain deformity on reverse stimulation considering the overflow characteristics of third windows
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Houguang Liu, Lin Xue, Jianhua Yang, Gang Cheng, Lei Zhou, Xinsheng Huang
The assumption that the fluid-filled cochlea is surrounded by bone with only two mobile windows, i.e., the oval window and the round window has been generally accepted under forward stimulation (Zhang and Gan 2013; Zhang et al. 2018). This assumption is supported by experimental studies (Kringlebotn 1995; Stenfelt et al. 2004), which found that the fluid volume displacement of the oval window and the round window are equal under forward stimulation. Whereas, the actual anatomy of the cochlea has other smaller-scale and longer sound pathways, mainly the vestibular aqueduct and cochlear aqueduct, which were named as third windows (Rosowski et al. 2018). By stimulating the round window with an actuator in human temporal bone experiment, Stieger et al. (2013) reported that there exists fluid flow through the third windows in the cochlea. Meanwhile, based on the measurement of intra-cochlear sound pressure and ossicular chain motion, Frear et al. (2018) also found that the third windows have volume velocities leakage during reverse stimulation. Moreover, our theoretical investigation found that the third windows have an important effect on the reverse stimulation at low frequencies (Xue et al. 2020). Therefore, incorporating the third windows is essential for investigating the influence of OCD during reverse stimulation.