China
Africa
Explore chapters and articles related to this topic
Data and Picture Interpretation Stations Cases 1–42
Published in Joseph Manjaly, Peter Kullar, Alison Carter, Richard Fox, ENT OSCEs: A Guide to Passing the DO-HNS and MRCS (ENT) OSCE, 2019
Joseph Manjaly, Peter Kullar, Alison Carter, Richard Fox
Name the point where the scala vestibuli and scala tympani meet. Helicotrema
Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
The cochlea is the part of the inner ear concerned with hearing. An extensive albeit rather advanced review of cochlear anatomy and physiology may be found in Dallos et al. (1996). The human cochlea is about 35 mm long, and forms a somewhat cone-shaped spiral with about two 3/4 turns. It is widest at the base, where the diameter is approximately 9 mm, and tapers toward the apex. It is about 5 mm high. The modiolus is the core, which forms the axis of the cochlear spiral, as illustrated in Figure 2.14. Through the modiolus course the auditory nerve and the blood vessels that supply the cochlea. The osseous spiral lamina is a bony ramp-like shelf that goes up the cochlea around the modiolus much like the spiral staircase of a lighthouse, as illustrated in Figure 2.15. Notice how the basilar membrane is attached to the osseous spiral lamina medially, as it proceeds up the cochlea. Figure 2.16 illustrates how the osseous spiral lamina separates the scala vestibuli above from the scala tympani below. It also shows the orientation of the helicotrema at the apical turn, and the relationship between the round window and the scala tympani at the base of the cochlea.
Anatomy of the Cochlea and Vestibular System: Relating Ultrastructure to Function
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, 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.
Accuracy of radiological prediction of electrode position with otological planning software and implications of high-resolution imaging
Published in Cochlear Implants International, 2023
Franz-Tassilo Müller-Graff, Johannes Voelker, Anja Kurz, Rudolf Hagen, Tilmann Neun, Kristen Rak
Why do prediction errors occur and why do they seem to increase with lower resolution imaging? In order to understand these prediction inaccuracies, the measurement process and its sources of error in the software must be examined more closely. The main sources of error are as follows: (1) Identification of the cochlear landmarks, which can be a subjective and quite arbitrary process. (2) Consecutive visualization of the cochlear basal turn based on the landmarks. Misalignment of the basal turn leads to error contributions of multiple voxels. (3) The cochlear landmarks must be re-identified postoperatively, which could differ from the preoperative measurement. (4) The heuristic equation used to estimate the CDL, which is a rather simplified model of the cochlea shape, and can therefore only take into account the individual variation of a cochlea to a certain extent. Since it has been proven that CDL measurements in the software are more valid with higher resolution imaging, and have significantly lower intra variability (Müller-Graff et al., 2021), it seems understandable that this reduces the summation error and leads to lower prediction errors. Moreover, crucial reference landmarks such as the helicotrema and the modiolar axis, which are difficult to identify reliably (Wimmer et al., 2019) even for experts, can be recognized more precisely (Schendzielorz et al., 2021) and thus result in smaller pre- and postoperative measurement differences. In fact, also in this study, measurements of CDL with fpVCTSECO are most similar pre- and post-op (Table 2).
Numerical analysis of the effects of ossicular chain malformations on bone conduction stimulation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Yu Zhao, Wen Liu, Houguang Liu, Jianhua Yang, Lei Zhou, Xinsheng Huang
The human ear FE model was developed based on a fresh human temporal bone, which comprises an ear canal, a middle ear and a spiral cochlea, as shown in Figure 2. This study was approved by the Ethics Committee of Affiliated Hospital of Xuzhou Medical University. The middle ear portion of the model comprises the middle ear cavity, the tympanic membrane (TM), ossicular chain, ligaments, and tendons. The cochlea is filled with lymph fluid and includes the scala vestibuli, scala tympani, helicotrema, basilar membrane (BM), bony spiral plate, and RW membrane. In addition, the bony wall was built as a layer shell elements at the outer layer of the cavities (the ear canal and the middle ear cavity) and the cochlea, which was in contact with the air and the lymph fluid in this model. The BM was connected with the bony wall via the bony spiral plate.
EAS-Combined electric and acoustic stimulation
Published in Acta Oto-Laryngologica, 2021
Anandhan Dhanasingh, Ingeborg Hochmair
It is now understood that once the sound hits the OW, it creates an intracochlear vibration, and more precisely, it causes a vibration of the basilar membrane (BM) – all the way from OW to its apical end, the helicotrema. The travelling wave namely passes through different frequencies which are logarithmically distributed along the BM – from high at the OW, to lower towards the apex. Now depending on the cochlear health, inner-hair cells on stimulated pitch regions during the BM vibration (Figure 1(A)) get excited and fulfil their function as mechanoreceptor cells by transforming the mechanical force received from the BM underneath them into electric signals. This mechanical force actuates the inner-hair cells to bend against the tectorial membrane, which is covering them. The bending opens small channels in the inner-hair cells, allowing ions in the surrounding fluid (endolymph of the scala media) to rush in and convert the physical movement to an electrochemical signal which excites the auditory nerve, and which then sends the electric signals to the brainstem – and after subsequent auditory functionalities, the patient eventually perceives a relevant sound [1]. The outer-hair cells are different group that mechanically amplify low-level sound that enters the cochlea and such amplification may be powered by the movement of their hair bundles.