Anatomy
Stanley A. Gelfand in 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.
Pathophysiology of Lightning Injury
Christopher J. Andrews, Mary Ann Cooper, Mat Darveniza, David Mackerras in Lightning Injuries: Electrical, Medical, and Legal Aspects Editors, 1992
In 1974, we reported the first known case of lightning histopathology of the ear.10 Two possible mechanisms of lightning injury were suggested: direct effect and blast effect. The direct effect may have come through the external auditory canal. The external canal route seemed unlikely since the ossicles, especially the stapes footplate, was undisturbed, and there was no blood in the cochlea or vestibular labyrinth. A direct effect was hypothesized by injury to the central nervous system and transfer of electrical potential via the cerebrospinal fluid into the internal auditory canal, injuring the facial nerve, superior vestibular nerve, and possibly passing through the cribriform area of the fundus of the internal auditory canal into the cochlea (Figure 2). However, since the cochlear nerve, cribriform area, and modiolus were not injured, the authors concluded that cochlear injury occurred by another route or mechanism. The superior vestibular nerve showed minimal degeneration even though it lay adjacent to the facial nerve, which was very edematous. The minor pathology in the superior vestibular nerve does not explain these mild findings, and post-mortem degeneration is unlikely.
Cochlear Implants and Auditory Brainstem Implants
R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne in Scott-Brown's Essential Otorhinolaryngology, 2022
The main components of CI devices are shown in Figure 18.1. The electrode array consists of multiple electrode contacts (between 12 and 22 depending on the manufacturer), each of which is intended to stimulate a distinct population of auditory neurons. CIs attempt to mimic natural tonotopic encoding by representing high frequencies at the basal and low frequencies at the apical end of the array. The array is ideally placed in the lower compartment of the cochlea, the scala tympani, where it lies closer to target auditory neurons. Peri-modiolar electrodes are pre-curved and sit closer to target auditory neurons in the modiolus, while lateral wall electrodes are further from these neurons but are associated with less traumatic insertion.
Evaluating safety in hyaluronic acid lip injections
Published in Expert Opinion on Drug Safety, 2021
Tyler Safran, Arthur Swift, Sebastian Cotofana, Andreas Nikolis
The left and the right labial arteries connect with each other in the midline and form an anastomotic network, which explains why the diameter of the arteries diminishes toward the midline [31]. It has been shown that in the midline the artery is most frequently identified to course within the red portion of the lip whereas laterally the artery is found outside the vermillion in approximately 20% of the cases. This is understandable because the modiolus is located lateral to the oral commissure and each artery needs to travel cranially (for the superior labial arteries) or caudally (for the inferior labial arteries) around this muscular pillar to reach the lips while traveling from outside the vermillion toward the vermillion. The lower lip receives in addition to the inferior labial arteries, blood supply from the horizontal labiomental arteries, the ascending mental arteries and from the mental arteries as they emerge from their foramen. In contrast, the upper lip receives additional blood supply from the infraorbital and buccal arteries only which are less in supplying volume compared to the additional blood supply of the lower lip. Moreover, the superior labial arteries contribute to the blood supply of the columella, the nasal septum, and the nasal tip. This ‘steal volume’ could be one of the potential explanations why clinically the upper lip is more frequently affected by adverse vascular events compared to the lower lip.
Human inner ear blood supply revisited: the Uppsala collection of temporal bone—an international resource of education and collaboration
Published in Upsala Journal of Medical Sciences, 2018
Xueshuang Mei, Francesca Atturo, Karin Wadin, Sune Larsson, Sumit Agrawal, Hanif M. Ladak, Hao Li, Helge Rask-Andersen
The unique arterial plexus along the modiolus serves to supply the cochlea with a large amount of oxygenated blood. Levin (34) and Malan (49) described vascular convolutions with specialized arterio-venous connections. Schwalbe (40) has already described glomus-like structures and speculated on these functions to even out pulsatile pressure waves. Such pulses could negatively influence the sensitive mechanoreceptors and hearing. Furthermore, Balogh and Koburg (50) described a ‘plexus cochlearis’ in the modiolus with very high metabolic turnover rates, even higher than those of the spiral ganglion. This resembled the choroid plexus with extending spider-web-like connective tissue processes, and they speculated on a secretory function. We found that veins traversed the arterial system in close proximity before joining the inferior cochlear vein (ICV). We speculate that the vascular convolutes could monitor gas exchange and pressure alterations and thereby regulate cochlear blood flow via this well-vascularized zone. Thus, further analyses of the vascular plexus are indicated.
Endoscopic intracanalicular vestibular schwannoma excision via middle ear approach: A surgical option
Published in Acta Oto-Laryngologica, 2021
Tengku Mohamed Izam Tengku Kamalden, Khairunnisak Misron, Puvan Arul Arumugam
The telescope was used all the time to inspect, drill and excise the tumor. The middle ear corridor identified was an imaginary triangle made between processus cochleariformis, the funiculus and the second genu of the facial nerve. The outer limitation of the corridor was bounded by the internal carotid artery anteriorly, jugular bulb inferiorly and the segment of facial nerve superior and posteriorly. The subfacial recess was drilled at the tympanic segment of the facial nerve to get access to the fundus of IAC. The area of interest from our anatomical research showed that the likelihood and shortest route to the fundus is an area called the cochlear-vestibular junction. This area was in fact floor of the oval window which gradually turn into scala vestibuli of cochlea. The junction provided a stable landmark for drilling and allowed identification of the modiolus.
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