Ear, Nose, and Paranasal Sinus
Swati Goyal in Neuroradiology, 2020
The external auditory canal (EAC), with lateral one-third cartilaginous and medial two-thirds bony composition, extends from the auricle to the tympanic membrane. The middle ear cavity is within the petrous portion of the temporal bone and consists of the tympanic cavity (containing the ossicles, namely the malleus, incus, and stapes) and the antrum. The mastoid antrum communicates with the epitympanum via aditus ad antrum. The middle ear also contains muscles (tensor tympani and stapedius), the round and oval windows, and the chorda tympani nerve. The inner ear consists of the osseous labyrinth (cochlea, vestibule, and the three semicircular canals, namely the superior, posterior, and lateral canals) and the membranous labyrinth (the cochlear duct, utricle, saccule, semicircular ducts, endolymphatic duct, and endolymphatic sac). The membranous labyrinth contains endolymph, surrounded by perilymph, and is enclosed within the bony labyrinth. The internal auditory canal (IAC) is located in the petrous bone and transmits facial and vestibulocochlear nerves along with the labyrinthine artery. The pars flaccida is the upper delicate part that is associated with Eustachian tube dysfunction and cholesteatoma. The pars tensa is larger and more robust, and associated with perforations.
Nonconventional Clinical Applications of Otoacoustic Emissions: From Middle Ear Transfer to Cochlear Homeostasis to Access to Cerebrospinal Fluid Pressure
Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm in Advances in Audiology and Hearing Science, 2020
Currently, MD is viewed as a multifactorial condition in which the triad of symptoms requires the coexistence of several factors for which many possibilities have been proposed, whether anatomic, inflammatory, hormonal or viral and which come with hydrops, provoked by either past or present disruption of fluid homeostasis. It would be important to search for markers of some abnormal feature in the inner ear that might lead to an attack of MD and to keep in mind that this feature may disappear when the symptoms vanish, while volume inflation of the endolymph may persist as a long-lasting reflection of the said feature. Besides, cochlear and vestibular sensory cells might be functionally affected by two categories of reasons, either a change in their electrochemical environment (e.g., K+ ion concentration or endocochlear potential) or a disruption of their micromechanics, for example, if the resting position of their stereocilia bundle is altered. The latter may well occur if the geometry of the organ of Corti is modified as would happen if the basilar membrane is bent by a difference in hydrostatic pressure between endolymph and perilymph. A shift in the resting position of OHC stereocilia would be produced, as stereocilia tips are embedded in the lower side of the tectorial membrane that loads them, while their roots follow OHC displacements induced by changes in basilar-membrane position.
Micronutrients in Prevention and Improvement of the Standard Therapy in Hearing Disorders
Kedar N. Prasad in Micronutrients in Health and Disease, 2019
The fluid-filled hearing and balance membranous structures of the inner ear normally function independent of other fluid systems in the body, and the volume of the fluid (known as endolymph) remains constant. However, this changes with the injury or degeneration of the inner ear structures. One of the established pathological features includes fluctuating pressure of the fluid within the inner ear, referred to as endolymphatic hydrops or excess fluid in the inner ear. The membranous structure in the inner ear called labyrinth contains endolymph. This structure can become dilated like a balloon when pressure increases due to either blockage of the drainage system or entry of excess amounts of fluid. It is believed that endolymphatic fluid bursts from its normal channel in the ear and flows into other areas, causing damage to the auditory and vestibular systems.
Volume ratio and distribution rate in patients with orthostatic vertigo/dizziness using MR imaging: a comparison with vertiginous diseases
Published in Acta Oto-Laryngologica, 2023
Hiroshi Inui, Tsuyoshi Sakamoto, Keita Ueda, Taeko Ito, Tadashi Kitahara
Our method can be used to evaluate the volume of the endolymph fluid as an absolute value. Therefore, it was possible to consider the distribution of the endolymph. In this study, we measured the ELS/TFS volume ratio and ELS distribution rates in patients with ODV and compared them with those in patients with CS. We used the ELS/TFS volume ratio for the evaluation because TFS and ELS volumes have individual differences. In addition, the high ELS distribution rate does not indicate the existence of endolymphatic hydrops (ELH) but indicates the distribution and ELF flow only within the ELS. Because the ELS is thought to be filled with ELF, this study allows us to understand the volumetric and dynamic changes in the ELF. As in the CS, in the inner ear of patients with ODV, no extended ELS was observed, and no hydrops was observed. However, the ELS distribution in patients with ODV was different from that in the CS. Although the ELS distribution rate in the vestibule + SCCs in the ODV group did not differ from that in the CS, the ELF in the vestibule moved to the SCCs and a large amount of ELF was distributed only in the SCCs.
Presence of endolymphatic hydrops on listening difficulties in patients with normal hearing level
Published in Acta Oto-Laryngologica, 2023
Tadao Yoshida, Masumi Kobayashi, Satofumi Sugimoto, Yukari Fukunaga, Daisuke Hara, Shinji Naganawa, Michihiko Sone
We identified the presence of EH in patients with normal hearing and suspected LiD based on symptoms such as listening difficulties and APT results. EH is a hallmark of Ménière’s disease and can now be visualized using MRI [11]. Ménière’s disease is a disorder in which excessive endolymph accumulates in the inner ear and damages ganglion cells. In most cases, the clinical symptoms of Ménière’s disease appear after significant endolymph accumulation. However, some patients have symptoms early in the development of EH, although the reason for this variation in symptoms is unknown [12]. MRI often identifies EH in the affected ear of people with Ménière’s disease and sometimes in the asymptomatic ear or the ear contralateral to that affected by Ménière’s disease [13]. A previous study using control ears reported significant EH in the cochlea in 4 of 42 ears and mild EH in 12 ears. On the other hand, 37/52 (71.2%) of the patients with definite Ménière’s disease had significant EH in the cochlea [6]. A temporal bone study also reported a higher frequency of EH in the apical turn of the cochlea in asymptomatic ears [14].
Magnetic resonance imaging of endolymphatic hydrops in patients with unilateral Meniere’s disease: volume ratio and distribution rate of the endolymphatic space
Published in Acta Oto-Laryngologica, 2021
Hiroshi Inui, Tsuyoshi Sakamoto, Taeko Ito, Tadashi Kitahara
The inner-ear labyrinth comprises two parts: the osseous labyrinth and the membranous labyrinth. The membranous labyrinth, which includes the utriculus, sacculus, ampulla of the semi-circular canals, endolymphatic sac, and cochlear duct, is continuous and filled with endolymph. In 1938, Hallpike and Cairns [1] and Yamakawa [2] revealed that an extended endolymphatic space (ELS), also called endolymphatic hydrops (ELH), is a pathological feature of Meniere’s disease (MD), which is a chronic disease characterized by recurrent vertigo, tinnitus, aural fullness, and fluctuating hearing loss in the affected ear. Currently, ELH in patients with MD is being studied with the use of magnetic resonance imaging (MRI). In 2009, Nakashima et al. employed MRI to grade of ELH in the vestibule and cochlea by calculating the ratio of the area of the ELS to the area of the total fluid space (TFS) [3]. In our previous study, 3D MRI was used to obtain quantitative volumetric measurements of inner-ear components and inner-ear ELH as well as to define the range of normal ELS volumes in healthy volunteers without vertiginous or cochlear symptoms [4]; the average cochlear and vestibular ELS/TFS volume ratios in the healthy volunteers were found to be 10.2% and 17.7%, respectively. In the present study, we sought to measure the distribution rate of endolymphatic fluid in the membranous labyrinth of inner-ear components in patients with MD.
Related Knowledge Centers
- Bony Labyrinth
- Cochlear Duct
- Inner Ear
- Mechanotransduction
- Membranous Labyrinth
- Perilymph
- Potassium
- Sodium
- Ion
- Stria Vascularis of Cochlear Duct