Ultrastructure of the Guinea Pig Cochlear Aqueduct: An Electron Microscopic Study of Decalcified Temporal Bones

Toriya, Ryuzo; Arima, Toshio; Kuraoka, Akio; Uemura, Takuya

doi:10.3109/00016489109138402

Cited by 9 publications

(5 citation statements)

References 19 publications

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“…This soft tissue (Fig. 10a′, asterisk) may represent a fibrous meshwork previously reported in humans (Gussen 1978;Toriya et al 1991). This is not a fixation artefact, as the meshwork was also observed in non-fixed cochlea using optical coherence tomography (OCT) (Fig.…”

Section: Location and Curvature Of Sheep Rwm Relative To Surrounding Structuressupporting

confidence: 56%

Characterization of the Sheep Round Window Membrane

Han

Suzuki-Kerr

Suwantika

et al. 2020

JARO

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Intratympanic injection is a clinically used approach to locally deliver therapeutic molecules to the inner ear. Drug diffusion, at least in part, is presumed to occur through the round window membrane (RWM), one of the two openings to the inner ear. Previous studies in human temporal bones have identified a three-layered structure of the RWM with a thickness of 70-100 μm. This is considerably thicker than the RWM in rodents, which are mostly used to model RWM permeability and assess drug uptake. The sheep has been suggested as a large animal model for inner ear research given the similarities in structure and frequency range for hearing. Here, we report the structure of the sheep RWM. The RWM is anchored within the round window niche (average vertical diameter of 2.1 ± 0.3 mm and horizontal diameter of 2.3 ± 0.4 mm) and has a curvature that leans towards the scala tympani. The centre of the RWM is the thinnest (55-71 μm), with increasing thickness towards the edges (G 171 μm), where the RWM forms tight attachments to the surrounding bony niche. The layered RWM structure, including an outer epithelial layer, middle connective tissue and inner epithelial layer, was identified with cellular features such as wavy fibre bundles, melanocytes and blood vessels. An attached "meshwork structure" which extends over the cochlear aqueduct was seen, as in humans. The striking anatomical similarities between sheep and human RWM suggest that sheep may be evaluated as a more appropriate system to predict RWM permeability and drug delivery in humans than rodent models.

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Section: Location and Curvature Of Sheep Rwm Relative To Surrounding Structuressupporting

confidence: 56%

Characterization of the Sheep Round Window Membrane

Han

Suzuki-Kerr

Suwantika

et al. 2020

JARO

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“…7 (NIC and NUC) that such a difference was not measured and therefore additional experiments are needed to resolve this discrepancy. (15)]. This clearly shows the close relation between the meshwork of broblasts and the loose connective tissue lling the CA and the round window membrane (RWM).…”

Section: Discussionmentioning

confidence: 91%

“…Its internal ori ce is situated very close to the round window. About half a century ago it was thought that this opening was closed by an overlying structure (16), but later studies could not con rm the presence of such a barrier membrane (11,14,15,17). It is now generally assumed that the cochlear aqueduct is normally open and has a function in equalizing inner ear pressure (5,8).…”

Section: Discussionmentioning

confidence: 98%

Change of Guinea Pig Inner Ear Pressure by Square Wave Middle Ear Cavity Pressure Variation

Feijen¹,

Segenhout²,

Albers³

et al. 2002

Acta Oto-Laryngologica

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The inner ear fluid pressure of guinea pigs was measured during square wave middle ear cavity pressure variation. Time constants were derived for the slopes of the inner ear pressure recovery curves after middle ear pressure change. A "single exponential" function did not fit well and therefore more complicated functions were used for this purpose. For middle ear pressure increasing from zero to a few centimetres of water, returning to zero again, decreasing from zero to minus a few centimetres of water and then returning to zero again, time constants for the inner ear pressure recovery curves were on average 15.0, 8.6, 2.5 and 2.5 s, respectively. The results could not be described using a linear model with constant window membrane compliance and cochlear aqueduct flow resistance. A possible explanation for the large difference in time constants for positive or negative middle ear pressure changes is a dependence on aqueduct flow resistance or round window membrane position.

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“…This indicates that the soft tissue can respond defensively to infections [29]. It has been shown that blood cells and fluid can pass the fibrous tissue mesh inside the perilymphatic duct [7,26]. Holden and Schuknecht [7] demonstrated that the cochlear aqueduct is patent for cells like erythrocytes.…”

Section: Discussionmentioning

confidence: 99%

The cochlear aqueduct in pediatric temporal bones

Bachor¹,

Byahatti

Karmody

1997

Eur Arch Otorhinolaryngol

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The cochlear aqueduct is a bony channel which contains the fibrous periotic duct and connects the perilymphatic space of the basal turn of the cochlea with the subarachnoid space of the posterior cranial cavity. Previous histological studies suggested that patency depended on age, whereas a more recent study showed no statistical correlation between age and patency. To clarify patency in pediatric cochlear aqueducts, we selected 21 temporal bones from 12 infants and children, varying in age from birth to 9 years, in which the cochlear aqueduct was fully visible on one histological section. Photographs were taken for documentation and the length and width of the orifice of the external aperture of the aqueduct at the scala tympani were measured and followed to the internal aperture at the subarachnoid space. The lumen of the duct was examined for mononucleated cells, blood cells and fibrous tissue. Measurements revealed that the mean length of the cochlear aqueduct was 4.6 mm (range, 2.4-10.7 mm), mean width of the external aperture was 484 microm (range, 225-869 microm), and mean width of the internal aperture was 1293 microm (range, 699-2344 microm). The mean diameter of the narrowest part (isthmus) was 151 microm (range, 75-244 microm). In all temporal bones the cochlear aqueduct was patent, with one exception. This latter temporal bone was from a 2-month-old girl with multiple intralabyrinthine anomalies, with the missing cochlear aqueduct believed to be due to an aplasia. Our results support prior measurements of the cochlear aqueduct and demonstrate a short and patent cochlear aqueduct in newborns. With growth, a significant increasing length of the duct was found.

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Ultrastructure of the Guinea Pig Cochlear Aqueduct: An Electron Microscopic Study of Decalcified Temporal Bones

Cited by 9 publications

References 19 publications

Characterization of the Sheep Round Window Membrane

Characterization of the Sheep Round Window Membrane

Change of Guinea Pig Inner Ear Pressure by Square Wave Middle Ear Cavity Pressure Variation

The cochlear aqueduct in pediatric temporal bones

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