Characterization of Stapes Anatomy: Investigation of Human and Guinea Pig

Abstract

The accuracy of any stapes model relies on the accuracy of the anatomical information upon which it is based. In many previous models and measurements of the stapes, the shape of the stapes has been considered as symmetric with respect to the long and short axes of the footplate. Therefore, the reference frame has been built based upon this assumption. This study aimed to provide detailed anatomical information on the dimensions of the stapes, including its asymmetries. High-resolution microcomputed tomography data from 53 human stapes and 11 guinea pig stapes were collected, and their anatomical features were analyzed. Global dimensions of the stapes, such as the size of the footplate, height, and volume, were compared between human and guinea pig specimens, and asymmetric features of the stapes were quantitatively examined. Further, dependence of the stapes dimensions on demographic characteristics of the subjects was explored. The height of the stapes relative to the footplate size in the human stapes was found to be larger than the corresponding value in guinea pig. The stapes showed asymmetry of the footplate with respect to the long axis and offset of the stapes head from the centroid of the medial surface of the footplate for both humans and guinea pigs. The medial surface of the footplate was curved, and the longitudinal arches of the medial surface along the long axis of the footplate were shaped differently between humans and guinea pigs. The dimension of the footplate was gender-dependent, with the size greater in men than in women.

Details of human middle ear morphology based on micro‐CT imaging of phosphotungstic acid stained samples

“…Finally, in Sim et al () inertia data for the stapes were published which were very different from our results. PMI values are normalized to the stapes mass, and their results of 0.47 mm 2 for the malleus, 1.00 mm 2 for the incus, and 1.35 mm 2 for the stapes are very different from our results of, respectively, 0.688 mm 2 , 1.457 mm 2 , and 1.97 mm 2 , even when taking into account the uncertainty of approximately 10% for both data.…”

“…An asterisk (*) indicates data that does not overlap our data. References: (Kirikae, ; Ars, ; Anson and Donaldson, ; Hemila et al, ; Gan et al, ; Unur et al, ; Sim et al, ; Todd and Creighton, ; Quam et al, ).…”

“…Figure provides a visual representation of this comparison. References: (Wever and Lawrence, ; Kirikae, ; Ars, ; Molvaer et al, ; Rosowski, ; Hemila et al, ; Nummela, ; Stenfelt et al, ; Gan et al, ; Schraven et al, ; Salih et al, ; Sim et al, )…”

Local Drug Delivery to the Entire Cochlea without Breaching Its Boundaries

“…A stapes displacement of 80 mm in our experiments corresponds to 1.6 mm linear displacement of the fluid in the apical parts of ST, because in guinea pigs the apical ST cross-sectional area is almost 20 times smaller (Thorne et al, 1999) than the stapes area (Sim et al, 2013) and both the cochlear bony wall and fluid are poorly compressible. Therefore, although salicylate effect in the most apical 25% of the cochlear length was not measured due to poor hearing sensitivity of guinea pigs below 1 kHz, most of the fluid in this region was replaced by fluid from more basal regions during a single cycle of CP.…”

Direct Intracochlear Acoustic Stimulation Using a PZT Microactuator

“…Because the actuator diaphragm is completely immersed in perilymph, it should not cause any net fluid displacement, and there may be a small amount of leakage around the device. The reported average stapes dimensions in the guinea pig are 1.44 ± 0.034 × 0.66 ± 0.029 mm, with an effective area of 0.79 ± 0.039 mm 2 ( Sim, Röösli, Chatzimichalis, Eiber, & Huber, 2013 ). However, we find that the actuator diaphragm measuring 0.8 mm × 0.8 mm is effective at stimulating responses across a range of frequencies.…”