Analysis of Vestibular Labyrinthine Geometry and Variation in the Human Temporal Bone

Abstract

Stable posture and body movement in humans is dictated by the precise functioning of the ampulla organs in the semi-circular canals. Statistical analysis of the interrelationship between bony and membranous compartments within the semi-circular canals is dependent on the visualization of soft tissue structures. Thirty-one human inner ears were prepared, post-fixed with osmium tetroxide and decalcified for soft tissue contrast enhancement. High resolution X-ray microtomography images at 15 μm voxel-size were manually segmented. This data served as templates for centerline generation and cross-sectional area extraction. Our estimates demonstrate the variability of individual specimens from averaged centerlines of both bony and membranous labyrinth. Centerline lengths and cross-sectional areas along these lines were identified from segmented data. Using centerlines weighted by the inverse squares of the cross-sectional areas, plane angles could be quantified. The fit planes indicate that the bony labyrinth resembles a Cartesian coordinate system more closely than the membranous labyrinth. A widening in the membranous labyrinth of the lateral semi-circular canal was observed in some of the specimens. Likewise, the cross-sectional areas in the perilymphatic spaces of the lateral canal differed from the other canals. For the first time we could precisely describe the geometry of the human membranous labyrinth based on a large sample size. Awareness of the variations in the canal geometry of the membranous and bony labyrinth would be a helpful reference in designing electrodes for future vestibular prosthesis and simulating fluid dynamics more precisely.

Enhanced contrast in X‐ray microtomographic images of the membranous labyrinth using different X‐ray sources and scanning modes

“…; Johnson Chacko et al. ), the quality of the images obtained by our conventional μCT measurements is comparable to, or sometimes even better than, that of a larger specimen (including human, guinea pig, rhesus macaque and squirrel monkey specimens). The samples were decalcified in one of the investigations (Johnson Chacko et al.…”

“…The samples were decalcified in one of the investigations (Johnson Chacko et al. ), but our results as well as the other cited investigations show that this step can be omitted, avoiding artefacts. Further, our results, together with those of David et al.…”

“…() and Johnson Chacko et al. ()]. Hence, the use of the volatile, toxic and expensive osmium tetroxide staining can be circumvented (Metscher, ).…”

“…; Johnson Chacko et al. ). Our investigation is the first to compare scanning and reconstruction parameters and several types of X‐ray sources in order to obtain the best contrast of the membranous labyrinth.…”

Visualization of the Membranous Labyrinth and Nerve Fiber Pathways in Human and Animal Inner Ears Using MicroCT Imaging

“…This shall allow engineers and surgeons to find best ways to access and stimulate malfunctional sensory structures. The data from 52 human temporal bones shall provide a basis for a morphometric analysis of the variability of human inner ear anatomy ( Johnson Chacko et al, 2018 ) and simulation of current spread with finite element analysis ( Handler et al, 2017 ).…”