Visualization of human vestibular aqueduct with computer-aided serial section reconstruction system

Three-dimensional course of the vestibular aqueduct

Three-dimensional (3-D) reconstruction methods were employed to study the anatomy of the vestibular aqueducts (VAs) in ten postmortem temporal bone specimens obtained from ten individuals aged 4 months to 70 years at death. After reconstruction, the ten 3-D images of VAs were superimposed on one another and differences evaluated. The VA showed postnatal growth and variations in size and shape. However, the variations in angle at which the VA bends near the isthmus were not correlated with age. Furthermore, study of the superimposed images revealed that the 3-D course of the VA was essentially the same in individuals of all ages, despite its wide variability in size and shape. These results indicate that the basic course of the VA is determined before early infancy although the VA grows thereafter, suggesting that VA anomalies such as "large vestibular aqueduct syndrome" (in which the VA takes an abnormally straight and wide course) may be established prenatally.

Computer-aided three-dimensional reconstruction of guinea pig cochlear aqueduct

A computer-aided method of three-dimensional reconstruction was applied to the determination of the overall spatial configuration of the guinea pig cochlear aqueduct. The rotation function of the reconstructed images was useful in showing the individual small parts of the duct. A semi-translucent display of the segmental reconstruction of the duct demonstrated a difference in the density of the cellular components between the opening to the perilymphatic space and the duct portion. We propose that the cochlear aqueduct serves as a protective mechanism against a sudden change in CSF pressure in the subarachnoid space.

The course of the internal auditory artery and its branches. Computer-aided three-dimensional reconstructions

The course and branches of the internal auditory artery (IAA) were studied in 7 vertically-sectioned normal adult human temporal bones, and three-dimensional reconstructions of the anatomical structures were made with the aid of a computer system. Single IAAs existed in 3 or 7 temporal bones whereas double IAAs existed in 4. The IAA ran either between the facial nerve and the VIIth nerve, or on the inferior-posterior surface of the VIIIth nerve at the porus. Branching and anastomosis of the IAA were highly variable in the middle to proximal portion of the internal auditory canal (IAC). The anterior vestibular artery ran on the anterior surface of the superior vestibular nerve, and the vestibulocochlear artery ran on the inferior surface of the inferior vestibular nerve. The main cochlear artery ran at the center of the cochlear nerve near the fundus. The course of the vessels was less variable at the distal portion of the IAC than at the proximal portion.

Computer-aided three-dimensional reconstruction of the osseous and membranous labyrinths

In order to obtain an adequate knowledge of the stereoscopic anatomy of the temporal bone, it is very useful to make three-dimensional reconstructions of the bone. By using the histological sections of a human temporal bone processed for routine evaluation, we have undertaken computer-aided reconstruction of the osseous and the membranous labyrinths, as well as the inner ear sensory organs. Reconstructions were done either separately or simultaneously. Owing to the "semitransparent display" function of the computer system, it was possible to observe the reconstructed membranous labyrinth through the simultaneously reconstructed osseous labyrinth, and the sensory organs through the membranous labyrinth. The results were satisfactory for understanding the spatial relationships among these structures. We also attempted computer-aided measurements of the reconstructed sensory organs and calculated the length of the organ of Corti and the angle between the saccular and the utricular maculae.