No abstract

High-resolution X-ray microtomography (micro-CT) was used to show the spatial configuration of the membranous labyrinth of the fixed guinea pig and human inner ear. Whole temporal bones were en bloc stained in 2% osmium tetroxide for 2 days or more to allow the osmium to attach to the membranes of the inner ear, and then scanned with a Skyscan 1172 micro-CT with highest resolution of 8 microns. The scans were segmented and reconstructed. The findings for guinea pigs and humans are similar. The saccular macula is closely attached to the curved medial wall of the temporal bone, but in both human and guinea pig the utricular macula is attached to the temporal bone only at the anterior region of the macula, and, as others have reported previously, much of the caudal area of the utricular macula is tenuously supported by a thin membrane, just above the dorsal margin of the stapes. This tenuous support may have important consequences for the sensing of forces by the utricular macula. Combining information from a dissected human horizontal canal with CT images allows an estimate of the orientation of the horizontal canal crista in human subjects, data which are necessary for treatment of benign paroyxsmal positional vertigo of the horizontal canal. The very high resolution achieved by micro-CT shows that reconstruction from inadequately sampled CT data produces images that are not anatomically correct, so that canal deformations and aplasias may appear to be present.

Two-dimensional information about vestibular end organ location should serve as a guideline only because the operative field is 3D, and the relationship of the piston to the vestibular labyrinth changes with the angle of placement.

Temporal bone studies show that the SRA appears to cause no intracochlear trauma if used as an EAS electrode up to 20 mm depth of insertion.