Morphometric Analysis of the Human Endolymphatic Sac:Section 4. Distribution of Canaliculi in Sacs from Four Normal-hearing Cases and Four Meniere's Disease Cases

Abstract

Most previous investigations seeking morphological manifestations of endolymphatic sac dysfunction in Meniere's disease have been descriptive reports. None looked for differences in the canalicular architecture between normal and Meniere's disease sacs. Sections 1 and 2 demonstrated a correlation between histological findings and canalicular structure, and quantitative histological differences between normal and Meniere's disease sacs. Section 3 showed qualitative differences in the canalicular architecture in computer-aided three-dimensional reconstructions of a normal sac and a Meniere's disease sac. This study evaluates differences in canalicular architecture between normal and Meniere's disease sacs. We used an image analysis computer to examine sections from four normal and four Meniere's disease sacs. We counted the number of canaliculi, measured the surface area and volume, and determined the surface-to-volume ratio. Fewer small canaliculi were found in Meniere's disease sacs than in normal sacs. The surface area, volume, and surface-to-volume ratio of small canaliculi were significantly less in Meniere's disease sacs. The same parameters in large canaliculi were not noticeably different between normal and Meniere's disease sacs. Measures of these parameters in the two reconstructed sacs were very similar to the measures from the four sacs per group. This study shows definite differences in canaliculi of normal and Meniere's disease sacs. The canaliculi are lined predominantly with the type of cells involved in resorption. Results of this last study correlate remarkably well with results in Sections 1, 2, and 3. We conclude that the resorptive function of the sac lies primarily in the small canaliculi and that our results demonstrate a substantial reduction of the resorptive capacity in Meniere's disease sacs.