Muscle dystrophies

Abstract

In histologic studies, the volumetric status of the intralabyrinthine fluids is judged by the position of the endolymphatic membranes. Bulging of the membranes, commonly known as endolymphatic hydrops, is assumed to be caused by excess of endolymph. The opposite situation, retraction of the membranes is, however, only incidentally described and relatively little attention has been paid to its significance. Almost one hundred years ago Wittmaack described retraction of the endolymphatic membranes, which has since been considered to be preparation artifact - a concept that essentially remains unchallenged. To test the validity of this long held premise, we examined two sets of temporal bones from different centers. We studied the following collections: 1. The Wittmaack collection in Hamburg, Germany. The original material of 67 temporal bones (patient ages 0-92 years, average age 35.2 years) on which Wittmaack based his opinions. 2. For comparison and to exclude age related phenomena, 125 temporal bones from 73 children between the ages newborn to ten years (average age 13.4 months, median 1.5 months) from the temporal bone collection of the Department of Otolaryngology Tufts University School of Medicine. All specimens were studied by light microscopy. Retraction was defined as depression of Reissner's membrane toward the stria vascularis and the Organ of Corti in more than one cochlear turn and was graded into mild, moderate and severe. Additionally the saccule, utricle and semicircular ducts were examined for collapse. The reevaluation of the 67 temporal bones described by Wittmaack, including those of 7 children below the age of 10 years, showed retraction of Reissner's membrane in 81% compared to 33% of the temporal bones from the Tufts collection. In contrast to the high incidence of retraction in the cochlear duct, fewer saccules (12%) and utricles (4%) were collapsed in the Tufts collection. In the Wittmaack collection no significant differences between the underlying diseases were found, however in the Tufts collection the group of children who suffered from extracochlear infections and malignancies had a higher frequency of retraction. Mild retraction might be to some extent physiologic or even artifactual. Severe retraction, however, is a definitive finding that is a part of a local or regional otopathologic process. Of material, it is quite possible that Wittmaack's original observations of what he called "hypotonic collapse" was of viral origin (viruses were not known during Wittmaack's time), ototoxicity or even of genetic origin.