Retraction of the endolymphatic membranes in temporal bones of the Wittmack and Tufts collection.

Background: In histologic studies, the volumetric status of the intralabyri nthine fluids is judged by the position of the endolymphatic membranes. Bul ging 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 littl e attention has been paid to its significance. Almost one hundred years ago Wittmaack described retraction of the endolymphatic membranes, which has s ince been considered to be preparation artifact - a concept that essentiall y remains unchallenged. To test the validity of this long held premise, we examined two sets of temporal bones from different centers. Material and Me thods: 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 m onths, median 1.5 months) from the temporal bone collection of the Departme nt of Otolaryngology Tufts University School of Medicine. All specimens wer e studied by light microscopy. Retraction was defined as depression of Reis sner'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. Addit ionally the saccule, utricle and semicircular ducts were examined for colla pse. Results: The reevaluation of the 67 temporal bones described by Wittma ack, including those of 7 children below the age of 10 years, showed retrac tion of Reissner's membrane in 81 % compared to 33% of the temporal bones f rom the Tufts collection. In contrast to the high incidence of retraction i n the cochlear duct, fewer saccules (12%) and utricles (4%) were collapsed in the Tufts collection. In the Wittmaack collection no significant differe nces between the underlying diseases were found, however in the Tufts colle ction the group of children who suffered from extracochlear infections and malignancies had a higher frequency of retraction. Conclusion: Mild retract ion might be to some extent physiologic or even artifactual. Severe retract ion, 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 o rigin (viruses were not known during Wittmaack's time), ototoxicity or even of genetic origin.