Endolymphatic Periductal Channels: Possible Role in Ménière's Disease

Abstract

Objectives: Characterize the osseous periductal channels surrounding the human endolymphatic duct. Endolymphatic hydrops is the fundamental pathophysiology underlying Ménière’s disease. Elucidating the regulation of endolymphatic circulation is central to understanding the cause of Ménière’s disease attacks of vertigo and hearing loss. Methods: Formalin-fixed, celloidin-embedded human temporal bones were sectioned to 20 microns, and every section was stained with hematoxylin & eosin. Amira software was used to construct a three dimensional image of the periductal channels. We performed immunohistochemical analysis using antibodies directed against vascular, lymphatic, and neural crest markers. The microanatomy was investigated with electron microscopy of the periductal channel epithelium. Finally, we injected horseradish peroxidase into the scala media of guinea pigs to investigate the flow patterns involving these peri-ductal channels. Results: Surrounding the human endolymphatic duct is a group of small channels that originate in the proximal cisternal area of the endolymphatic sac and terminate in the supporting tissue of the saccule, as demonstrated by 3D reconstructions. Endolymphatic hydrops was found in eight bones with blocked ducts and blocked or absent periductal channels. Proliferation of channels was evident in temporal bones when the channels were disrupted on one side. Immunohistochemical analysis results suggest a neuroectodermal origin, similar to the cells of the cochlear spiral ligament. Some contain micro-vessels with single endothelial walls that could represent lymphatics or empty capillaries while others suggest a complex absortive epithelium. Conclusions: This temporal bone study suggests a role for the periductal channels in absorption of endolymph.