Effect of opening the endolymphatic duct in hydropic guinea pig ears

Zusammenfassung

Bei 36 Meerschweinchen wurde der Ductus endolymphaticus geöffnet sowohl an normalen Ohren als auch an solchen, an denen ein Labyrinthhydrops durch Obliteration von Ductus und Saccus entstanden war. Bei Öffnung des normalen Ductus entwickelte sich kein oder nur ein geringer Hydrops des Innenohres. Die Wiedereröffnung des blockierten Ductus hatte keine Änderung des bestehenden Hydrops zur Folge. Dabei zeigte eine spätere Wiedereröffnung (5 Monate) im Vergleich zur frühen (2 Monate) eine stärkere Schädigung der Strukturen der Cochlea. Das Anlegen einer Fistel zwischen Endolymph- und Subarachnoidalraum hatte eine zusätzliche Schädigung des Cortischen Organes dann zur Folge, wenn der Labyrinthhydrops stark ausgeprägt war.

Summary

In 36 guinea pigs the endolymphatic ducts were opened in normal ears as well as in ears in which hydrops had been induced by obliteration of the endolymphatic duct and sac. When the normal endolymphatic duct was opened and disconnected from the sac, either hydrops did not develop or mild hydrops developed after short survival times. However, when the blocked duct of the hydropic inner ear was reopened, there was no remarkable difference in the extent of hydrops in comparison to specimens with routine blockage alone after short to long survival times. When the effects of reopening in the early (2 months) and late stages (5 months) of hydrops were compared with the effects of routine blockage alone, the late reopening showed more severe sensorineural atrophy in the cochlea. Although the early reopening resulted in less atrophic changes than the late reopening, the results were no better than that following blockage alone. The opened duct was covered by connective tissue or epithelial cell layers within 7 days, and by new bone at about 21 days after opening.

The early reopening did not alter the natural course of the developing endolymphatic hydrops. Creation of a fistula between the endolymphatic and subarachnoid spaces showed a tendency to produce additional damage to the organ of Corti when performed in the advanced stage of hydrops.