Histologic and ultrastructural features of explanted Arenberg shunts

Four Arenberg endolymphatic shunts that had been implanted in patients for 6 years, 3 years, 24 months, and 11 months were removed during retrolabyrinthine nerve sections (two cases), labyrinthectomy (one case), or cochlear implant (one case). The shunts were examined and photographed grossly and the components were prepared for light and scanning electron microscopy. Acellular debris filled the vestibule around the valve in all cases. The same material filled the inside of the valve in two cases and could be seen coming through the valve in two cases. Two shunts had ingrowth of fibrous tissue into the sponge. The finding of greatest concern was multiple erosions seen in the Supramid tube (S. Jackson Inc, Alexandria, Va) that inserts into the endolymphatic sac. On scanning electron microscopy, these erosions appeared as a network of cracks in the outer surface of the tube. The two shunts implanted for the longest time had fenestrae completely through the tube wall. These findings question the long-term functioning and integrity of the Arenberg shunt.