Fine structure of the human cochlear aqueduct: a light and transmission electron microscopic study of decalcified temporal bones.

The morphologic features of the human cochlear aqueduct were examined using both light and electron microscopy. The lumen of the cochlear aqueduct was observed to be filled with dense, irregular connective tissue corresponding to dura mater. At the entrance to the cerebrospinal fluid space, the dense connective tissue in the ductal lumen was covered with a thin layer of a few flattened cells, which was contiguous with the arachnoid membrane of the brain. A simple low cuboidal epithelium also separated the perilymphatic space from the lumen of the duct. Our observations confirm the presence of a barrier membrane at the opening to the perilymphatic space, and suggest that no transport occurs in the human cochlear aqueduct.