Ependymal foldings and other related ependymal structures in the cerebral aqueduct and fourth ventricle of man.

The ependymal lining of the cerebral aqueduct and fourth ventricle of 100 normal humans was studied with the light microscope. Ependymal foldings with normal morphology and a constant distribution pattern were detected in all. The most common sites were the median sulcus and sulcus limitans in the fourth ventricle, and the ventral and lateral walls in the cerebral aqueduct. Rows, islands and rosettes of ependymal cells embedded in normal subependyma were present in 25/82 adults (30%) and in 3/18 children (16%) in a similar distribution pattern as that of the ependymal foldings. We illustrate these normal structures which probably result from fusion between the walls of the ependymal foldings and distinguish them from granular ependymitis and postmortem artifact.