The loss of a slight-to-moderate amount of perilymph during stapes surgery is not uncommon. A few cases have been encountered in which there was a massive welling up of fluid from the vestibule that filled the middle ear and external canal. Since the volume of the perilymphatic spaces is small, it is likely that this excessive fluid came from the subarachnoid space, possibly by a new pathway. The purpose of this paper is to postulate and attempt to demonstrate histologically how a new communication between the perilymphatic and subarachnoid spaces might occur. The close anatomical relationships of the oval-window region are discussed, and measurements of the distances between the various structures and the stapes footplate are presented. Very little has been said in the literature about the loss of perilymph during stapes surgery, except to caution against aspirating it from the vestibule after footplate fracture or removal. In general, the