Dimensional anatomy of the vestibular aqueduct and the endolymphatic sac (rugose portion) in human temporal bones. Statistical analysis of 79 bones.

The purpose of this study was to investigate the anatomy of the vestibular aqueduct (VA) and rugose portion (RP) of the endolymphatic sac. Serial horizontal sections of 79 normal temporal bones of individuals aged 20 to 102 years were used. Medial view graphic reconstruction of the VA was performed for each specimen to determine the area, length, angle and position of the VA. The relationship between the width of the VA and the area of the VA, and the relationship between the degree of development of the VA and the degree of development of the temporal bone (periaqueductal pneumatization and the otic capsule in the periaqueductal region) were also investigated. Measurements of the RP were also made and further histological study of the RP was performed on 30 selected specimens. We found that 1) the VA in adult temporal bone varies in size and can be classified as hypoplastic, normoplastic, or hyperplastic; 2) many of the VAs in each group have similar sizes, although they vary in length, angle, or position; 3) all or most of the RP was located within the VA in all but one specimen, which had a hypoplastic VA (in this specimen more than half of the entire RP extended into the posterior cranial fossa); 4) the histology of the RP was characteristic in each type of VA; and 5) the degree of development of the VA seems to correlate with the degree of development of the otic capsule in the periaqueductal region.