Variations of the Vestibular Aqueduct, Endolymphatic Sac and Pneumatization of the Temporal Bone

Variations of the vestibular Aqueduct (VA), endolymphatic Sac (ES) and the development of the peri-aqueductal air cell were studied using ten horizontally sectioned human temporal bones. Ten temporal bones consisted of each, two well pneumatized and poorly pneumatized ears without particular pathological finding in the ES, 3 ears with narrow lumen and various pathological conditions of the ES, a ear of neonate and both sides from a case of unilateral meniere's disease. Medial view graphic reconstruction of the cochela VA, ES and peri-aqueductal air cell were performed for the better understanding of the three dimensional anatomy among these structures.The ear with well developed peri-aqueductal air cells showed well developed funnel shape dilatation of the distal VA, and the poorly developed ear showed poorly developed funnel shape dilatation, respectively. The ES extended from near the upper margin to the lower margin of the VA in either well or poorly pneumatized ears. No direct relation was detected between the penumatization of the ear and the patency of the ES lumen. However, 3 cases which showed the narrowing of the ES lumen by various pathological findings such as eosinophilic deposit in the lumen, polypoid change in the perisaccular space and the tree-branch-like separation of the ES showed underdeveloped pneumatization. One case of Meniere's disease showed a decreased patent area of the ES in the affected side. Poorly developed pneumatization of the temporal bone may be considered as a predisposing factor of the endolymphatic hydrops due to decreased anatomical volume of the VA and ES.