High jugular bulb: different osseous landmarks and their clinical implications.

PURPOSE: The purpose of this investigation was to compare the rate of high jugular bulb (HJB) in relation to internal acoustic meatus (IAM), round window (RW) and endolymphatic sac and to study their clinical implications.

METHODS: Eighty-seven cadaveric non-pathologic human temporal bones were micro-dissected to expose the jugular fossa (JF) and RW. The minimum distance of JF from RW was measured. On the inner surface of petrous part of temporal bone, minimum vertical distance of JF from IAM and saccus endolymphaticus (E sac) was also measured. If the distance of summit of JF from RW or IAM was ≤2 mm or if there was no distance between JF and slit on which E sac opens, they were classified as HJB cases.

RESULTS: The mean minimum distance of JF from the RW, IAM and E sac was found to be 2.85 ± 1.58, 3.83 ± 2.38 and 2.06 ± 2.38 mm and the rate of HJB was 32.2, 24.1 and 41.4 % respectively.

CONCLUSIONS: The rate of HJB varies even in a particular specimen using different landmarks i.e. the RW, IAM and E sac. The preoperative awareness in relation to these landmarks will be useful in cochlear implantation, surgical removal of vestibular schwanommas and clinical findings of Meniere's disease.