The high position of the jugular bulb.

The relationship between the bottom of the hypotympanon and the jugular bulb has been investigated on the basis of a histological analysis of 815 temporal bones. A high position of the jugular bulb has been found in 3.5% of the temporal bones examined. Only exceptionally does it occur bilaterally and is more often found on the right than left side. We distinguish two localizations of the high position of the bulb in the hypotympanon: the lateral and the medial. In either case the bulb may be damaged during myringotomy or during the removal of granulation tissue in middle ear surgery. Injury at myringotomy can be avoided only if there is a reinforcement of the bony wall. In the lateral position, the jugular bulb may be damaged when the tympanomeatal flap is being elevated. The bulb can occasionally be mistaken for a jugular glomus tumour. There is hardly any difference between cases where the bone between the bulb and the middle ear space is dehiscent or only very thin. The thickness of the bony shell is only 0.1-0.3 mm--thus there is no real protection against instrumental injuries.