Anatomical variations and relations of large blood vessels to the tympanic cavity.

Purpose: The aim of this study was to assess the protrusion of the upper bulb of the internal jugular vein (UBJV) and the internal carotid artery (ICA) into the cavum tympani, the thickness and the structure of the bone wall that separates these blood vessels from the middle ear cavity, as well as the bone wall absence between these blood vessels and the cavum tympani.

Methods: The study included a total of 150 samples of temporal bones of elderly people, both sexes. The methods used in the study were anatomic and histologic, while analyses were done by a surgical microscope.

Results: In 38 (25.3%) of the 150 studied temporal bones, the UBJV protruded into the cavum tympani, elevating its bottom. In 3 (7.8%) of the samples the bulb had a high position, thus filling the hypotympanum, and closing the lower half of the fenestra rotunda. The most frequent thickness of the bone wall that separates the ICA and the Eustachian tube was 2 mm (48.2%), less frequently it was 2-4 mm (29.6%), while least frequently it was of paper consistency (22.2%).

Conclusion: High jugular bulb, aberrant ICA and anomalies of their wall structures are a pitfall and risk for middle ear surgery. Awareness of this variation is very important in the presurgical evaluation of the temporal bone to avoid vascular injury.