Enlargement of the cochlear aqueduct: does it exist?

Our intention was to evaluate whether enlargement of the cochlear aqueduct could play a role in dysfunctions of the inner ear. There is little literature dealing with the question of cochlear aqueduct (CA) enlargement and results of reported radiological examinations are contradictory. Therefore, we decided to analyse 400 high-resolution CT-scans of the temporal bone to examine the diameter of the CA. We used scan-data from a 64-line multislice spiral-CT-scanner stored in our PACS-System. CA-enlargement was defined as a diameter of more than 1 mm in the whole otic capsule portion. A classification with four types of CA’s proposed by Migirov and Kronenberg in 2005 was applied. Statistical analysis of diameters, different CA-types and side asymmetry was performed. We did not find any CA exceeding 1 mm in diameter in the otic capsule portion, there is no evidence of CA-enlargement, not even in patients with inner ear malformation. A new aspect compared with published literature to date is that nearly in all cases CA was identified, but in different degrees. According to our findings, it seems to be very unlikely that CA-enlargement is a reason for pathologic inner ear condition as it is in case of large vestibular aqueduct.