Anatomic study of middle fossa approach landmarks using an image guidance system

We sought to verify the relevance and reliability of the main temporal bone anatomic landmarks commonly used for the middle fossa approach and to test the use of digital technology to perform an accurate analysis of these landmarks.

Ten fresh cadaveric temporal bones (5 heads) were analyzed by both computed tomographic imaging and dissection procedures, with the help of an image guidance system (DigiPointeur). Eight landmarks, which were selected for their wide citation in the otoneurosurgical literature, were studied.

Of the 8 landmarks studied, we obtained results similar to previously published data for 2 (the distance between the temporal squama and the internal auditory meatus [IAM] fundus, and the distance between the top of the anterior semicircular canal [ASCC] arch and the IAM fundus), but divergent measurements for the other 6 (the distance between the temporal squama and the arcuate eminence; the distance between the top of the ASCC arch and the cochlear promontory; the IAM roof thickness; the angle formed by the ASCC arch plane orientation and the IAM axis; the angle formed by the head of the malleus, the geniculate ganglion, and the IAM fundus; and the correspondence between the arcuate eminence and the top of the ASCC arch).

The use of an image guidance system allowed us to make sharp and precise measurements of the main anatomic landmarks used during a middle fossa approach. We found 6 measurements to be different from those reported in previously published data out of the 8 landmarks studied.