Morphometric analysis of arcuate eminence: A distinctive landmark for middle cranial fossa approach

Background: The arcuate eminence (AE) is a bony prominence on the middle fossa plate of the temporal bone, hypothesized to be variably associated with superior semicircular canal (SSC) relief, temporal lobe sulcus, and subjacent air cells. We present various morphometric parameters of the AE, as seen using a middle fossa approach.

Materials and methods: The study used 18 formalin-preserved cadaveric human temporal bones. Various morphological and morphometric parameters pertaining to topographic orientation of the AE in relation to surrounding landmarks used in a middle mossa approach were noted, before and after microdissection of the AE under a Leica M320 F12 microscope, using otologic microdrills and suction irrigation. The morphometric parameters were analyzed using ImageJ 1.46r software.

Results: The overall incidence of AE was 83% (n = 15/18). The most common shape and pattern noted were linear (53.3%, 8/15) and dual arc (46.7%, 7/15), respectively. Mean angle between the AE and SSC was 19°, with a standard deviation of 15° and a range of 2-49°. The AE overlapped the SSC in 40% (6/15) of bones, and did not correspond to the SSC in 7% of cases. A partially overlapping positional correspondence was noted in 53.3% (8/15).

Conclusion: When present, the AE corresponds to the SSC in 40% of cases, but it can serve as a rough guide to the SSC in up to 93% of cases. Surgeons need to be familiar with the varying morphology of AEs in order to execute a rapid and safe dissection during middle fossa approaches.