Exposure of the petrous segment of the internal carotid artery through the extradural subtemporal middle cranial fossa approach: a systematic anatomical study.

The relationships between the horizontal segment of the internal carotid artery (ICA) and other petrous apex structures was studied in 14 anatomical specimens obtained from routine autopsies and on 10 magnetic resonance images obtained from healthy volunteers. The dissection was performed under an operating microscope using the middle fossa transpetrous approach. A pentagonshaped area of 67.91 mm(2) posterior to the trigeminal nerve and bordered by anatomical structures was identified inside the petrous apex. The results suggest a method for exposing the ICA when the artery is not visible after dural elevation.