Petrous ridge

The petrous ridge forms the upper edge of the petrous part of the temporal bone. It divides the middle cranial fossa, which is at the front, from the posterior cranial fossa located behind. Along this border runs a groove that houses the superior petrosal sinus. This sinus links the transverse venous sinus to the cavernous sinus. Additionally, the tentorium cerebelli, a dural covering that lies over the contents of the posterior cranial fossa and separates them from the occipital cortex above, is anchored to the petrous ridge.

At the inner end of the ridge is a trigeminal notch that permits the passage of the trigeminal nerve. This nerve traverses from the posterior cranial fossa to the middle cranial fossa, slipping through the space between the petrous ridge and the superior petrosal sinus above. It then extends to the trigeminal ganglion, which resides within the trigeminal impression.