Petromastoid canal

Last revised by Yahya Baba on 13 Jan 2024

The petromastoid (or subarcuatecanal is a channel in the petrous temporal bone that joins the mastoid antrum to the posterior cranial fossa. It contains the subarcuate artery and vein 1.


The canal has been categorized by its size 1:

  • type I - invisible

  • type II - less than 0.5 mm width

  • type III - 0.5-1 mm width

  • type IV - greater than 1 mm width

Radiographic features


On axial petrous temporal bone fine slices, the petromastoid canal is seen as a thin canal between the ascending and descending limb of the superior semicircular canal and has a slight anterior convex course 2. It can easily be mistaken for a fracture line.

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