Petromastoid canal

Last revised by Dr Henry Knipe on 14 Sep 2021

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 petrous temporal bone fine slices, the petromastoid canal is seen as a thin canal between the anterior and posterior part of the superior semicircular canal. It can easily be mistaken for a fracture line.

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