Accessory sutures

Last revised by Dalia Ibrahim on 15 Oct 2020

The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centers.

It is important to know these anatomic variations, mainly on the head trauma image studies in children, where it could be difficult to differentiate non-depressed skull fractures from an accessory suture.

Radiographic differentiation of skull fracture and accessory suture

Accessory sutures usually:

  • make a "zig-zag" pattern with interdigitations
  • have sclerotic borders similar to major calvarial sutures
  • are often present on both sides and are fairly symmetric especially in the parietal bones
  • occipital accessory sutures can be complex and multiple but are also frequently bilateral

Simple non-depressed skull fractures usually:

  • have sharp lucencies with non-sclerotic edges
  • widen as they approach the suture or there is associated diastasis of the adjacent synchondrosis or suture
  • can cross suture lines or extend from one major suture to another (in high impact fractures)
  • have associated soft tissue swelling or hematoma
    • absence does not exclude a fracture

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