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Age: 4

Sex: Female

Indication: MVC

Mendosal Suture

Mimicking a Fracture



Findings Relating to the Mimic

  • Non-depressed zigzag lucency involving the right occipital bone, which is located medial to the lambdoid suture and superior to the occipitomastoid suture.  No diastasis.  Given the appearance and location, this finding is consistent with a persistenet mendosal suture rather than an acute fracture.
  • No overlying soft tissue contusion and no intracranial hemorrhage.


Discussion

  • The mendosal suture (aka the accessory occipital suture) usually closes well before birth, but it can persist into childhood and very rarely adulthood.
  • The suture is located in the occipital bone.  On axial images it is seen medial to the lambdoid suture and on coronal images it is located superior to the occipitomastoid suture.
  • This suture is easy to misdiagnose as a fracture and is often unilateral (as in this case).  Knowing the normal location of the mendosal suture is key.  Use your 3D reformatted imaging to help you.
  • There also are some general principals that can help you differentiate suture from fracture.  Sutures tend to join other sutures (not cross them) and are more likely to have a “zigzag” appearance.  Fractures may cause diastasis (widening) of sutures, cross sutures, cause depression of fracture fragments, and generally have non-sclerotic margins and a more linear (versus “zigzag”) in appearance.
  • Look for any overlying soft tissue contusion or subjacent extra-axial hemorrhage to increase your suspicion for fracture.
  • Of note, this patient also has a partially fused metopic suture best seen near the bregma.


Images

Typical location of the mendosal suture (blue) in relation to the lambdoid suture (red) and the occipitomastoid suture (black arrow). Illustration modified from original by I, RosarioVanTulpe / CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/) via WikiMedia (https://commons.wikimedia.org/wiki/File:Lambdoid_suture.png) Typical appearence of the mendosal suture (red arrow) on 3D reconstructed image Typical location of the mendosal suture (red arrow) on axial, medial to the lambdoid suture (blue arrow) Of note, this patient also has a persistent metopic suture (red arrow).

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