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Dehiscent jugular bulb

A dehiscent jugular bulb is present when the sigmoid plate between a high riding jugular bulb and the middle ear is absent, allowing the wall of the jugular bulb to bulge into the middle ear cavity.

It is one of the causes of pulsatile tinnitus and is a common cause of a retrotympanic vascular mass. Clearly, if it is mistaken for a middle ear tumour and biopsied, then the consequences can be disasterous (as is biopsying an aberrant internal carotid artery).

Radiographic features

  • given the often turbulent flow within the jugular bulb, signal on MRI can be confusing.
  • the presence of the sigmoid plate can only be ascertained on CT.

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