dehiscent jugular bulb

Dehiscent jugular bulbs are 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.


The estimated incidence is ~5% (range 3.5-7%) of the symptomatic population (e.g. those with tinnitus) .

Clinical presentation

It is one of the causes of pulsatile tinnitus and is a common cause of a retrotympanic vascular mass.

Patients can present with conductive hearing loss. This may occur when the jugular bulb contacts the tympanic membrane, interferes with the ossicular chain, or obstructs the round window .

Radiographic features

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

Differential diagnosis

Practical points

Clearly, if it is mistaken for a middle ear tumor and biopsied, then the consequences can be disastrous (as is biopsying an aberrant internal carotid artery).

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