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Aberrant internal carotid artery

The aberrant internal carotid artery is a variant of the internal carotid artery (ICA) and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the ICA 5.

There is consequent enlargement of the usually small collaterals which course through the middle ear. The result of this enlargement is an artery that passes lateral to the cochlear promontory and appears during otoscopic examination as a retrotympanic vascular mass. If mistaken for a paraganglioma and biopsied, the results can be disastrous not to mention surprising.

The two vessels that enlarge to form the aberrant ICA are:

The two vessels enlarge, sometimes with a stenosis producing objective tinitus, and rejoin the horizontal segment of the petrous portion of the ICA.

Radiographic features


Findings of aberrant ICA on CT include:

  • absent or hypoplastic vertical segment of carotid canal
  • enlarged inferior tympanic canal within the caroticojugular spine with reduced calibre aberrant ICA is traversing through it

Characteristic findings of aberrant ICA  on angiography include:

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