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.
Gross anatomy
There is consequent enlargement of the usually small collaterals which course through the middle ear, appearing as an artery that passes lateral to the cochlear promontory.
The two vessels that enlarge to form the aberrant ICA are:
inferior tympanic artery: a branch of the external carotid artery (usually ascending pharyngeal artery) which enters from below via the inferior tympanic canaliculus
caroticotympanic artery: a branch of the petrous portion of the ICA known as the hyoid artery when enlarged
The vessels rejoin the horizontal segment of the petrous portion of the ICA.
The anomaly may be associated with a persistent stapedial artery 7.
Clinical presentation
Patients may present with pulsatile tinnitus, particularly if there is stenosis in the vessel. On otoscopic examination, it appears as a retrotympanic vascular mass. If mistaken for a paraganglioma and biopsied, the results can be disastrous.
Radiographic features
CT
Findings of aberrant ICA on CT include:
enlarged inferior tympanic canaliculus within the caroticojugular spine with small vessel traversing it
retrotympanic mass, as vessel enters the posterior mesotympanum and courses across the inferior cochlear promontory to the anterior mesotympanum
absent carotid plate, as vessel connects to the normal horizontal portion of the petrous ICA
absent or hypoplastic vertical segment of the carotid canal
Angiography
Characteristic findings of aberrant ICA on angiography include:
enlarged tympanic branch of ascending pharyngeal artery
more lateral and posterior route of petrous part of ICA than usual
lateral extension of the ICA well (pinched contour of the vessel) beyond the vestibular line of Lapayowker
Differential diagnosis
lateralized internal carotid artery: protrudes into the anterior mesotympanum but does not course across the cochlear promontory from the posterior mesotympanum nor enlarge the inferior tympanic canaliculus 7
aneurysm of the petrous segment of the ICA
glomus tympanicum
glomus jugulare
dehiscent jugular bulb
References
Related Radiopaedia articles
Anatomy: Brain
brain
grey matter
white matter
cerebrum [+]
brainstem [+]
cerebellum (part of metencephalon)[+]
cerebral meninges (meninx primitiva)[+]
CSF spaces[+]
cranial nerves (mnemonic)[+]
functional neuroanatomy[+]
CNS development[+]
cerebral vascular supply
arteries
vascular territories
circle of Willis
internal carotid artery (ICA) (segments)[+]
vertebral artery[+]
normal variants
intracranial arterial fenestration
internal carotid artery (ICA)
absent ICA
aberrant ICA
anterior cerebral artery (ACA)[+]
middle cerebral artery (MCA)[+]
posterior cerebral artery (PCA)[+]
basilar artery[+]
persistent carotid-vertebrobasilar artery anastomoses (mnemonic)[+]
cerebral venous system[+]
glymphatic pathway
Gross anatomy
There is consequent enlargement of the usually small collaterals which course through the middle ear, appearing as an artery that passes lateral to the cochlear promontory.
The two vessels that enlarge to form the aberrant ICA are:
inferior tympanic artery: a branch of the external carotid artery (usually ascending pharyngeal artery) which enters from below via the inferior tympanic canaliculus
caroticotympanic artery: a branch of the petrous portion of the ICA known as the hyoid artery when enlarged
The vessels rejoin the horizontal segment of the petrous portion of the ICA.
The anomaly may be associated with a persistent stapedial artery 7.
Clinical presentation
Patients may present with pulsatile tinnitus, particularly if there is stenosis in the vessel. On otoscopic examination, it appears as a retrotympanic vascular mass. If mistaken for a paraganglioma and biopsied, the results can be disastrous.
Radiographic features
CT
Findings of aberrant ICA on CT include:
enlarged inferior tympanic canaliculus within the caroticojugular spine with small vessel traversing it
retrotympanic mass, as vessel enters the posterior mesotympanum and courses across the inferior cochlear promontory to the anterior mesotympanum
absent carotid plate, as vessel connects to the normal horizontal portion of the petrous ICA
absent or hypoplastic vertical segment of the carotid canal
Angiography
Characteristic findings of aberrant ICA on angiography include:
enlarged tympanic branch of ascending pharyngeal artery
more lateral and posterior route of petrous part of ICA than usual
lateral extension of the ICA well (pinched contour of the vessel) beyond the vestibular line of Lapayowker
Differential diagnosis
lateralized internal carotid artery: protrudes into the anterior mesotympanum but does not course across the cochlear promontory from the posterior mesotympanum nor enlarge the inferior tympanic canaliculus 7
aneurysm of the petrous segment of the ICA
glomus tympanicum
glomus jugulare
dehiscent jugular bulb
References
Related Radiopaedia articles
Anatomy: Brain
brain
grey matter
white matter
cerebrum [+]
brainstem [+]
cerebellum (part of metencephalon)[+]
cerebral meninges (meninx primitiva)[+]
CSF spaces[+]
cranial nerves (mnemonic)[+]
functional neuroanatomy[+]
CNS development[+]
cerebral vascular supply
arteries
vascular territories
circle of Willis
internal carotid artery (ICA) (segments)[+]
vertebral artery[+]
normal variants
intracranial arterial fenestration
internal carotid artery (ICA)
absent ICA
aberrant ICA
anterior cerebral artery (ACA)[+]
middle cerebral artery (MCA)[+]
posterior cerebral artery (PCA)[+]
basilar artery[+]
persistent carotid-vertebrobasilar artery anastomoses (mnemonic)[+]
cerebral venous system[+]
glymphatic pathway
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