Case of the
Patient is a 67 y/o
male that presented with a recent episode of diplopia
lasting several minutes and then cleared. He had no
recurrent episodes. On physical exam, he was also noted
to a soft bilateral carotid bruit and so carotid duplex
exam was ordered
The technologists physical exam revealed -
Radial pulses are equal; brachial blood pressure was
176/84 mm/Hg on the right and 180/84 mm/Hg on the left. A
soft carotid bruit was appreciated
Here are the findings - not a great diagnostic mystery
but a very unusual finding!
It is fairly clear that there is an
internal carotid artery branch bilaterally in this
otherwise completely normal study. This branch
possibly represent an Anomalous ascending pharyngeal
artery but this cannot really be proven with duplex.
Anomalous branches of the internal carotid artery are
quite rare and I was unable to find a "incidence"
reported n the literature. Most cases reported in
the literature involve branches in the intracranial
circulation. In more than 25 years of carotid duplex
scanning, this technologist has seen this anomaly three
times (actually 4 as this would count as two!) One case
more than 15 years ago involved a patient how has a short
occlusion of the proximal internal carotid artery with
continued patency distally via an anomalous proximal ICA
branch. This patient underwent angiography which failed
to show a patent ICA branch. Repeat duplex scanning
confirmed its continued presence however as the patient
was currently stable, he did not undergo endarterectomy.
A similar case has been reported in the
The presence of branches in the extracranial
cerebrovascular vessels are a very important diagnostic
finding. Virtually every anatomy text describes the ICA as
having no extracranial branches, the first being the opthalmic
artery which arises intracranially. Differentiation of the ICA
from the external carotid artery is a common beginner mistake.
Differentiation is typically easy in normal bifurcation (as in
this case) but more difficult in diseased vessels.
The ICA is posterior in the neck
(dorsal/lateral) compared to the ECA
The ICA is typically larger than the ECA
The ECA has a characteristic high resistance
waveform compared to the low resistance ICA
Temporal tapping to watch for oscillations in
the ECA flow can also be used but this can
sometimes be misleading unless using
I have typically used the presence of branches
to be the best method for differentiation but in carotid
duplex scanning, as in most things, there are few absolutes!
I would love to hear of any cases