IS Case 181: Internalization of external carotid artery due to bilateral ICA occlusion.

Scott Mooney, MD

Imaging Sciences URMC 2008
Publication Date: 2009-05-21


A 47-year-old male presented to emergency department with left-sided weakness and facial droop.


Carotid ultrasound demonstrated bilateral internal carotid artery occlusion. The spectral Doppler waveforms in the external carotid arteries have a low-resistance pattern. Head MRA demonstrated no anterior circulation signal.


Internalization of external carotid artery due to bilateral ICA occlusion.


Ultrasound is an inexpensive and non-invasive test for evaluation of the carotid arteries. While grayscale and color Doppler images provide information in evaluating the severity of disease within the carotid arteries, spectral Doppler tracings, in particular the peak systolic velocities, are primarily used to quantify disease. In addition to the velocities, the waveform patterns can provide further detail.

Typically the internal carotid arteries have a low-resistance waveform, which indicates constant flow to the brain, and is seen in other end-organ arterial systems. The external carotid arteries, however, have a high-resistance waveform, providing supply to the facial musculature. With occlusion of the internal carotid arteries, collateral supply to the brain can be provided through branch arteries of the external carotid artery including orbital and ophthalmic arteries.


  1. Dogra V, Rubens DJ (eds). Ultrasound Secrets. Philadelphia, PA: Hanley and Belfus; 2004:350-370.
  2. Rumack C, Wilson S, Charboneau JW, Johnson J-A. Diagnostic Ultrasound. 3rd ed., Mosby, 2005:943-987.

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