Absence of the internal carotid artery (ICA) is an uncommon disorder, occurring in <0.01% of the population. Very few of these cases have reported ultrasonographic findings. A 47-year-old woman with a history of hypertension presented to the hospital with a three-day history of headache. Color-coded duplex ultrasonography revealed a left common carotid artery (CCA) of diminished caliber terminating in the external carotid artery (ECA) with no remnants of a cervical ICA. Brain MRI showed absence of the bony carotid canal, cervical, and petrous portions of the ICA. The MR angiographic findings were consistent with the ultrasonographic findings. The left CCA terminates in the ECA with absence of the ICA. Filling of the left anterior circulation by way of the posterior and anterior communicating arteries is also seen. Color-coded duplex ultrasonography appears to be a sensitive and effective method for detecting absence of the ICA.

Journal of Neurosonology 3(1):20-23, 2011
Key Words: Agenesis, Internal carotid artery, Ultrasonography