'Pseudostring Sign' on Carotid Computed Tomographic Angiography

We present 3 cases of unilateral internal carotid artery (ICA) occlusions with prominent single collateralizing vessel of vasa vasorum on computed tomographic angiography. The features on axial source and 3-dimensional images of computed tomographic angiography include "pseudostring sign," serpigenous course of the vasa vasorum, eccentric dot appearance in the wall of chronically thrombosed ICA, and termination in the neck or reconstituting into the ICA at or below the skull base.