UCLA Radiological Sciences Proceedings

Fenestration of the internal carotid artery (ICA) is an extremely rare congenital abnormality thought to be secondary to incomplete segmental fusion of vessels at the early stages of their development. Fenestration is usually asymptomatic and often misdiagnosed as arterial dissection. Distinction between the two can be challenging on both magnetic resonance angiography and computed tomography angiography, and digital subtraction angiography must often be utilized for precise characterization of the abnormalities. Certain imaging features, namely the length of the involved arterial segment, the regularity of luminal contour, the symmetry of arterial limbs, and the absence/presence of fusiform dilatation of either limb, produced by noninvasive angiography have the potential to help distinguish between an ICA fenestration and dissection. We report a case of an asymptomatic, true fenestration of a short segment of ICA and discuss its imaging characteristics.