Multidetector CT angiography of the persistent primitive hypoglossal artery

In a 64-year-old woman suffering from arterial hypertension and actually presenting with headache, the persistence of the primitive hypoglossal artery on the right side of the head was demonstrated by cerebral multidetector CT angiography. The right vertebral artery was entirely replaced by the hypoglossal artery which, in turn, arose from the internal carotid artery at the level of the second cervical vertebra. The basilar artery thus was formed by an anastomosis of the left vertebral and the hypoglossal artery. Interestingly and most probably as a consequence of the persistence of an otherwise regressed carotico-basilar anastomosis, the right posterior communicating artery was also found to be entirely absent. Several three-dimensional reconstructions of the CT data set were proven to be helpful in the diagnosis and documentation of these anomalous vascular conditions at the skull base. Finally, the embryogenesis and clinical significance of this rare entity as well as alternative diagnostic modalities are discussed.