Bilateral hypoplasia of the internal carotid artery: A focused review

Abstract

Introduction/Aim. The internal carotid artery (ICA) is a paired artery that primarily supplies the anterior two-thirds of the brain, the pituitary gland, the eye structures, and some other cranial structures. The ICA variations or abnormalities have been more or less described; especially, bilateral ICA hypoplasia (ICAH) was a very rare description that inspired authors to its evaluation. Methods. The definition of ICAH was based on an artery diameter smaller than 3 mm. Human cases of bilateral ICAH were found by using the corresponding keywords in online bases. Results. Only 64 cases (28 females, 19 males, and 17 cited cases) were found. Some (ab)normal morphological features such as a narrowing of the ICA beyond a normal initial cervical subpart, the presence of a hypertrophic collateral network, small carotid canals, ICA termination in the ophthalmic artery, an increase of the total flow volume in the vertebral arteries, and a possibility of ICA occlusion and/or cerebral ischemia or hemorrhage at an unusually early age were evidenced. The statistical analysis of cases of known age and gender was performed. A comparison between the main morphological and pathological findings of bilateral hypoplasia and bilateral absence of the ICA was done. Conclusion. The literature on the ICAH topic provides confirmative and contradictory examples of suggested bilateral ICAH criteria. Some types of cranial hemorrhage and/or aneurysms of the vertebrobasilar system in patients were proven. Paradoxically, aneurysms occurred more frequently in ICAH than in a similar number of cases that described bilateral absence of ICA.