AGenesis of the internal carotid artery (ICA agenesis): an integrative review

Introduction: The ICA agenesis is a rare anomaly, an incidental finding whose incidence is lower than 0,01%. It is predominantly asymptomatic, because of the development of a collateral circulation, though it can present nonspecific symptoms, that result from insufficient blood flow, due to the development of atherosclerosis in vessels that previously supported the blood flow in the absence of the ICA, and by the association with brain aneurysm. Objectives: Conduct an integrative review about the ICA agenesis, describing the aspects and importance of vascular changes. Methods: It is an integrative revision that includes articles indexed in the SCIELO and PUBMED databases, using descriptors, with articles from the last 5 years. Results: The ICA agenesis can be unilateral or bilateral, predominantly on the left side. The main collateral pathways are the Circle of Willis and the transcranial collateral vessels of the external carotid artery. Differential diagnosis, like total occlusion or dissection, should be excluded by the inspection of the carotid canal in the CT, because the demonstration of a normal carotid canal excludes developmental anomalies of the ICA. The MRI and the angiography, combined with CT and Doppler ultrasound allow an accurate diagnosis. Conclusion: It is important to consider the possibility of ICA agenesis in the investigation of nonspecific symptoms, when other more prevalent causes have already been discarded, since these patients have an increased incidence of several other intracranial diseases, such as cerebral aneurysms with an association of 25-44%, that if identified in time, can avoid severe damages.