Introduction: The arterial circle of the base of the skull is an anastomotic arterial system between the carotid and vertebrobasilar territory. It has an interest in ischemic or hemorrhagic vascular disease and tumor pathology of the skull base. Observation: We describe the case of a patient with a rare anatomical variant of the anterior complex of the arterial circle of the skull base which has produced severe neurological disorders. Discussion: The anterior complex of the arterial circle of the skull base is formed by the two anterior cerebral arteries and the anterior communicating artery. The main vascular changes occur very early in fetal life. There takes place complex phenomena of appearance, regression and anastomosis. These anatomical variants would favor the developpement of vascular malformations due to modified hemodynamics. It is necessary to accurately map the anterior cerebral vascularization in particular in case of aneurysms. Conclusion: A perfect knowledge of these variants is essential for a good neurosurgical and endovascular treatment of patients.