Right anterior cerebral artery A1 segment defect refers to the phenomenon that the blood vessels of the beginning segment of the right anterior cerebral artery are not visualized in the imaging examination, which can be seen in congenital defect and acquired vascular occlusion. 1. Congenital defects: some patients are born with a variant of cerebral vessels, and the right anterior cerebral artery section A1 is absent, which is manifested as the left anterior cerebral artery section A1 is dominant, and the blood is supplied to the right anterior cerebral artery section A2 through the anterior communicating artery. This phenomenon belongs to normal variation and does not need special treatment. 2. Acquired vascular occlusion: mostly caused by atherosclerosis, which is a pathological phenomenon. Oral antiplatelet drugs such as aspirin and plaque stabilizing drugs such as atorvastatin are recommended. If the a1 segment of the right anterior cerebral artery is found to be defective, it is recommended to consult a medical professional as to whether intervention and treatment are needed.