Localized fibrillation of the a1 segment of the left anterior cerebral artery refers to a localized narrowing of the horizontal segment of the anterior cerebral artery on that side of the patient’s brain, which may be the result of congenital vascular dysplasia or atherosclerosis. The left anterior cerebral artery is located in the left longitudinal fissure of the brain, and segment a1 refers to the horizontal segment of the vessel. Localized fibrillation of the a1 segment of the left anterior cerebral artery is a clinical imaging finding, which refers to the stenosis of the horizontal segment of the blood vessel in the patient, and the common clinical causes are congenital vascular dysplasia and arteriosclerosis, and the clinical symptoms of stenosis caused by different causes are not the same. If the patient’s left anterior cerebral artery a1 segment is locally thin due to congenital vascular dysplasia, due to the strong compensatory ability of the cerebral blood vessels, the patient generally will not experience uncomfortable symptoms, and the patient can follow the doctor’s instructions for regular follow-up, and there is no need for special treatment for the time being. If the patient is due to atherosclerosis-induced localized fibrillation, it will cause insufficient blood supply and oxygenation to the brain, resulting in dizziness, headache, nausea, vomiting and other uncomfortable symptoms. When the examination found that the left anterior cerebral artery a1 segment localized fibrillation, it is recommended that the patient consult the doctor in time, further improve the examination under the guidance of the physician, to clarify the specific causes of the disease, and standardized treatment as soon as possible, to avoid delays in the condition.