A left internal carotid aneurysm is a left internal carotid aneurysm, which is more serious at 3mm, and the main reason for the risk is that rupture of the aneurysm can cause serious acute complications, so regardless of the size of the aneurysm, once it is detected, it needs to be actively treated. Left internal carotid aneurysms carry a certain risk of rupture, and rupture of the aneurysm can lead to life-threatening emergencies such as cerebral hemorrhage. Secondly, blood clots can easily form inside the aneurysm, which can be dislodged and lead to cerebral embolism, which in turn can lead to cerebral infarction. Left internal carotid aneurysms usually form as a result of atherosclerosis, injury, or bacterial infection. Since rupture of the aneurysm can lead to serious consequences, it should be treated as soon as possible after detection. It is recommended that patients with left internal carotid artery aneurysm 3mm should go to the hospital in time and under the guidance of the doctor for regular treatment to prevent further progression of the disease.