The severity of symptoms of basilar artery occlusion should be determined according to whether the basilar artery occlusion is an acute occlusion or a chronic occlusion. If an elderly patient with previous risk factors such as hypertension, diabetes mellitus, hyperlipidemia, and prolonged heavy smoking and alcohol consumption develops a vertebral basilar artery occlusion on top of atherosclerosis, at which time the internal carotid artery system has already been adequately compensated for or other blood vessels in the brain are compensated for, and the patient may have dizziness, unsteady walking and symptoms of cerebellar and brainstem infarction, which may not be very severe. In case of acute occlusion of the vertebral basilar artery, the patient may have severe dizziness, nausea, vomiting, unsteady walking, and soon develop large infarctions of the cerebellum and brainstem leading to coma.