It is puzzling what the cause of the onset of cerebral infarction in the patient’s young female Organize a department-wide case discussion, analyze the condition, and consider the possible etiology of (1) arterial entrapment. (2) Smoke disease. (3) Arteritis. (4) Other unknown factors (30%). From the clinical point of view, the patient had no previous history of head and neck trauma, but arterial entrapment could not be easily excluded, and there was no strong evidence to support the existence of endarteritis, and the possibility of smog was suspected, while all the above etiological diagnoses required cranial DSA to confirm the diagnosis. It was decided that the patient should undergo a cranial DSA examination, and the results showed that the right internal carotid artery was occluded, with a smoky proliferation of vessels in the occluded area, and the blood was supplied by the left side through the anterior traffic, confirming the diagnosis of smog as the first case in our hospital. The cause of the patient’s disease was clear, and the patient’s condition improved significantly after being given intensive cerebrovascular medication and rehabilitation treatment. The patient and his family are satisfied with the outcome.