There are many manifestations of what we normally call “confusion”, all of which fall within the scope of mental disorders. Human mental activities are very complex, including sensation, perception, language, thinking, memory, intelligence, emotion, behavior and other aspects. Mental activity is a unique function of the brain, and like various nerve centers, mental activity also has its own central site, which is generally located in the deep part of the brain and involves many structures such as the temporal lobe and the thalamus. These areas are mainly supplied with blood by the posterior cerebral artery of the basilar artery system, and if an ischemic or hemorrhagic lesion involving the above structures occurs, a mental disorder can suddenly appear. The most common clinical condition is memory loss and confusion caused by ischemia of the posterior cerebral artery, which leads to damage to the medial temporal lobe or medial thalamus, and in severe cases, dementia. Memory loss is the most common symptom of “confusion”, especially near memory loss. Patients often have trouble remembering what just happened, and may also have partial loss of memories that have been retained, called amnesia. Patients with amnesia alone may be otherwise completely normal and concerned about their situation. However, patients with psychotic disorders are more severe, as they may not recognize friends or relatives, may not be able to find their homes after going out, may talk to themselves, say inexplicable things, or act in a purposeless manner, and are often indifferent to their situation. If the patient has a general decline in intelligence on examination, it is called dementia. Most strokes have an acute onset, so the symptoms of stroke, which are manifested by “confusion”, occur suddenly. Other causes of memory loss, mental confusion or dementia may also occur more quickly, such as encephalitis and traumatic brain injury, so it is important to pay attention to the difference. Some of the sudden “confusion” after a stroke is transient, for example, transient ischemic attacks can cause temporary general amnesia that can be recovered in a few hours. However, if lasting damage occurs, full recovery of mental or memory impairment is difficult.