The reasons for sudden memory loss are as follows: 1. If the patient is a middle-aged or elderly person, he or she should consider cerebrovascular disease, such as infarction of the temporal lobe, frontal lobe, and hippocampus, which can lead to serious memory loss. The patient may also be accompanied by mental and behavioral abnormalities, which can be clarified by doing magnetic resonance brain function imaging, and then give the patient symptomatic treatment.2. Patients with sudden memory loss should pay attention to whether it is caused by autoimmune encephalitis, if the patient is accompanied by symptoms such as inflexible limb movement and headache, etc..3. Patients with sudden memory loss should also pay attention to whether it is caused by exposure to chemical toxins, such as brain poisoning. For example, the occurrence of brain poisoning and other problems.