1, concept: is a group of primary degenerative brain degenerative diseases of unknown etiology, a large number of primary dementia occurring in old age and pre-geriatric (40-65 years old), latent onset, slow and irreversible course, clinical manifestations are mainly intelligent damage, the onset of the disease before the age of 65 years old old old called pre-geriatric dementia, or progeria, more family history of the same disease, faster development of lesions, temporal lobe and parietal lobe lesions are more significant. There is often aphasia and loss of use. In the old age, it is called Alzheimer’s disease old age type. 2, the pathological changes of Alzheimer’s disease are mainly: brain atrophy, the most significant in the parietal and temporal lobes, especially the hippocampus damage is the most serious; there is a widening of the cerebral sulcus and enlargement of the ventricles. Microscopically, the brain cortical neuronal cells are reduced, stellate cells are proliferated, and silverophilic staining reveals age spots and neuronal fiber tangles, which are characteristic changes of the disease. Clinical manifestations: The disease generally starts slowly, with a persistent and progressive course without remission, and lasts for an average of about 8-10 years from onset to death, but in some patients the disease can last for 15 years or more. The clinical course of AD is roughly divided into 3 stages: Stage 1 (1-3 years): the mild dementia stage. Initially, amnesia is manifested, especially near event amnesia; the symptoms are mild and often do not attract the attention of others. However, it can be combined with other physical illnesses and suddenly intensify, and acute delirium of consciousness (called senile delirium) appears. Early personality changes are prominent, with patients becoming stubborn, selfish, suspicious, depressed, euphoric, apathetic, or emotionally unstable. There may be fragmentary hallucinations or delusions. Delusions of jealousy may be one of the early manifestations; delusions of hypochondria, poverty, exaggeration or persecution may also be present. Patients have poor sleep and often get up at night to move around. Stage 2 (2-10 years): A moderate stage of dementia. It shows severe impairment of distant and near memory, and its memory impairment and intellectual impairment progressively increase, and there may be memory misconstruction or fiction. Patients have poor simple structured visual-spatial ability, time and place orientation disorder; they are unable to perform outdoor activities independently, and need help in dressing, personal hygiene and maintaining personal appearance; they have significantly reduced intellectual activities such as comprehension, judgment and calculation, vague pronunciation, garbled speech, childish emotions, absurd behavior, inordinate eating, often collect scraps as treasures, and become disoriented when they go out, followed by speech dysfunction, naming The next stage is the emergence of speech dysfunction, naming, loss of recognition, and loss of use. The third stage (8-12 years): the stage of severe dementia. It is a comprehensive dementia state and motor system disorder. In the late stage, the patient is bedridden, mumbling, and eventually aphasic, groping with hands aimlessly, unable to take care of personal life, incontinence, tonic and flexed body position, primitive reflexes such as strong grip, sucking reflex, etc., and eventually dies of infection or failure. The course of the disease is progressive, with death occurring on average 4 to 5 years after the onset of the disease; there are also cases that develop faster or up to 10 years. The prognosis is worse in cases with parietal symptoms. 4.Treatment: Improve cognitive dysfunction: commonly used cholinesterase inhibitors such as Anlisin and Staphylococcus aureus can improve patients’ memory. Non-pharmacological treatment and pharmacological treatment of psychiatric-behavioral symptoms: The principle of treatment is to improve the patient’s quality of life and to reduce the burden that patients bring to their families. Antipsychotic drugs can be used to counteract psychotic symptoms, agitated behavior or aggressive behavior. Antidepressants can be used in patients with dementia accompanied by depression and can significantly improve the dementia syndrome.