Cerebral atrophy is a chronic progressive disease in which brain tissue shrinks in size and cell number decreases due to multiple causes. There are three major syndromes, including intellectual changes, neurological changes and motor dysfunction. Clinical manifestations include memory loss, emotional instability, reduced thinking ability, inattention, and eventual intellectual loss and paralysis. Adult onset of the disease: mostly occurs above the age of 50 years, the course of the disease can reach several years to decades, more men than women. There are diffuse brain atrophy including cortical atrophy, cerebellar atrophy and atrophy of the cortex, cerebellum and brainstem; and limited brain atrophy, mostly seen after limited organic brain lesions such as trauma, vascular disease, and intracranial limited infection. Because of its complex etiology, slow onset, not easily detected, long course, slow progress, and may gradually aggravate, affecting the normal life and work of patients. Brain atrophy was originally named after the use of imaging in clinical practice, when brain tissue volume reduction and ventricular enlargement were found during CT or MRI examinations, etc. Therefore, brain atrophy is an imaging manifestation of many diseases.