Because there are many diseases that present similarly to dementia and hundreds of causes of dementia, a thorough examination is required if dementia is suspected in the elderly. In addition to a detailed history with the doctor, a neurological and psychiatric examination is necessary, and a thorough medical examination can help rule out other physical illnesses. Therefore, the doctor may recommend one or more of the following ancillary tests: 1. Laboratory tests: mainly thyroid function, folic acid and vitamin B12, blood count, liver and kidney function, blood sugar, electrolytes, etc. 2.Electroencephalogram. 3, neuroimaging: brain CT helps to differentiate dementia from normal brain aging, and can exclude organic encephalopathy due to hydrocephalus, chronic subdural hematoma, brain tumor and cerebral infarction. Cranial MRI is more sensitive to subtle changes in brain tissue, which can improve the specificity of etiological diagnosis and help to diagnose the etiology and monitor the progress of the disease. 4. Neuropsychological assessment can help in the diagnosis and identification of dementia. Commonly used are the Simple Mental State Examination Scale, the Wechsler Adult Intelligence Scale, and the Clinical Dementia Rating Scale. Therefore, it is really not an easy task to determine whether dementia is present and to figure out its specific etiology, and it even requires a period of observation before valuable clues can be found. However, most patients are able to reach a scientific judgment as long as they receive the relevant tests as recommended by their specialist.