The principle underlying reasons of dementia and it's miles very tough to apply them in each day clinical paintings. Therefore, it's far very critical to identify disease-precise signs and symptoms from an in depth history taking and clinical examination of the patient after effectively know-how the pathology of every disease as a way to make a complete analysis with the help of imaging exams and other modalities. The differential diagnoses of dementia and comparable conditions, specially senile depression and delirium, are defined first, accompanied by means of the diagnostic steps on the premise of symptomatology and outlined the underlying causes of dementia. Subsequently, the symptomatology of Alzheimer’s disorder (AD) is discussed in element, as accurate diagnosis of AD is the basis of dementia prognosis and AD money owed for approximately half of all dementia instances. As for causes of dementia other than AD, crucial factors for differential analysis,in particular with reference to AD, are also noted.