<unk>  manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively impact a person's ability to function and carry out everyday activities. Aside from memory impairment and a disruption in thought patterns, the most common symptoms include emotional problems, difficulties with language, and decreased motivation. The symptoms may be described as occurring in a continuum over several stages. Consciousness is not affected.<unk>  ultimately has a significant effect on the individual, caregivers, and relationships in general. A diagnosis of<unk>  requires a change from a person's usual mental functioning and a greater cognitive decline than what is caused by normal aging. Several diseases and injuries to the brain, such as a stroke, can give rise to<unk> . However, the most common cause is Alzheimer's disease, a neurodegenerative disorder. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), has re-described<unk>  as a major neurocognitive disorder with varying degrees of severity and many causative subtypes. The International Classification of Diseases (ICD-11) also classes<unk>  as a neurocognitive disorder with many forms or subclasses.<unk>  is listed as an acquired brain syndrome, marked by a decline in cognitive functions, and is contrasted with neurodevelopmental disorders. Causative subtypes of<unk>  may be based on a known potential cause such as Parkinson's disease, for Parkinson's disease<unk> ; Huntington's disease for Huntington's disease<unk> ; vascular disease for vascular<unk> ; brain injury including stroke often results in vascular<unk> ; or many other medical conditions including HIV infection for HIV<unk> ; and prion diseases. Subtypes may be based on various symptoms possibly due to a neurodegenerative disorder such as Alzheimer's disease; frontotemporal lobar degeneration for frontotemporal<unk> ; or Lewy body disease for<unk>  with Lewy bodies. More than one type of<unk> , known as mixed<unk> , may exist together. Diagnosis is usually based on history of the illness and cognitive testing with imaging. Blood tests may be taken to rule out other possible causes that may be reversible such as an underactive thyroid, and to determine the subtype. One commonly used cognitive test is the Mini-Mental State Examination. The greatest risk factor for developing<unk>  is aging, however<unk>  is not a normal part of aging. Several risk factors for<unk> , such as smoking and obesity, are preventable by lifestyle changes. Screening the general older population for the disorder is not seen to affect the outcome. There is no known cure for<unk> . Acetylcholinesterase inhibitors such as donepezil are often used and may be beneficial in mild to moderate disorder. The overall benefit, however, may be minor. There are many measures that can improve the quality of life of people with<unk>  and their caregivers. Cognitive and behavioral interventions may be appropriate.
Dementia
Delirium
Pseudodementia
Procidentia
Hypothyroidism
Subcortical dementia
Anti-Hu associated encephalitis
Vascular dementia