PET scan of the brain of a person with<unk>  showing a loss of function in the temporal lobe<unk>  is usually diagnosed based on the person's medical history, history from relatives, and behavioral observations. The presence of characteristic neurological and neuropsychological features and the absence of alternative conditions supports the diagnosis.<unk> vanced medical imaging with computed tomography (CT) or magnetic resonance imaging (MRI), and with single-photon emission computed tomography (SPECT) or positron emission tomography (PET), can be used to help exclude other cerebral pathology or subtypes of dementia. Moreover, it may predict conversion from prodromal stages (mild cognitive impairment) to<unk> . FDA-approved radiopharmaceutical diagnostic agents used in PET for<unk>  are florbetapir (2012), flutemetamol (2013), florbetaben (2014), and flortaucipir (2020). Because many insurance companies in the United States do not cover this procedure, its use in clinical practice is largely limited to clinical trials as of 2018. Assessment of intellectual functioning including memory testing can further characterise the state of the disease. Medical organizations have created diagnostic criteria to ease and standardise the diagnostic process for practising physicians. Definitive diagnosis can only be confirmed with post-mortem evaluations when brain material is available and can be examined histologically for senile plaques and neurofibrillary tangles. Criteria There are three sets of criteria for the clinical diagnoses of the spectrum of<unk> : the 2013 fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5); the National Institute on Aging-Alzheimer's Association (NIA-AA) definition as revised in 2011; and the International Working Group criteria as revised in 2010. Three broad time periods, which can span decades, define the progression of<unk>  from the preclinical phase, to mild cognitive impairment (MCI), followed by<unk>  dementia. Eight intellectual domains are most commonly impaired in<unk> —memory, language, perceptual skills, attention, motor skills, orientation, problem solving and executive functional abilities, as listed in the fourth text revision of the DSM (DSM-IV-TR). The DSM-5 defines criteria for probable or possible<unk> 's for both major and mild neurocognitive disorder. Major or mild neurocognitive disorder must be present along with at least one cognitive deficit for a diagnosis of either probable or possible<unk> . For major neurocognitive disorder due to<unk> , probable<unk>  can be diagnosed if the individual has genetic evidence of<unk> 's or if two or more acquired cognitive deficits, and a functional disability that is not from another disorder, are present. Otherwise, possible<unk>  can be diagnosed as the diagnosis follows an atypical route. For mild neurocognitive disorder due to<unk> 's, probable<unk>  can be diagnosed if there is genetic evidence, whereas possible<unk>  can be met if all of the following are present: no genetic evidence, decline in both learning and memory, two or more cognitive deficits, and a functional disability not from another disorder. The NIA-AA criteria are used mainly in research rather than in clinical assessments. They define<unk>  through three major stages: preclinical, mild cognitive impairment (MCI), and<unk> 's dementia. Diagnosis in the preclinical stage is complex and focuses on asymptomatic individuals; the latter two stages describe individuals experiencing symptoms. The core clinical criteria for MCI is used along with identification of biomarkers, predominantly those for neuronal injury (mainly tau-related) and amyloid beta deposition. The core clinical criteria itself rests on the presence of cognitive impairment without the presence of comorbidities. The third stage is divided into probable and possible<unk>  dementia. In probable<unk>  dementia there is steady impairment of cognition over time and a memory-related or non-memory-related cognitive dysfunction. In possible<unk>  dementia, another causal disease such as cerebrovascular disease is present. Techniques Cognitive tests such as the Mini–Mental State Examination (MMSE) can help in the diagnosis of<unk> . In this test instructions are given to copy drawings like the one shown, remember some words, read, and subtract numbers serially. Neuropsychological tests including cognitive tests such as the Mini–Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) and the Mini-Cog are widely used to aid in diagnosis of the cognitive impairments in<unk> . These tests may not always be accurate, as they lack sensitivity to mild cognitive impairment, and can be biased by language or attention problems; more comprehensive test arrays are necessary for high reliability of results, particularly in the earliest stages of the disease. Further neurological examinations are crucial in the differential diagnosis of<unk>  and other diseases. Interviews with family members are used in assessment; caregivers can supply important information on daily living abilities and on the decrease in the person's mental function. A caregiver's viewpoint is particularly important, since a person with<unk>  is commonly unaware of their deficits. Many times, families have difficulties in the detection of initial dementia symptoms and may not communicate accurate information to a physician. Supplemental testing can rule out other potentially treatable diagnoses and help avoid misdiagnoses. Common supplemental tests include blood tests, thyroid function tests, as well as tests to assess vitamin B12 levels, rule out neurosyphilis and rule out metabolic problems (including tests for kidney function, electrolyte levels and for diabetes). MRI or CT scans might also be used to rule out other potential causes of the symptoms – including tumors or strokes. Delirium and depression can be common among individuals and are important to rule out. Psychological tests for depression are used, since depression can either be concurrent with<unk>  (see Depression of<unk>  disease), an early sign of cognitive impairment, or even the cause. Due to low accuracy, the C-PIB-PET scan is not recommended as an early diagnostic tool or for predicting the development of<unk>  when people show signs of mild cognitive impairment (MCI). The use of 18F-FDG PET scans, as a single test, to identify people who may develop<unk>  is not supported by evidence.
Alzheimer's disease
Lewy body dementias
Parkinson's disease dementia
Down syndrome
Vascular dementia
Aging brain
Alcohol-related dementia
Chronic traumatic encephalopathy