neurologic disorders
Dementia
Diagnosis of Dementia
Differentiation of delirium from dementia by history and neurologic examination (including mental status) Identification of treatable causes clinically and by laboratory testing and neuroimaging Sometimes formal neuropsychologic testing Recommendations about diagnosis of dementia are available from theAmerican Academy of Neurology(see alsoThe diagnosis of dementia due to Alzheimer’s disease). Distinguishing type or cause of dementia can be difficult; definitive diagnosis often requires postmortem pathologic examination of brain tissue. Thus, clinical diagnosis focuses on distinguishing dementia from delirium and other disorders and identifying the cerebral areas affected and potentially reversible causes. Dementia must be distinguished from the following: Delirium : Age-associated memory impairment:Memory impairment does not affect daily functioning. If affected people are given enough time to learn new information, their intellectual performance is good. Mild cognitive impairment:Memory and/or other cognitive functions are impaired, but impairment is not severe enough to interfere with daily activities. Cognitive symptoms related to depression:This cognitive disturbance resolves with treatment of depression. Depressed older patients may experience cognitive decline, but unlike patients with dementia, they tend to exaggerate their memory loss and rarely forget important current events or personal matters. Neurologic examinations are normal except for signs of psychomotor slowing. When tested, patients with depression make little effort to respond, but those with dementia often try hard but respond incorrectly. When depression and dementia coexist, treating depression does not fully restore cognition. The National Institute on Aging–Alzheimer's Associationdiagnostic guidelinesspecify that a general diagnosis of dementia requires all of the following: Cognitive or behavioral (neuropsychiatric) symptoms interfere with the ability to function at work or do usual daily activities. These symptoms represent a decline from previous levels of functioning. These symptoms are not explained by delirium or a major psychiatric disorder. The cognitive or behavioral impairment should be diagnosed based on a combination of history from the patient and from someone who knows the patient plus assessment of cognitive function (a bedside mental status examination or, if bedside testing is inconclusive, formal neuropsychologic testing). In addition, the impairment should involve ≥ 2 of the following domains: Impaired ability to acquire and remember new information (eg, asking repetitive questions, frequently misplacing objects or forgetting appointments) Impaired reasoning and handling of complex tasks and poor judgment (eg, being unable to manage a bank account, making poor financial decisions) Language dysfunction (eg, difficulty thinking of common words, errors speaking and/or writing) Visuospatial dysfunction (eg, inability to recognize faces or common objects) Changes in personality, behavior, or comportment If cognitive impairment is confirmed, history and physical examination should then focus on signs of treatable disorders that cause cognitive impairment (eg, Vitamin B12 Deficiency , (see sidebar Examination of Mental Status ) or the Neuropsychologic testingshould be done when history and bedside mental status testing are not conclusive. It evaluates mood as well as multiple cognitive domains. It takes 1 to 3 hours to complete and is done or supervised by a neuropsychologist. Such testing helps primarily in differentiating the following: Age-associated memory impairment, mild cognitive impairment, and dementia, particularly when cognition is only slightly impaired or when the patient or family members are anxious for reassurance Dementia and focal syndromes of cognitive impairment (eg, amnesia, aphasia, apraxia, visuospatial difficulties, impairment of executive function) when the distinction is not clinically evident Testing may also help characterize specific deficits due to dementia, and it may detect depression or a personality disorder that is contributing to poor cognitive performance. Tests should include thyroid-stimulating hormone and vitamin B12 levels. Routine complete blood count (CBC), kidney and liver function tests are sometimes recommended, but yield is very low. If clinical findings suggest a specific disorder, other tests (eg, for HIV or syphilis) are indicated. Lumbar puncture should be considered if a chronic infection or neurosyphilis is suspected or if prion disease or an autoimmune disorder is suspected in patients with rapidly progressive dementia. Other tests may be used to exclude causes of delirium. Biomarkers for Alzheimer disease can be useful in research settings but are not yet routine in clinical practice. For example, in the cerebrospinal fluid (CSF), the tau level increases and beta-amyloid decreases as Alzheimer disease progresses. Also, for people with two epsilon-4 alleles of theapolipoprotein E4gene, the risk of developing Alzheimer disease by age 75 is 10 to 30 times greater than that for people without the allele. However, routine genetic testing for the apolipoprotein E4 allele (apo epsilon-4) is not recommended, because the E4 allele is neither necessary nor sufficient to cause Alzheimer disease and because currently, no treatment can prevent or slow the progression of Alzheimer disease. should be done in the initial evaluation of dementia and after any unexplained change in cognition or mental status. Neuroimaging can identify potentially reversible structural disorders (eg, Normal–Pressure Hydrocephalus , Occasionally, electroencephalography (EEG) is useful (eg, to evaluate episodic lapses in attention or bizarre behavior). PET with fluorine-18 (18F)–labeled deoxyglucose (fluorodeoxyglucose, or FDG) or single-photon emission CT (SPECT) can provide information about cerebral perfusion patterns and help with differential diagnosis (eg, in differentiating Alzheimer disease from frontotemporal dementia and dementia with Lewy bodies). Amyloid radioactive tracers that bind specifically to beta-amyloid plaques (eg, fluorine-18 [18F] florbetapir, [18F] flutemetamol, [18F] florbetaben) have been used with positron emission tomography (PET) to image amyloid plaques in patients with mild cognitive impairment or dementia. This testing should be used when the cause of cognitive impairment (eg, mild cognitive impairment or dementia) is uncertain after a comprehensive evaluation and when Alzheimer disease is a diagnostic consideration. Determining amyloid status via PET is expected to increase the certainty of diagnosis and management. [18F] flortaucipir-PET, using a tau radioactive tracer, can be used to estimate the density and distribution of aggregated tau neurofibrillary tangles in adults who have cognitive impairment and are being evaluated for Alzheimer disease ( Diagnosis reference ). 1.Fleisher AS, Pontecorvo MJ, Devous Sr MD, et al: Positron emission tomography imaging with [18F] flortaucipir and postmortem assessment of Alzheimer disease neuropathologic changes.JAMANeurol. Published online April 27, 2020. doi:10.1001/jamaneurol.2020.0528 