neurologic disorders
Alzheimer Disease
Diagnosis of Alzheimer Disease
Similar to that of other dementias Formal mental status examination History and physical examination Laboratory testing Neuroimaging Generally, diagnosis of Alzheimer disease is similar to the Diagnosis . However, despite clinical and specific laboratory and imaging characteristics, definitive diagnosis of Alzheimer disease can only be confirmed by histologic evaluation of brain tissue. Recommendations about diagnosis of dementia, including Alzheimer's disease, are available from theNational Institute for Health and Care Excellence. Evaluation includes a thorough history and standard neurologic examination. Clinical criteria are 85% accurate in establishing the diagnosis and differentiating Alzheimer disease from other forms of dementia, such as Vascular Cognitive Impairment and Dementia and Traditional diagnostic criteria for Alzheimer disease include all of the following: Dementia established clinically and documented by a formal mental status examination Deficits in≥2 areas of cognition Gradual onset (ie, over months to years, rather than days or weeks) and progressive worsening of memory and other cognitive functions No disturbance of consciousness Onset after age 40, most often after age 65 No systemic or brain disorders (eg, tumor, stroke) that could account for the progressive deficits in memory and cognition However, deviations from these criteria do not exclude a diagnosis of Alzheimer disease, particularly because patients may have mixed dementia. The 2011 National Institute on Aging–Alzheimer's Association diagnostic guidelines ( Diagnosis references , A low level of beta-amyloid in cerebrospinal fluid (CSF) Beta-amyloid deposits in the brain detected by positron emission tomography (PET) imaging using radioactive tracer that binds specifically to beta-amyloid plaques (eg, Pittsburgh compound B [PiB], florbetapir) Other biomarkers indicate downstream neuronal degeneration or injury: Elevated levels of tau protein in CSF or tau deposits in the brain detected by PET imaging using radioactive tracer that binds specifically to tau Decreased cerebral metabolism in the temporoparietal cortex measured using PET with fluorine-18 (18F)–labeled deoxyglucose (fluorodeoxyglucose, or FDG) Local atrophy in the medial, basal, and lateral temporal lobes and the medial parietal cortex, detected by MRI These findings increase the probability that dementia is due to Alzheimer disease. However, the guidelines ( Diagnosis references , Laboratory tests (eg, thyroid-stimulating hormone, vitamin B12 levels) and neuroimaging (MRI or CT) are done to check for other, treatable causes of dementia and disorders that can worsen symptoms. If clinical findings suggest another underlying disorder (eg, HIV, syphilis), tests for those disorders are indicated. Distinguishing Alzheimer disease from other dementias is difficult. The Modified Hachinski Ischemic Score is sometimes used to help distinguish Vascular Cognitive Impairment and Dementia from Alzheimer disease; it has limited clinical usefulness, but it is helpful when neuroimaging is not available ( Patients with Alzheimer disease are often better-groomed and neater than patients with other dementias. 