Alzheimer's disease overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
|
Alzheimer's disease Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Alzheimer's disease overview On the Web |
|
American Roentgen Ray Society Images of Alzheimer's disease overview |
|
Risk calculators and risk factors for Alzheimer's disease overview |
Overview
Alzheimer's disease is the most common cause of dementia among older people. Dementia is a loss of thinking, remembering, and reasoning skills that interferes with a person's daily life and activities. Other causes of dementia include blood vessel disease in the brain (called vascular dementia), Parkinson's disease, frontotemporal dementia, and Lewy body dementia.
Historical Perspective
The first case of Alzheimer's disease was described by a German psychiatrist named Alöis Alzheimer in the year 1901. For many decades after Alzheimer's original description, there was little progress in defining the pathogenesis of AD occurred. In the mid 1970's, it was found that the levels of acetylcholine decrease in brains of individuals undergoing neurodegeneration due to Alzheimer's disease. In early 1980's major advances in biochemistry and molecular genetics allowed the use of compositional analyses and immunocytochemistry to explain the structure of tangles and plaques found in the brains of Alzheimer patients. The term Alzheimer's disease was subsequently formally adopted in medical nomenclature to describe individuals of all ages with a characteristic common symptom pattern, disease course, and neuropathology.
Classification
Alzheimer's disease may be classified according to severity into mild, moderate and severe dementia. It may also be classified based on age of onset into early onset and late onset Alzheimer's disease. Another method of classification of Alzheimer's disease is based on the course of disease into pre-dementia, early dementia, moderate dementia and advanced dementia.
Pathophysiology
Alzheimer disease (AD), is a progressive neurodegenerative disorder. The dysfunction of amyloid precursor protien (APP) metabolism and the resulting build up of of Aβ peptides and their aggregation in the form of senile plaques in the brain parenchyma of individuals have been considered pivotal for neurodegeneration in the disease. Cognitive impairment in patients with AD is closely associated with synaptic loss in the neocortex and limbic system. In familial forms of AD, mutations result in an increased Aβ production or aggregation, in sporadic AD, failure of the clearance mechanisms might play a key role. Loss of mature neurons and alterations in neural progenitor cells (NPCs) in areas such as the dentate gyrus (DG) of the hippocampus have been found to be responsible for manifestations of AD. On gross pathology, temporal atrophy (hippocampus in particular), dilation of lateral ventricles and third ventricle are characteristic findings of Alzheimer's disease. The microscopic histopathological features of alzheimer's disease consist neurofibrillary tangles, senile plaques, neuronal loss, and with or without cerebral amyloid angiopathy.
Causes
Differentiating alzheimer's disease from Other Diseases
Epidemiology and Demographics
Alzheimer's disease is the most frequently observed form of dementia, and it typically develops in elderly patients.
Risk Factors
Screening
Natural History, Complications, and Prognosis
Alzheimer's disease (AD) is a slow-progressing condition that involves complications such as the inability to take care of oneself. There is no cure for Alzheimer's disease; patients typically pass away from a cause associated with the condition.
Diagnosis
Diagnostic Criteria
The diagnosis of Alzheimer's disease (AD) is made on the basis of clinical criteria described by either the National Institute on Aging and the Alzheimer's Association (NIA-AA) or DSM-V (Diagnostic and Statistical Manual of Mental Disorders, fifth edition). Histopathologic examination for diagnosis of Alzheimer's disease is rarely done. Elderly patients presenting with progressive decline in memory and other cognitive impairments such as aphasia, agnosia or apraxia should be suspected for Alzheimer's disease. In these patients, mental status examination (MSE) and neuropsychological testing should be performed to further evaluate the status of cognitive abilities. Laboratory investigation are not required to diagnose Alzheimer's and are done to exclude other conditions which may present with similar symptoms as seen in Alzheimer's disease (such as vit B12 deficiency, syphilis, or tuberculosis). Patients with atypical clinical presentation may also be tested for biomarkers such as Aβ and total and phosphorylated Tau protein.
History and Symptoms
Although each patient experiences Alzheimer's in a unique way, there are many common symptoms.[1] The earliest observable symptoms are often mistaken for normal effects of aging or manifestations of stress.
Physical Examination
When a doctor or physician has been notified, and AD is suspected, the diagnosis is usually further supported by behavioral assessments and cognitive tests, often followed by a brain scan if available.
Laboratory Findings
There are no specific diagnostic laboratory findings associated with Alzheimer's disease. However, laboratory findings are done to rule out other conditions which may mimic Alzheimer's disease symptoms. These include CSF analysisfor Aβ 2 and tau protein, [14-3-3 protein]], vitamin B12 levels, thyroid hormones, electrolytes, HIV serology, complete blood count, blood glucose, renal function test, liver function test, and urine screen for drug abuse.