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The most common symptoms of AD include cognitive deficits and functional impairments. These deficits progress over time and eventually result in loss of activities of daily living, frequently necessitating admission to nursing homes and leading to eventual death. The majority of patients with AD initially present with slowly progressive memory impairments; however, in up to 40% patients the initial presentation might involve nonmemory symptoms like language impairments, symptoms of depression, personality changes, extrapyramidal manifestations, and visuospatial deficits. These patients are very likely to be misdiagnosed and require comprehensive evaluation by a physician with special expertise in dementia.
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Typical Clinical Presentation of AD
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Slowly progressive memory loss for recent events is the most common clinical presentation of AD. Patients with AD frequently have problems remembering recent conversations, dates, appointments, and may misplace items at home. Many patients are not aware of these deficits and are brought to medical attention by their family members or friends. The memory deficits of AD are generally differentiated from those caused by normal aging by the fact that these deficits are progressive and interfere with daily living activities. Cognitive changes associated with healthy aging, although frustrating, are caused by age-associated decline in mental processing speed and difficulty learning new material. However, these changes are not associated with alterations in day-to-day function. Memory loss leading to a change in functional status is not a part of normal aging and warrants further evaluation.
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The second most common clinical presentation of AD is impairment in language function. Seen in up to 40% to 50% patients, these impairments generally start with word-finding problems followed by paraphasic errors and circumlocution. These initial deficits lead to expressive aphasia accompanied later with receptive and global aphasia. Unfortunately, given the impairments in communication, patients with AD having significant language impairments generally progress rapidly and have a poor prognosis.
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Impairments in executive function are common early deficits in AD, leading to poor judgment, organization, reasoning and abstract thinking, and resulting in inability to complete complex demanding tasks. Deficits in concentration and attention are other common symptoms seen in patients with AD. These impairments lead to tangential tendencies, disorientation, and an inability to successfully complete daily tasks. Persons exhibiting deficits in visuospatial abilities may have problems with driving, dressing, using eating utensils, and walking.
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As the disease progresses, changes in personality are commonly seen in patients with AD and may include increased passivity, lack of interest, restlessness, and overactivity. More than 30% of persons with AD develop symptoms of depression, which may be the first clinical presentation of the disease. Early signs of depression in patients with AD include changes in behavior, loss of appetite, alterations in sleep, social withdrawal, and a decline in physical function. Sundowning, or worsening of behavior and cognitive symptoms in the evening, is also common in patients with AD and may be because of changes in circadian rhythm from loss of sunlight.
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In the later stages of the disease, individuals may have increased confusion, dysphagia, poor gait, and repeated falls. In some patients with AD, disruptive behaviors may increase with aggression, agitation, and physical or verbal hostility; in others, these behavioral symptoms lessen with disease progression. The majority of patients become increasingly frail and dependent for self-care and activities of daily living with many patients developing bowel and bladder incontinence. Persons in the late stages of AD may become immobile and bed-bound, which increases their risk of developing pressure sores, malnutrition, and dehydration. The most common causes of death in patients with AD include pneumonia, urinary sepsis, dehydration, pressure sores, fractures, and malnutrition. The median survival period from the time of diagnosis to death generally varies between 8 and 10 years, although some patients, especially those with FAD, die earlier.
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Atypical Clinical Presentations of Alzheimer's Disease
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It is widely reported that between 20% and 40% of patients with AD will initially present with atypical features of the disease. Unfortunately, these patients are commonly misdiagnosed with either a personality or related disorder, and may need to be evaluated by a specialist. As noted earlier, one of the common atypical presentations of AD is impairment in language. These patients are frequently misdiagnosed as having suffered a stroke. The other atypical presentation of AD includes prominent extrapyramidal manifestations. Between 5% and 10% of patients with AD might initially present with features resembling Parkinson disease, consisting of mild rigidity of extremities, hypokinesia, and expressionless face. However, these patients generally do not present with the classical Parkinsonian tremors and do not respond well to dopaminergic drugs. Another atypical feature of AD, seen in approximately 10% patients with AD, includes symptoms of behavioral disinhibition. These patients may make socially unacceptable remarks, become increasingly difficult to live or work with, and may be misdiagnosed with a personality disorder. Finally, less than 5% patients with AD present with symptoms of Balint syndrome, consisting of visual agnosia and ataxia, and complaints of inability to see.
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Overall, it is important to recognize that AD can present itself with varied clinical features, and while memory impairment is a critical component of the disease, it is not the only clinical manifestation. Atypical clinical presentations of AD are common and should be evaluated by a physician with special expertise in dementia. Clearly, a misdiagnosis of AD has major serious adverse consequences including emotional, occupational, social, and financial.