Progressive Amnestic Dementia Probable Alzheimers Disease

The most common pattern is a progressive amnestic dementia, in which deterioration in memory functions is the salient feature. The course is insidiously progressive, with memory impairments usually being the initial source of disruption of daily activities. Informants often provide a history of progressive problems with recalling recent events, misplacing objects, repeating questions, becoming disoriented or lost, producing the wrong words, or exhibiting fluent but "empty" speech. Early on, there may be subtle changes in personality in the form of increased disengagement or withdrawal from activities, but grossly inappropriate behaviors are unusual (81,82).

On mental state testing, the dominant problems involve the storage, retention or retrieval components of memory. Language and visuospatial functions also are usually abnormal and over time insight, attention and executive functions deteriorate. Atrophic changes on CT or MRI are most common. When functional imaging is done, the most likely pattern reflects abnormalities in temporoparietal regions bilaterally.

This dementia profile is the most frequent one seen in the elderly and is most often associated with the plaque and tangle pathology of Alzheimer's disease. The National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRA) (10) has codified the clinical criteria associated with the high likelihood of Alzheimer's pathology (Table 3). The major elements defining "probable Alzheimer's disease" (PrAD) include:

1. Presence of dementia

2. Progressive worsening of memory and other cognitive functions

3. Deficits in two or more areas of cognition

4. No disturbance of consciousness

5. Age of onset between 40 and 90

6. Absence of systemic or CNS disorders that could account for the dementia

The diagnosis of "possible Alzheimer's disease" is appropriate when a patient exhibits an atypical presentation or clinical course, progressive decline of a single cognitive deficit, or in the presence of a second systemic or brain disorder sufficient to produce the dementia that is not considered to be the cause of the dementia. "Definite Alzheimer's disease" can only be diagnosed when in life the patient had met criteria for probable Alzheimer's disease and at autopsy (or by biopsy) there is appropriate histopathological evidence of Alzheimer's pathology. DSM-IV criteria for "dementia of the Alzheimer's type" (DAT) are simi-

lar to the NINCDS-ADRDA criteria. First, one needs to ensure that a patient fits the criteria for dementia as noted on Table 1. Furthermore, according to DSM-IV, the course of DAT is characterized by gradual onset, continuing cognitive decline, and is not due to other CNS or systemic conditions that cause progressive deficits in memory and cognition (Table 4).

Other degenerative diseases that have been associated with a progressive amnestic dementia include diffuse Lewy body disease, Pick's disease, and focal neuronal atrophy (34,83-85). However, these pathological processes are much less common than Alzheimer's disease. In addition, there are a number of nondegenerative processes that have been associated with the "amnestic syndrome." Most often, however, these are not progressive processes. They include anoxia, carbon monoxide poisoning, posterior cerebral artery strokes, anterior cerebral artery aneurysm with bleed or surgery, Korsakoff's syndrome, head trauma, and herpes encephalitis.

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