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Dementia and Cognitive Disorders

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A 75-year-old woman with suspected normal-pressure hydrocephalus undergoes lumbar puncture. Forty milliliters of fluid are removed. Three hours later, she is able to walk unassisted and turns well. Spinal fluid would be expected to show which of the following?

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a. No abnormalities

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b. Elevated protein

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c. Low protein

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d. Atypical lymphocytes

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e. Low glucose

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The answer is a. The CSF in patients with normal-pressure hydrocephalus (NPH) is typically normal. Abnormalities in protein or cellularity should suggest an alternative diagnosis. The pressure of the CSF is also usually normal, although studies using long-term pressure monitoring in these patients have shown that they have periods of pressure elevation, often at night.

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A physician believes that her patient has Alzheimer disease. Which of the following is most characteristic of the brain in patients with Alzheimer disease?

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a. Neuronal loss in the cerebral cortex

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b. Demyelination in the cerebral cortex

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c. Posterior column degeneration

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d. Neuronal loss in the cerebellar cortex

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e. Pigmentary degeneration in the hippocampus

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The answer is a. The most prominent characteristics of Alzheimer disease are neuronal loss, fibrillary tangles, loss of synapses, and amyloid (or neuritic) plaque formation. These histopathologic features are evident throughout the cerebral cortex, but the neurofibrillary tangles and neuronal loss are most prominent in the hippocampus and adjacent structures of the temporal lobe. The tangles and loss of synapses are most closely linked to the development of dementia. The cell loss may be so substantial that the patient develops marked compensatory enlargement of the ventricles, a condition called hydrocephalus ex vacuo.

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An 80-year-old man has had a gradual memory decline over the past 10 years. A reversible cause of dementia cannot be found, and positron emission tomography scan supports the diagnosis of Alzheimer disease. In the dementia associated with Alzheimer disease, the electroencephalography (EEG) will usually show which of the following?

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a. Spike-and-wave discharges

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b. Periodic frontal lobe discharges

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c. Focal slowing

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d. Generalized background slowing

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e. An isoelectric record

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The answer is d. The background posterior-dominant rhythm on the normal adult EEG is a activity at 8 to 12 Hz. With Alzheimer disease, the frequency of ...

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